Treatment of Cancer (A Hodder Arnold Publication) - 5th edition

Treatment of Cancer

Fifth Edition

Edited by

Pat Price MA MD FRCP FRCR Professor of Radiation Oncology Academic Department of Radiation Oncology School of Cancer and Imaging Sciences Christie Hospital and University of Manchester Manchester, UK

Karol Sikora MB PhD FRCP MRCR Medical Director Cancer Partners UK and Visiting Professor of Cancer Medicine Imperial College Hammersmith Hospital London, UK

Tim Illidge BSc PhD MRCP FRCR Professor of Targeted Therapy and Oncology School of Cancer and Imaging Sciences Christie Hospital and University of Manchester Manchester, UK

PART OF HACHETTE LIVRE UK

First published in Great Britain in 1982 by Chapman & Hall This second edition published in 2008 by Hodder Arnold, an imprint of Hodder Education, part of Hachette Livre UK, 338 Euston Road, London NW1 3BH http://www.hoddereducation.com

©

2008 Edward Arnold (Publishers) Ltd

All rights reserved. Apart from any use permitted under UK copyright law, this publication may only be reproduced, stored or transmitted, in any form, or by any means with prior permission in writing of the publishers or in the case of reprographic production in accordance with the terms of licences issued by the Copyright Licensing Agency. In the United Kingdom such licences are issued by the Copyright Licensing Agency: Saffron House, 6–10 Kirby Street, London EC1N 8TS. Whilst the advice and information in this book are believed to be true and accurate at the date of going to press, neither the author[s] nor the publisher can accept any legal responsibility or liability for any errors or omissions that may be made. In particular (but without limiting the generality of the preceding disclaimer) every effort has been made to check drug dosages; however it is still possible that errors have been missed. Furthermore, dosage schedules are constantly being revised and new side-effects recognized. For these reasons the reader is strongly urged to consult the drug companies’ printed instructions before administering any of the drugs recommended in this book. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN-13 978 0 340 912218 1 2 3 4 5 6 7 8 9 10 Commissioning Editor: Gavin Jamieson Project Editor: Francesca Naish Production Controller: Andre Sim Cover Designer: Helen Townson Typeset in 10/12 pt Minion by Charon Tec Ltd (A Macmillan Company) Chennai, India Printed in India

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Contents

Colour plates appear between pages 728 and 729 Contributors

vi

Foreword

xiv

Preface

xv

List of abbreviations used

xvi

Evidence scoring

xxiii

Reference annotation

xxiii

PART ONE: PRINCIPLES 1 2 3 4 5 6 7 8 9 10 11 12 13

Introduction Karol Sikora Molecular Biology Hani Gabra, Euan Stronach, Rohini Sharma Clinical radiobiology Michele I Saunders, Stanley Dische Mathematical modelling and its application in oncology Roger G Dale, Bleddyn Jones Principles of chemotherapy and drug development Jeffry Evans, Meenali M Chitnis, Denis C Talbot Tumour imaging in oncology Anju Sahdev, Rodney H Reznek Interventional radiology Tarun Sabharwal, Anne P Hemingway, Andreas Adam Vaccination strategies for malignant diseases Deepak P Assudani, Stephanie McArdle, Murrium Ahmad, Geng Li, Robert C Rees, Selman A Ali Biological therapies: cytokines and adoptive cell therapy Fiona C Thistlethwaite, Peter L Stern, Robert E Hawkins Radioimmunotherapy Tim Illidge, Mike Bayne Monoclonal antibodies and treatment of cancer Hossein Borghaei, Liat Binyamin, Igor Astsaturov, Louis M Weiner Angiogenesis as a target for the treatment of cancer Srinivasan Madhusudan, Daniel Patterson, Adrian L Harris Gene therapy Kate Relph, Kevin Harrington, Hardev S Pandha

1 3 23 40 58 75 112 146 167 186 203 226 251 269

PART TWO: PRACTICE

285

14

287

Central nervous system Roy Rampling

iv Contents

15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

41 42

Ocular and adnexal tumours John L Hungerford, P Nicholas Plowman Head and neck cancer Alastair J Munro, Nicholas D Stafford Thyroid Masud Haq, Clive Harmer Endocrine cancer Maria Gueorguiev, Ashley B Grossman, P Nicholas Plowman Breast cancer Navita Somaiah, John Yarnold Bronchus Vanessa A Potter, Nicholas Thatcher, Penella J Woll Oesophageal cancer David B Smith, Brian J Haylock Liver Daniel H Palmer, Philip J Johnson, Pancreas Patrick G Johnston, Martin M Eatock Biliary tract Hemant M Kocher, Ajit T Abraham, Satya Bhattacharya Stomach Marianne C Nicolson, Kenneth GM Park, Leslie M Samuel Bladder cancer Robert Huddart, Paula Wells, Alan Horwich Prostate cancer Malcolm Mason Colorectal cancer Richard HJ Begent, Astrid Mayer, Christopher H Collis, Russell N Moule Anus Bernard J Cummings Germ-cell cancers of the testis and related neoplasms Graham M Mead Renal cell cancer Tom R Geldart Ovary and fallopian tubes Daniela D Rosa, Andrew R Clamp, Gordon C Jayson Uterus Bleddyn Jones Cervix Peter Blake Carcinoma of the vagina and vulva Sadaf Ghaem-Maghami, W Pat Soutter Gestational trophoblastic tumours Peter Schmid, Michael J Seckl Non-melanoma skin cancer Stephen L Morris, Sean Whittaker, Margaret Spittle Malignant melanoma Susana Banerjee, Martin Gore Bone Jeremy S Whelan, Rob C Pollock, Anna M Cassoni Soft tissue sarcomas Thomas F DeLaney, Andrew E Rosenberg, David C Harmon, Frances J Hornicek, Sam Yoon, David G Kirsch, Henry J Mankin, Daniel Rosenthal Leukaemias Tariq I Mughal, John M Goldman Hodgkin’s lymphoma Beate Klimm, Andreas Engert

320 343 408 438 468 502 539 559 573 585 602 614 645 666 695 706 729 748 764 777 796 809 835 879 905 925

981 1027

Contents v

43 44 45 46 47

Non-Hodgkin’s lymphoma Adrian J C Bloor, David C Linch Multiple myeloma Jennifer M Bird, Cathy Williams Introduction to haematopoietic stem cell transplantation Effie Liakopoulou, David I Marks Paediatric oncology Stephen Lowis, Eddy Estlin, Keith Sibson, AIDS-related malignancy Mark Bower, Tom Newsom-Davis

1045 1073 1098 1118 1167

PART THREE: MANAGEMENT

1187

48

1189

49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 Index

Medical care Clare E Green, Richard H J Begent Interstitial brachytherapy J Roger Owen, David Bottomley Principles of external beam radiotherapy planning techniques Stephen L Morris, H Jane Dobbs, Conformal radiotherapy, intensity-modulated radiotherapy and image-guided radiotherapy Vincent Khoo Concomitant chemo-radiotherapy principles and management Syed A Hussain, Anjali Zarkar, Nicholas D James Palliative care Anne Naysmith, Karol Sikora Communications with the cancer patient Justin Stebbing, Maurice L Slevin Clinical cancer genetics Lisa J Walker, Ros A Eeles Large-scale randomized evidence: trials and overviews Richard Gray, Rory Collins, Richard Peto, Keith Wheatley The economics of cancer care Nick Bosanquet Medical audit Amit K Bahl, Gareth J G Rees, The organisation of cancer services: a UK perspective Ian Kunkler New drug development George Blackledge Late effects of cancer therapy Susan E Davidson Surgical oncology David Merrilees, David Neal Cancer prevention strategies William P Steward, Andreas Gescher

1210 1233 1254 1280 1290 1305 1318 1338 1352 1365 1377 1407 1415 1423 1433 1445

Contributors

Ajit T Abraham MS MA FRCS Consultant Surgeon Hepato-biliary and Pancreatic Surgery Unit The Royal London Hospital London, UK

Mike Bayne BSc MBChB MRCP FRCP DM Consultant Clinical Oncologist Dorset Cancer Centre, Poole Dorset, UK

Andy Adam MBBS (Hons) FRCP FRCS FRCR FFRRCSI (Hon) Professor of Interventional Radiology Department of Radiology St Thomas’ Hospital King’s College London London, UK

Richard H J Begent MD FRCP FRCR FMedSci Department of Oncology Royal Free and University College Medical School University College London London, UK

Murrium Ahmad BSc MSc PhD Post-Doctoral Research Fellow/ Research Project Manager School of Science and Technology Nottingham Trent University Nottingham, UK

Satya Bhattacharya MS MPhil FRCS Consultant Hepato-biliary Surgeon Hepato-biliary and Pancreatic Surgery Unit The Royal London Hospital London, UK

Selman A Ali PhD BVM&S Senior Lecturer School of Science and Technology Nottingham Trent University Nottingham, UK

Liat Binyamin PhD Postdoc Associate Fox Chase Cancer Centre Philadelphia, USA

Deepak Assudani MBBS MSc PhD Post-Doctoral Research Fellow Moffitt Cancer Centre and Research Institute Florida, USA Igor Astsaturov Fox Chase Cancer Centre Philadelphia, USA Amit K Bahl MD MRCP FRCR FFR RCSI Consultant in Clinical Oncology Bristol Haematology and Oncology Centre Bristol, UK Susana Banerjee MA MBBS MRCP Clinical Fellow The Breakthrough Breast Cancer Research Centre at the Institute of Cancer Research Chester Beatty Laboratories London, UK

Jennifer M Bird MD FRCP FRCPaTH Avon Haematology Unit Bristol Haematology and Oncology Centre Bristol, UK Peter Blake MD FRCR Consultant Clinical Oncologist The Royal Marsden Hospital London, UK George Blackledge Hospira UK Ltd Warwickshire, UK

MB MD PhD FRCP

Adrian J C Bloor PhD MRCP MRCPath Consultant Haematologist Christie Hospital Manchester, UK

Contributors vii

Hossein Borghaei DO MS Medical Oncology Fox Chase Cancer Centre Philadelphia, USA

Susan E Davidson MD FRCR FRCP(Glas) BW Consultant and Honorary Senior Lecturer in Clinical Oncology Christie Hospital NHS Foundation Trust Manchester, UK

Nick Bosanquet BA Msc Professor of Health Policy Imperial College London, UK

Thomas F DeLaney MD Associate Professor of Radiation Oncology Harvard Medical School Associate Radiation Oncologist Department of Radiation Oncology Medical Director Francis H Burr Proton Therapy Center Massachusetts General Hospital Boston, USA

David Bottomley MBBS MRCP FRCR Consultant Clinical Oncologist Cookridge Hospital Leeds, UK Mark Bower PhD FRCP FRCPath Consultant Medical Oncologist Chelsea and Westminster Hospital London, UK Anna M Cassoni BSc FRCR FRCP Consultant Clinical Oncologist University College Hospital London, UK Meenali M Chitnis BmedSci MBBS MRCP Specialist Registrar in Medical Oncology Churchill Hospital Oxford, UK Andrew R Clamp MRCP PhD Senior Lecturer and Honorary Consultant in Medical Oncology Cancer Research UK Department of Medical Oncology Christie Hospital Manchester, UK Rory Collins FRCP FMedSci Co-director, Clinical Trial Service Unit (CTSU) University of Oxford Oxford, UK Christopher H Collis MB BChir Clinical Oncologist Royal Free and University College Medical School London, UK Bernard J Cummings MBChB FRCPC FRCR FRANZCR Department of Radiation Oncology Princess Margaret Hospital University of Toronto Toronto Ontario, Canada Roger G Dale MSc PhD FlnstP FIPEM FRCR (Hon) Director Department of Radiation Physics and Radiobiology Professor of Cancer Radiobiology Hammersmith Hospitals NHS Trust Faculty of Medicine Imperial College London, UK

Stanley Dische MD FRCR FACR Marie Curie Research Wing Centre for Cancer Treatment Mount Vernon Hospital Middlesex, UK H Jane Dobbs MA FRCP FRCR Consultant in Clinical Oncology Department of Clinical Oncology Guy’s and St. Thomas’ NHS Foundation Trust London, UK Martin M Eatock MbChB FRCP(Lond) FRCP(Glasg) Consultant/Honorary Senior Lecturer in Medical Oncology Northern Ireland Cancer Centre Belfast City Hospital Belfast, UK Ros A Eeles MA MRCP FRCP PhD Translational Cancer Genetics Team Institute of Cancer Research and Cancer Genetics Unit Royal Marsden NHS Foundation Trust Sutton and London, UK Andreas Engert MD Professor for Internal Medicine Hematology and Oncology University Hospital of Cologne Department of Internal Medicine I Cologne, Germany Eddy Estlin BSc(Hons) PhD MRCP(UK) FRCPH Macmillan Consultant in Paediatric Oncology Department of Paediatric Oncology Royal Manchester Children’s Hospital Manchester, UK Jeffry Evans MBBS MD MRCP(UK) FRCP(Glasgow) FRCP(London) Professor of Translational Cancer Research University of Glasgow Honorary Consultant Medical Oncologist Beatson West of Scotland Cancer Centre Honorary Group Leader Beatson Institute for Cancer Research Glasgow, UK

viii Contributors

Hani Gabra PhD FRCPE FRCP Professor of Medical Oncology Ovarian Cancer Action Research Unit and Section of Molecular Therapeutics Department of Oncology, Imperial College London, UK

Masud Haq BSc MRCP MD Locum Consultant in Diabetes & Endocrinology Chelsea & Westminster Hospital NHS Foundation Trust London, UK

Tom R Geldart BSc MBBS MRCP DM Consultant in Medical Oncology Poole and Royal Bournemouth Hospital NHS Tusts Dorset, UK

Clive Harmer FRCP FRCR Consultant Oncologist Former Head of the Thyroid Unit Royal Marsden Hospital London, UK

Andreas Gescher BSc PhD DSc Professor of Biochemical Toxicology Leicester Royal Infirmary Leicester, UK Sadaf Ghaem-Maghami PhD MRCOG Senior Lecturer and Honorary Consultant in Gynaecological Oncology Imperial College Faculty of Medicine Division of Surgery, Oncology, Reproduction and Anaesthetics Department of Reproductive Biology Hammersmith Hospitals Trust London, UK John M Goldman DM FRCPath Hematology Branch, National Heart Lung and Blood Institute National Institutes of Health Bethesda, USA Martin Gore PhD FRCP Professor of Cancer Medicine The Royal Marsden Hospital London, UK Richard Gray MA MSc Professor of Medical Statistics Director, Birmingham Clinical Trials Unit Robert Aitken Institute University of Birmingham Birmingham, UK Clare E Green Bsc MRCP MBBS Department of Oncology Southampton General Hospital Southampton, UK Ashley B Grossman BA BSc MD FRCP FMedSci Department of Endocrinology St Bartholomew’s Hospital London, UK Maria Gueorguiev MD Department of Endocrinology St. Bartholomew’s Hospital London, UK

David C Harmon MD Massachusetts General Hospital Division of Hematology & Medical Oncology Boston, USA Kevin Harrington FRCP FRCR The Institute of Cancer Research Royal Marsden Hospital London, UK Adrian L Harris BSc Hons MB ChB MA DPhil FRCP Director Cancer Research UK Molecular Oncology Laboratories Weatherall Institute of Molecular Medicine John Radcliffe Hospital Oxford, UK Robert E Hawkins MBBS PhD FRCP Professor and Director of Medical Oncology Cancer Research UK Department of Medical Oncology Christie Hospital NHS Foundation Trust and University of Manchester Manchester, UK Brian J Haylock BSc Hons Pharm MB MRCP DRCOG FRCR FRCP(C) Consultant Clinical Oncologist Clatterbridge Centre for Oncology Bebington Wirral, UK Anne P Hemingway BSc MBBS MCRP FRCR FRCP Department of Diagnostic Radiology Hammersmith Hospital Imperial College NHS Trust London, UK Francis Hornicek MD PhD Department of Orthopedics Massachusetts General Hospital Boston, USA

Contributors ix

Alan Horwich PhD MRCP FRCR Professor of Radiotherapy Academic Radiotherapy Unit The Institute of Cancer Research The Royal Marsden Hospital Surrey, UK Robert Huddart PhD MRCP FRCR Reader in Urological Oncology Academic Radiotherapy Unit The Institute of Cancer Research The Royal Marsden Hospital Surrey, UK John L Hungerford Ocular Oncology Service Department of Ophthalmology St Bartholomew’s Hospital London, UK Syed Hussain Clinical Lecturer in Oncology Cancer Research UK Institute for Cancer Studies University Hospital Birmingham Birmingham, UK Tim Illidge BSc PhD MRCP FRCR Professor of Targeted Therapy and Oncology School of Cancer and Imaging Sciences Christie Hospital and University of Manchester Manchester, UK Nicholas D James SSc MBBS FRCP FRCR PhD Professor of Clinical Oncology Cancer Research UK Institute for Cancer Studies University of Birmingham Birmingham, UK Gordon C Jayson FRCP PhD Professor of Medical Oncology Cancer Research UK Department of Medical Oncology Christie Hospital Manchester, UK Philip J Johnson MD FRCP Clinical Head Professor of Oncology Director, Clinical Trials Unit Institute of Cancer Studies The University of Birmingham Birmingham, UK Patrick Johnston Centre for Cancer Research & Cell Biology Queen’s University Belfast University Floor Belfast City Hospital Belfast, UK

Bleddyn Jones MA MSc MD FRCP FRCR med FIPEM FBIR Consultant in Oncology and Applied Radiobiology University Hospital Birmingham Birmingham, UK Vincent Khoo MBBS FRACR FRCR MD Consultant & Honorary Senior Lecturer in Clinical Oncology Royal Marsden Hospital London, UK David G Kirsch MD PhD Department of Radiation Oncology Duke University Medical Center North Carolina, USA Beate Klimm, MD Department I of Internal Medicine University Hospital Cologne Cologne, Germany Hemant M Kocher MS MD FRCS Department of Health National Clinician Scientist Senior Lecturer and Hon Consultant Surgeon Tumour Biology Laboratory Cancer Research UK Clinical Centre Barts and The London School of Medicine and Dentistry London, UK Ian Kunkler MA MBBChir DMRT FRCR FRCPE FRSA Consultant Clinical Oncologist Edinburgh Cancer Centre Western General Hospital University of Edinburgh Edinburgh, UK Geng Li, MBBS, MSc, PhD Senior Clinical Scientist Central Labs Alconbury Cambridgeshire, UK Effie Liakopoulou Consultant in Haematology and Stem Cell Transplantation Christie Hospital NHS Trust Honorary Senior Lecturer in Cancer Studies University of Manchester Manchester, UK David C Linch FRCP FRCPath FMedSci Professor of Haematology Royal Free and University College Medical School London, UK

x Contributors

Stephen Lowis BA (Hons) BM BCh Phd MRCP(UK) FRCPCH Macmillan Consultant in Paediatric and Adolescent Oncology Department of Paediatric Oncology Bristol Royal Hospital for Children Bristol, UK Srinivasan Madhusudan MBBS MRCP PhD Clinical Associate Professor and Consultant in Medical Oncolgy School of Molecular Medical Sciences Academic Unit of Oncology University of Nottingham Nottingham, UK Henry J Mankin MD Orthopaedic Oncology Massachusetts General Hospital Boston, USA David I Marks Consultant in Haematology and Stem Cell Transplantation Director Adult Bone Marrow Transplant Unit United Bristol Health Trust Honorary Clinical Reader in Haematopoietic Cell Transplantation University of Bristol Bristol, UK Malcolm Mason MD FRCP FRCR Cancer Research Wales Professor of Clinical Oncology Department of Oncology and Palliative Medicine Cardiff University Velindre Hospital Cardiff, UK Astrid Mayer PhD Senior Lecturer in Medical Oncology Hampstead Site Royal Free and University College Medical School London, UK Stephanie McArdle BSc PhD Senior Post-Doctoral Research Fellow School of Science and Technology Nottingham Trent University Nottingham, UK Graham M Mead DM FRCP FRCR Department of Medical Oncology Royal South Hants Hospital Southampton, UK David Merrilees FRACS (Urol) Auckland Hospital Auckland New Zealand

Stephen L Morris MBBS MRCP FRCR MacMillan Consultant Clinical Oncologist Skin Tumour Unit St Johns Institute of Dermatology St Thomas’ Hospital Clinical Oncology Department London, UK Russell N Moule Department of Oncology Royal Free and University College Medical School University College London London, UK Tariq I Mughal MB MD MRCP MRCS FACP CRC Department of Medical Oncology Royal Preston Hospital Preston, UK Alastair J Munro Tayside Cancer Centre NHS Tayside Ninewells Hospital Dundee, UK Anne Naysmith FRCP Pembridge Unit St. Charles Hospital London, UK David Neal FMed Sci MS FRCS Professor of Surgical Oncology Honorary Consultant Urological Surgeon University of Cambridge/Addenbrooke’s Hospital Cambridge, UK Tom Newsom-Davis BSc MRCP Specialist Registrar Medical Oncology Department of Oncology Hammersmith Hospitals NHS Trust London, UK Marianne C Nicolson BSc MD FRCP ANCHOR Unit – Clinic D Aberdeen Royal Infirmary Aberdeen, UK J Roger Owen MBBS FRCP FRCR Cheltenham General Hospital Cheltenham, UK Daniel H Palmer BSc MBChB MRCP PhD Cancer Research UK Clinician Scientist and Honorary Consultant in Medical Oncology Cancer Research UK Institute for Cancer Studies University of Birmingham Birmingham, UK

Contributors xi

Hardev Pandha FRCP FRACP PhD Department of Oncology Postgraduate Medical School University of Surrey Guildford, UK Kenneth GM Park MB ChB MD FRCS (Ed) Consultant Surgeon/Honorary Senior Lecturer Aberdeen Royal Infirmary Aberdeen, UK Sir Richard Peto FRS Co-director, Clinical Trial Service Unit (CTSU) University of Oxford Oxford, UK P Nicholas Plowman MA MD FRCP FRCR Ocular Oncology Service Department of Ophthalmology St Bartholomew’s Hospital London, UK Rob Pollock FRCS Consultant Orthopaedic Surgeon Royal National Orthopaedic Hospital Stanmore Middlesex, UK Vanessa A Potter BSc MRCP PhD Consultant Medical Oncologist Nottingham City Hospital Nottingham, UK Pat Price MA MD FRCP FRCR Professor of Radiation Oncology Academic Department of Radiation Oncology School of Cancer and Imaging Sciences Christie Hospital and University of Manchester Manchester, UK Roy Rampling PhD FRCR FRCP MBBS Professor of Neuro-Oncology Beatson West of Scotland Cancer Centre Glasgow, UK Gareth J G Rees FRCP FRCR Consultant in Clinical Oncology Bristol Haematology and Oncology Centre Bristol, UK Robert Rees BSc PhD Dean of School School of Science and Technology Nottingham Trent University Nottingham, UK Kate Relph BSc PhD Department of Oncology Postgraduate Medical School University of Surrey Guildford, UK

Rodney Reznek Academic Department of Radiology St Bartholomew’s Hospital London, UK Daniela D Rosa MD, PhD Medical Oncologist Cancer Research UK Department of Medical Oncology Christie Hospital Manchester, UK Andrew E Rosenberg MD Department of Pathology – WRN 2 Massachusetts General Hospital Boston, USA Daniel Rosenthal Harvard Medical School Boston, USA Tarun Sabharwal MBBCH FRCSI FRCR Consultant Interventional Radiologist And Honorary Senior Lecturer Guy’s and St Thomas’ Hospital London, UK Anju Sahdev MBBS MRCP FRCR Consultant Radiologist St Bartholomew’s Hopsital Barts and the London Trust London, UK Denis C Talbot BSc MB Bchir MA PhD FRCP Consultant Medical Oncologist and Reader in Cancer Medicine Cancer Research UK Experimental Cancer Centre University of Oxford Oxford, UK Leslie M Samuel BSc MSc FRCP (Edin) FRCR (Lond) Macmillan Consultant Oncologist ANCHOR Unit Aberdeen Royal Infirmary Aberdeen, UK Michele I Saunders MD FRCP FRCR Windeyer Professor of Oncology University College London, UK Peter Schmid MD PhD Consultant Medical Oncologist and Senior Clinical Lecturer Director, Hammersmith Early Clinical Trials Unit Charing Cross Campus, Imperial College NHS Trust Imperial College London London, UK

xii Contributors

Michael J Seckl PhD FRCP Head of Section of Molecular Oncolgy Director of the Charing Cross Gestational Trophoblastic Disease Centre Charing Cross Campus of Imperial College NHS Trust London, UK Rohini Sharma FRACP Clinical Fellow Ovarian Cancer Action Research Unit and Section of Molecular Therapeutics Department of Oncology Imperial College London, UK Keith Sibson MB ChB MRCP Haematology Department University College Hospital London, UK Karol Sikora MB PhD FRCP FRCR Medical Director Cancer Partners UK and Visiting Professor of Cancer Medicine Imperial College Hammersmith Hospital London, UK Maurice L Slevin MD FRCP Department of Medical Oncology St Bartholomew’s Hospital London, UK David B Smith MB FRCP Consultant in Medical Oncology Clatterbridge Centre for Oncology Merseyside, UK Navita Somaiah MBBS MD FRCR Clinical Research Fellow Academic Radiotherapy Department Royal Marsden Hospital and Institute of Cancer Research Surrey, UK

Nicholas D Stafford MB FRCS Professor of Otolaryngology & Head and Neck Surgery Postgraduate Medical Institute University of Hull Hull Royal Infirmary Hull, UK Justin Stebbing Imperial College School of Medicine Department of Medical Oncology Hammersmith Hospital London, UK William P Steward MB ChB PhD FRCPC FRCP(Lon, Gla) Head of Department of Cancer Studies and Molecular Medicine University of Leicester Leicester Royal Infirmary Leicester, UK Peter L Stern BSc PhD Head of Cancer Research UK Immunology Group Paterson Institute for Cancer Research University of Manchester Manchester, UK Euan Stronach PhD Senior Research Associate Ovarian Cancer Action Research Unit and Section of Molecular Therapeutics Department of Oncology, Imperial College London London, UK Herman D Suit MD DPhil Department of Radiation Oncology Massachusetts General Hospital Boston, USA Denis C Talbot ICRF Medical Oncology Unit The Churchill Hospital Oxford, UK Fiona C Thistlethwaite MB BChir PhD MRCP Clinical Fellow Cancer Research UK Department of Medical Oncology Christie Hospital NHS Foundation Trust Manchester, UK

W Pat Soutter MSc MD FRCOG Honorary Reader in Gyanecological Oncology Department of Obstetrics and Gynaecology Imperial College Faculty of Medicine Hammersmith Hospital London, UK

Nicholas Thatcher Professor of Medical Oncology CRC Department of Medical Oncology Christie CRC Research Centre Christie Hospital NHS Trust Manchester, UK

Margaret Spittle MSc FRCR FRCP Consultant Clinical Oncologist Meyerstein Institute of Oncology The Middlesex Hospital London, UK

Lisa J Walker MRCPCH Dphill Consultant in Cancer Genetics Department of Clinical Genetics The Churchill Hospital Oxford, UK

Contributors xiii

Louis M Weiner MD Vice President, Translational Research Chairman, Department of Medical Oncology G Morris Dorrance, Jr Endowed Chair in Medical Science Fox Chase Cancer Center Philadelphia, USA Paula Wells PhD MRCP FRCR Consultant Clinical Oncologist Department of Radiotherapy St Bartholomew’s Hospital London, UK Keith Wheatley DPhil Professor of Medical Statistics Director, Birmingham Clinical Trials Unit Robert Aitken Institute University of Birmingham Birmingham, UK Jeremy Whelan MD FRCP Consultant Medical Oncologist University College Hospital London, UK Sean Whittaker MD FRCP Consultant Dermatologist Skin Tumour Unit St Johns Institute of Dermatology St Thomas’ Hospital London, UK

Cathy Williams MRCP FRCPath Consultant Haematologist Centre for Clinical Haematology Nottingham University Hospitals Nottingham, UK Penella J Woll MBBS PhD FRCP Professor of Medical Oncology Weston Park Hospital Sheffield, UK John Yarnold MBBS BSc MRCP FRCR Professor of Clinical Oncologist and Honorary Consultant Academic Radiotherapy Department Royal Marsden Hospital Surrey, UK Sam Yoon MD Division of Surgical Oncology Massachusetts General Hospital Harvard Medical School Boston, USA Anjalia Zarkar MBBS MRCP MD FRCR Consultant Clinical Oncologist The Cancer Centre University Hospital Birmingham Birmingham, UK

Foreword

HISTORICAL FOREWORD Cancer has been present since time immemorial, before man himself had developed; sarcoma have been seen in bones of dinosaurs and of our predecessor Pithecanthropus erectus. We have feared cancer especially after it was first recognized by Hippocrates (c. 460–370 BC), and named by Galen of Pergamon (AD 129–216). Surgery was the natural first treatment, and was usually extensive and often mutilating, even more so after anaesthesia came into use in the nineteenth century; but unfortunately for the patient, recurrence was frequent. The many drug and medicines available were of little avail, even when caustics were applied. Then X-rays were discovered in 1895, and radium in 1898, and soon each began to be used with some success. Nevertheless, the energy of the rays was low, in kilovolts only, and their use in cancer treatment was of lasting benefit against no more than basal and squamous cell skin cancers. Radium, however, was soon found to have remarkable value when inserted into tumours of the uterus and then implanted into superficial and accessible cancers. Replication of treatments necessarily required definition and measurement of units – the ro˝ntgen, rad and gray for dose; and the curie and becquerel for activity. Methods and results were steadily improved up to the 1930s. Therapy units had then become available to produce X-rays of energy as high as 500 kV, and two of these were constructed in series to make the first millionvolt machine, installed in St. Bartholomew’s Hospital in 1938; ‘Megavoltage X-ray therapy’ had begun, but only in one privileged centre. The Second World War intervened for six long years, from 1939 to 1945, with peace coming in the Far East only after the atomic bombs were dropped. Artificial radioactive isotopes then became freely available, not only those such as iodine-131 and phosphorus-32 but more importantly cobalt-60, emitting megavoltage γ-rays. Sources were constructed with activities of tens and hundreds of curies, far more than even the largest radium ‘bombs’. These were, first of all, placed into teleradium housings with great benefit, and soon into purpose-built ‘cobalt units’, operating at 80 or 100 cm source-skin distances. In 1952, an even better unit

arrived – the linear accelerator, operating at 4 Mev ore more. This was truly revolutionary – with the help of wedge filters and good planning one could now treat deep tumours anywhere within the body; there was also no skin reaction, which had long been an unpleasant side-effect limiting prescribed dosage. The ‘LA’, as it became known, had also been achieved as a result of wartime research – at the heart of the linear accelerator was a high-power electron source, the magnetron, which had been developed at the Malvern Telecommunications and Radar Establishment for use in radar equipment. Within a few years megavoltage treatment became available everywhere. One other revolutionary discovery had also come from the war: nitrogen mustard had been shown to be sensationally effective against Hodgkin’s disease about 1948, and then bleomycin in 1972 against squamous carcinoma. More drugs followed, together with more hormones, particularly tamoxifen. They began to be used in combinations, and chemotherapy joined surgery and radiotherapy as another ally against cancer. The first edition of Treatment of Cancer was published in 1982; at this time it was sorely needed. After the Second World War, two texts had been published, from David Smithers in London in 1946 describing X-ray therapy, and Ralston Paterson in Manchester in 1948 (second edition in 1963) comprehensively covering both X-ray and radium treatment. These were followed in 1955 by Rock Carling, Windeyer and Smithers’ British Practice in Radiotherapy, and Ronald Raven’s Cancer in 1960. By the 1970s these were beginning to become out of date. I began planning my own book in 1977. The first edition was well received and a second edition was requested after I had retired and had begun work for 2 years in Hong Kong. Karol Sikora kindly took over as joint editor for the second edition, published in 1990, bringing in molecular biology, oncogenes, sensitizers, hypothermia and AIDS. Pat Price joined him as editor for the third edition in 1995, by which time cost-efficiency, genetics and audit needed further space. Yet more is to come. I am looking forward with much pleasure to the publication of the fifth edition. Keith Halman, FRSH

Preface

Cancer is an increasingly common problem; by the year 2020, it is likely that one in two of the global population will develop the disease at some time. This striking increase is mainly due to an increasingly ageing population. The treatment of cancer is therefore a vital component of modern healthcare provision. Oncology crosses the traditional boundaries in which medicine is taught, researched and practiced, thereby providing a great challenge for those involved in its treatment. It is a truly multidisciplinary subject. One of the current dogmas, almost a cliché, is the importance of integration and teamwork between those involved in its management: surgeons, radiotherapists, medical oncologists and a myriad of other organ-based specialists. But the most exciting discoveries of the past two decades have been in the laboratory. Our understanding of the process of growth control and its deregulation has gone through a remarkable transformation, with the discovery of oncogenes, tumour suppressor genes and their encoded products. Coupled with the tremendous advances in imaging and the likely explosion in our understanding of the genome, we are set for a dramatic improvement in cancer therapy over the next decade. This book attempts to synthesize in one place scientific discoveries together with the best of current practice. Tumours of all kinds, common and esoteric, are considered so that authoritative help on how bet to manage an individual patient can be found rapidly. Our authors come from many disciplines, to paint as broad a canvas as possible of oncological knowledge. Many are associated in some way with Hammersmith Hospital, but we have also invited colleagues from the UK and abroad to share with us their special expertise. In many cases, we have teamed a surgeon with an oncologist to give a complete overview of the management of an individual tumour type. The book is divided into three parts. The first section considers the principles of cancer treatment and the likely developments that will take place over the next decade. The contributors here are active participants in current research programmes in their area. The second and main

part – practice – is an extensive series of chapters covering every individual class of tumour. They represent the distillation of considerable experience from senior clinicians. For many tumours, such as early carcinoma of the larynx, treatment has become standardized as well as successful. For others, such as breast cancer, there is considerable controversy. We have given more space to those tumours where controversy reigns, for it is here that difficulties in management are most likely to arise. We have used some diplomatic editing, with the agreement of the authors, to make their management plans widely applicable. In this way, we hope the book will provide sufficient guidance to point the way to the best contemporary treatment protocols for individual patient care throughout the world. The final section – management – gives further essential detail on the general problems of caring for the cancer patient. Here we consider medical problems that commonly arise, and also the development of continuing care philosophies, which have revolutionized the management of those patients for whom no cure is yet available. We consider radiotherapy planning techniques as well as new developments in conformal planning. We review medical audit and clinical trials, both essential tools of progress in an emerging discipline. We also consider complementary medicine and cancer, for the first time, we believe, in an orthodox oncology text. We have been greatly helped by the expertise and writing skills of our authors who have produced truly excellent manuscripts. We hope that this unique, multiauthor text will continue to educate a new generation of oncologists at a time of considerable progress. Delivering optimal care requires far more teamwork than ever before and the integration of many specialities. The success of modern cancer treatment is transforming the lives of many of our patients. We hope that this contribution will help to do this. Pat Price, Christie Hospital, Manchester Karol Sikora, Hammersmith Hospital and Cancer Partners UK, London

List of abbreviations used

AAF 17-AAG AAVs ABC ABVD AC ACE ACNU ACT ACTH ACTION ADC ADDC ADEPT AEs AF AFP AIM AIN AIs AJCC ALA ALL ALP AML AP APC APCs APL APT ara-CTP ARCON ASCO ASCT ASH ASTEC AT ATG

IFN-alpha-activated factor 17-allylaminogel-danamycin adeno-associated viruses Adjuvant Breast Cancer trial doxorubicin, bleomycin, vinblastine, dacarbazine Audit Commission doxorubicin, cyclophosphamide Adult Comorbidity Evaluation 1-(4-amino-2-methylpyrimidine-5-yl)methyl3-(2-chloroethyl)-3-nitrosurea adoptive cell transfer adrenocorticotrophic hormone Adjuvant Cytotoxic Chemotherapy In Older Women (trial) apparent diffusion coefficient antibody dependent directed cytotoxicity antibody-directed enzyme prodrug therapy adverse events accelerated fractionation alpha-fetoprotein doxorubicin, ifosfamide, mesna anal intra-epithelial neoplasia aromatase inhibitors American Joint Committee on Cancer 5-aminolevulinic acid acute lymphoblastic leukaemia alkaline phosphatase acute myeloid leukaemia antero-posterior fields adenomatous polyposis coli antigen presenting cells promyelocytic leukaemia Antiplatelet Trialists Collaborative Group cytarabine triphosphate accelerated radiotherapy, carbogen and nicotinamide American Society of Clinical Oncology autologous stem-cell transplantation American Society of Hematology A Study in the Treatment of Endometrial Cancer trial ataxia telangiectasia anti-thymocyte globulin

AT/RTs ATAC ATBC ATLAS ATLL ATP ATRA aTTom AUC BAL BCG BCIRG BCNU BDSs BEACOPP BEAM BEC BED BEP BER BIG 1–98 BIPSS BNCT BOLD bp BrdUrd BRT BSO BU C-HDT C225 CA CAD CALG cAMP CAR CARET CASH

atypical teratoid/rhabdoid tumours Arimidex or Tamoxifen Alone or in Combination trial Alpha-Tocopherol, Beta-Carotene study Adjuvant Tamoxifen Longer Against Shorter trial adult T-cell leukaemia/lymphoma adenosine phosphate all-trans retinoic acid adjuvant Tamoxifen Treatment offer more trial area under time/concentration curve bronchoalveolar lavage bacillus Calmette—Guerin Breast Cancer International Research Group 1,3-bis-(2-chloroethyl)-1-nitrosurea (carmustine) beam direction shells bleomycin, doxorubicin, cyclophosphamide, prednisone, gemcitabine BCNU, etoposide, cytarabine, melphalan bleomycin, etoposide, carboplatin biologically effective dose bleomycin, etoposide, platinum base excision repair Femera-Tamoxifen Breast International Group (FEMTA) bilateral inferior petrosal sinus sampling boron neutron capture therapy blood oxygen level-dependent base pair bromodeoxyuridine brachytherapy bilateral salpingo-oophorectomy busulphan conventional high-dose therapy cetuximab carbohydrate antigen; carbonic anhydrase computer-aided diagnosis Cancer and Leukaemia Group cyclic adenosine monophosphate coxsackie and adenovirus receptor Beta-Carotene and Retinol Efficacy Trial Cancer and Steroid Hormone study

List of abbreviations used xvii

CaSR CAV CCNU CCT CD138 CD CDC CDKs CEA CED CEUS CEV CF CGH CHART CHF CHI/NAO CIN CIRs CIS CLDR CLIP CLL CM CMF CML CMV CNS CNS CODE COG COX-2 CPR CPT-11 CR3-DCC CR CRC CRE CRM CRP CRu CSCG CSF CTAs CTD CTLs CTV

calcium-sensing receptor cyclophosphamide, doxorubicin and vincristine lomustine combination chemotherapy syndecan cytosine deaminase complement-dependent cytotoxicity cyclin-dependent kinases carcinoembryonic antigen convection-enhanced delivery contrast enhanced ultrasound etoposide, cyclosphosphamide and vincristine conventional fractionation comparative genomic hybridization continuous hyperfractionated accelerated radiotherapy congestive heart failure Commission for Health Improvement/ National Audit Office conjunctival (or corneal) intraepithelial neoplasia chimeric immune receptors carcinoma-in-situ continuous low-dose-rate Cancer of the Liver Italian Programme chronic lymphocytic lymphoma complete hydatidiform mole disease cyclophosphamide, methotrexate, 5-fluorouracil chronic myeloid leukaemia cisplatin, methotrexate, vinblastine; cytomegalovirus central nervous system coagulase negative Staphylococcus cisplatin, vincristine, doxorubicin and etoposide Clinical Outcomes Group cycloxygenase-2 cardio-pulmonary resuscitation irinotecan complement-receptor-3-dependent cellular cytotoxicity complete response Cancer Research Campaign cumulative radiation effect continual reassessment method C-reactive protein complete remission unconfirmed Cancer Services Coordinating Group cerebrospinal fluid cancer—testis antigens cyclophosphamide, thalidomide, dexamethasone cytotoxic T lymphocytes clinical target volume

CVB CVC CVF CU CUPI Cy CYP D&C DACH DAHANCA DALM DC, NOS or NST DCE-MRI DCIS DCs DES 5-DFCR DFS 5-DFUR DHFR DISC-HSV DLBCL DLIs DLTs DNES DNP DPD DR DRE DRs DTCH dThdPase DTIC DTPA dTTP dUMP DUS DWI EAG EASL EBCTCG EBRT EBV ECD ECM ECMV ECOG ECST EF-RT EFS

cyclophosphamide, etoposide, BCNU central venous catheter cobra venom factor 1-(2-chloroethyl)-3-cyclohexyl1-nitrosurea (lomustine) Chinese University Prognostic Index cyclophosphamide cytochrome P450 dilatation and curettage 1, 2-diaminocyclohexane Danish Head and Neck Cancer Study dysplasia-associated lesion or mass Ductal Carcinoma, Not Otherwise Specified or of No Special Type dynamic contrast-enhanced MRI ductal carcinoma-in-situ dendritic cells diethylstilbestrol 5-deoxy-5-fluorocytidine disease-free survival 5-deoxy-5-fluorouridine dihydrofolate reductase disabled infectious single cycle-herpes simplex virus diffuse large B-cell lymphoma donor lymphocyte infusions dose-limiting toxities diffuse neuroendocrine system dinitrophenyl dihydropyrimidine dehydrogenase duration of remission digital rectal examination duration of responses delayed-type cutaneous hypersensitivity thymidine phosphorylase dacarbazine diethylenetriamine penta-acetic acid deoxynucleotide, deoxythymidine triphosphate deoxyuridylate colour Doppler ultrasound diffusion-weighted imaging Expert Advisory Group European Association for Study of the Liver Early Breast Cancer Trialistsí Collaborative Group external-beam radiotherapy Epstein—Barr virus extracellular domain extracellular matrix etoposide, cyclophosphamide, methotrexate and vincristine Eastern Cooperative Oncology Group European Carotid Surgery Trial extended field radiotherapy event-free survival

xviii List of abbreviations used

EGF EGP-2 ELISA ELVIS EM EMA EMEA EMP EMR EORTC EPO EPIC ER ERCP ESR ETT EUA EUD EUROCARE EUROMEN EUS EV 18 F-FDG PET 18

F-FLT FAC FAMMM FAP FASG FBC fCT FDA FDG FdUMP FdUTP FEC FEMTA FEV FFTF FGF FHDR FIGO FIHP FISH FLAIR FLR FLT-3 FMTC FNAC FPGS

epidermal growth factor epithelial cell adhesion molecule Enzyme-Linked ImmunoSorbent Assay Elderly Lung Cancer Vinorelbine Study trial electron microscopy etoposide, methotrexate and actinomycin European Medicines Agency extramedullary plasmacytoma endoscopic mucosal resection European Organisation for Research and Treatment of Cancer erythropoietin European Prospective Investigation into Cancer and Nutrition oestrogen receptor endoscopic retrograde cholangiopancreaticography erythrocyte sedimentation rate epithelioid trophoblastic tumour examination under anaesthetic equivalent uniform dose Survival of Cancer patients in Europe study 172 European Multiple Endocrine Neoplasia study group endoscopic ultrasound etoposide and vincristine fluorodeoxyglucose-positron emission tomography fluorine-18 fluorothymidine 5-fluorouracil, doxorubicin, cyclophosphamide familial atypical mole/malignant melanoma familial adenomatous polyposis French Adjuvant Study Group full blood count functional CT Food and Drug Administration (US) fluorodeoxyglucose 5-fluoro-deoxyuridine monophosphate 5-fluoro-deoxyuridine-5-triphosphate 5-fluorouracil, epirubicin, cyclophosphamide Femara-Tamoxifen Breast International Group forced expiratory volume freedom from treatment failure fibroblast growth factor fractionated high-dose-rate International Federation of Gynecology and Obstetrics familial isolated hyperparathyroidism in-situ hybridization fluid-attenuated inversion recovery future liver remnant FMS-like tyrosine kinase-3 familial medullary thyroid carcinoma fine-needle aspiration cytology folypoly-gamma-glutamate synthetase

FSE FSH FSRT FT FTT 5-FU FUDR FUTP GARFT

fast spin echo follicle stimulating hormone fractionated stereotactic radiotherapy farnesyl transferase Fibrinolytic Trialists Collaborative Group 5-fluorouracil 5-fluoro-2-deoxyuridine fluorouridine triphosphate glycinamide ribonucleotide formyl transferase GBM glioblastoma multiforme GC gemcitabine/cisplatin doublet GCSF granulocyte colony-stimulating factor GCT granulosa cell tumour GCV gangiclovir Gd-BOPTA gadobenate dimeglumine Gd-EOB-DTPA gadoxetate GDEPT gene-directed enzyme prodrug therapy GDNF glial-cell-derived neurotropic factor GEP gastro-enteropancreatic, gene expression profiling GERD gastro-oesophageal reflux disease GFAP fibrillary acidic protein GFR glomerular filtration rate GH growth hormone GHSG German Hodgkin Study Group GISTs gastrointestinal stromal tumours GITSG Gastrointestinal Tumour Study Group GM CSF granulocyte—macrophage colony-stimulating factor GMP Good Manufacturing Practice GnRH gonadotrophin-releasing hormone GOG Gynaecologic Oncology Group GRE gradient-echo pulses (RF pulses) GTD gestational trophoblastic disease GTT gestational trophoblastic tumours GTV gross tumour volume GVHD graft-versus-host disease GVL graft-versus-leukaemic effect GVM graft-versus-myeloma GVT graft-versus-tumour effect HAART highly active anti-retroviral therapy HACA human anti-chimeric antibody HAMA human anti-mouse antibody HATS histone acetyltransferases HAV hepatitis A virus HB-EGF heparin-binding EGF-like growth factor HBV hepatitis B virus HCC hepatocellular carcinoma hCG human chorionic gonadotrophin HCV hepatitis C virus HDAC histone-deacetylase HDCT high-dose chemotherapy HDM high-dose melphalan HDR high dose rate HDT high-dose therapy her herceptin

List of abbreviations used xix

HERA HGF HGPRT 5-HIAA HIFU HL HLA HM HMO HNSCC HNPCC hPL HPT-JT HPV HR HRT HSCs HSPs HSV HSVtk 5-HT HTLV HU 131 I-BC8 IAP IARC IBC IBCS IBIS ICE ICRU IDC IDM IES IF-RT IFA IFM IFN IFIs IFL IgH IGF IgG1 IL-2 ILC ILP IMC IMRT INT101 IP IR ISGF3

herceptin in adjuvant breast cancer, Herceptin Adjuvant (trial) hepatocyte growth factor hypoxanthine-guanine phosphoribosyl transferase 5-hydroxyindole acetic acid high-intensity focused ultrasound Hodgkin’s lymphoma human leukocyte antigen hydatidiform mole Health Maintenance Organization squamous cell carcinoma of head and neck hereditary non-polyposis colon cancer syndrome human placental lactogen hyperparathyroidism—jaw tumour syndrome human papillomavirus Hazard Ratio; homologous recombination hormone replacement therapy haematopoietic stem cells heat shock protein(90) herpes simplex virus HSV thymidine kinase 5-hydroxytrypamine human T-lymphotropic virus Hounsfield units murine anti-CD45 mAb inhibitors of apoptosis proteins International Agency for Research on Cancer inflammatory breast carcinoma International Breast Cancer Study Group International Breast Cancer Intervention Study ifosfamide, carboplatin and etoposide International Commission for Radiation Units and Measurements invasive ductal carcinoma intermediate-dose melphalan Intergroup Exemestane Study trial involved field radiotherapy incomplete Freund’s adjuvant Intergroupe Francais du Myelome interferon invasive fungal infections irinotecan, 5-FU, leucovorin immunoglobulin heavy chain insulin-like growth factor immunoglobulin G1 interleukin-2 invasive lobular carcinoma interstitial laser photocoagulation; isolated limb perfusion internal mammary chain intensity-modulated radiation therapy Intergroup 101 trial irinotecan and cisplatin interventional radiology IFN-stimulated gene factor-3

ISIS IVUs JACIE kb kDa KGF KIT LAKs LCIS LD LDH LDHRS LET LGAs LH LHRH LI LIMIT LOD score LOH LR LQ LQC LTRs LTCRs MA-170 MAbs MAC MAGE MAHA MAID MALT MAP MCA MCL MCM MCNs MDAH MDM2 MDR MDS MDTC MeCCNU MEN MEPs MESNA MFs MGMT MGUS MHC MIBG

International Study of Infarct Survival intravenous urograms Joint Accreditation Commitee for ISCT and EBMT kilobase kiloDalton keratinocyte growth factor kinase inhibitor therapy lymphokine-activated killer cells lobular carcinoma-in-situ latissimus dorsi (flap) lactate dehydrogenase low-dose hyper-radiosensitivity linear energy transfer low-grade diffuse astrocytomas luteinizing hormone luteinizing hormone releasing hormone labelling indices Leicester Intravenous Magnesium Intervention Trial logarithm to base 10 of the odds loss of heterozygosity local recurrence linear quadratic last qualifying chemotherapy long terminal repeats long-term reconstituting cells Letrozel and Tamoxifen trial monoclonal antibodies membrane attack complex melanoma antigen microangiopathic haemolytic anaemia mesna, doxorubicin, ifosfamide, and dacarbazine mucosa-associated lymphoid tissue mitogen-activated protein methylcholanthrene mantle cell lymphoma mini-chromosome maintenance Managed Clinical Networks MD Anderson Hospital mouse double minute 2 multi-drug resistance myelodysplastic syndromes multi-detector computed tomography semustine multiple endocrine neoplasia motor-evoked potentials sodium-2-mercaptoethane multiplying factors methyl guanine methyl transferase monoclonal gammopathy of undetermined significance major histocompatability complex 123 I-meta-iodobenzylguanidine

xx List of abbreviations used

MINDACT MIRD MLC MM MMC MMF MP MMPs MP-T MPNST Mn-DPDP MOPP 6-MP MRA MRC MRD MRCP MRI MRP MRS MSKCC MTC MTD MUC-1 MVAC MVD MVEC MVP NAA NAC NAT nBCC NCAM N-CAM NCCTG NCI NCIC NCRI NCRN NDA NEAT NER NF-κ-B NHL NI NICaN NICE NIHPILCO

NK NMDA NMPs NMS

Microarray In Node negative Disease may Avoid Chemotherapy Trial Medical Internal Radiation Dosimetry multi leaf collimator multiple myeloma mitomycin C mycophenolate mofetil melphalan and prednisolone matrix metalloproteinases melphalan, prednisolone plus thalidomide malignant peripheral nerve sheath tumours mangafadipir trisodium mustine, vincristine, procarbazine, prednisone 6-mercaptopurine magnetic resonance angiography Medical Research Council minimal residual disease magnetic resonance cholangio-pancreatography magnetic resonance imaging MDR-associated protein magnetic resonance spectroscopy Memorial Sloan Kettering Cancer Centre medullary carcinoma of the thyroid maximum tolerated dose mucin-1 methotrexate, vinblastine, doxorubicin, cisplatin micro-vessel density methotrexate, vinblastine, epirubicin, cisplatin mitomycin C, vinblastine and cisplatin N-acetyl acetate neoadjuvant chemotherapy N-acetyl transferase nodular basal cell carcinoma neural cell adhesion molecule neural cell adhesion molecule North Central Cancer Treatment Group National Cancer Institute National Cancer Institute of Canada National Cancer Research Institute National Cancer Research Network new drug application national breast cancer study of epirubicin nucleotide excision repair nuclear factor-κ-B non-Hodgkin’s lymphoma Nottingham Index Northern Ireland Cancer Network National Institute for Health and Clinical Excellence National Institute of Health, Prostate and Lung, Colorectal and Ovarian Cancer Screening Trial natural killer cell N-methyl D-aspartate nuclear matrix proteins New Member States

NMSG NOS NPV NSABP P-1 NSAIDs NSCLC NSE NST NTCPs OECD OLT ONJ OPSI OPG ORR OS PACS PAM PARP PBD PBSCT PBPCs PBSCs PCCL PCG/T PCI PCNA PCNSL PCNU PCP PCR PCTs PCV PD PDGF PDT PECAM PE PEG PEIT PERCHE PES PFS PGE2 PGL PHPT PIAF PICC PKA PLL PLAP PLG

Nordic Myeloma Study Group not otherwise specified negative predictive value National Surgical Adjuvant Breast and Bowel Project P-1 non-steroidal anti-inflammatory drugs non-small-cell lung cancer neurone-specific enolase no special type normal-tissue complication probabilities Organization for Economic Cooperation and Development orthotopic liver transplantation osteonecrosis of the jaw overwhelming post-splenectomy syndrome osteoprotegerin overall response rate overall survival Programme Adjuvant Cancer du Sein primary acquired melanosis poly ADP-ribose polymerase percutaneous biliary drainage peripheral stem cell transplantation peripheral blood progenitor cells peripheral blood stem cells Primary Care Cancer Lead Primary Care Group/Trusts prophylactic cranial irradiation proliferating cell nuclear antigen primary CNS lymphoma 1-(2-chloroethyl)-3-(2,6-dioxo-3-piperidyl)-1nitrosurea Pneumocystis carinii pneumonia polymerase chain reaction Primary Care Trusts procarbazine, CCNU and vincristine progressive disease platelet-derived growth factor photodynamic therapy platelet endothelial cell adhesion molecule platinum and etoposide polyethylene glycol percutaneous ethanol injection therapy Premenopausal Endocrine-Responsive Chemotherapy post-embolization syndrome progression-free survival prostaglandin E2 paraganglioma primary hyerparathyroidism cisplatin, rINF-alpha, doxorubicin, and 5-fluorouracil peripherally inserted central catheters protein kinase A prolymphocytic leukaemia placental alkaline phosphatase poly-lactide-coglycolide microspheres

List of abbreviations used xxi

PM PNETS POEMS PPAR gamma PPV PR PR-negative PSA PSC PSTT PTC PTCLu PTEN PTH PTV PVE PWI QALY QOL QUASAR R-CHOP RARs RANKL RB RBE RCA RCC RCHOP RCR RE RECIST RES RF RFA RFC RFLPs RFS rhTSH RIA RIC RISC RIT RMSs RNAi ROI ROTI RR RT RT-PCR RTK RTOG RXRs

partial hydatidiform mole disease primitive neuro-ectodermal tumours polyneuropathy, organomegaly, endocrinopathy, and skin changes syndrome peroxisome proliferator-activated receptor gamma positive predictive value partial remission; partial response progesterone-receptor-negative prostate-specific antigen primary sclerosing cholangitis placental-site trophoblastic tumour percutaneous transhepatic cholangiogram peripheral T cell lymphoma unspecified phosphatase and tensin homologue parathyroid hormone planning target volume portal vein embolization perfusion weighted imaging quality adjusted life year quality of life Quick and Simple and Reliable rituximab, cyclophosphamide, doxorubicin, vincristine, prednisolone retinoid acid receptors receptor activator of nuclear factor kappaB ligand retinoblastoma relative biological effect replication-competent adenovirus renal cell carcinoma rituximab plus cyclophosphamide, doxorubicin, vincristine and prednisolone Royal College of Radiologists relative effectiveness response evaluation criteria in solid tumours reticuloendothelial system repopulation factor radiofrequency ablation reduced folate carrier restriction fragment length polymorphisms relapse-free survival recombinant TSH stimulation radio-immunoassay reduced intensity conditioning RNA-induced silencing complex radioimmunotherapy rhabdomyosarcomas RNA interference therapy region of interest related organ or tissue impairment relative risk; ribonucleotide reductase radiotherapy reverse transcriptase polymerase chain reaction receptor tyrosine kinase Radiation Therapy Oncology Group retinoid X receptors

sBCC SBP SCAN SCF SCF SCLC SCT SD SDH SDT SE SEER SF SF2 SFV SHAs SHH SIGN SIN siRNA SNB sNDA SNPs SOBP SOFT SOS SPD SPECT SRS STR STS START SUPREMO SUV SVCO SWOG T1/T2W TAA TACE TAH Taxol TBI TCCs TCDD TCH TCNU TCP TCR TD TDF TE TEXT 6-TG TGF

superficial based cell carcinoma solitary plasmacytoma of bone South East Cancer Network supraclavicular fossa stem cell factor, supraclavicular fossa small-cell lung cancer stem cell transplantation stable disease succinate dehydrogenase gene skin directed therapy spin echo (RF pulses) Surveillance, Epidemiology, and End Results (NCI) scatter factor surviving fraction Semliki forest virus Strategic Health Authorities sonic hedgehog pathway Scottish Intercollegiate Guidelines Network sinbis virus small inhibitory RNAs sentinel node biopsy supplementary new drug application single nucleotide polymorphisms spread-out Bragg peaks Suppression of Ovarian Function Trial sinusoidal obstruction syndrome sum of products of greatest diameters single photon emission computed tomography stereotactic radiosurgery short tandem repeat soft tissue sarcoma STandardization of breast Radiotherapy Trial Selective Use of Postoperative Radiotherapy aftEr MastectOmy standard uptake value superior vena caval obstruction South West Oncology Group study weighted MRI image effects tumour-associated antigen transarterial chemoembolization total abdominal hysterectomy taxanes paclitaxel total body irradiation transitional cell carcinomas tetrachlorodibenzo-dioxin taxotere, carboplatin, herceptin tauromustine tumour cure probability T cell receptor total physical dose time—dose factor time to echo Tamoxifen and Exemestane Trial 6-thioguanine transforming growth factor

xxii List of abbreviations used

TH1 TILs TME TMP TNF TNF-alpha TNM TP TR TRAIL TRAM TREGS TRUS TRM TS TSH TSP TTF-1 TTP TUR TURBT TURPS TUUS TVUS UAPI UC UCAs UCNT UCSF

T helper 1 cytokines tumour-infiltrating lymphocytes total mesorectal excision tumour marker production tumour necrosis factor tumour necrosis factor-alpha tumour, node, metastasis thymidine phosphorylase time to repeat TNF-related apoptosis-inducing ligand transverse rectus abdominis myocutaneousfree flap regulatory T cells transrectal ultrasound transplant related mortality thymidylate synthase thyroid-stimulating hormone thrombospondin thyroid transcription factor-1 thrombocytopenic purpura, time to progression transurethral resection transurethral resection of bladder tumour transurethral resection of the prostate transurethral ultrasound transvaginal ultrasound uterine artery pulsatility index ulcerative colitis ultrasound contrast agents undifferentiated carcinomas of the nasopharynx University California San Francisco

UFT UICC UKCTOCS USPIO V-DMSA VAD VAIN VATS VDAs VDR VEE VEGF VHL VI VICE VIN VIP VLPs VNPI VNTRs, VOD VUDs VP-16 WAGR WBD WBRT WL WW Z-Dex

uracil/tegafur Union Internationale Contre Cancer UK Collaborative Trial of Ovarian Cancer Screening ultra-small particles of iron oxide pentavalent dimercapto succinic acid vincristine, adriamycin, dexamethasone vaginal intra-epithelial neoplasia video-assisted thoracic surgery vascular disrupting agents vitamin D receptor Venezuelan equine encephalitis vascular endothelial growth factor von Hippel—Lindau syndrome vascular invasion vincristine, ifosfamide, carboplatin and etoposide vulval intra-epithelial neoplasia vasoactive intestinal peptide virus-like particles Van Nuys prognostic scoring index system variable number of tandem repeats veno-occlusive disease volunteer unrelated donors etoposide Wilms—Aniridia—Gentitourinary— Retardation syndrome whole-body dose whole-brain radiotherapy window level window width dexamethasone

Evidence scoring

★★★ ★★

★

systematic review or meta-analysis one or more well designed randomized controlled trials nonrandomized controlled trials, cohort study etc.

Reference annotation

The reference lists are annotated, where appropriate, to guide readers to key primary papers and major review articles as follows: ● ◆ ★

Key primary papers as indicated by Major review articles as indicated by Papers that represent the first normal publication of a management guideline are indicated by

We hope that this feature will render extensive lists of references more useful to the reader and will help to encourage self directed learning among both trainees and practising physicians.

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PART

1

PRINCIPLES

1 Introduction Karol Sikora 2 Molecular biology Hani Gabra, Euan Stronach, Rohini Sharma 3 Clinical radiobiology Michele I Saunders, Stanley Dische 4 Mathematical modelling and its application in oncology Roger G Dale, Bleddyn Jones 5 Principles of chemotherapy and drug development Jeffrey Evans, Meenali M Chitnis, Denis C Talbot 6 Tumour imaging in oncology Anju Sahdev, Rodney H Reznek 7 Interventional radiology Tarun Sabharwal, Anne P Hemingway, Andreas Adam 8 Vaccination strategies for malignant diseases Deepak P Assudani, Stephanie McArdle, Murrium Ahmad, Geng Li, Robert C Rees, Selman A Ali 9 Biological therapies: cytokines and adoptive cell therapy Fiona C Thistlethwaite, Peter L Stern, Robert E Hawkins 10 Radioimmunotherapy Tim Illidge, Mike Bayne 11 Monoclonal antibodies and treatment of cancer Hossein Borghaei, Liat Binyamin, Igor Astsaturov, Louis M Weiner 12 Angiogenesis as a target for the treatment of cancer Srinivasan Madhusudan, Daniel Patterson, Adrian L Harris 13 Gene therapy Kate Relph, Kevin Harrington, Hardev Pandha

3 23 40 58 75 112 146 167 186 203 226 251 269

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1 Introduction KAROL SIKORA

Cancer’s timeline Epidemiology Prevention Screening Diagnosis Surgery

3 4 6 8 10 10

This book is written by many authors around one common theme – the optimal treatment of cancer. The problem at first seems relatively simple. There are about 1013 cells in the human body. From the fertilized egg to death in old age, a human being is the product of 1016 cell divisions. Like all complex systems, growth control can go wrong, resulting in the loss of normal territorial restraint, producing a family of cells that can multiply indefinitely. But it is not just the local growth of tumour cells that makes them so lethal. It is their spread, directly through invasion and by metastases to other sites of the body. Tumours that remain localized can usually be cured by surgery or radiotherapy, even when enormous. Patients with large, eroding basal cell skin cancers, for example, can be treated successfully, as these tumours seldom invade deep into the skin or spread to lymph nodes. Yet a breast lump less than 1 cm in diameter, which causes the patient no problems and is picked up in a screening clinic, can be lethal if metastases have already arisen from the primary site. It is this spread that provides the plethora of clinical problems. Just as no two individuals are alike, no two tumours behave in exactly the same way, although we can make some broad generalizations from clinical experience. The physical and psychological interactions of a patient with a growing cancer require careful analysis and action by those involved in the patient’s care. Cancer is not universally fatal. Tremendous advances have been made in the treatment of leukaemia, lymphoma, testicular cancer, choriocarcinoma and several other rare tumours, for which cure of even widespread disease is now common. Even with lung cancer, the most common

Radiotherapy Chemotherapy The future – getting innovation into practice Conclusion References

11 11 13 20 21

single tumour type throughout the world, about 8 per cent of patients survive for many years and die of other causes. However, although there are some pointers, we do not understand why this 8 per cent should be spared. If they can be cured, why not the rest? Vast sums of money are currently spent worldwide on research and yet for most common tumours there has been little change in overall cure rates over the last 30 years. As an intellectual problem to the scientist, malignant disease has always appeared eminently soluble. After all, it would seem a relatively straightforward task to identify the differences between normal and malignant cells and devise a selective destruction process. Yet we still do not know precisely the first biochemical step that takes a cell down the road to neoplasia. The recent advances in molecular biology seem poised to rectify this and to give us new avenues for clinical exploitation, but we have to treat our patients now – providing for them the best of today’s technology with the skill of the caring physician.

CANCER’S TIMELINE The first recorded reference to cancer was in the Edwin Smith Papyrus of 3000 BC, in which eight women with breast cancer are described. The writings of Hippocrates in 400 BC contain several descriptions of cancer in different sites. But our understanding of the disease really began in the nineteenth century with the advent of cellular pathology. Successful treatment by radical surgery became possible in the later part of that century thanks to advances in

4 Introduction

anaesthetics and antiseptics. Radical surgery involved the removal of the tumour-containing organ and the draining of its lymph nodes in one block. Halstead in Johns Hopkins was the main protagonist of the radical mastectomy, Wertheim of the hysterectomy, Trotter of the pharyngectomy and Miles of abdomino-perineal resection of the rectum. These diverse surgical procedures all followed the same principles. The twentieth century ended with the conservation of organs by minimizing the destruction caused by surgery and replacing it with radiotherapy and, for some sites, effective adjuvant therapy with drugs (Box 1.1).

Box 1.1 Cancer’s timeline 3000 BC 400 BC 1880 1896 1898 1899 1946 1953 1958 1999 2000 2006

First recorded description Hippocrates describes six cancer types Successful radical mastectomy Oophorectomy for breast cancer Discovery of radium Discovery of X rays First publication on successful chemotherapy for cancer Double-helical structure of DNA elucidated Successful use of combination chemotherapy First molecularly targeted therapy approved for use Human genome mapped More than ten targeted therapies available

Radiotherapy has come a long way since the first patient with a nasal tumour was treated in 1899, only a year after the discovery of radium by Marie Curie. Although radiobiology developed as a research discipline, it has really contributed little to clinical practice. The rationale behind modern fractionated radiotherapy comes as much from empirical trial and error as from experimental results. Radiotherapy is remarkably successful for certain areas of the body. Increasing sophistication in equipment coupled with dramatic strides in imaging have led to great precision in the planning and execution of treatment, thus sparing critical normal tissues and increasing the dose to the tumour. The sinking of the US battleship John B Harvey in Bari Harbour in Italy by the Germans in 1942 led to the development of effective chemotherapy. The warship was carrying canisters of mustard gas for use in chemical warfare. Survivors developed leucopenia and this led Goodman and others back in the USA to experiment with halogenated alkylamines in patients with high white cell counts – lymphomas, leukaemias and Hodgkin’s disease. From the first publication in 1946, the field has blossomed, with more than 200 drugs now available in our global pharmacopoeia. But as with radiotherapy, our clinical practice is based mainly

Table 1.1 Chemotherapy for advanced cancer High CR/high cure 5% HD ALL Testis Choriocarcinoma Childhood BL

High CR/low cure

Low CR/low cure

40% AML Breast Ovary SCLC Sarcoma Myeloma

55% NSCLC Colon Stomach Prostate Pancreas Glioma

CR, complete response; HD, Hodgkin’s disease; ALL, acute lymphoid leukaemia; BL, Burkitt’s lymphoma; AML, acute myeloid leukaemia; SCLC, small-cell lung cancer; NSCLC, non-small-cell lung cancer.

on empiricism. Most currently used drugs were found serendipitously from plants or fungi – paclitaxel, vincristine, doxorubicin – and not by rational drug design. Although very successfully used in combination for lymphoma, leukaemia, choriocarcinoma, testicular cancer and several childhood cancers, results in metastatic common solid tumours have been disappointing, with little more than palliative benefit (Table 1.1). The advent of molecularly targeted drugs promises to change this dramatically.

EPIDEMIOLOGY The global incidence of cancer is soaring due to the rapid increase in the number of elderly people in most countries. By the year 2020, there will be 20 million new cancer patients each year, and 70 per cent of them will live in countries that collectively will have less than 5 per cent of the world’s resources for cancer control (Box 1.2). We have seen an explosion in our understanding of the disease at a molecular level and are now poised to see some very significant advances in prevention, screening and treatment.

Box 1.2 The global cancer burden Current population 6 billion 10 million new cancer patients – 6 million deaths 50% in developing countries with 5% resources 2020 population 8 billion 20 million new cancer patients – 12 million deaths 70% in developing countries

Dramatic technological change is likely in surgery, radiotherapy and chemotherapy, leading to increased cure rates, but at a price.1 The completion of the Human Genome Project will almost certainly bring sophisticated genetic risk assessment methods requiring careful integration into existing screening programmes.2 Preventive strategies

p.c. GNP US$ (1995)

Epidemiology 5

45000 40000 35000 30000 25000 20000 15000 10000 5000 0 0

20

40

60

80

Life expectancy (1997)

could considerably reduce the global disease burden at low cost, and palliative care to relieve pain and suffering should be a basic right of all cancer patients. The next 25 years will be a time of unprecedented change in the way in which we will control cancer. However, the optimal organization of prevention and detection programmes as well as of treatment services is a universal problem in all economic environments. The world is in a health transition. Infection as a major cause of suffering and death is giving way to new epidemics of non-communicable disorders such as cardiovascular disease, diabetes and cancer.3 Different countries are in different stages of this transition depending on their age structure and economy. Some countries are faced with a double burden, with increasing infection problems compounded by surging cancer rates. This is fuelled in part by the globalization of unhealthy lifestyles.4 Cancer is often thought to be the problem of rich countries. The 1998 World Health Organisation World Health Report5 life expectancy data for 1997 and the World Bank data on per capita gross national product expressed in US dollars (pcGNP$) is available for 155 countries. Cancer in Five Continents6 and the Electronic Database for Cancer provide incidence figures for 1990 and those predicted for 2020.7 The incidences for men and women were analysed separately. The ratio of cancer incidence per 100 000 population in 2020 to 1990 can be compared and correlated to the wealth of the population. Many relatively poor countries with already inadequate treatment facilities will see an explosion in cancer incidence.

Longevity and wealth Figure 1.1 examines the relationship between life expectancy at birth for both men and women and wealth of the 155 countries. There is a clear relationship between increasing GNP and longer life. There are relatively large gains for small increases in pcGNP$ in the poorer countries, reflecting reduced infant and childhood mortality. Above a pcGNP$ of 1000, the proportional gain in longevity is markedly reduced. This almost certainly reflects the importance of basic measures such as vaccination, good water supply,

100

Figure 1.1 Longevity and wealth.

Table 1.2 Longevity and wealth Longevity lower than expected pcGNP$  2000 Longevity  60 years Namibia, Botswana, Gabon

Longevity higher than expected pcGNP$  1000 Longevity  65 years Egypt, Trinidad, Honduras, Nicaragua, Vietnam, Mongolia, Indonesia, China, Surinam, Kyrgistan, Sri Lanka, Tajikstan, Turkmenistan, Uzbekistan, Armenia, Georgia, Azerbaijan, Albania, Macedonia, Solomon Islands

pcGNP, per capita gross national product.

improved health education and access to simple medical care. After this, longevity continues to increase with wealth, but the increase is slow, reflecting the biological determinants that cause disease and death in all human populations. There are two interesting clusters (Table 1.2). The first is those countries where longevity is significantly less than expected for their relative wealth, with a pcGNP$ of above 2000 but a longevity of less than 60 years. These are three African countries – Namibia, Botswana and Gabon. The high level of disease related to human immunodeficiency virus (HIV) is the responsible factor. The second cluster is those states with a higher than expected longevity of greater than 65 years but a pcGNP$ of below 1000. Common factors are efficient public health systems, low infant and childhood mortality and an integrated primary care system: A further confounding factor is the relatively recent reductions in pcGNP$ in these countries caused by external factors and political change. Clearly there is a long incubation period between the factors responsible for longevity and the outcome. Major changes over the last decade will have considerable impact over the next 25 years.

Wealth and cancer incidence Figure 1.2 shows the relationship between wealth and cancer. There is a clear correlation between increasing wealth

6 Introduction

45000 p.c. GNP US$ (1995)

40000 35000 30000 25000 20000 15000 10000 5000 0 0

100

200 300 Cancer incidence per 100,000

400

500

Figure 1.2 Cancer incidence and wealth.

Table 1.3 Cancer incidence and wealth Incidence lower than expected pcGNP$  5000 Incidence  150 per 100 000 Kuwait, Quatar, Saudi Arabia, Bahrain, UAE

Incidence higher than expected pcGNP$  5000 Incidence  250 per 100 000 Bulgaria, Czech Republic, Hungary, Poland, Romania, Russian Federation, Kazakstan, Belarus, Slovakia, Ukraine, Estonia, Croatia, South Africa, Albania

pcGNP, per capita gross national product.

45000 p.c. GNP US$ (1997)

40000 35000 30000 25000 20000 15000 10000 5000 0 0

1

2

3

4

5

Ratio of cancer incidence 2020 : 1990

and cancer incidence. This is almost certainly due to the influence of tobacco and dietary factors as well as other more complex lifestyle factors together with increased longevity of the population. Exceptions include a cluster with a pcGNP$ of greater than 5000 and a cancer incidence of less than 150 per 100 000. These are all Arabian Gulf states (Table 1.3). This almost certainly reflects the benefit of the traditional lifestyle maintained by the majority of the population. The second cluster is the former socialist countries of Europe, certain former Soviet republics and South Africa, where the cancer incidence exceeds 250 per 100 000 but the pcGNP$ is less than 5000. This reflects increased longevity due to good public health and efficient healthcare systems, a Western lifestyle and again a reduction in real pcGNP$ due to political factors. Figure 1.3 shows the ratios of cancer incidence in 2020:1990 correlated to relative wealth. The largest changes

6

Figure 1.3 Change in cancer incidence by 2020.

in incidence are clearly predicted for poorer countries, with a good correlation between poverty and greatly increased incidence. Countries with the greatest increase will have the least facilities to deal with the healthcare problems posed by the disease. In many parts of the world patients usually present with late-stage disease that is not amenable to simple surgery.

PREVENTION Tobacco Optimal use of current knowledge could reduce the overall cancer incidence by at least 3 million. Tobacco control is the most urgent need.8 We need to look for longterm solutions here. The politics of tobacco is a complex

Prevention 7

conspiratorial web of industrialists, farmers, manufacturers, politicians and the pensions business, all looking after their own interests.9 Reduce cigarette consumption in many countries and the economy simply collapses. Governments are naturally cautious. In democracies they are subject to intense lobbying. In less democratic societies corruption, using the massive profits generated by the industry, usually achieves the desired endpoint. Advertising blatantly exploits the young of the developing world, associating images of sex, success and wealth with cigarettes as a lifestyle marker. The solutions are complex and require considerable political will. But with forceful and concerted international action against cigarette promotion, we could reduce cancer incidence by 20 per cent by the year 2020.

Diet Dietary modification could result in a further 30 per cent reduction across the board. The problem is refining the educational message and getting it right in different communities. Changing our current high-fat, low-fibre diet with a low fruit and vegetable intake is a common theme for cancer prevention. But many features of the modern Western diet are now being adapted globally as branded fast-food makers seek out new markets. Again, political will is necessary to reduce the costs to the public of healthy foods. We need to obtain more data so that we can make firmer recommendations. The European Prospective Investigation into Cancer and Nutrition (EPIC) study currently in progress is a good example of how painstaking data and serum collection from 400 000 Europeans could, over the years, provide a vast resource for investigating prospectively the complex inter-relationships between diet and cancer.10 Cancer incidence varies enormously across Europe, providing an excellent natural laboratory for such studies. Interventional epidemiology using rigorously controlled studies could produce the evidence that could lead to major changes. The current problem is the difficulty in making dietary advice specific and in some countries affordable. Although several groups have produced guidelines, there are so far few data about their uptake or significance in large populations. Box 1.3 provides a summary of the main consensus from several sources.

Box 1.3 Common dietary guidelines for cancer prevention ● ● ● ● ● ●

Avoid animal fat Increase fibre intake Reduce red meat consumption Increase fruit and vegetable intake Avoid obesity and stay fit Avoid excess alcohol

Table 1.4 Infection and cancer Hepatitis B virus Human papilloma virus Helicobacter pylori Epstein-Barr virus Human immunodeficiency virus Schistosomiasis Liver fluke

Hepatoma Cervix, anus Stomach Lymphoma, nasopharynx Kaposi’s sarcoma, lymphoma Bladder Cholangiocarcinoma

Infection Infection causes around 15 per cent of cancer worldwide and is potentially preventable (Table 1.4). This proportion is greater in the developing world, where an estimated 22 per cent of cancer has an infectious cause.11 Hepatitis B immunization in children has significantly reduced the incidence of infection in China, Korea and West Africa. Shortly we will see if it has reduced the incidence of hepatoma, which begins in endemic regions by the third decade of life. The unconfirmed trends are already encouraging.12 Cancer of the cervix, the commonest women’s cancer in parts of India and South America, is clearly associated with certain subtypes of human papilloma virus. Vaccines are now becoming available and entering trial.13 Helicobacter pylori is associated with stomach cancer. Here, without any intervention, there has been a remarkable downward trend in incidence worldwide. Dissecting out the complex factors involved, including food storage, contamination, preparation and content, is a considerable challenge. Other cancer-causing infections are schistosomiasis, the liver fluke, the human T-cell leukaemia virus and the ubiquitous hepatitis B virus. Although geographically localized, their prevention by lifestyle changes and vaccination programmes is a realistic short-term goal. Clearly, the effectiveness of any infection control or immunization programme at reducing the cancer burden will depend on many factors and require careful research and field evaluation.

Targeting The key to success in cancer prevention is careful targeting. Figure 1.4 shows estimates of the three main reversible cancer-causing factors, which between them are responsible for 7.5 million out the 10 million new patients annually. Targeted prevention programmes are very cost effective and can be shared by different countries with similar cancer patterns, and therefore countries with limited resources need not keep reinventing the wheel. Prevention packages can be tailored and adapted widely. To do this we need good data of incidence in relation to geography. Descriptive epidemiology provides a fertile hunting ground for patterns of carcinogenesis. Relating genetic changes in cancer to their cause and geography – the emerging discipline of

8 Introduction

lung orophx larynx bladder kidney pancreas TOBACCO

Table 1.5 Advantages and disadvantages of screening Advantages Better outcome Less radical therapy

stomach colon oesop breast liver orophx prostate DIET stomach cervix liver npx NHL bladder INFECTION

Figure 1.4 Global causes of cancer: (a) tobacco; (b) diet; (c) infection. Orophx, oropharynx; Oesop, oesophagus; Npx, nasopharynx; NHL, non-Hodgkin’s lymphoma.

molecular epidemiology – will complete the circle and point the way to specific interventions. The future of prevention will almost certainly be about using such techniques carefully to target preventive strategies to those who would benefit most. In the post-genomic era it is likely that cancer prevention programmes, at least in developed countries, will be completely individualized: a combination of environmental and lifestyle data will be used to construct very specific personalized messages.

Reassurance for those with negative results Psychological benefit to population Attractive to politicians Savings because therapy is less complex

Disadvantages Longer morbidity if prognosis unaltered Over-treatment of borderline abnormalities False reassurance for false negatives Unnecessary investigation Risks of screening test Resource costs of screening system

application of a test to individuals who have not sought medical attention. It may be opportunistic (offered to patients consulting their doctors for other reasons) or population based (covering a predefined age range, with elaborate call and recall systems). The risk of dying from a cancer increases with its degree of spread or stage; thus, the aim of screening is to detect cancer in its early, asymptomatic phase. The problem is that many screening tests are relatively crude, and cancers may have metastasized before they are detected. Sensitivity varies between tests. A 100 per cent sensitive test detects all cancers in the screened population. The most rigorous means of calculating sensitivity is to determine the proportion of expected cancers not presenting as interval cases between screens. Good cancer registration is essential when making this calculation. Specificity is the proportion of negative results produced by a test in individuals without neoplasia. A 100 per cent specific test gives no falsepositive results. Investigation of patients without cancer is a major factor in the cost of screening.

SCREENING Cancer screening is one of the great controversies of medicine. At the interface between public health and specialist care, economics creates tensions between professional groups, politicians and the public: a screening test may be cheap, but applying it to a population (with rigorous quality control and effective processing of patients with abnormal results) creates a huge workload and therefore cost. Screening can also have psychological effects on individuals with false-positive results who require investigation but are eventually found not to have cancer. Unless screening can be shown to reduce the mortality from a specific cancer, the money used is better spent on improving care, and this has led to a disparity in screening recommendations between countries. The Human Genome Project is likely to provide new approaches to cancer risk assessment and will bring new challenges to this complex area. Cancer screening is defined as the systematic

Advantages and disadvantages of screening The advantages and disadvantages of screening (Table 1.5) must be considered carefully; they vary between cancers and tests. The three main problems in assessing the benefit of any screening test for cancer are lead-time bias, length bias and selection bias, all of which impair the effectiveness of screening as a method of reducing cancer mortality. Lead-time bias advances the diagnosis but does not prolong survival, as occurs when the disease has already metastasized although the primary tumour is still small – patients die at the same time as they would if the disease had not been detected early. Length bias results in the diagnosis of less aggressive tumours. Rapidly growing cancers with a poorer prognosis present in the screening interval, reducing the value of the screening process. Selection bias occurs even in the best

Screening 9

organized healthcare systems. Worried but healthy individuals (who would present with cancer symptoms early) comply with screening, whereas less well-educated and socially disadvantaged individuals do not. In the UK National Health Service (NHS) breast cancer screening programme, compliance rates vary between communities depending on their relative deprivation.

Developing a screening programme Rational decision-making about cancer screening requires a detailed analysis of factors that may vary between populations.14 The cancer should be common and its natural history should be properly understood. This allows a realistic prediction of the probable value of the proposed test. The test should be effective (high sensitivity and specificity) and acceptable to the population. Cervical smears, for example, are difficult to perform in many Islamic countries, where women prefer not to undergo vaginal examination, and the take-up rate for colonoscopy is low in asymptomatic individuals because it is uncomfortable and sometimes unpleasant. The healthcare system must be able to cope with patients who produce positive results and require investigation. This may be a particular problem at the start of a population-based study. Ultimately, screening must improve the survival rate in a randomized controlled setting. The natural history of many cancers (including incidence and mortality) may change over time for reasons that are poorly understood. In Europe, the incidence of stomach cancer has decreased dramatically over the last few decades, whereas breast cancer deaths reached a peak in the UK in 1989 and have decreased slightly each year since then. Lobby groups often exercise political pressure to implement screening programmes (even when their effectiveness is undemonstrated), and manufacturers of equipment or suppliers of reagents may exercise commercial pressure. In fee-for-service-based provider systems, there is a financial inducement for doctors to investigate because doing nothing earns no money. The launch of the NHS breast screening service by the UK government in 1989 was viewed by many as a pre-election vote-winning exercise rather than a rational public health intervention, and there are now similar pressures to introduce prostate cancer screening, though uncertainty remains about the management of men with slightly elevated prostate-specific antigen (PSA). Many groups (e.g. governmental organizations, medical charities, health maintenance organizations, professional bodies) have produced guidelines on cancer screening. These guidelines vary widely between countries, reflecting bias in the interpretation of evidence and cultural values in the practice of medicine. For example, annual PSA testing and digital rectal examination in men over 50 years of age are recommended by the American Cancer Society, but are not advocated in most other countries. The incidence of a particular cancer in a particular country and the economics of screening must be considered carefully – the cost

of the technology required must correspond with the gain. Low-cost, direct inspection techniques for oral and cervical cancer by non-professional health workers seem attractive in achieving tumour downstaging and hence better survival results, but cervicoscopy programmes in India and China have shown surprisingly poor overall effectiveness.15 It remains to be seen whether intra-vital staining with acetic acid can enhance specificity at little extra cost. A major cost in instituting any screening procedure is informing the public and then developing the logistics, often under difficult geographical conditions. Cultural barriers may be insurmountable without better education, particularly of girls, who as mothers will become responsible for family health. Low-technology tests have low specificity; as a result, hard-pressed secondary care facilities are inundated with patients with non-life-threatening abnormalities. Detailed field assessment, preferably in a randomized setting, is essential before firm recommendations can be made, but political factors often interfere with this process.16 The wellmeaning charitable donation of second-hand mammography units to some African countries has led to haphazard introduction of breast screening in populations in which the incidence of breast cancer is low and where there are few resources to deal with abnormal results.

Assessing the benefits of screening programmes The ultimate measure of success in a screening programme is a demonstrable reduction in mortality in the screened population. This needs large numbers of individuals, however, and at least 10 years’ assessment for most of the common cancers. Although randomized studies may show conclusive benefit, it must be remembered that the expertise and professional enthusiasm available to a study population may be considerably greater than those achievable under subsequent field conditions. Quality of mammography interpretation and investigation of breast abnormalities are good examples of this, and may explain the relatively disappointing results of breast screening in practice. Case-control studies using agematched individuals from the same population and nonrandomized comparison between areas providing and not providing screening may provide useful indicators, but are not as conclusive as randomized trials. Surrogate measures of effectiveness can be used to assess a programme with relatively small numbers of patients soon after its implementation, but are insufficient to prove that screening saves lives. When a population is first screened, a higher than expected incidence of cancer should be seen because screening is detecting cancer that would not present with symptoms for several years. Subsequent rounds of screening are less productive. Tumour downstaging is a second measure of impact. An increase in early-stage cancer detection and, consequently, reduction in advanced disease are expected over 3–5 years. The third, short-term evaluation

10 Introduction

is a comparison of the survival of screen-detected patients with that of patients presenting symptomatically. Success in terms of these three indices may not necessarily be translated into a useful screening programme. In the 1970s, a study of routine chest radiography and sputum cytology to detect lung cancer showed a 5-year survival of 40 per cent in screendetected patients compared with an overall figure of 5 per cent, but a reduction in mortality from lung cancer in large populations has not been seen.

DIAGNOSIS Cancer presents with a myriad of symptoms depending on the site, size and growth pattern of the tumour. Although some symptoms alarm patients more than others, there is tremendous variability in the speed at which cancer can be diagnosed. A lump can be biopsied, but many deep-seated tumours present late, long after they have already spread: most patients have actually been harbouring the cancer for several years before it becomes apparent. Trying to speed up the diagnostic process and to get on with definitive treatment makes good sense. But delays plague all healthcare systems. In Britain, the current obsession is for all patients with cancer-related symptoms to be seen within 2 weeks. This was politically inspired to show something could be achieved quickly. The problem is defining what constitutes a cancer-related symptom – there are just so many. Studies show that having two queues for entry into the hospital system – one urgent and one not – leads to either excess system capacity or serious delays in the slow queue. Forming a unified entry system and shortening it makes more sense. A far bigger problem is getting a complex series of investigations performed with a reasonable start time for definitive therapy. Attempts to do this have been hampered by poor information technology systems, which are fragmented, non-communicative and primitive. In an age when a WAP cellphone can be used to book instantly a complex travel itinerary including hotels and opera tickets, it is a huge indictment that general practitioners (GPs) in many parts of the world cannot fix a hospital appointment for a potential cancer patient without posting a letter. The two drivers of the improvement of cancer diagnosis are imaging and biomarkers. The last two decades have seen a massive rise in the use of computed tomography (CT) and magnetic resonance imaging (MRI) scans to outline beautifully and in great detail the anatomy of a cancer and its surrounding normal structures. Positron emission tomography (PET), in which a molecule is labelled with a radioactive marker, allows us to examine the living biochemistry of the body. The future of imaging is coupling high-definition structural information with real-time functional change. In this way the precise effects of drug or other treatment can be monitored in three dimensions. It is also likely that the telecom revolution will produce new devices for examining the interior compartments of the body without causing distress to the patient.

Biomarkers are biochemical changes produced by the presence of a cancer. They may be synthesized directly by the cancer, such as PSA, or represent a complex change in an organ system, such as abnormal liver function tests caused by liver metastases. As we understand more about the molecular abnormalities that lead to cancer through the science of genomics and proteomics, novel biomarkers will be identified. These will give us the ability not only to diagnose cancer at an earlier stage, but also to predict the probable natural history of the cancer – whether it will spread rapidly or invade neighbouring structures. This information will be essential for planning optimal care. The basic tests are likely to be converted to kits sold in pharmacies. It is possible that a cancer screening kit for the four major cancers will be on sale within the next decade. Already there is great variation in the practice of cancer screening in different countries, and it is likely that the availability of commercial kits will increase consumerism. There will be a rise in cancer screening and prevention clinics in the private sector, almost certainly attached to the ‘cancer hotels’ of the future. Looking further forward, it is likely that continuous monitoring for potentially dangerous mutations will be possible. Up-market car engines have systems to measure performance against baseline, sending a signal to the driver if a problem arises. Implanted devices to identify genomic change and signal abnormalities to a home computer may allow the detection of cancer well before any metastasis. It will be essential to carry out careful outcome research on such new diagnostic and screening techniques to validate their benefits.

SURGERY Cancer surgery has been a dramatic success. Effective cancer surgery began in the late nineteenth century when it was realized that tumours could be removed along with their regional lymph nodes. This enhanced the chances of complete cure, as it had the greatest possibility of avoiding any spread of the cancer. Surgery still remains the single most effective modality for cancer treatment. Increasingly, it has become far more conservative, able to retain organs and structures and in turn to maintain good function in many parts of the body. Breast cancer is an excellent example. The radical mastectomy performed until 30 years ago left women with severe deformity of the chest wall. This was replaced first by the less mutilating simple mastectomy and now by simple excision followed by radiotherapy, the breast remaining fully intact. New technology permits minimally invasive (keyhole) surgery for many cancer types. The science of robotics will allow completely automated surgical approaches with enhanced effects and minimal damage to surrounding structures. Ultimately, it is likely that surgery will disappear as an important treatment and become confined simply to biopsy performed under local anaesthetic with image guidance to check that the correct sites are biopsied (Box 1.4).

Chemotherapy 11

Box 1.4 Future of surgery ● ● ● ● ● ● ●

Organ conservation Minimally invasive surgery Robotic surgery Distance surgery Tailored adjuvant approaches Biopsy only for many cancers All fast tracked – next-day service

RADIOTHERAPY Radiotherapy was first used for cancer treatment over 100 years ago. Originally crude radium was used as the radiation source, but we now have a variety of sophisticated techniques available. Modern linear accelerators – the workhorses for radiotherapy – allow precise dose delivery to the shape of the tumour. Conformal therapy aims to deliver a high dose just to the tumour volume in three dimensions, killing the cancer cells and avoiding sensitive normal surrounding tissue. Novel computer-based imaging techniques have revolutionized our ability to understand the precise anatomy of cancer in a patient and therefore to deliver far more effective radiotherapy. The future of radiotherapy is about further computerization with multimedia imaging and optimized conformal planning. We have also learnt to understand the biological differences between different tumours in patients and can begin to plan individualized treatment courses to optimize selective destruction. With remarkable technological changes in imaging and computerization, continued development is essential (Box 1.5). Radiotherapy in many parts of the world is the Cinderella of cancer care.

Box 1.5 Future of radiotherapy ● ● ● ● ●

Multi-media imaging Robotic set-up Optimized conformal planning Biological optimization Designer fractionation

CHEMOTHERAPY After the sinking of the battleship John B Harvey during the Second World War, naval physicians treated survivors suffering from lymphoma and leukaemia with nitrogen mustard. In 1946, 67 patients were reported to have a good, but brief, response to injections of this drug16 – and a new era of cancer care had begun. The current position of chemotherapy for advanced cancer is shown in Table 1.1. Essentially, there are three groups

of cancers, in the first of which we can achieve a high complete response rate and a high cure rate. This first group includes diseases such as Hodgkin’s disease, childhood leukaemia and testicular cancer. Unfortunately, this group of cancers that can be successfully treated represents less than 5 per cent of the global cancer burden. At the other end of the spectrum, we have a group with a low complete response and low cure rate, such as lung cancer, colon cancer and stomach cancer. So far, chemotherapy has made few inroads into their treatment, although some useful palliation and prolongation of survival, sometimes for months, can be achieved. In the middle we have a group of diseases with a high complete response but a low cure rate. These cause problems to those involved in rationing cancer care. The use of taxanes in breast and ovarian cancers is a classic example. High-cost drugs can achieve extension of life by several months for many patients and when deciding on priorities, we have to assess how much we are willing to pay for a month of reasonable quality of life. We are at the beginning of a revolution in cancer care. The pharmaceutical industry has taken on the new challenge, and is now going through a massive transition from an era of classical chemotherapy drugs (not too dissimilar to nitrogen mustard) that were discovered by screening programmes for their potential to destroy cells, to a molecular targeted approach. Currently there are 370 molecules in clinical development by 43 pharmaceutical companies. It is likely that fewer than 30 will actually make it to the marketplace, and fewer than 5 will make a significant impact on cancer care. Increasing consolidation in the industry has resulted in a shrinking of the total number of key players in cancer drug development. However, there has been a dramatic increase in research into molecular therapies. The Human Genome Project has created a dictionary of the genome, but we can now interrogate it through sophisticated bio-informatic systems. Not only do we have the library, we also have the search tools. We can now predict the three-dimensional structural biology of many proteins and create images of drugs in silico using computers to design small molecules that can then be synthesized in the laboratory to check their activity. A platform approach to drug discovery is creating a massive increase in new candidate molecules for cancer therapy. One of the problems currently is the large numbers of cellular targets that have been identified and to which new drugs can be developed. These targets include growth factors, cell-surface receptors, signal transduction cog molecules, transcription factors, apoptosis-stimulating proteins and cell-cycle-control proteins. Which one to target and invest research funds into is a difficult decision. The total cost of bringing an anti-cancer drug to market exceeds £300 million. Well-defined targets are the starting point on the road to our future treatments. It is likely that classical cytotoxic drugs will continue to be used for the next 25 years, although they will have a declining share of the total marketplace. By 2015, successful molecular targeted approaches will overtake cytotoxics and transform cancer

12 Introduction

medicine (Fig. 1.5). These new drugs will be individualized, chosen on the basis of molecular measurements of the patient’s tumour and normal cells, and taken orally for long periods of time. The classical way in which we develop cancer drugs is split into three phases. In phase I, maximally tolerable doses are determined by gradually escalating the dose in patients with cancer. From this we can determine a workable dose that patients can tolerate and yet is likely to have

a therapeutic effect based on animal studies. We then carry out phase II studies, in which a series of patients with cancers that can be easily measured by X-rays or photographs is given the drug to see what effect it has on their cancer. This allows us to determine the response rate. Phase III is the last and longest phase, in which patients are randomized to receive either the new drug or the best available treatment and their long-term survival is determined (Fig. 1.6).

Base case launch years in the US Breast 2000

2005

2010

2015

2020

2000

2005

2010

2015

2020

2000

2005

2010

2015

2020

2000

2005

2010

2015

2020

Lung

Colorectal

Prostate

Key MAbs Vaccines Anti-angiogenesis Kinase inhibitors

Apoptosis inducers Anti-sense Gene therapy

Figure 1.5 Predicted new drug application (NDA) dates for molecular therapies in the USA. The years 2005–2010 will see an explosion of novel therapies coming into clinical use outside a research setting. PD endpoint on downstream biomarker and MTD determined

Molecular target clinical assay

IHC screen as criterion for entry into phase II/III

I 30 pts

Short term surrogate response for randomization entry using second biopsy or serum test

II 60 pts selected by molecular pathology

III 400 pts selected by molecular pathology and short term surrogates

Mechanism of action and downstream biomarkers Diagnostic kits for patient selection and surrogates via specialist CRO

sNDA approval on surrogate IV alone sNDAs based on molecular pathology and short term response surrogates

Clinical research

Laboratory research

Figure 1.6 In future cancer drugs will be administered to patients accompanied with effective biomarkers. These will lead to novel surrogate markers of response. This will change the dynamic of the phase I, phase II and phase III studies currently used in cancer drug development. PD pharmacodynamic; sNDA supplementary new drug application; CRO contract research organisation; MTD maximum tolerable dose

The future – getting innovation into practice 13

This traditional approach may not be appropriate for many of our new agents. Toxicity may be minimal and effectiveness may be greatest well below the maximally tolerated dose. Furthermore, tumours may not actually shrink but just become static, so no responses are seen. As the new agents have been discovered by measuring their effect on specific molecular targets in the laboratory, it should be feasible to develop the same assay for use in patients. This gives us a short-term pharmacodynamic endpoint and tells us that we are achieving our molecular goals in a patient. Genomic technology has come to our aid. Gene chips allow us to examine the expression of thousands of genes simultaneously before and after administration of the drug. If a second biopsy can be obtained for the tumour, we can compare gene expression patterns in both tumour and normal cells in the same patient after exposure to a new drug. This enables us to get the drug to work in the most effective way. A particularly intriguing approach for the future is to use gene constructs, which signal tiny light pulses when their molecular switches are affected by a drug. We would also like to obtain information about how a drug distributes itself within the body, and ideally to get a picture of the changes it causes in a tumour. Functional imaging allows us to do just this. The aim is to understand the living biochemistry of a drug in the body: we label the drug with a radioactive tracer and then image using PET. Such techniques promise to revolutionize our ability to understand drug activity and to select and improve the way in which we choose anti-cancer drugs for further development. The next decade is likely to be a new golden age for cancer drug discovery, with many novel targeted molecules coming into the clinic. These agents will eventually transform cancer care forever.

THE FUTURE – GETTING INNOVATION INTO PRACTICE The age of the world’s population is rising dramatically. This will increase the total burden of cancer, with many patients living with considerable co-morbidity. At the same time, new technology in many areas of medicine is bringing improvements to the quality and length of life. Major innovations in the following six areas are likely to have the greatest impact on cancer. 1. Molecularly targeted drugs with associated sophisticated diagnostic systems to personalize care. 2. Biosensors to detect, monitor and correct abnormal physiology and to provide surrogate measurements of cancer risk. 3. Our ability to modify the human genome through systemically administered, novel, targeted vectors. 4. The continued miniaturization of surgical intervention through robotics, nanotechnology and precise imaging.

5. Computer-driven interactive devices to help with everyday living. 6. The use of virtual reality systems which, together with novel mood-control drugs, will create an illusion of wellness. Over the last 20 years, a huge amount of fine detail of the basic biological processes that become disturbed in cancer has been amassed. We now know the key elements of growth-factor binding, signal transduction, gene transcription control, cell-cycle checkpoints, apoptosis and angiogenesis. These have become fertile areas to hunt for rationally based anti-cancer drugs. This approach has already led to a record number of novel compounds currently being in trials. Indeed, targeted drugs such as rituximab, trastuzumab, imatinib, sunitinib, sorafenib, bevacizumab and cetuximab are now all in routine clinical use. Over the next decade there will clearly be a marked shift in the types of agents used in the systemic treatment of cancer. Because we know the precise targets of these new agents, there will be a revolution in how we prescribe cancer therapy. Instead of defining drugs for use empirically and relatively ineffectively for different types of cancer, we will identify a series of molecular lesions in tumour biopsies. Future patients will receive drugs that target these lesions directly. The Human Genome Project provides a vast repository of comparative information about normal and malignant cells. The new therapies will be more selective, less toxic and given for prolonged periods of time, in some cases for the rest of the patient’s life. This will lead to a radical overhaul of how we provide cancer care.17 Investment in more sophisticated diagnostics is now required (Table 1.6). Holistic systems such as genomics, proteomics, metabolomics and methylomics provide fascinating clues as to where needles can be found in the haystack of disturbed growth. By developing simple, reproducible and cheap assays for specific biomarkers, a battery

Table 1.6 Cancer diagnostics in drug development Diagnostic Predisposition screen Screen for presence of cancer Pharmacodynamic biomarker Surrogate marker of clinical efficacy Predictive reclassification of disease Patient-specific toxicity prediction

Value Identify patients for chemo prevention Increase in patients with earlier disease Establish pharmacological dose of drug Early indication of proof of concept Target therapy to those likely to respond Avoid adverse events, adjust dose

14 Introduction

of companion diagnostics will emerge.18 It is likely that for the next decade these will be firmly rooted in tissue pathology, making today’s histopathologists essential in moving this exciting field forward. Ultimately, the fusion of tissue analysis with imaging technologies may make virtual biopsies of any part of the body – normal and diseased – a possibility.19 Individual cancer risk assessment will lead to tailored prevention messages and a specific screening programme to pick up early cancer and will have far-reaching public health consequences. Cancer preventive drugs will be developed that will reduce the risk of further genetic deterioration. The use of gene arrays to monitor serum for fragments of DNA containing defined mutations could ultimately develop into an implanted gene chip. When a significant mutation is detected, the chip would signal the holder’s home computer and set in train a series of investigations based on the most likely type and site of the primary tumour. There will be an increase in the total prevalence of cancer as a result of improved survival, as well as change in cancer types to those of older age groups such as prostate cancer which has a longer survival. This will create new challenges in terms of assessing risks of recurrence, designing care pathways, use of information technology (IT) and improving access to services. There will be new opportunities for further targeting and development of existing therapies as experience grows with risk factors over the longer term. Careful monitoring of patient experiences could help in improving results. Cancer could soon be a longterm management issue for many patients who would enjoy a high quality of life even with a degree of chronic illness.20 The funding of cancer care will become a significant problem.21 Already we are seeing inequity in access to the taxanes for breast and ovarian cancer and gemcitabine for lung and pancreatic cancer. These drugs are only palliative, adding just a few months to life. The emerging compounds are likely to be far more successful and their long-term administration considerably more expensive. Increased consumerism in medicine will lead to increasingly informed and assertive patients seeking out novel therapies and bypassing traditional referral pathways through global information networks. It is likely that integrated molecular solutions for cancer will develop, leading to far greater inequity than at present. Cost-effectiveness analyses will be used to scrutinize novel diagnostic technology as well as therapies. Within 20 years, cancer will be considered a chronic disease, joining conditions such as diabetes, heart disease and asthma, conditions that impact on the way people live but will not inexorably lead to death. The model of prostate cancer – many men dying with it rather than from it – will be more usual. Progress will be made in preventing cancers. Even greater progress will be made in understanding the myriad causes of cancer. Our concepts will be different to those of today, and the new ways in which cancer will be detected, diagnosed and treated will be crucial to understanding in the future.

When a cancer does develop, refinements of current technologies and techniques – in imaging, radiotherapy and surgery – together with the availability of targeted drugs will make it controllable. Cure will still be sought, but will not be the only satisfactory outcome. Patients will be closely monitored after treatment, but fear that cancer will definitely kill, which is still prevalent in the early years of the twenty-first century, will be replaced by an acceptance that many forms of cancer are a consequence of old age. Looking into the future is fraught with difficulties. Who could have imagined in the 1980s the impact of mobile phones, the Internet and low-cost airlines on global communication. Medicine will be overtaken by similarly unexpected step changes in innovation. For this reason, economic analysis of the impact of developments in cancer care is difficult. The greatest benefit will be achieved simply by assuring that the best care possible is on offer to most patients, irrespective of their socio-economic circumstances and of any scientific developments. But this is unrealistic. Technologies are developing fast, particularly in imaging and the exploitation of the human genome. Wellinformed patients, with adequate funds, will ensure that they have rapid access to the newest and the best – wherever it is in the world. More patients will benefit from better diagnosis and newer treatments, with greater emphasis on quality of life.22 Innovation will bring more inequality to health. The outcome of the same quality of care differs today between socio-economic groups and will to continue to do so. Clinicians in Europe will continue to be dependent on technologies primarily designed for the major health market in the world – the USA, which currently consumes nearly 55 per cent of cancer medication but contains less than 5 per cent of the world’s population. European legislation covering clinical trials could bring research in the UK to a grinding halt, while ethicists – zealously interpreting privacy legislation – could impose restrictions on the use of tissue. Targeted niche drugs will be less appealing to industry, as the costs of bringing each new generation of drugs to market will not be matched by the returns from current blockbusters. The delivery of innovation will be underpinned by patient expectation. The well informed will be equal partners in deciding the health care they will receive, much of which will take place close to their homes using mechanisms devised by innovative service providers.23 This has huge implications for the training of health professionals and the demarcations between specialties. Emerging technologies will drive the change. Intraprofessional boundaries will blur – doctors from traditionally quite distinct specialties may find themselves doing the same job – and clinical responsibilities will be taken up by health professionals who will not be medically qualified.24 All professionals are likely to find challenges to their territory hard to accept. Box 1.6 shows the challenges that need to be addressed in order to deliver most health benefit.

The future – getting innovation into practice 15

Box 1.6 The challenges of cancer care ● ●

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Increasing the focus on prevention. Improving screening and diagnosis and the impact of this on treatment. New targeted treatments – how effective and affordable will they be? How expectations of patients and their carers will translate into care delivery. Reconfiguration of health services to deliver optimal care. The impact of reconfiguration on professional territories Will society accept the financial burden of these opportunities?

Prevention and screening At the beginning of the twenty-first century, 10 million people in the world develop cancer each year.25 The cause of these cancers is known in roughly 75 per cent of cases: 3 million are tobacco related; 3 million are a result of diet; and 1.5 million are caused by infection. In the UK, 120 000 people die from cancer each year, even though many of these cancers are preventable, a third being related to smoking. But cancer prevention absorbs only 2 per cent of the total funding of cancer care and research. Anti-smoking initiatives are considered to be successful, although it has been 50 years since the association between smoking and cancer was first identified. In the 1960s, 80 per cent of the population smoked; by 2005 the average was under 30 per cent. This masks real health inequality: the percentage of smokers in the higher socio-economic classes is in low single figures, whereas the percentage amongst socio-economically deprived classes is still about 50 per cent in parts of the country. Despite the known risks, if friends and family smoked and there was no social pressure to stop, there was no incentive to do so. Banning smoking in public places will lead to a further drop of about 4 per cent. Increases in tax were a powerful disincentive to smoke, but the price of a packet of cigarettes is so high that smokers turn to the black market: as many as one in five cigarettes smoked is smuggled into the country. Lung cancer, for example, is a rare disease in higher socio-economic groups – it is a disease of poverty. Lessons from anti-smoking initiatives will be instructive for prevention in the future. Although the link between poor diet, obesity and lack of exercise, and cancer has not been confirmed, there is sufficient circumstantial evidence to suggest that strong associations will be found. There will be bans on advertising for crisps, sweets and soft drinks on television, the introduction of a health tax on these products and a ban on the sponsorship of any public event by manufacturers of these products. By 2010, obesity among

the middle classes will be socially unacceptable, but it will remain common among the economically disadvantaged. Creating meaningful, imaginative incentives for people to adopt healthy lifestyles will be a major challenge. The future prevention picture will be coloured by postgenomic research. In 2005, it was accepted that about 100 genes are associated with the development of a whole range of cancers. The detection of polymorphisms in lowpenetrance cancer-related genes – or a combination of changed genes – will identify people at increased risk. Within 20 years, most people will be genetically mapped and the information – gained from a simple blood test – will be easily stored on a smart-card. Legislation will be required to prevent this information being used to determine an individual’s future health status for mortgage, insurance and employment purposes. However, the process of mapping will reveal that every person who has been screened will carry a predisposition to certain diseases – and people will learn to live with risk. Today, the average age of diagnosis of cancer is 68. Improvements in screening, detection and diagnosis will reduce this. A predisposition for some cancers that manifests itself in a patient’s seventies or eighties will be found in young adult life and detected and corrected successfully in the patient’s thirties. Increasing age will remain the strongest risk predictor. Little of what has been described is not happening already in some form, but the computing power of the future will bring accurate calculation of risk, and predictions will take place on an unimaginable scale. Screening programmes will be developed on a national basis if they are simple, robust and cheap. Patients will expect the screening to take place at a venue that is convenient for them – for example in shopping malls – and not be painful or overly time consuming. Health professionals will demand that any programme is accurate and does not give misleading results, and governments will demand that its costs will lead tomore effective use of other resources. Novel providers of risk assessment services are likely to emerge (Box 1.7).

Box 1.7 Balancing cancer risk ●

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Great health inequity exists in smoking-related diseases. Novel prevention strategies are likely to lead to similar inequity. Creating meaningful incentives to reduce risk will be essential. Individually tailored messages will have greater power to change lifestyles. Biomarkers of risk will enhance the validation of cancer preventive drugs. Novel providers of risk assessment and correction will emerge.

16 Introduction

Detecting cancer Cancers are fundamentally somatic genetic diseases that result from several causes: physical, viral, radiation and chemical damage. There are other processes implicated, for example chronic inflammatory change, immuno-surveillance and failure of apoptosis. In the future, cancer will no longer be understood as a single entity; it will be considered to be a cellular process that changes over time. Many diseases labelled as cancer today will be renamed, as their development will not reflect the new paradigm. Patients will accept that cancer is not a single disease and will increasingly understand it as a cellular process. Many more old people will have increased risk or a pre-cancer. This has huge implications for cancer services. Today, most diagnoses of cancer depend on human interpretation of changes in cell structures seen down a microscope. Microscopes will be superseded by a new generation of scanners to detect molecular changes. These scanners will build up a picture of change over time, imaging cellular activity rather than just a single snapshot. We will have the ability to probe molecular events that are markers for early malignant change. This dynamic imaging will lead to more sensitive screening and treatments: imaging agents that accumulate in cells exhibiting tell-tale signs of pre-cancer activity will be used to introduce treatment agents directly.26 Imaging and diagnosis will be minimally invasive and enable the selection of the best and most effective targeted treatment (Box 1.8). Even better imaging will be able to pick up pre-disease phases and deal with them at a stage long before they are currently detectable. These techniques will also be crucial in successful follow-up. A patient who has a predisposition to a certain cancer process will be monitored regularly and treatment offered when necessary. However, not all cancers will be diagnosed in these earliest of stages – some patients will inevitably fall through the screening net. Nevertheless, there will be opportunities to offer less invasive treatment than at present. Surgery and radiotherapy will continue, but in greatly modified form as a result of developments in imaging. Most significantly, surgery will become part of integrated care. The removal of tumours or even whole organs will remain necessary on occasion. However, the surgeon will be supported by three-dimensional imaging, by radiolabelling techniques to guide incisions and by robotic instruments. Although many of the new treatments made possible by improved imaging will be biologically driven, there will still be a role for radiotherapy – the most potent DNA-damaging agent – to treat cancer with great geographical accuracy. The targeting of radiotherapy will be greatly enhanced, enabling treatment to be more precise. In addition to the reconfiguration and merging of the skills of clinicians, the delivery of care will also change. Minimally invasive treatments will reduce the need for long stays in hospital. As more patients are diagnosed with cancer, the provision of care close to where patients live will be both desirable and possible and, as this report will show later, expected. The prospect of highly sophisticated

Box 1.8 Innovation in diagnostics ● ●

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Radiology and pathology will merge into cancer imaging. Dynamic imaging will create a changing image of biochemical abnormalities. Cancer changes will be detected prior to disease spread from primary site. Greater precision in surgery and radiotherapy will be used for pre-cancer. Molecular signatures will determine treatment choice. Cost control will be essential for healthcare payers to avoid inefficient diagnostics.

scanning equipment and mobile surgical units being transported to where they are required is not unrealistic. Technicians, surgical assistants and nurses would provide the hands-on care, while technical support would be provided by the new breed of clinician – a disease-specific imaging specialist working from a remote site. Cost control will be an essential component of the diagnostic phase. Healthcare payers will create sophisticated systems to evaluate the economic benefits of innovative imaging and tissue analysis technology.

New treatment approaches Future cancer care will be driven by the least invasive therapy consistent with long-term survival. Eradication, although still desirable, will no longer be the primary aim of treatment. Cancers will be identified earlier and the disease process regulated in a way similar to that for chronic diseases such as diabetes. Surgery and radiotherapy will still have a role, but the extent of their role will depend on the type of cancer a patient has and the stage at which the disease is identified, as well as on how well the drugs being developed today perform in the future. Cancer treatment will be shaped by a new generation of drugs (Box 1.9). What this new generation will look like will critically depend on the relative success of agents currently in development. Over the next 3–5 years, we will understand more fully what benefits compounds such as kinase inhibitors are likely to provide. It is estimated that there are about 500 drugs currently being tested in clinical trials. Of these, around 300 inhibit specific molecular targets.27 But this number is set to rise dramatically: 2000 compounds will be available to enter clinical trials by 2007 and 5000 by 2010. Many of these drug candidates will be directed at the same molecular targets, and industry is racing to screen those most likely to make it through to the development process. Tremendous pressures are coming from the loss of patent protection from the majority of high-cost chemotherapy drugs by 2008. Unless new

The future – getting innovation into practice 17

premium-priced innovative drugs are available, cancer drug provision will come from global generic manufacturers currently gearing up for this change.

Box 1.9 Drivers of molecular therapeutics ● ● ● ● ● ● ●

Human Genome Project and bioinformatics Expression vectors for target production In-silico drug design Robotic high throughput screening Combinatorial chemistry Platform approach to drug discovery Huge increase in number of molecular targets

So what will these drug candidates look like? Small molecules are the main focus of current research, most of which are designed to target specific gene products that control the biological processes associated with cancer such as signal transduction, angiogenesis, cell-cycle control, apoptosis, inflammation, invasion and differentiation. Treatment strategies involving monoclonal antibodies, cancer vaccines and gene therapy are also being explored. Although we do not know exactly what these targeted agents will look like, there is growing confidence that they will work. More uncertain is their potential overall efficacy at prolonging survival. Many could just be expensive palliatives. In future, advances will be driven by a better biological understanding of the disease process. Already we are seeing the emergence of drugs targeted at a molecular level – trastuzomab, directed at the HER2 protein, imatinib, which targets the Bcr-Abl tyrosine kinase, and gefitinib and erlotinib, directed at epidermal growth factor receptor (EGFR) tyrosine kinase. These therapies will be used across a range of cancers. What will be important in future is whether a person’s cancer has particular biological or genetic characteristics. Traditional categories will continue to be broken down and genetic profiling will enable treatment to be targeted at the right patients. Patients will understand that treatment options are depen-dent on their genetic profile, and the risks and benefits of treatment will be much more predictable than today. Therapies will emerge through our knowledge of the human genome and the use of sophisticated bio-informatics. Targeted imaging agents will be used to deliver therapy at screening or diagnosis. Monitoring cancer patients will also change as technology allows the disease process to be tracked much more closely. Treatment strategies will reflect this, and drug resistance will become much more predictable. Biomarkers will allow those treating people with cancer to assess whether a drug is working on its target. If it is not, an alternative treatment strategy will be sought. Tumour regression will become less important as clinicians look for molecular patterns of disease and its response.

There will be more of a focus on therapies designed to prevent cancer. A tangible risk indicator and risk-reducing therapy along the lines of cholesterol and statins would allow people to monitor their risk and seek intervention. Delivering treatment early in the disease process will also be possible because subtle changes in cellular activity will be detectable. This will lead to less aggressive treatment. The role of industry in the development of new therapies will continue to change. Smaller, more specialized companies linked to universities will increasingly deliver drug candidates and innovative diagnostics to the large commercially driven multinational pharmaceutical companies who will market them globally. People will be used to living with risk and will have much more knowledge about their propensity for disease. Programmes will enable them to determine their own predisposition to cancer. This in turn will encourage health-changing behaviour and will lead people to seek out information about the treatment options available to them. Patients will also be more involved in decision-making as medicine becomes more personalized. Indeed, doctors may find themselves directed by well-informed patients. This, and an environment in which patients are able to demonstrate choice, will help drive innovation towards those who will benefit. However, inequity based on education, wealth and access will continue (Box 1.10).

Box 1.10 The uncertainty of novel drugs for cancer ●

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Will the new generation of small molecule kinase inhibitors really make a difference or just be expensive palliation? How will big pharma cope with most high-value cytotoxics becoming generic by 2008? Can expensive late-stage attrition really be avoided in cancer drug development? How will sophisticated molecular diagnostic services be provided? Will effective surrogates for cancer preventive agents emerge? Will patient choice involve cost considerations in guiding therapy?

Barriers to innovation Innovation in cancer treatment is inevitable. However, there are certain prerequisites for the introduction of new therapies. First, innovation has to be translated into usable therapies. These therapies must be deliverable, to the right biological target, and to the right patient in a way that is acceptable to the patient, healthcare professional and society. Innovation must also be marketed successfully

18 Introduction

Table 1.7 Marketed targeted therapies Drug Herceptin Mabthera Glivec Erbitux Avastin Tarceva Iressa

Generic

Manufacturer

Yearly cost

Traztuzumab Rituximab Imatinib Cetuximab Bevacizumab Erlotinib Gefitinib

Roche Roche Novartis BMS Genentech Roche AZ

£60 K £40 K £50 K £60 K £70 K £65 K £40 K

so that professionals, patients and those picking up the cost understand the potential benefits. Those making the investment in research will inevitably create a market for innovation even if the benefits achieved are minimal. The explosion of new therapies in cancer care is going to continue, and pricing of these drugs will remain high. The cost of cancer drugs in 2005 is estimated to be $24 billion globally, of which $15 billion is spent in the USA. If effective drugs emerge from the research and development pipeline, the cancer drug market could reach $300 billion globally by 2025, with this cost spreading more widely around the world (Table 1.7). But parallel to this explosion in therapies and increase in costs, a number of confounding factors will make markets smaller. The technology will be available to reveal which patients will not respond to therapy, so making blockbuster drugs history. Doctors will know the precise stage of the disease process at which treatment is necessary, and as cancer transforms into a chronic disease, people will have more co-morbidities, which will bring associated drug–drug interactions and an increase in care requirements (Box 1.11).

that pharmaceutical companies will stop developing drugs for cancer and focus instead on therapeutic areas where there is less individual variation and therefore more scope for profit. Furthermore, development costs are rising. Ten years ago, the average cost of developing a new cancer drug was around $400 million; now it is $1 billion. At this rate of growth, the cost of developing a new drug could soon reach $2 billion, an amount unsustainable in a shrinking market. With this in mind, the process of developing drugs needs to be speeded up. However, instead of research being made simpler, changes in legislation concerned with privacy and prior consent are making it more difficult. The EU Clinical Trials Directive will make quick hypothesis-testing trials impossible. Other challenges exist as well, such as the need to obtain consent for new uses of existing human tissue, following political anxiety when consent for removing and storing tissues had not been obtained in the early years of the twenty-first century. However, surveys have shown that patients who gave consent for tissue to be used for one purpose were happy for it to be used for another; they do not wish to be reminded of their cancer years later. To overcome these constraints, regulators will have to start accepting surrogate markers rather than clinical outcomes when approving therapies. Outcome studies may well move to post-registration surveillance of a drug’s efficacy, similar to cholesterol-lowering agents today. The rise of personalized medicine will mean that the temptation to over-treat will disappear. Doctors and patients will know whether a particular treatment is justified. The evidence will be there to support their decisions. As a consequence of this, treatment failure – with all its associated costs – will be less common.

The patient’s experience Box 1.11 Barriers to innovation ●

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The drug industry will continue to compete for investment in a competitive, capitalist environment. Blockbuster drugs drive profit – niche products are unattractive in today’s market. Personalized therapies are difficult for today’s industry machine. Surrogate endpoints will be essential to register new drugs. Novel providers will emerge providing both diagnostic and therapy services. Payers will seek robust justification for the use of high-cost agents.

How do we balance this equation? The pharmaceutical companies will not necessarily want to do the studies to fragment their market; research leading to rational rationing will need to be driven by the payers of health care. There is a risk

Two separate developments will determine the patient’s experience of cancer care in future. Increasing expectations of patients as consumers will lead health services to become much more responsive to the individual, in the way that other service industries have already become. Targeted approaches to diagnosis and treatment will also individualize care. People will have higher personal expectations, be less deferential to professionals and more willing to seek alternative care providers if dissatisfied. As a result, patients will be more involved in their care; they will take more responsibility for decisions rather than accepting a paternalistic ‘doctor knows best’ approach. This will be fuelled partly by the Internet and competitive provider systems. By 2025, the overwhelming majority of people in their seventies and eighties will be familiar with using the Internet to access information through the massive computing power that they will carry personally. With patients having access to so much health information, they will need someone to interpret the huge volumes available and to help them assess the risks and benefits as

The future – getting innovation into practice 19

well as to determine what is relevant to them. These patient brokers will be compassionate but independent advocates who will act as patients’ champions, guiding them through the system. They will be helped by intelligent algorithms to ensure patients understand screening and the implications of early diagnosis, and they will spell out what genetic susceptibility means and guide patients through the treatment options. Patients and health professionals will have confidence in computer-aided decision-making because they will have evidence that the programs work. How the service will be designed around patients’ needs and expectations will be determined by the improved treatments available and their individualization (Box 1.12). When cancer centres developed in the mid-twentieth century, the diseases were relatively rare, and survival was low. Although distressing for patients when they were referred to a centre, their existence concentrated expertise. Cancers will be commonly accepted chronic conditions and therefore even when inpatient care is required, patients will be able to choose from many places in the world where they will receive care at a ‘cancer hotel’. But for many patients even that option will not be necessary: most new drugs will be given orally, so patients will be treated in their communities.28 However, this approach to cancer and other concomitant chronic conditions will place a huge burden on social services and families. Systems will be put in place to manage the ongoing control of these diseases and conditions – psychologically as well as physically. Pain relief and the control of other symptoms associated with cancer treatment will be much improved.

Box 1.12 Experiencing cancer in future ●

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Patient brokers will guide people with cancer through the system. Choice will be real and will involve cost decisions. Patients will make a contribution to their care costs. Complementary therapies will be widely available and well regulated. Themed death chosen by patients will be possible.

Today, 70 per cent of the cancer budget in the United States is spent on care associated with the last 6 months of people’s lives. Although many recognize that such treatment has more to do with the management of fear than with the management of cancer, medical professionals have relatively few treatment options available and there has been limited awareness of which patients would benefit. There is also an institutional reluctance to destroy patients’ hopes, which led to confusion between the limits of conventional medicines, and a reluctance to face the inevitable – by patients and their families and doctors. There is a widespread perception that if patients are continuing to be offered anti-cancer treatment, there is a possibility that their health might be restored.

With better treatments, consumers of services will be able to focus on quality of life, and much of the fear now associated with cancer will be mitigated. Demand for treatments with few side effects or lower toxicity will be high, even if there are only quite modest survival gains. The transition between active and palliative care is often sudden, but in future, because patients will be in much greater control of their situation, the change in gear will not be as apparent.29

Professional reconfiguration One of the greatest challenges to providing the best cancer care in future will be having the right people in the right jobs. It will be essential not to continue to train people for jobs that will no longer exist. Policy makers have begun to grasp some of the workforce difficulties that lie ahead, and there are moves to ensure that healthcare professionals have responsibilities commensurate with their level of education and professional skills. Nurses and pharmacists are being encouraged to take over some responsibilities that have been held firmly by doctors, such as prescribing, while their traditional roles have been handed on to technicians and other support staff.30 The appropriate skill mix will become even more critical (Box 1.13). Barriers between healthcare professions will have to be broken down in order for the new approaches to the care of patients with cancer and many other diseases to be delivered. The work of pathologists and radiologists will become one, as their traditional skills are augmented by the new generation of diagnostic and treatment devices. Oncologists will find that many forms of chemotherapy will be delivered with the aid of the new technology, and surgeons will be using robots to enable them to operate. Fewer of the most highly trained specialists will be required, since much of their responsibility will be delegated to specialist technicians and nurses working to protocols. In addition, the most highly trained individuals will be able to work at a number of sites on the same day, since the technology will be mobile and skills will be used remotely. The balance between skills will be driven by a number of factors: the size of the medical workforce and the capacity of the system to provide care, as well as the availability of trained support staff.31

Box 1.13 The right person for the right job – key challenges ● ● ●

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Manpower planning for new technology. Doctors and other healthcare specialists. Prescribing cancer drugs by nurses, pharmacists and others. Training carers for elderly people with co-morbidities. Making patients equal partners in decision-making.

20 Introduction

CONCLUSION Cancer will become incidental to day-to-day living. Cancers will not necessarily be eradicated, but that will not cause patients the anxiety that it does today. People will have far greater control over their medical destinies. Patients in all socio-economic groups will be better informed. In addition, surgery and chemotherapy will not be rationed on grounds of age, since all interventions will be less damaging – psychologically as well as physically. How true this picture will be will depend on whether the technological innovations emerge. Will people, for example, really live in ‘smart houses’ where their televisions play a critical role in monitoring their health and well-being? It is also dependent on healthcare professionals working alongside each other, valuing the input of carers who, even more than today, will provide voluntary support because of the number of people in older age groups compared with those of working age. The reality for cancer care may be rather different: the ideal may exist for a minority of patients, but the majority may not have access to the full range of services. Old people, having been relatively poor all their lives, may suffer from cancer and a huge range of co-morbidities that will limit their quality of life. Looking after them all – rich and poor – will place great strains on younger people: will there be enough of them to provide the care? As with all health issues, the question of access will be determined by cost and political will. In 2005 a cancer patient consumes about £25 000 worth of direct medical care costs, with 70 per cent being spent in the last 6 months of life. Conservatively, with patients living with cancer, rather than dying from it, and with access to new technologies, this could reach £100 000 per patient per year by 2025. Table 1.7 shows the annual cost of currently marketed targeted therapies. In theory, cancer care could absorb an ever-increasing proportion of the healthcare budget. Would this be a reflection of what patients want? Probably ‘yes’. Surveys reveal that

three-quarters of the UK population believe cancer care should be the NHS priority, with no other disease area coming even a close second. But to achieve that expenditure – and assuming that part of the health service will be funded from taxation – the tax rate might have to rise to 60 per cent. Inevitably, there will be conflicting demands on resources: the choice may be drugs or care costs. How are the costs computed? Although the technology will be expensive, it will be used more judiciously since it will be better targeted. Another argument suggests that when patients are empowered they use less and fewer expensive medicines, in effect lowering the overall costs. An extension of that argument is that although costs will increase for treating each individual patient, the overall costs will decrease because more care will be delivered at home. But because people will live longer, the lifetime costs of cancer care will rise along with co-morbidity costs. Politicians will be faced with a real dilemma: if the prevalence of cancer increases, the cost of delivering innovative care could be massive. Will cancer care need to be rationed in a draconian way? One dilemma for the future will be the political power of old people. More will be living longer and their chronic problems will not necessarily incapacitate them physically or mentally. This educated gerontocracy will have high expectations that will have been sharpened through the first two decades of the twenty-first century and they will not tolerate the standards of care now offered to many old people. They will wield considerable influence. Will a tax-based health system be able to fund their expectations? Politicians will have to consider the alignment between patients’ requirements and the wishes of taxpayers and voters. Fewer than 50 per cent of voters now pay tax, and the percentage of tax-paying voters is set to fall as the population ages. Will the younger taxpayers of the future tolerate the expensive wishes of non-taxpayers? The interests of voters may be very different from the interests of taxpayers. It seems

INNOVATION

SOCIETY

prevention screening diagnosis surgery radiotherapy drugs supportive care

willingness to pay expectation economy selfishness spirituality family integrity ethics political ideology

DELIVERY hospital-hotel specialist-primary care-DTC professionals role public v private globalization

THE CANCER FUTURE

FINANCE self pay co–payment optional insurance mandatory insurance state insurance HMO NHS charity

Figure 1.7 The four components of the future of cancer are innovative technologies, societal changes, the delivery infrastructure and the financial mechanisms. DTC direct to consumer; HMO Health maintenance organisation; NHS National Health Service (UK)

References 21

likely, therefore, that the days of an exclusively tax-funded health service are numbered. Co-payments and deductibles will be an inevitable part of the new financial vocabulary. Figure 1.7 shows the four components of cancer’s future: innovation, delivery, finances and society. Whatever system is put in place, there is the prospect of a major socio-economic division in cancer care. A small percentage of the elderly population will have made suitable provision for their retirement, in terms of both health and welfare, but the vast majority will not be properly prepared. Policy-makers need to start planning now, as they are doing for the looming pensions crisis. The most productive way forward is to start involving cancer patient and health advocacy groups in the debate, to ensure that difficult decisions are reached by consensus. Societal change will create new challenges in the provision of care. A decline in hierarchical religious structures, a reduction in family integrity through increasing divorce, greater international mobility and the increased selfishness of a consumer-driven culture will leave many lonely and with no psychological crutch to lean on at the onset of serious illness. There will be a global shortage of carers – the unskilled, low-paid but essential component of any health delivery system. The richer parts of the world are now harnessing this from the poorer, but eventually the supply of this precious human capital will evaporate. New financial structures will emerge with novel consortia from the pharmaceutical, financial and healthcare sectors enabling people to buy into the level of care they wish to pay for. Cancer, cardiovascular disease and dementia will be controlled and will join today’s list of chronic diseases such as diabetes, asthma and hypertension. Hospitals will become attractive health hotels run by competing private sector providers. Global franchises will provide speciality therapies through these structures similar to the internationally branded shops in today’s malls. Governments will have long ceased to deliver care. Britain’s NHS, one of the last centralized systems to disappear, will convert to UK Health – a regulator and safety net insurer – by the end of this decade. The ability of technology to improve cancer care is assured. But this will come at a price: the direct costs of providing it and the costs of looking after the increasingly elderly population it will produce. We will eventually simply run out of things to die from. New ethical and moral dilemmas will arise as we seek the holy grail of compressed morbidity. Living long and dying fast will become the mantra of twenty-first-century medicine. Our cancer future will emerge from the interaction of four factors: the success of new technology, society’s willingness to pay, future healthcare delivery systems and the financial mechanisms that underpin them (Fig. 1.7).

REFERENCES 1 Sikora K (ed.). The future of cancer care. Expert Rev Anticancer Ther 2004; 4. 1–78

2 Holtzman NA, Shapiro D. Genetic testing and public policy. Br Med J 1998; 316:852–6. 3 World Health Organisation. The World Health Report. Geneva: WHO, 2000. 4 Murray CT, Lopez AD. The Global Burden of Disease. Boston: Harvard University Press, 1996. 5 WHO Executive Board, EB 102. WHO: Geneva, 1998. 6 Parkin D, Whelan S, Ferlay J, Raymond L, Young J. Cancer in Five Continents, Vol. VII. Lyon: International Agency for Research on Cancer, Scientific Publications, 1997. 7 Cancer in Five Continents. Electronic Database for Cancer. Lyon: IARC/WHO, 1998. 8 Doll R, Peto R. The Causes of Cancer. Oxford: Oxford University Press, 1985. 9 Taylor P. Smoke Ring – The Politics of Tobacco. London: Bodley Head, 1984. 10 Riboli E, Kaaks R. European perspective investigation into cancer and nutrition. Int J Epidemiol 1997; 26(Suppl. 1):6–14. 11 Pisani P, Parkin DM, Munoz N, Ferlay J. Cancer and infection: estimates of the attributable fraction in 1990. Cancer Epidemiol, Biomarkers and Prevention 1997; 6:387–400. 12 Chang M-H, Chen CJ, Lai MS, et al. Universal hepatitis B vaccination in Taiwan and the incidence of hepatocellular carcinoma in children. Taiwan Childhood Hepatoma Study Group. N Engl J Med 1997; 336:1855–9. 13 Monsonego J, Franca E. Cervical Cancer Control. General Statements and Guidelines. Paris: EUROGIN, 1996. 14 Sikora K. Cancer screening Cancer Screening Med 1999; 27:35–9. 15 Sankaranarayanan R, Wesley R, Somanthan T, et al. Visual inspection of the uterine cervix after the application of acetic acid in the detection of cervical carcinoma and its precursors. Cancer 1998; 83:2150–6. 16 Goodman L, Wintrobe M, Dameshek W, Goodman M, Gilman A, Mclennan M. Nitrogen mustard therapy. JAMA 1946; 132:126–32. 17 2020 Vision. Our Future Healthcare Environments. Norwich: The Stationery Office, 2003. 18 Nicolette CA, Miller GA. The identification of clinically relevant markers and therapeutic targets. Drug Discovery Today 2003; 8:31–8. 19 Adam BL, Qu Y, Davis JW, et al. Serum protein fingerprinting coupled with a pattern-matching algorithm distinguishes prostate cancer from benign prostate hyperplasia and healthy men. Cancer Res 2002; 62:3609–14. 20 Tritter JQ, Calnan N. Cancer as a chronic illness? Reconsidering categorisation and exploring experience. Eur J Cancer 2002; 11:161–5. 21 Bosanquet N, Sikora K. The Economics of Cancer Care. Cambridge: Cambridge University Press, 2006. 22 Symonds RP. Radiotherapy. BMJ 2001; 323:1107–10. 23 Wanless D. Securing Good Health for the Whole Population. London: Department of Health, 2003. 24 Laing A. Meeting patient expectations: healthcare professionals and service re-engineering. Health Services Management Res 2002; 15:165–72. 25 World Cancer Report. Lyons: IARC Press, 2003.

22 Introduction

26 Watters JW, McLeod HL. Cancer pharmacogenomics: current and future applications. Biochim Biophys Acta 2003; 1603:99. 27 Blackledge G. Cancer drugs: the next ten years. Eur J Cancer 2003; 39:273. 28 Brumley RD. Future of end of life care: the managed care organisation perspective. J Palliat Med 2002; 5:263–70.

29 Melzer D. My Very Own Medicine: What Must I Know? Cambridge: Cambridge University Press, 2003. 30 Locock L. Redesigning health care: new wine from old bottles? J Health Serv Res Policy 2003; 8:120–2. 31 Crossing the Quality Chasm: A New Health System for the 21st Century. Washington, National Academy Press, 2001.

2 Molecular biology HANI GABRA, EUAN STRONACH AND ROHINI SHARMA

Introduction Molecular biology: the central dogma A molecular genetic basis to cancer

23 24 25

INTRODUCTION Molecular biology is no longer a revolution in medicine. It is now the very fabric of clinical practice and this is particularly so in the practice of oncology. Understanding of the molecular processes underlying cancer, whether for prevention, diagnosis, treatment or palliation, is essential for the practitioner. The purpose of this chapter is twofold: first, to describe the concepts and language underlying this discipline, and second, to integrate these concepts into a clinical overview of where molecular biology currently impacts cancer treatment. Oncogenesis is a process of molecular dysfunction from the first initiation of inherited or somatic events through clonal selection and expansion by accumulated multi-step progression of genomic, transcriptional, translational and post-translational events to the clinical entity that we recognize as cancer. Reductionism and scientific method are the cornerstones of progress in this disease, and whilst psychosocial issues are important, reduction of the incidence of and mortality from cancer will require a continued scientific approach grounded in a molecular understanding of the disease. Cancer can be regarded as a disease of genes. The initiating genetic reduction can be inherited in a Mendelian fashion or acquired, and these principal events initiate cancer as a process. Subsequently, the process of oncogenesis is driven (promoted) by further somatic (non-inherited) events, which may be modified by heritable components (modifier polymorphisms) that are subject to non-Mendelian complex genetics that interact with the environment. Clonal development of cancer is essentially a Darwinian process of natural selection.

Molecular profiling Future impact of molecular biology in cancer References

29 35 36

The molecular biology of cancer demonstrates that many fundamental cellular processes are disrupted, and so the biology of cancer has been hugely informative for elucidating biology itself and therefore for informing other areas of human health. However, even as we engage in reductionism and analysis, an opposite synthetic process is occurring to inform our understanding of cancer. This process has been driven by evolving technologies that allow us to look at whole biological compartments simultaneously during a change of state or phenotype in the cancer. Thus it is possible to look at the entire genome (genomics), the entire RNA compartment (transcriptomics), the entire protein compartment (proteomics), or the sum of metabolic endpoints in the cancer state (metabonomics or metabolomics). These ‘omics’ technologies represent a huge challenge in cancer research, but the potential for diagnostics, prognostics and therapeutics is profound. However, the problem of the meaningful analysis of huge datasets brings enormous challenges for the field of bio-informatics, and it will take empirical development of these (and novel) analysis methodologies in rigorously defined large prospective patient cohorts to make sense and full use of this approach. Systematic analysis of particular biochemical compartments is also very informative, particularly for molecules involved in cell signalling (kinome) and for cell-surface molecules altered by aberrant sugar residues (glycomics). The rebuilding of these complex networks to demonstrate the impact of cellular changes and perturbations in biology and cancer is known as systems biology, and this is expected to be an area of great growth in the biology, and especially the molecular biology, of cancer.

24 Molecular biology

This chapter summarizes the principal components of the molecular biology of cancer and gives examples of the importance of these components in clinical practice.

MOLECULAR BIOLOGY: THE CENTRAL DOGMA The description of the structure of DNA in 1953 by Watson and Crick began the most profound revolution in our understanding of biology. The recognition that DNA replicates semi-conservatively suddenly opened up our understanding of the genetic basis of inheritance and of life. Another profound insight came from the understanding of transcription – that is, how the process of gene expression commences by the generation of messenger RNA, along with ribosomal RNA and transfer RNA to form basic components of the ribosome where the translation of RNA into protein occurs. This process of DNA replication, RNA transcription and protein translation is referred to as the central dogma and forms the most important basic principle of biology.

DNA and its replication DNA is composed of a long double-stranded chain of a sugar, deoxyribose, linked by phosphate on its 5’ carbon to the next deoxyribose on its 3’ carbon. This phosphatelinking process extends the sugar backbone into long chains. The chain can pair with another DNA chain utilizing one of four nitrogenous bases – adenine (A), thymine (T), guanine (G), cytosine (C) – that connect to deoxyribose via the 1’ carbon. These bases recognize a complementary base on the opposite strand, thus allowing a double helix to form. Non-covalent bonding between adenine with thymine and guanine with cytosine occurs to efficiently create this double-helix structure. The two strands of the double helix run in opposite orientations: 5’ to 3’ in each direction. Since DNA is extremely long, it is compacted into nucleosomes, protein complexes around which DNA is wound. Nucleosomes are composed of histone proteins, with around 146 bases of DNA wound around each histone H1 protein with a linker of variable size of up to 100 nuceotides.

RNA and its transcription RNA is typically a single-stranded molecule with a ribose (rather than deoxyribose) chain. The main forms of RNA are messenger RNA (mRNA), which carries the genetic information for proteins, transfer RNA (tRNA), which mediates the attachment of amino acids during translation, and ribosomal RNA (rRNA), which helps form the ribosome. The synthesis of mRNA is followed by a cap on the 5’ end and a polyA tail at the 3’ end. This approach extends to the removal of introns and splicing together of exons to produce the mature mRNA. Messenger RNA is the RNA

generally considered in the central dogma, and it is this type of RNA that communicates the information content from the gene in the DNA to its translation as a protein. mRNA makes up only a small proportion of the cell’s RNA content; more RNA is actually committed to rRNA and tRNA. Ribosomal RNA is a crucial component, together with ribosomal proteins of the ribosomes where translation of mRNA into protein occurs. A single precursor RNA is processed into three ribosomal RNAs, designated by size as 28S, 18S and 5.8S. Transfer RNAs are small RNAs with a high degree of secondary structure and which have an amino acid attached to them. Transfer RNAs recognize the triplet codons on mRNA via an anticodon complementary triplet and therefore bring the correct amino acid to the ribosomal machinery at the correct position to extend the protein chain correctly. Transcription is initiated by RNA polymerases on the DNA template to form RNA transcripts. The efficiency of RNA transcription is determined by transcriptional promoters, usually located upstream of transcriptional initiation sites (although not invariably so). These promoter regions are GC rich, and in cancer can be subject to aberrant methylation, which results in transcriptional repression. This so-called somatic methylation is an epigenetic modification in cancer that is a powerful and common mechanism of activating tumour suppressor genes or negative regulators of cancer.

Protein and its translation Proteins are the effector molecules of life. They are the functional industrial end product of the information content encoded by nucleic acids. They deliver almost all enzymatic and structural processes, including storage, motion and structural support (along with lipids and sugars). Their functional diversity is generated by alternative sequence combinations of amino acids, of which there are 20. The amino acids are linked together during translation by peptide bonds between the carboxyl group of one amino acid and the amino group of the next amino acid. The primary sequence structure of a protein gives rise to secondary structure of folding of defined regions called domains in sheets or helices. These then take up an overall conformation of the protein, the so-called tertiary structure. Proteins can then associate into complexes, making up quaternary structures. The process of translation involves distinct phases of initiation of the polypeptide chain, then its elongation, and finally termination. Initiation at the AUG (start) codon locates an initial methionine, and subsequent codon recognition incorporates amino acids into the growing chain. The tRNA separates from its amino acid and the next tRNA occupies the site of nascent synthesis. Finally there is a stop codon to terminate the protein chain. The central dogma is therefore a rich and complex system process of high fidelity based on information content recognition and flow. Mistakes in this process represent the primary lesion in cancer, and so in that sense cancer

A molecular genetic basis to cancer 25

can be considered as a disease of dysfunctionality of the central dogma, usually in some way either genetically or epigenetically disrupting DNA itself.

A MOLECULAR GENETIC BASIS TO CANCER The major future advances in the treatment of cancer will almost certainly centre around strategies that take our current understanding of cancer biology and turn it upon the disease in the form of targeted therapeutics either singly or, more likely, sequentially or in combination with other conventional or targeted therapeutic approaches. To understand how such strategies are working now and where this approach may lead us we must view cancer at the molecular level. Although it is now clear that cancer is the result of defects in the genetic machinery within the cells that make up our bodies, this conclusion was slow to emerge. Epidemiological studies identified strong associations between certain cancers and particular exposures or lifestyles. For example, a high incidence of scrotal cancer was observed in men who had worked as chimney sweeps; the use of X-rays was associated with skin cancer and leukaemia; and smoking was linked to lung cancer.1–3 This and other evidence suggested an environmental cause for cancer as opposed to a random tissue breakdown, as had been thought previously. This theory was strengthened by work that showed that chemicals present in the soot to which chimney sweeps were exposed caused tumours in animals. Later it was shown that both X-rays and certain carcinogenic chemicals caused heritable damage, leading to the suggestion that cancer may be caused by alterations to the base structure of DNA. This was further substantiated by the Ames test, which revealed that previously identified carcinogens were also potent inducers of DNA mutation in bacteria.4 The definitive proof that carcinogens caused genetic mutations resulting in cancer would, however, require the mutant genes to be found in tumour samples. Interestingly, this evidence came from research suggesting that cancer was the result of infection with tumour-causing viruses – research that at the time seemed to be in opposition to the carcinogen hypothesis.

Oncogenes Peyton Rous demonstrated in 1909 that viral particles from the tumour of one chicken could induce new tumours in other chickens, and subsequent research identified several other such examples of tumour-causing viruses.5 These viruses were linked by their ability to induce uncontrolled growth in the infected cells of the host. It was later revealed that the tumour virus genomes all contained an additional gene when compared to their non-tumour-causing counterparts and that these genes, when isolated, promoted cell growth.6 This seemed to contradict the carcinogen theory,

which suggested that damage to the endogenous genome was responsible for tumour formation and not the addition of a foreign gene. These two theories were ultimately united by the observation that the growth-promoting viral ‘oncogenes’ from the viruses were mirrored by normal genes already present in our own genomes.7 A new theory was thus proposed, for which there is now good evidence, that the genomic mutations cased by carcinogens may affect the behaviour of these endogenous ‘proto-oncogenes’, causing them to promote uncontrolled cellular proliferation in exactly the same manner as their viral counterparts. Sequencing analysis of one of these genes, the ras oncogene, implicated in bladder cancer, revealed that the normal proto-oncogene and the cancer-causing oncogene differed only by a single nucleotide base, changing one critical amino acid in the translated protein.8 The result of this is a constitutive activation of the gene product and consequent acceleration of the cell cycle. Other oncogenes have been shown to be amplified (e.g. myc, PI3K) or genomically rearranged such that they are under the control of the wrong genetic elements (e.g. Bcr–Abl gene fusion).9,10 A comprehensive review of known oncogenes is beyond the scope of this text; however, the function of a few, in the context of intracellular signalling pathways aberrant in cancer, will be discussed later. The discovery of oncogenes was a revelation in our understanding of cancer at the molecular level. However, it rapidly became clear that oncogenic mutations were not sufficient to explain the complexity of cancer.

Tumour suppressor genes Epidemiological studies revealed that the incidence of most cancers rises exponentially with age, which suggests a multi-step process in which several distinct events must occur for a cancer to result. Consequently, the simple idea that a single oncogenic mutation could explain the development of cancer had to be modified. However, mutations in multiple oncogenes within a single tumour were very rarely encountered, suggesting that further cancer genes remained to be identified. A second set of cancer genes, called tumour suppressor genes, were postulated as a result of experiments in which normal and tumour cells were fused together. Surprisingly, these experiments revealed that the fusion cells did not grow as tumours, as was expected, but rather that some component of the normal cells’ genome, presumably absent from the tumour cells, acted to prevent this inappropriate growth.11 Ongoing research has now identified several tumour suppressor genes that have been found to be mutated or inactivated, by varied and unexpected mechanisms, in well-described hereditary cancers and in sporadic tumours (Table 2.1). The study of these genes has provided a deeper understanding of fundamental cancer biology and, indeed, of the normal processes that regulate growth, differentiation and cellular biology.

26 Molecular biology

KNUDSON’S TWO-HIT HYPOTHESIS

The identification of tumour suppressor genes allowed some peculiarities surrounding sporadic and inherited tumours to be explained and led Alfred Knudson to propose his famous ‘two-hit hypothesis’. It was known that in rare, sporadic cases of retinoblastoma, single, unilateral tumours tended to be seen, whereas the inherited form of the disease is typified by multiple, bilateral tumours. Knudson reasoned that in the familial form of retinoblastoma, one of the two cellular copies of a tumour suppressor gene carried an inherited mutation and as such was mutated in every cell in the body. He suggested that a tumour would arise subsequent to any retinal cell sustaining damage to the second, normal copy of the gene – an event that could occur relatively frequently, thus leading to multiple bilateral tumours. Conversely, in the sporadic form of the disease, both copies of the gene would have to be mutated de novo in a single cell in order for a tumour to form. This would be a far less likely scenario and therefore the observed rare unilateral tumours would be the expected phenotype.12 The tumour suppressor gene responsible for retinoblastoma, RB, has since been identified and its protein product, Rb, has been shown to have a pivotal role in the control of the cell cycle, functioning as an inhibitor of another gene, E2F, which has powerful growth stimulatory effects.13 This two-hit model of cancer predisposition has since been found to hold true for a large number of other tumour suppressors and cancer syndromes (see Table 2.1).

Stability genes The final broad category of cancer genes that have been described to date are the so-called stability genes. Unlike the oncogenes and tumour suppressor genes, which tend to have functions in the control of cell growth and differentiation, the normal function of the stability genes is in the maintenance of genomic integrity. Exposure to a wide variety of cellular and environmental agents such as reactive oxygen species, ultraviolet radiation or cigarette smoke causes considerable damage to our genomic DNA. In addition, the basic process of DNA replication, which must occur at

each cell division, is inherently error prone, and therefore without complex DNA-repair mechanisms we would rapidly accumulate mutations within our cells. Studies of several cancer syndromes such as hereditary non-polyposis colon cancer (HNPCC), ataxia telangiectasia and xeroderma pigmentosum revealed that the predisposing genes were not typical growth-controlling tumour suppressor genes or oncogenes, but stability genes, the absence of which results in an increased rate of genetic mutation.14 HNPCC results from defects in any one of a number of DNA mismatch repair genes; these genes control the process by which mispaired stretches of DNA, resulting from errors in DNA replication, are repaired.15 The consequence of such defective repair mechanisms is, of course, an increased rate of accumulation of mutations, which in time will result in defects affecting growth-controlling oncogenes and tumour suppressor genes – the end result being an increased incidence of tumours.

Cancer cell biology The identification of the many and varied cancer genes outlined very briefly earlier has been critically important to our understanding of cancer. However, in isolation the information that can be obtained from any one gene is limited. Through understanding the pathways these genes are involved in and the subtle interplay that occurs between pathway components, we are truly beginning both to realize fully the complexity of the problem and to identify new and unexpected ways to combat it. THE CELL CYCLE

The cell cycle describes the typical states in which a viable, somatic cell can exist and follows the orderly sequence: gap phase 0/gap phase 1 (G0/G1), synthesis phase (S), gap phase 2 (G2) and mitosis (M). Non-dividing cells tend to exist in a G0 state. However, when stimulated to do so, either in a normally controlled manner or in an aberrant manner, following oncogene activation/tumour suppressor gene inactivation, the cells will undergo DNA replication (S phase) followed by a (usually short) G2 phase prior

Table 2.1 A selection of tumour suppressor genes associated with hereditary cancer syndromes and the molecular pathways they impinge on. A more complete overview can be found elsewhere14 Gene CDKN2A RB1 TP53 WT1 PTEN STK11 TSC1, TSC2

Cancer syndrome

Tumour types

Molecular pathway

Familial malignant melanoma Retinoblastoma Li-Fraumeni syndrome Familial Wilms’ tumour Cowden syndrome Peutz–Jeghers syndrome Tuberous sclerosis

Melanoma, pancreas Eye Adrenal, brain, breast, ovary etc. Wilms’ tumour Hamartoma, glioma, uterus Intestine, ovary, pancreas Hamartoma, kidney

RB RB p53 p53 PI3K/AKT PI3K/AKT PI3K/AKT

A molecular genetic basis to cancer 27

to the mitotic process of cell division (Fig. 2.1). The critical nature of this pathway is highlighted by the discovery that several of the oncogenes and tumour suppressor genes identified, without prior functional knowledge, were revealed to have roles in the control of various ‘checkpoints’ throughout the cell cycle. The retinoblastoma gene product (Rb), as mentioned earlier, is a key regulator of the G1/S phase transition and acts by binding to and repressing the activity of another protein, E2F.12 In the normal situation, upon appropriate mitogenic stimulation, Rb is phosphorylated and consequently releases bound E2F protein.16 The E2F protein acts as a transcription factor and once freed from Rb mediates expression of genes that drive the cell cycle.16 Hence, in a cancer situation in which both copies of the RB gene have been inactivated by mutation, the control over E2F transcriptional activity is absent and therefore the cell cycle is driven through G1/S phase. However, the situation is more complex still, as the phosphorylation, and thus inactivation of Rb, is catalysed by a cyclin/cyclindependent kinase (CDK) dimer, which is in turn activated by mitogenic signalling, resulting, for example, from growth factor stimulation.17 Specifically, cyclin D/CDK4 and cyclin E/CDK2 activation drives the cell cycle from G1 to S phase by inhibiting Rb. These cyclin/CDK molecules have been reported to be hyperactive in certain cancers.18

p16ink4a

p21Cip1

p27Kip1

CyclinD

CyclinE

Cdk4/6

Cdk2 P

Finally, cyclin/CDK activity is under the control of CDK inhibitors such as p16Ink4a, which inhibits cyclinD/CDK4, and p21Cip1/p27Kip1, which inhibits cyclinE/CDK2.17. These genes have tumour suppressor functions and indeed inactivating mutations in p16 are associated with familial malignant melanoma.19 The hierarchy of proteins controlling every aspect of the cell cycle is evidently complicated and these proteins have been found to be the target of mutations in several cancers.

Control of cell fate Circumventing the control mechanisms inherent to the cell cycle is fundamental to the carcinogenic process. However, our cells have another safety feature built in, which must also be bypassed if a cell is to survive and proliferate to form a tumour. Apoptosis is a term that describes a complex and varied set of events by which a cell can be induced to die or ‘commit suicide’.20 Checkpoints exist whereby if damage is detected, the cell cycle can be halted to allow the repair process to proceed, or if the damage is too great, the cell can be eliminated so as to prevent an accumulation of mutated cells. Inherent to this process is the best known tumour suppressor gene of them all, p53, which is often referred to as ‘the guardian of the genome’.21 It is estimated that p53 is mutated in 50 per cent of all solid tumours22 and in fact the pathways it governs are altered in

DNA damage

P

ATM/ATR

Rb

Rb

E2F

CHK1/2 p53

E2F

G1

Puma

p21cip1

S

MDM2

Bax Noxa G1 M

M

G2

S G2

Cell cycle arrest

Figure 2.1 Cell-cycle control: the G1/S checkpoint

Apoptosis

Figure 2.2 Control of cell fate following DNA damage

28 Molecular biology

almost all cancers.23 At the most basic level, the p53 protein functions as a transcription factor controlling the expression of a plethora of genes involved in cell-cycle arrest, cell senescence, apoptosis and DNA repair (Fig. 2.2).24 It is this functionality that makes p53 such a pivotal molecule in determining cell fate following damage and which makes it such a central target for mutation if cancer is to progress. Indeed, it has been found that almost all known DNA tumour viruses encode proteins that inactivate the p53 and Rb pathways.25 When DNA is damaged, sensor assemblies activate the effectors ataxia telangiectasia mutated (ATM) and ATM and Rad3 related (ATR).26 As the name reflects, ATM is the tumour suppressor gene mutated in the familial cancer syndrome ataxia telangiectasia. ATM and ATR lead to activation of checkpoint kinases CHK2 and CHK1, respectively,27 CHK2 having been recently found to harbour inherited mutations in a small percentage of hereditary breast cancer families.28* CHK2 and ATM elicit their cellular responses through p53, which subsequently induces expression of the CDK inhibitor p21Cip1 which, as described previously, inhibits the cyclin E/CDK2 complex preventing G1/S phase transition of the cell cycle. Additionally, pro-apoptotic factors, including PUMA, Bax and NOXA, are induced by p53. Interestingly, p53 also induces expression of its own negative regulator, murine double minute 2 (MDM2), which ubiquitinates p53, targeting it for proteasomal degradation.29,30 Unsurprisingly, hyperactivity of MDM2 is a recognized feature of many cancers, and amplification of the MDM2 locus has been described in certain sarcomas.31,32 Once initiated, apoptosis can occur by two broad mechanisms, the extrinsic pathway (also known as the death receptor pathway) and the intrinsic pathway (also known as the mitochondrial pathway).33 The extrinsic pathway is activated by ligand binding of extracellular death receptors such as TRAIL, Fas or tumour necrosis factor (TNF) receptor. Receptor activation mediates the formation of a death-inducing signalling complex (DISC) comprised of oligomerized receptor, an adaptor protein and the initiator caspase, caspase-8. Autoactivation of the caspase-8 protease leads to cleavage-induced activation of effector caspases, caspase-3, caspase-6 and caspase-7.33 The intrinsic apoptosis pathway can be initiated by a wide variety of stimuli, including the detection of DNA damage, and is defined by characteristic events focused at the mitochondria. The mitochondrial outer membrane becomes permeable, under the control of the Bcl-2 family of proteins, allowing cytoplasmic release of cytochrome c, which in turn binds apoptosis-protease-activating factor 1 (Apaf-1) and procaspase-9 to form the ‘apoptosome’. Activation of caspase-9 within the apoptosome triggers a cascade of caspase activation, leading ultimately to activation of caspase-3.34 The final steps of apoptosis, the formation of apoptotic bodies containing the contents of the dead cells and the clearance of these bodies by phagocytosis, are common to both pathways.

Signal transduction pathways The alteration in the actively maintained balance between progress though the cell cycle and cell elimination by induction of apoptosis is of central importance in the accumulation of a tumour cell mass and can be hugely influenced by the transduction of signals from the cell surface into the cell. Cell signalling is a highly active area of research, and many diverse cell signalling pathways have been discovered, several of which extensively cross-talk with other pathways, resulting in an enormously complex network of molecular interactions. In the interests of brevity and simplicity, this chapter will describe one of the best established pathways: the phosphatidylinositol-3-kinase (PI3K)/AKT pathway (Fig. 2.3), which recent estimates have suggested is mutated, in at least one of its components, in up to 30 per cent of all cancers.35 Interest in PI3K arose in the 1980s, when it was discovered that proteins such as the src kinase enzyme, the protein product of the oncogene isolated from the Rous sarcoma virus, and polyomavirus middle T antigen were physically and functionally associated with PI3K.36 It has since been shown that both the non-receptor tyrosine kinase, src, and transmembrane receptor tyrosine kinases (RTKs), activate PI3K.37 PI3K itself is composed of two subunits, a catalytic subunit (p110) and a regulatory subunit (p85) and upon activation of RTKs by growth-factor binding, the receptors become phosphorylated on their intracellular side, thus promoting the binding of the p85 subunits of PI3K. It is thought that this binding alleviates a repressive effect of p85 on the catalytic subunit and thus increases PI3K activity.38 The primary catalytic function of PI3K is the phosphorylation of the cell membrane phospholipid, phosphoinositol-4,5-diphosphate (PIP2) to produce

PIP2 P P

P P

FKHR

p85

p110

BAD

P

Apoptosis

P

PIP3

PTEN P

GSK3β P

P

PDK1/ PDK2

MDM2 P

Cell cycle

PIP3 Akt P P

mTOR P

Cell growth

Figure 2.3 Intracellular signalling: the PI3K/AKT pathway

Molecular profiling 29

phosphoinositol-3,4,5-triphosphate (PIP3). The fundamental importance of PI3K in cancer was further highlighted by the discovery that the tumour suppressor gene PTEN, which is associated with Cowden syndrome, catalyzes the reverse reaction to PI3K – that is, the conversion PIP3 to PIP2.39 The formation of the so-called second messenger PIP3 within the cell membrane allows it to act as a ligand, recruiting proteins containing a specific sequence of amino acids known as a plecstrin homology (PH) domain.37 One such critical protein is the serine/threonine kinase AKT/ protein kinase B (PKB), which has three family members, AKT1, AKT2 and AKT3. Upon binding to PIP3, the AKT protein is phosphorylated at two residues, one event catalysed by the protein phosphoinositide-dependent protein kinase-1 (PDK1), which also has a PH domain, and the other by PDK2, the precise identity of which is unclear.37 AKT is activated by phosphorylation and in turn phosphorylates a huge number of downstream targets which can either promote or repress their normal functions. The net effect of AKT activation is a pro-survival phenotype resulting either from inhibition of apoptosis, promotion of cell growth and protein translation or from increased rate of proliferation.40 The number and variety of targets that have been found to be under the control of AKT make the subversion of the PI3K/AKT pathway an important event in the carcinogenic process. Various alterations in this pathway have been described, including PI3K p110α subunit amplification;41 PI3K p85α subunit mutations42 elevated AKT1 activity;43 AKT2 amplification and over-expression;44 and PTEN loss/mutation.45 Downstream effects of AKT activity include: MDM2 activation, which, as discussed earlier, leads to the degradation of the p53 tumour suppressor and consequent release from its cell-cycle arrest/pro-apoptotic properties; inhibition of the forkhead transcription factor, FKHR, which, when active, positively regulates the expression of proapoptotic genes;46 and inhibition of glycogen synthase kinase3β (GSK3β), which, when active, phosphorylates cyclin D, targeting it for proteasomal degradation and thus abrogating its effect in driving the G1/S phase cell-cycle checkpoint.47 What has been outlined above is merely a glimpse at the complexity of the intracellular signalling involved in the tumorigenic process. A more in-depth history of cancer molecular biology can be found elsewhere.48 Our knowledge and understanding of this signalling biology and of the many and varied means by which it is subverted in human cancer are rapidly deepening. As will be seen later, this understanding is already being used to develop rationally designed therapeutics aimed at treating patients with a particular subset of tumour mutations.

advances are the family of approaches that have grown up around the genome sequencing projects of the 1990s, and these have given rise to an explosion in so-called ‘omic’ research. Broadly, these refer to the rapid study of large numbers of a particular type of molecule and as such are often referred to as high-throughput technologies. There are currently several tens of omic technologies available for the study of ever-more specialized subsets of molecules; however, the most well recognized and broadly applicable are transcriptomics (concerned with gene expression levels), genomics (concerned with varied DNA level analyses), proteomics (concerned with protein level) and metabonomics (concerned with levels of metabolites). Owing to space limitations, only transcriptomics will be discussed here. Transcriptomics describes the study of the profile of genes expressed within the system under investigation, be it a cell, tissue or organ. To date this has been the most widely publicized of the ‘genome-wide’ approaches to studying the biology of cancer. Typically transcriptomics, also known as gene expression profiling, requires that RNA from the sample under investigation, representing the range and level of genes expressed at the time of collection, is labelled with a detectable reagent. The RNA is then selectively bound to a solid matrix containing precisely defined detectors, or probes, with a large number of gene sequences: this technology is often referred to as a microarray. The binding of target RNA sequences in the sample to the probes on the microarray, which are simply immobilized nucleic acid sequences homologous to their gene target, occurs by the process of hybridization. When a labelled RNA sample is hybridized to a microarray slide, the transcripts in the sample bind to their homologous probes such that when the microarray is scanned using a suitable detector, the presence and level of expression of each gene in the sample can be determined. The applications of this technology are almost unlimited and it has been used extensively to examine global changes in transcription following various treatments of cultured cells; changes in gene expression throughout a time course; the profile of genes expressed in different tissues; the differences between ‘normal’ and ‘cancer’ tissue; the differences between clinicopathological subtypes of a particular cancer, for example histological subtype or tumour grade;49,50 and the correlation between particular gene expression profiles and patient outcome, such as response to chemotherapy, progression-free survival or overall survival.51,52 This last example has led to a very exciting use of this technology: the prediction of outcome for patients with a particular cancer based on the gene expression profiles of their tumours.

MOLECULAR PROFILING

Molecular classification of cancer

There have been many technological advances in molecular biology and these advances frequently allow new avenues of research to be opened. Among the most significant recent

In a paper by Alizadeh and colleagues,53 molecular profiling was used to analyze diffuse large B-cell lymphoma (DLBCL), a histologically indivisible subtype of non-Hodgkin’s

30 Molecular biology

lymphoma that carries a highly unpredictable outcome following treatment. The authors hypothesized that this variability in outcome may reflect an underlying molecular heterogeneity. In their study, they generated transcript profiles for 42 DLBCL patients and used a mathematical technique called hierarchical clustering to look for similarities within the gene expression profiles of the various tumours. This technique works by defining each sample on the basis of its measured levels of gene expression and then comparing each sample to all the others until the two most similar are identified. These two samples are then grouped together as a ‘cluster’ and the process is allowed to continue iteratively until eventually all samples are clustered as one. In the DLBCL study this was done using a subset of all the genes studied and revealed two fundamentally different types of DLBCL. Interestingly, when the authors compared the survival outcome data for the patients belonging to each group, they were found to be very different: 76 per cent versus 16 per cent 5-year survival. It appeared therefore that the careful application of gene expression profiling could provide new clarity in previously heterogeneous disease populations. Many other such examples of cancer classification by expression profiling have also been described. 49,50,54

Prediction of outcome In 2001 a paper appeared in the journal Nature describing a more elaborate, and more far reaching, application of microarray-based expression profiling.55 In their paper the authors reported that by measuring gene expression in primary breast tumours with known clinical outcome it was possible to identify a ‘signature’ within the transcripts that could be used to predict the outcome of an ‘unknown’ patient sample. The rationale of the study was that the current practice of treating women with breast cancer with chemotherapy or hormonal therapy in order to reduce the risk of metastasis is unnecessary in some cases as the women would survive equally well without it. However, predicting who would and who would not benefit is very difficult by conventional means. Expression profiles from 78 primary breast carcinomas were therefore generated using microarray technology and analyzed for their ability to predict a short interval to metastasis, defined in the study as less than 5 years. First, the 25 000 transcript measurements for each tumour were reduced to a more manageable number by elimination of those transcripts that did not vary among the tumour set. The resulting subset of genes was next ordered in terms of the strength of association between gene expression level and outcome. The genes were then tested for their ability to predict the prognosis of an unknown sample. By this process the authors arrived at a final set of 70 genes from the initial 25 000 which, when considered together, made the most accurate possible predictions of the metastatic potential of a primary tumour. The success of this approach led the authors to propose that, because there are genes expressed in the primary tumour

which can predict whether or not the cancer will metastasize, primary tumours appear to be pre-programmed for metastasis at an early time point. Furthermore, the predictive power of this gene classifier suggested that many women could be spared the ill-effects of unnecessary therapy if it is found that their tumours do not contain the metastatic gene expression signature. The validity of this bold suggestion is the subject of the MINDACT (Microarray In Nodenegative Disease may Avoid ChemoTherapy) clinical trial. Several further examples of the use of gene expression profiling to predict clinical outcome have been described.51,52,56,57

MOLECULAR BIOLOGY IN THERAPEUTIC DEVELOPMENT As can be seen from the preceding section, there has been startling progress in the molecular biology of cancer since the last edition of this textbook. These advances in molecular biology have led to a new generation of molecular therapeutics that target specific pathways or molecules involved in proliferative signal transduction, cell-cycle transit, apoptosis/survival, invasion, angiogenesis and metastasis (Table 2.2, 58–61). There is increasing clinical interest in these molecules, with the regulatory approval of a number of targeted therapies including trastuzumab, a humanized monoclonal antibody for the treatment of ErbB2-positive breast cancer; imitanib mesylate, a Bcr-Abl and c-Kit inhibitor effective in chronic myeloid leukaemia and gastrointestinal stromal tumour; cetuximab for the management of colorectal cancers that over-expresses EGFR; and bevacizumab, a monoclonal antibody directed towards VEGF for the management of advanced colorectal cancer.62–66* Unlike traditional agents, the targeted therapies are not necessarily cytotoxic in that they can result in inhibition of tumour growth or prevention of metastases. Because of this, there is a need to incorporate measures of anti-tumour behaviour other than an objective measurable reduction in tumour size into clinical practice. Furthermore, these novel compounds are often characterized by a lack of the typical clinically significant organ toxicities associated with conventional chemotherapy, traditionally the determinant of the starting dose for early clinical trials. Therefore, the use of toxicity as a surrogate endpoint for activity in these agents may be unnecessary or unachievable. There is, therefore, a growing interest in alternatives derived from molecular biology instead of objective tumour response and toxicity as surrogate endpoints both in clinical practice and in early trial design.

Molecular biology and clinical study endpoints Despite the number of molecular targeted therapies used in routine practice, clinically meaningful and stringent endpoints remain unclear. Objective tumour response is felt not to be the best possible endpoint, and different endpoints

Molecular biology in therapeutic development 31

Table 2.2 A selection of targeted agents currently under clinical development Drug ANTI-ANGIOGENIC TARGETS Monoclonal antibody Bevacizumab IMC-1121B 2C3 Receptor tyrosine kinase inhibitors PTK-787 AEE788 ZD6474 AZD2171 SU112248 AG13925 AG013736 CEP-7055 CP-547,632 GW786024 Bay 43-9006 AMG706 SU5416 SU6668 SU11248 SU14813 Soluble receptor chimeric protein VEGF-Trap Inhibitors of endothelial cell proliferation ABT-510 Angiostatin Thalidomide Inhibitors of integrin activity Medi-522 EMD12194 (Cilengitide) Vascular targeting agents Combretastatin A4 AVE8062A ZD6126 AS1404 Matrix metalloproteinase inhibitors Marimastat Prinomastat BMS 275291 Neovastat Other CDP-791 EGFR-TARGETED THERAPIES Receptor tyrosine kinase inhibitors Quinazoline tyrosine kinase inhibitors Gefitinib Erlotinib Lapatinib Canertinib EKB-569 PD153035

Target

Clinical Development

VEGF-A VEGFR-2 VEGF-A

Approved Phase I Pre-clinical

VEGFR-1, VEGFR-2 VEGFR-2, EGFR VEGFR-1, VEGFR-2, VEGFR-3, EGFR VEGFR-1, VEGFR-2 VEGFR-1, VEGFR-2, PDGFR VEGFR-1, VEGFR-2 VEGFR-1, VEGFR-2 VEGFR-1, VEGFR-2, VEGFR-3 VEGFR-1, VEGFR-2, EGFR, PDGFR VEGFR-1, VEGFR-2, VEGFR-3 VEGFR-1, VEGFR-2, PDGFR VEGFR-1, VEGFR-2, VEGFR-3 VEGFR-1, VEGFR-2 VEGFR-2 VEGFR, PDGFR, kit, FLT3 VEGFR, PDGFR, kit, FLT3

Phase III

VEGF-A, PIGF

Phase I

Endothelial CD36 Various Reduction of TNF-alpha production

Phase I/II Phase I Approved

Integrin alphaV Integrin alphaV

Phase I/II Phase I/II

Endothelin tubulin Endothelin tubulin Endothelin tubulin Induction of TNF-alpha;

Phase I/II Phase I Phase I Phase I

MMP-1, MMP-2, MMP-3, MMP-7, MMP-9 MMP-2, MMP-9 MMP-1, MMP-2, MMP-8, MMP-9, MMP-13, MMP-14 MMP-2, MMP-9, MMP-12, VEGF

Phase III Phase III Phase III

Phase II Phase I Phase II/III Phase II Phase I Phase I/II Phase I Phase I Phase III (discontinued) Phase I Phase III Phase I

Phase III

VEGFR-2

erbB1 erbB1 erbB1/2 erbB1/2 erbB1/2 erbB1/2

Approved Approved Phase II/III Phase I/II Phase II Pre-clinical

32 Molecular biology

Table 2.2 (Continued) Drug Pyrrolotriazine tyrosine kinase inhibitors BMS 599626 AEE788 PKI-166 Pyridopyrimidine tyrosine kinase inhibitors ARRY-334543 PD158780 CP-724,714 TAK165 Monoclonal antibodies Cetuximab Panitumumab Trastuzumab Pertuzumab Nimotuzumab Matuzumab MDX-447 TheraCIM Mab 806 IMC-225 ABL, SRC TARGETED THERAPIES Receptor tyrosine kinase inhibitors Imatinib mesylate SKI-606 BMS354825 AZD0530 AP23464 CGP76030 AMN107 Monoclonal antibodies Panitumumab EMC 72000 MDX-447 TheraCIM Mab 806

Target

Clinical Development

erbB1/2

Phase I Pre-clinical/phase I Phase I

erbB1/2 erbB1/2 HER-2 HER-2

Pre-clinical/phase I Pre-clinical

EGFR EGFR HER-2 HER-2 EGFR EGFR EGFR/CD64

Approved Phase III Approved Phase II PhaseI/II Phase II Phase I/II

EGFRvIII EGFR

Pre-clinical Phase III

BCR-ABL Abl, Src Abl, Src Abl, Src Abl, Src Src PDGF, Abl, kit

Approved Phase I Phase II Pre-clinical Pre-clinical Pre-clinical Phase I-II Phase II

FARNESYL TRANSFERASE INHIBITORS BMS-214662 Tipifarnib Lonafarnib FTI-277 L-744832 FTI-276 FTI-2148 L-739,750 BZA-2B

CAAX CAAX CAAX Farnesyl transferase Farnesyl transferase Farnesyl transferase Farnesyl transferase Farnesyl transferase Farnesyl transferase

Phase II Phase III Phase III Pre-clinical Pre-clinical Pre-clinical Pre-clinical Pre-clinical Pre-clinical

PROTEASOME INHIBITORS Bortezomib

Proteasome

Phase III

Molecular biology in therapeutic development 33

Table 2.2 (Continued) Drug

Target

Clinical Development

Phase III

PD184352 PD0325901 ARRY-142886 CGP 69846A

Raf-1 kinase, B-Raf, VEGFR-2, VEGFR-3, c-Kit, PDGFR-β MEK 1/2 MEK 1/2 MEK 1/2 C-Raf

M-TOR INHIBITORS Temsirolimus Everolimus AP23573

mTOR mTOR mTOR

Phase III Phase I/II Phase II

AURORA KINASE INHIBITORS ZM447439 Hesperadine VX680

Aurora-B Aurora-A, Aurora-B Aurora-A, Aurora-B, Aurora-C

INHIBITORS OF ERK PATHWAY Sorafenib

have therefore been proposed, such as time to disease progression and stabilization of disease. An improvement in overall survival is also being increasingly reported as a standard by which these agents can be evaluated in the first-line setting. For example, in the development of trastuzumab, a 25 per cent improvement in overall survival was documented in those patients randomized to receive trastuzumab and chemotherapy versus chemotherapy alone.62* Pre-clinical/phase I data therefore play a pivotal role in determining potential biomarkers. Furthermore, it is possible that the development and validation of a predictive assay of response from pre-clinical/early trial data may enable the selection of those patients who are likely to benefit from targeted therapy.67

Molecular biology and pre-clinical/ phase I endpoints In classic phase I trials with investigational drugs, the agents are administered to patients starting with a very low dose based on mouse toxicology data. Dose escalation is then performed to determine the highest dose that a patient can reasonably tolerate. This is based on the underlying assumption that the higher the dose, the greater the likelihood of drug efficacy.68 In addition to the relationship between dose and anti-tumour response, cytotoxic agents also exhibit a dose–toxicity relationship. Thus, dose-related toxicity is regarded as a surrogate for efficacy and is the pharmacodynamic (PD) endpoint employed in early clinical trial design. It can be questioned whether this is relevant for targeted agents that predominantly act as biochemical modulators. For pre-clinical and clinical development of a targeted therapy it is essential that (i) adequate or optimal exposure to the drug is being obtained in the target tissues of the patient, (ii) the molecular target is being appropriately modulated, and (iii) the desired biological effect is obtained.

Phase II Phase I/II Phase I Phase II

It is important to make these observations as part of the phase I/II trials, particularly in phase I trial design where, as described, the maximally tolerated dose and dose-limiting toxicity may not be sufficient to determine the optimal starting dose for phase II study.69*** The optimal biological dose is defined as the dose that reliably inhibits a drug target or achieves a target plasma concentration.70 The optimal dose is based on either pharmacokinetic (PK) endpoints or direct evidence of biochemical effect on the target molecule. In the case of the PK endpoint, plasma protein binding, which determines the amount of free drug available to bind with the receptor, as well as inter-individual variation in drug absorption and metabolism, need to be accounted for.70 The rationale behind PD studies is that by sequentially analyzing the effects of a given therapy on a patient’s tissue, it may be possible to determine the expression level of the target and monitor the effects of the drug on its molecular target. In addition, if the study agent results in the modulation of expression of genes that are related to the target, PD studies could also be instrumental in the identification of the subpopulation of patients that may derive benefit from treatment. The ideal tissue on which to perform PD studies is the tumour tissue itself. However, given the difficulty of obtaining biopsies, the use of surrogate tissues is being explored. In choosing appropriate surrogate tissues, a series of conditions needs to be met: (i) the tissue must express the target and/or markers downstream of the target, (ii) the target and/or additional pathways have to be affected by the experimental therapy, and (iii) in pre-clinical studies a tight correlation has to exist between the optimal therapeutic effect and the observed changes in the selected biomarker. Furthermore, it is preferable that the surrogate tissue be readily accessible for repeat biopsy. In this setting, peripheral blood cells, buccal mucosa and skin are ideal. In the early studies with EGFR inhibitors, the skin was proposed as a surrogate tissue for EGFR inhibition

34 Molecular biology

in vivo.71–73 Skin was proposed not only because of ease of access, but also because of the established role of EGFR in the regeneration of the dermis.74,75 In normal adult skin, EGFR is strongly expressed in keratinocytes and in the cells of the eccrine and sebaceous glands. In initial studies with the EGFR inhibitor gefitinib, sequential skin biopsies demonstrated changes in phosporylation of EGFR, mitogen-activated protein kinase (MAPK) and STAT-3, as well as the levels of CDK inhibitor, proliferation marker Ki67 and skin maturation markers.72* These changes were noted at 150 mg/day, well below the maximal tolerated dose of 700 mg/day. These results have been mirrored with other anti-EGFR agents, including OSI-774, PKI-166, CI-1003, and the monoclonal antibody EMD72000.76–79* What remains unclear is whether PD changes in the skin correlate with the inhibition of EGFR at tumour sites and whether qualitative changes in these biomarkers at either site predict tumour sensitivity. It is possible that blood flow may be different in the skin and the heterogeneous, and at times poorly vascularized tumour, and this may affect drug delivery to the tumour tissue. Furthermore, it is possible that downstream effects of target inhibition may be different within the tumour tissue. As an example, tumours frequently exhibit mutations that result in the activation of the AKT pathway which could render the cells independent of upstream EGFR inhibition.37 A number of studies have been conducted using tumour tissue during phase I development.80* In a dose-finding study of lapatinib in heavily pre-treated patients with metastatic cancers over-expressing ErbB2 and/or ErbB1, the biological effects of treatment on tumour growth and survival pathways were assessed by serial tumour biopsies.81* The study reported variable levels of inhibition of p-ErbB1, p-ErbB2, pErk1/2, p-AKT, cyclin D1 and transforming growth factor alpha in those patients who responded to treatment. Furthermore, the study reported increased tumour apoptosis (TUNEL) in patients with tumour regression compared with non-responders. Studies such as this serve to generate hypotheses regarding the use of biomarkers that can be used to guide the clinical development of the drug. This process of obtaining serial tumour biopsies requires careful patient selection in terms of biopsy-accessible tumours, and close collaboration with institutional interventional radiologists. Whilst most tumour types may be amenable to computed tomography (CT)-guided biopsy, certain histology types, for example colon cancer with live metastases, are more amenable to this approach. Another approach has been the preoperative administration of the drug and the subsequent analysis of the drug concentration and target activity in the tumour at timed, planned surgical intervention. As many tumours are initially managed with preoperative biopsies, a comparison is then possible with non-drug-treated controls.80* Although measurement of a molecular target effect is optimal, it is associated with a number of difficulties. First, given the complexity of cellular pathways and signalling processes, it may be difficult to define the appropriate measure of achieved target effects for a specific drug.69***

Second, restricting patient enrolment to those with accessible disease for assessment of the drug effect on tumour decreases the eligible numbers and increases the complexity of the conduct of the trial. Even if patients consent to serial biopsies, serial tumour biopsies are invasive and associated with sampling errors resulting from the heterogeneous tissue composition of cancer. It is not always possible to measure the direct target of the drug within tumour tissues or in surrogate tissues; there is a role therefore for the identification of other proteins that may be affected by the drug, and which can then be analyzed as potential biomarkers. To facilitate clinical drug development, pharmacogenomics and proteomic approaches are being applied to identify gene or protein biomarkers that could predict the responsiveness of patients to drug treatment. It has been shown that certain proteins are potentially involved in the resistance mechanism of cetuximab therapy,82 where the different expression levels of proteins may serve as biomarkers predicting resistance; this same approach has been used to identify a set of gene and protein biomarkers predicting response to cetuximab.83 A wide range of invasive techniques is available to determine PK and PD endpoints and, as discussed, these procedures are important in early clinical trials. However, because of logistic and ethical considerations, there is an increasing need for non-invasive techniques.84 The role of functional imaging is therefore increasing in the setting of PK/PD trial design. Imaging biomarkers allow non-invasive serial studies of the entire tumour. This is in contrast with tumour biopsies, where only small parts of the tumour can be evaluated at any one time, and intra-tumoral heterogeneity may therefore confound the analysis of potential biomarkers. Serum biomarker studies, whilst non-invasive, may be altered by metabolism and excretion of tumour-derived biomarkers. By allowing the direct assessment of the tumour tissue, positron emission tomography (PET) scans and other imaging tools are likely to complement these biomarker studies without the interference of metabolic processes in plasma or normal organs.

In-vivo molecular biology: magnetic resonance techniques Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) are increasingly being used in anti-cancer drug trials. MRI is routinely used in the initial evaluation of the anatomical appearance of the malignancy, and changes in this can be used to assess and quantify the PD effect of a drug. Dynamic contrast enhancement-MRI (DCE-MRI) involves serial evaluations of images obtained every few seconds following tracer injection. These serial evaluations can then be used for assessment of the kinetics of the contrast agent in the tumour. The kinetic parameters derived from this approach depend on tissue perfusion and on the permeability and surface area of tumour blood vessels. Therefore

Future impact of molecular biology in cancer 35

DCE-MRI is of particular use in the evaluation of tumour vasculature before and after treatment. New blood vessels within tumours are structurally abnormal – leaky, with fragmented supportive structures (pericytes and basement membranes). A successful anti-angiogenic therapy would therefore result in stabilization of the vasculature, and reduction in permeability and levels of interstitial fluid hypertension and thus the size of the leakage space.85 Through PK modelling of the behaviour of a low-molecular-weight contrast agent, DCE-MRI allows measurement of these parameters: permeability, Ktrans and leakage space (Ve).86*,87 In a study of patients with liver metastases from colorectal cancer, PTK787/ZK 222584 (PTK/ZK), an orally active inhibitor of VEGF-R, the PD effects of PTK/ZK were evaluated by assessing changes in contrast-enhancement parameters of metastatic liver lesions using DCE-MRI in dose-escalating phase I studies.88 A correlation was demonstrated between a reduction in Ki (equivalent to Ktrans) and of both dose and plasma levels of the study compound; DCE-MRI was seen to be a useful biomarker for defining the pharmacological response and this approach has been employed in a number of other phase I clinical trials of anti-angiogenic agents.89,90 Magnetic resonance spectroscopy (MRS) can be used for minimally invasive monitoring of anti-cancer drug uptake and metabolism. It is the only non-invasive method of chemically distinguishing between, and measuring, the concentrations of drugs and their metabolites. Instead of producing an anatomic image, MRS data are usually visualized as spectra, the peaks of which correspond to different chemicals.91 MRI can then be used to define tumour volume and MRS can be used to measure the concentration of drugs within that volume in real time.92 MRS can also be used for PK studies and concentrations of the drug can be monitored in target tumour and organs. This procedure alleviates the need for invasive drug sampling or radiation exposure. The use of MRS for PK studies, however, is limited by the lack of sensitivity and in general only drugs given in quantities of 0.5 mg/m2 can be detected. The use of MRI in PK/PD studies is likely to increase with improvements in imaging and availability of biologically targeted contrast agents.93,94

and those with specific biological endpoints.92 Studies that utilize generic endpoints are predominantly employed to assess the effects of novel therapeutic agents on biological systems such as cellular proliferation, which can be assessed using 11C-thymidine, and blood volume, with 15O-CO.98*,99* Studies that utilize specific biological endpoints are conducted to provide proof of principle for a proposed mechanism of action of existing and novel therapies, for example the detection of VEGF or its receptor expression can be assessed using 124I-labelled antibodies or peptides.100,101* Although PET imaging is a useful adjunct in drug development, it has some important limitations. First, not all compounds can be radiolabelled, and each compound needs to be considered individually. Second, the anatomic resolution of PET images is low and it is common practice to align images from PET with computed tomography (CT) or MRI data. PET is also limited by a lack of chemical resolution – that is, PET tracers cannot distinguish between the parent radiotracer and its labelled or unlabelled metabolites. This is a concern when investigating drugs that are extensively metabolized, and can complicate the interpretation of PET data. For some positron-labelled compounds, the combination of a short physical half-life and a short biological half-life can limit the type of pharmacological information that can be attained. Finally, because of the costs of labelling the compounds, quality control, radiographers’ time and modelling of the data, PET scanning is expensive and most centres can only focus on one or two tracers. Understanding the impact of the therapy on the tumour target and identification of the patient population most likely to benefit are critical steps in the drug development process. Despite this, only a minority of pre-clinical and early clinical trials incorporate non-traditional endpoints such as measures of molecular drug effects in tumour or surrogate tissue or functional imaging studies.69*** This increases the risk that these agents will fail in the clinical setting. It is therefore important to define the optimal clinical dose and regimen, which should be determined by the use of an array of biomarkers, including target exposure biomarkers and patient selection biomarkers, in combination with clinical response and toxicity profiles.

In-vivo molecular biology: positron emission tomography

FUTURE IMPACT OF MOLECULAR BIOLOGY IN CANCER

PET scanning enables dynamic, non-invasive measures of the three-dimensional distribution of positron-labelled compounds within the body. It can be used to evaluate intratumoral and normal tissue PK in patients prior to phase I studies or as part of phase I and II studies. This can be achieved by labelling the drugs of interest with positron-emitting isotopes such as 11C, 18F, 124I or 13N. A number of drugs have been evaluated in this manner, including 18F-5-fluorouracil (5-FU), 11C-temozolamide and 18F-tamoxifen.95–97* Pharmacodynamic studies performed by PET can be divided into two different types: those with generic endpoints

As can be seen, the molecular sciences permeate into every part of clinical cancer science. They inform and are embedded in the design of most rigorous diagnostic, prognostic and therapeutic developments in cancer care. The approaches encompass reductionism, analytical science, synthetic hypothesis formation and complete descriptions of biology of systems. This understanding is essential for future progress in the wet laboratory, for in-silico studies, for the biology of imaging, and for drug development. Molecular biology remains the horizontal language that unifies these apparently disparate areas. As we have shown, understanding of

36 Molecular biology

the fundamental molecular biology of cancer is starting to be mirrored by a steep increase in the number of available drugs that are targeted to these processes. Understanding the role of these targeted agents fully will be necessary to exploit them most appropriately. It is the combination of these drugs with each other and with chemotherapy that is most likely to help us with the redundancy of pathway inhibition. The molecular basis of drug action in the context of understanding of the molecular biology of cancer are therefore inseparable approaches.

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Molecular diagnostics and therapies are now part of mainstream clinical practice in oncology. The study of gene expression by transcriptomics is beginning to influence therapy choice for patients with common solid tumours. Downstream signalling proteins and their phosphorylated counterparts are promising biomarkers with which to assess the mechanism of a drug’s action. The burgeoning global cancer drug pipeline needs better mechanism for prioritising which drugs to take forward to large scale trail. It is simply not financially viable to take all promising candidates forward. Measuring the optimal biological dose rather than just the maximally tolerated dose is essential in phase I trials of molecularly targeted therapies. Determining pharmacodynamic endpoints for new drugs involves the discovery and utilisation of validated biomarkers of a drug’s target effect. The need for serial biopsies to study tissue biopsies is limited by ethical considerations. There is also the potential of selective sampling. Imaging biomarkers are becoming available that allow ethically acceptable, non invasive serial studies of the entire tumour. New imaging technologies are likely to help our understanding of gene and protein expression changes as well as the physiological processes that change after therapeutic intervention. The close interaction of clinical and laboratory investigators is vital to optimise the potential gain to patients from translational medicine.

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42 Philp AJ, Campbell IG, Leet C, et al. The phosphatidylinositol 3-kinase p85alpha gene is an oncogene in human ovarian and colon tumors. Cancer Res 2001; 61(20):7426–9. ●43 Sun M, Wang G, Paciga JE, et al. AKT1/PKBalpha kinase is frequently elevated in human cancers and its constitutive activation is required for oncogenic transformation in NIH3T3 cells. Am J Pathol 2001; 159(2):431–7. 44 Bellacosa A, de Feo D, Godwin AK, et al. Molecular alterations of the AKT2 oncogene in ovarian and breast carcinomas. Int J Cancer 1995; 64(4):280–5. 45 Saito M, Okamoto A, Kohno T, et al. Allelic imbalance and mutations of the PTEN gene in ovarian cancer. Int J Cancer 2000; 85(2):160–5. 46 Brunet A, Bonni A, Zigmond MJ, et al. Akt promotes cell survival by phosphorylating and inhibiting a Forkhead transcription factor. Cell 1999; 96(6):857–68. 47 Diehl JA, Cheng M, Roussel MF, Sherr CJ. Glycogen synthase kinase-3beta regulates cyclin D1 proteolysis and subcellular localization. Genes Dev 1998; 12(22):3499–511. 48 Weinberg RA. One Renegade Cell: The Quest for the Origins of Cancer. New York, Phoenix Press, 1998. 49 Alon U, Barkai N, Notterman DA, et al. Broad patterns of gene expression revealed by clustering analysis of tumor and normal colon tissues probed by oligonucleotide arrays. Proc Natl Acad Sci U S A 1999; 96(12):6745–50. 50 Perou CM, Jeffrey SS, van de Rijn M, et al. Distinctive gene expression patterns in human mammary epithelial cells and breast cancers. Proc Natl Acad Sci U S A 1999; 96(16):9212–17. 51 Beer DG, Kardia SL, Huang CC, et al. Gene-expression profiles predict survival of patients with lung adenocarcinoma. Nature Med 2002; 8(8):816–24. 52 Sorlie T, Perou CM, Tibshirani R, et al. Gene expression patterns of breast carcinomas distinguish tumor subclasses with clinical implications. Proc Natl Acad Sci U S A 2001; 98(19):10869–74. ●53 Alizadeh AA, Eisen MB, Davis RE, et al. Distinct types of diffuse large B-cell lymphoma identified by gene expression profiling. Nature 2000; 403(6769):503–11. 54 Schwartz DR, Kardia SL, Shedden KA, et al. Gene expression in ovarian cancer reflects both morphology and biological behavior, distinguishing clear cell from other poor-prognosis ovarian carcinomas. Cancer Res 2002; 62(16):4722–9. ●55 van’t Veer LJ, Dai H, van de Vijver MJ, et al. Gene expression profiling predicts clinical outcome of breast cancer. Nature 2002; 415(6871):530–6. ●56 Golub TR, Slonim DK, Tamayo P, et al. Molecular classification of cancer: class discovery and class prediction by gene expression monitoring. Science 1999; 286(5439):531–7. 57 Eschrich S, Yang I, Bloom G, et al. Molecular staging for survival prediction of colorectal cancer patients. J Clin Oncol 2005; 23(15):3526–35. 58 Garrett MD, Workman P. Discovering novel chemotherapeutic drugs for the third millennium. Eur J Cancer 1999; 35(14):2010–30.

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59 Gibbs JB. Mechanism-based target identification and drug discovery in cancer research. Science 2000; 287(5460):1969–73. 60 Hanahan D, Weinberg RA. The hallmarks of cancer. Cell 2000; 100(1):57–70. 61 Kaelin WG Jr. Choosing anticancer drug targets in the postgenomic era. J Clin Invest 1999; 104(11):1503–6. ●62 Slamon DJ, Leyland-Jones B, Shak S, et al. Use of chemotherapy plus a monoclonal antibody against HER2 for metastatic breast cancer that overexpresses HER2. N Engl J Med 2001; 344(11):783–92. ●63 Druker BJ, Sawyers CL, Kantarjian H, et al. Activity of a specific inhibitor of the BCR-ABL tyrosine kinase in the blast crisis of chronic myeloid leukemia and acute lymphoblastic leukemia with the Philadelphia chromosome. N Engl J Med 2001; 344(14):1038–42. ●64 Heinrich MC, Corless CL, Demetri GD, et al. Kinase mutations and imatinib response in patients with metastatic gastrointestinal stromal tumor. J Clin Oncol 2003; 21(23):4342–9. ●65 Cunningham D, Humblet Y, Siena S, et al. Cetuximab monotherapy and cetuximab plus irinotecan in irinotecanrefractory metastatic colorectal cancer. N Engl J Med 2004; 351(4):337–45. ●66 Hurwitz H, Fehrenbacher L, Novotny W, et al. Bevacizumab plus irinotecan, fluorouracil, and leucovorin for metastatic colorectal cancer. N Engl J Med 2004; 350(23):2335–42. ◆67 Arteaga CL, Baselga J. Clinical trial design and end points for epidermal growth factor receptor-targeted therapies: implications for drug development and practice. Clin Cancer Res 2003; 9(5):1579–89. 68 Skipper HE, Schabel FM Jr, Mellett LB, et al. Implications of biochemical, cytokinetic, pharmacologic, and toxicologic relationships in the design of optimal therapeutic schedules. Cancer Chemother Rep 1970; 54(6):431–50. ●69 Parulekar WR, Eisenhauer EA. Phase I trial design for solid tumor studies of targeted, non-cytotoxic agents: theory and practice. J Natl Cancer Inst 2004; 96(13):990–7. 70 Adjei AA. What is the right dose? The elusive optimal biologic dose in phase I clinical trials. J Clin Oncol 2006; 24(25):4054–5. 71 Albanell J, Codony-Servat J, Rojo F, et al. Activated extracellular signal-regulated kinases: association with epidermal growth factor receptor/transforming growth factor alpha expression in head and neck squamous carcinoma and inhibition by anti-epidermal growth factor receptor treatments. Cancer Res 2001; 61(17):6500–10. 72 Albanell J, Rojo F, Averbuch S, et al. Pharmacodynamic studies of the epidermal growth factor receptor inhibitor ZD1839 in skin from cancer patients: histopathologic and molecular consequences of receptor inhibition. J Clin Oncol 2002; 20(1):110–24. 73 Workman P. Challenges of PK/PD measurements in modern drug development. Eur J Cancer 2002; 38(16):2189–93. 74 Stoll SW, Benedict M, Mitra R, Hiniker A, Elder JT, Nunez G. EGF receptor signaling inhibits keratinocyte

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3 Clinical radiobiology MICHELE I. SAUNDERS AND STANLEY DISCHE

Introduction Radiosensitivity at the cellular level The radioresponsiveness of tumour and of normal tissues Time and radiation response Time, fractionation and the implications for current programming of radiotherapy Nutrition, environment and radiation response

40 40 41 45 47 47

INTRODUCTION All those caring for patients with cancer strive to attain the greatest degree of tumour control with the lowest level of treatment-related morbidity. Essential to the good and safe practice of radiation therapy is knowledge of the biology of tumours and of the normal tissues together with an understanding of the way in which they are affected by ionizing radiation.

RADIOSENSITIVITY AT THE CELLULAR LEVEL The immediate response In most normal tissues and tumours, little change can be demonstrated in the first few days after beginning a course of conventional radiotherapy. However, changes in the DNA are induced that become manifest in time.1 There are some normal tissues, such as the bone marrow and the salivary glands, that do show evidence of this damage during the first 24 hours after administration of a dose as low as 2 Gy, with steep falls in lymphocyte counts and steep rises in the serum amylase concentration respectively.

The differences between normal and tumour cells In early work, the inherent radiosensitivity of cells derived from animal and human tumours, as measured in the

The combination of chemotherapy with radiotherapy The combination of surgery with radiotherapy The biological basis for special approaches in radiotherapy Biological features of the tumour important to management Significant points References

49 51 51 52 52 53

laboratory by the survival of clonogenic cells after high radiation doses, did not appear to differ greatly from that of cells derived from normal tissues. However, Fertil and Malaise2 demonstrated (in cell lines derived from a range of animal tumours) that the surviving fractions of cells irradiated using a much lower and more clinically relevant dose of 2 Gy (SF2) did differ widely from each other and from normal cells. The results could in broad terms predict the radiocurability as determined when the tumours were grown in mice, with lymphomas the most sensitive and sarcomas most resistant to treatment. The responsiveness of types of human tumours as revealed in experiments using cell lines grown in nude mice was shown broadly to reflect that observed clinically.3

Extreme radiosensitivity Patients with the rare inherited ataxia telangiectasia show an extreme sensitivity to radiation that appears to be at a level several-fold greater than that normally exhibited. Patients with ataxia telangiectasia, Cockayne’s, Gardner’s, Down’s and basal cell naevoid syndromes and those with Fanconi’s anaemia may also show unusually severe reactions.1 Some patients with dermatomyositis and other collagen disorders may also show an increased sensitivity. In cell culture, fibroblasts taken from the skin of patients with ataxia telangiectasia have been shown to possess a high radiosensitivity. Cultures of fibroblasts from other patients exhibiting unexpectedly severe reactions have also been shown to demonstrate high radiosensitivity.4,5*

The radioresponsiveness of tumour and of normal tissues 41

Normal range of radiosensitivity It is important to identify patients with high degrees of radiosensitivity, preferably before embarking upon a course of treatment, but fortunately they represent only a fraction of 1 per cent of all patients requiring treatment. Patients given identical radiotherapy show a range of normal tissue reactions, both early and late. In a series of patients previously given a course of radiotherapy a correlation has been obtained between the radiosensitivity of their fibroblasts cultured in vitro and that of the reactions observed in their normal tissues.6* However, the technique is not a practical one to apply in everyday care, as the result may not be available for several weeks. There is an interest in the radiosensitivity of peripheral blood lymphocytes because these can easily be obtained. Some correlation has been reported,7 but there is no consensus as to the value of studies of lymphocyte sensitivity as a predictor of radiation response.

Planning treatment according to radiosensitivity of the individual tumour Using the techniques described above, attempts have been made to determine the SF2 prior to radiotherapy in individual cases. West and colleagues8* showed that in carcinoma of the cervix there was a close correlation between the SF2 and tumour control and survival. In contrast,9 no such correlation could be demonstrated in squamous cancer in the head and neck region. The demonstration of a relationship between inherent sensitivity and tumour response in one common tumour in humans is important in radiobiology, but as this relationship has not been confirmed in other types of tumour and because the results of an assay cannot be read for 4 weeks, this approach is, as yet, unpromising in terms of advancing the care of individual patients. A more immediate change can be seen in the micronuclei of radiation-damaged cells using in-situ hybridization (FISH).10 So far, however, no convincing evidence for a clinical application has been established.

avoid unacceptable morbidity. The demonstration of such differences on an individual case basis will demand the use of methods of observing normal tissue reaction that are sufficiently sensitive; however, there is currently no evidence that such a sensitive system is available. Of relevance to this approach is the relationship between the inherent sensitivity of the normal tissues and of the tumours in an individual patient. There are case descriptions that report a similar high sensitivity of the tumour in sensitive patients, but it is suspected that this is not a general rule.11

THE RADIORESPONSIVENESS OF TUMOUR AND OF NORMAL TISSUES The early and late reactions The pattern of response seen in a tumour can range from an obvious shrinkage observed within 24 hours to an absence of change for a number of weeks with reduction in size delayed for some months after the completion of treatment. Lymphomas and undifferentiated tumours such as oat-cell carcinomas show the earliest changes, whereas adenocarcinomas and well-differentiated sarcomas may exhibit the longest time course. In contrast, many normal tissues, including the skin and the mucosa of the upper aerodigestive tract, exhibit early reactions during and immediately after a course of treatment. These tend to be transitory and, provided the very highest doses have not been administered, are followed by healing. The same tissues may show late changes after some months or years, which, once established, do not readily resolve and may show steady progression. Other tissues, such as the spinal cord, liver, kidney, fat and subcutaneous tissues, show little early change but may show late changes. Late changes in the early-responding tissues are often secondary to effects on the supporting connective tissue. It has long been traditional to set 90 days as the border between early and late responses, but it is now considered that this is too rigid an approach.12 It is also recognized that severe early reactions may progress to late reactions without healing, which is called consequential damage.

Planning treatment according to the radiosensitivity of an individual patient Whole or part-organ irradiation The determination of the radiosensitivity of normal tissues in the management of an individual case remains a subject of research in clinical oncology.11 Among methods undergoing study is the determination of a relationship between the response of normal tissues, early and late, and molecular change. Genetic patterns may emerge to associate with radiosensitivity. It has been proposed that patients with relatively resistant normal tissues may be safely given higher doses of radiation, while those at the sensitive end of the spectrum may have their treatment modified so as to

The effect of part-organ or whole-organ irradiation differs according to the tissue concerned. Loss of a considerable portion of the liver or part (or even the whole) of one kidney may lead to little functional disability and be an acceptable consequence of radiotherapy if the clinical situation justifies it. With other structures, such as the intestine and the central nervous system, loss of, or severe damage to, a small part may have a vital and life-threatening effect.

42 Clinical radiobiology

Table 3.1 Guide to organ tolerance to fractionated radiotherapy in 2-Gy daily doses14,15 A (Gy)

B (Gy)

Eye Ovary Liver Oesophagus Stomach Intestine Rectum

– – 50 60 60 50 –

18 6 35 55 50 40 60

Optic nerve, chiasma Brachial plexus Brain Spinal cord Heart Lung Kidney

50 62 60 50 55 30 30

50 60 45 47 40 17.5 23

Common severe complication Cataract requiring surgery Sterility Liver failure Stricture/perforation Ulceration Ulceration/stricture Severe proctitis/necrosis Fistula/stenosis Blindness Plexopathy Necrosis Myelitis Pericarditis and pancarditis Pneumonitis/fibrosis Nephrosclerosis

A Tolerance to partial-organ (approx. 1⁄3) irradiation. Dose giving 5% incidence of severe morbidity in 5 years. B Tolerance to whole-organ irradiation. Dose giving 5% incidence of severe morbidity in 5 years.

Setting the level of normal tissue tolerance

The balance of the relationship between the responses of tumours and normal tissues Dose–response curves derived from work with animal models and from observation of patients have a sigmoid or S shape with a threshold level before the curves depart

Tumour Response

A broad guideline of normal tissue tolerance, based on the work of Rubin13 and Emami et al.14 is shown in Table 3.1. Considerable variations will occur with different dose fractionation regimes of radiotherapy and when treatment is combined with other modalities, such as cytotoxic chemotherapy. The table must be regarded as an approximate guideline and applied with extreme care. The acceptable risk of morbidity of any measure of treatment must be related to the purpose for which the treatment is being given and the result likely to be achieved. The functional loss of a considerable portion of a lung will give some disability, which could well be justified in the control of an advanced bronchial carcinoma; on the other hand, any impairment of respiratory function is not acceptable following radiotherapy given after lumpectomy for an early carcinoma of the breast in a young patient. Even in the management of advanced and inoperable tumours, level of risk must be low in certain vital tissues because of the dire consequences that may follow, which can be as distressing as uncontrolled tumour growth. An example would be radiation myelitis leading to paraplegia, for which a risk greater than 1 per cent can rarely be justified.

100

Normal tissues

0 Dose

Figure 3.1 A diagram showing the probability of tumour control and the incidence of late effects in the normal tissues. The actual curves in an individual case will depend on the characteristics of the tumour and of the normal tissues irradiated, as well as on the regime of radiotherapy.

significantly from the baseline (Fig. 3.1). In normal tissues, there is generally a higher threshold dose, but this is followed by a steeper dose–response curve. The steepness is described by the ‘gamma value’,15 which gives the increase in response in percentage points for a 1 per cent increase in dose. The commonly demonstrated gamma values for the cure of a squamous cancer of the head and neck region are in the range 1.5–2.5. With a gamma value of 2, a 10 per cent increase in dose can be expected to elevate the tumour cure probability by 20 per cent; this may mean an elevation in cure rate of from 60 to 80 per cent. Animal tumour models usually show much higher gamma values – commonly

The radioresponsiveness of tumour and of normal tissues 43

exceeding 10. The greater heterogeneity of human tumours and inhomogeneities of radiation dose, together with inevitable inaccuracies in staging and inadequacies in follow-up, probably account for the much lower values found in the human situation. At dose levels high in the therapeutic range, the gamma values for severe late reactions in normal tissues are greater, and emphasize the importance in the planning of radiotherapy of avoiding maximum doses to significant areas in excess of that prescribed to the tumour.16 Consideration of dose–response relationships leads to the important conclusion that once the therapeutic range is reached, very small differences in dose can considerably affect the chance of cure and also the incidence of normaltissue injury.17

Fractionation and total dose In the early years of radiotherapy, benefit in terms of increased tumour control, with acceptable tissue morbidity, was achieved by moving from a single (or a few) large dose fraction to small doses given daily over a number of weeks. To achieve this benefit, it was found that the total dose given in many small fractions needed to be increased. When, for example, treatment was changed from one single to 30 daily treatments over 6 weeks, the total dose needed to be multiplied by a factor of approximately 3. Strandqvist in 194418 proposed a mathematical formula to relate total dose and overall time to skin tolerance. Ellis in 196919 importantly suggested that the effects of fraction number and overall time needed to be separately included in a formula. The Ellis formula was widely used and was found to be very helpful in clinical practice. However, it later became apparent that when the number of fractions was reduced below 12, the incidence of normal-tissue effects was greater than predicted.20

The linear quadratic formula Laboratory studies have shown that at clinically relevant doses, tumours and early-reacting tissues respond to ionizing radiation, dominantly with a linear relationship between dose and effect – the α or linear element. In the late-reacting tissues, however, it is dominantly related to the square of the individual dose – the β or quadratic element. In 1982, Barendsen21 proposed the linear quadratic (LQ) formula that brought together this knowledge. The formula predicts that by giving radiotherapy in many small doses there is sparing of the damage in late-reacting tissues but little alteration in the response of the early-reacting normal tissues and in the responsiveness of the tumour. Clinical experience has given support to the LQ model, with the predicted increased damage in late-reacting tissues, such as the spinal cord, with the use of high doses per fraction and reduced damage when low doses per fraction are

employed. In a number of randomized controlled clinical trials using hyperfractionation with low doses per fraction, the total dose given in a standard period of time has been increased, with a modest and tolerable increase in acute morbidity but with significant improvement in tumour control (Table 3.2).22

α/β ratios for tumours and for normal tissues The relative importance of the two elements in the LQ formula for a given response in a given tissue is expressed by the α/β ratio.23 In animal studies, the ratio is in the range of 7–20 Gy for acutely responding tissues, whereas for the late-responding tissues it ranges from 0.5 to 6 Gy. In humans, values calculated for early reactions have ranged from 8 to 15 Gy and for late reactions from 0.8 to 4.0 Gy, giving good concordance with the laboratory data.23 High α/β ratios in excess of 10 have been recorded for animal tumours and similar values have long been accepted for human tumours. In carcinoma of the prostate, however, some evidence has accumulated to suggest that the α/β ratio may be as low as 1.0 Gy, but there is considerable controversy on the subject, with one study suggesting a much higher value of 8.3 Gy.24 If a low value is correct, the best radiotherapy might be with a few large fractions, and certainly such treatment is easier for the patient and less costly for the community. Randomized controlled studies of hypofractionation are underway and these may well give us an answer.24,25 Carcinoma of the breast is another situation in which it has been suggested that, in contrast to the generality of tumours, the α/β ratio may be low. However, hard evidence is lacking.26

Low-dose hyper-radiosensitivity Until recently, there was no reason for clinicians to be interested in the use of radiation doses below 1 Gy, but with the development of new techniques, research has shown an excess of cell kill at doses below 1 Gy relative to that predicted by the LQ model.27 This phenomenon is termed low-dose hyper-radiosensitivity (LDHRS) and has been shown to be present in many human tumour cell lines, its effect being generally greater in those that are radioresistant.28 The effect has been demonstrated in many laboratory tumour models and can be exhibited to a lesser extent in normal tissues such as skin and kidney, but not in spinal cord. Modelling suggested that there would be an increase in the therapeutic ratio.27 Clinical work in which volunteer patients underwent radiation of normal skin and of skin deposits of tumour provided proof, in principle, that LDHRS could be used to advantage in the management of human tumours.28 However, the prospect of treating two or three times daily for periods of 5 or 6 weeks or more has so far inhibited progress.

Table 3.2 Fractionation studies in head and neck cancer Normal Tissue reaction

Dose/F (Gy)

No.

Total dose (Gy)

Conventional Radiotherapy

2

33

66

45

24















Hyperfractionated EORTC 2279154 (RTOG 900356)

1.15

70

80.5

47

8

 

 

 

 

 

 

Acceleration but with split course EORTC61

1.6

42 or 45

67.2 or 72

47

3

  

  

Acceleration with shorter split EORTC 2285155

1.6

46

72

33

4

  

  

Acceleration with shorter split and reduction in total dose – WANG57 (RTOG 900356)

1.6

40

64

40

4

 

 

 

Concomitant boost Ang et al (1990)58 (RTOG 900356)

1.18 and 1.5

30 and 10

69

40

3–6









Highly accelerated GORTEC98 9402

2

31–32

62 64

21

8

 

 

 

 

Continuous Hyperfractionated accelerated with reduction in total dose CHART63

1 .5

36

54

12

6

  

  

Moderately accelerated DAHANCA 6&758

2

33

66 68

38  39

24 (and 8)





Radiotherapy schedule

total time (days)

Time between F and hours

Early

Late

Locoregional control

1

2

3

4

5

6

7

 

slight increase

equal

improved

benefit

  

slight increase

equal

equal

no benefit

increase

increase

improved

morbidity too great

Week

  





  

8

Overall assess.

 

 

slight increase

equal

equal

no benefit



 

slight increase

equal

improved

benefit

increase

increase

improved

concerns regarding morbidity

slight increase

reduced

equal

slight benefit

slight increase

equal

improved

benefit



In addition to the trial considered representative of the type of study, other similar trials are shown in brackets. F  fractionation



Time and radiation response 45

TIME AND RADIATION RESPONSE The mitotic cycle and radiosensitivity The phase in mitosis at the time of therapy is important in determining radiosensitivity and chemosensitivity.1 With ionizing radiation, the maximum resistance is in S phase and the greatest sensitivity in M and late G2; there may be a factor of two in the relative sensitivity. Cytotoxic drugs show a number of patterns, but generally S phase is the most sensitive period. However, with some drugs, restingphase cells have been reported to be more sensitive than those that are proliferating. The initial treatment in a fractionated course of radiotherapy may, after the period of mitotic arrest, lead to cell-cycle synchrony, and if the next treatment is given when the cells are in a sensitive phase of the cycle, an increase in cell kill may occur. So far, these experiments have been confined to the laboratory and there is no immediate application in clinical radiotherapy.1 With the multi-fraction techniques employed for cure in the clinic, it is difficult to see synchrony maintained beyond a second treatment. This makes it improbable that a manipulation of the cell cycle can be employed to improve the results of radiotherapy.

Repair of sublethal injury After exposure to radiation, some of the damage sustained within the cell can be repaired.1 The rate of repair falls in an exponential fashion, and in laboratory models the time for the rate to fall to half has been calculated to range from 30 to 120 minutes. Some variation is seen from one tissue to another, and two or more components of repair with different half-times may be present.29 It is important to note that the proportion of damage that is recoverable is smaller in tumours and in acutely responding tissues, such as skin and mucosa, than in the late-responding tissues, such as kidney and connective tissue. With treatments spaced 24 hours or more apart, we can assume that repair has been completed between fractions. However, when more than one treatment is given each day, the duration of time between fractions must be chosen with care in order to allow as much repair as possible to occur in the normal tissues. In the early clinical studies of hyperfractionation, intervals of 4 hours or less were often employed. Acute and late reactions were rather greater than expected, particularly when intervals of 2 hours or less were used. With intervals of 6–8 hours these were acceptable.30–33** In the CHART (continuous hyperfractionated accelerated radiotherapy) studies, particular care was taken to measure acute and late reactions, and when the comparison was made with the control arm treated conventionally, it was possible to calculate the halftimes of repair in human normal tissues. These were found to be 4 hours or more and there was evidence that in neural tissue the half-time was significantly greater, so accounting for

the unexpected incidence of a number of cases of radiation myelitis in the pilot study of CHART.34* We can conclude that in general the interval between fractions should never be less than 6 hours; when brain and spinal cord are irradiated, the interval should be 12 hours.

Tumour-cell proliferation When there is an opportunity to observe the natural progression of a carcinoma or sarcoma, several months may pass before the tumour doubles its size. When serial observations have been possible, volume doubling times have ranged from 30 to more than 300 days, with median values often greater than 100 days.1 These observations, together with knowledge that there is a period of mitotic arrest after exposure to ionizing radiation, led radiotherapists to the view that growth during a course of radiation therapy lasting 4–7 weeks was not likely to be important in influencing the result. Advances in knowledge have caused this opinion to be revised. In the past, it has only been possible to study growth at the cellular level by administering radiolabelled thymidine. Only patients with advanced disease could therefore be investigated, and the procedure is a complex one, requiring autoradiography of biopsy samples for the result to emerge. Begg and his colleagues35 were able to determine cell kinetics for tumour by giving a single injection of bromodeoxyuridine (BrdUrd) and performing a biopsy 4–6 hours later. With the use of a cell sorter, the proportion of cells preparing for division (the labelling index) and the duration of the S phase could be determined. From these values the potential cell doubling time was calculated. This is a measure of the proliferative activity of tumour cells, taking into account the presence of dividing and nondividing cells, but assuming the absence of cell loss.36 A wide range of values has been obtained in extensive studies in human tumours using this technique.37 In squamous cell cancer in the head and neck region and in the uterine cervix, median values lie between 4 and 5 days, whereas median values a little higher are seen in other tumours (Fig. 3.2). Spontaneous cell loss, due to apoptosis, necrosis, nutritional deprivation and differentiation, accounts for the 10–20-fold differences between cellular doubling times and volume doubling times observed clinically.38 With an immunohistochemical technique, the cells that have taken up the BrdUrd can be seen clearly under the microscope, and considerable variation in the proportion of labelled cells can be observed from field to field. At the growing edge of many squamous cell carcinomas, up to 60 per cent of the cells may appear to contain BrdUrd and therefore be in DNA synthesis.39 The advantage of the immunohistochemical technique over flow cytometry is that tumour cells can be readily differentiated from normal cells. This is particularly important in the case of diploid tumours for which it is not possible, using the flow cytometer, to separate the cells. In squamous cell cancers in the head and

46 Clinical radiobiology

Breast Melanoma Lung 7

Oesophagus

6

0

2

4

6

8

Awaad

Antognoni

0

Foster

1

Corvo

2

Hoyer

3

Bourhis

4

Wilson

Colorectal

5

Zackrisson

Cervix

Begg

Median Tpot (days)

Head and neck

10

Median Tpot (days)

Figure 3.2 Median values for potential doubling time (Tpot) measured in a variety of different tumours (data provided by George Wilson). The inset shows published data from different groups for head and neck tumours only.

neck region, the labelling indices determined by immohistochemistry have been combined with the duration of S phase determined by flow cytometry to calculate the potential doubling time. When the maximum labelling index, as seen microscopically, is used, half the tumours show extremely rapid potential cell doubling times of less than 2 days.39 The evidence showing that tumour cells may proliferate at such rapid rates has important clinical implications. When tumour cells are destroyed by radiotherapy or cytotoxic chemotherapy, it is likely that the pattern of cell division and loss will be altered considerably.40–42 It is probable that the high spontaneous cell loss occurring in the unperturbed tumour will be greatly reduced and the surviving tumour cells will realize their full reproductive potential. It is even possible that cellular division may be accelerated with an increased growth fraction of the surviving tumour cells, and the cell-cycle time may be reduced so that repopulation occurs at a rate even faster than that suggested by the cell kinetics performed prior to treatment.40,43 Evidence to support the view that repopulation is an important factor in determining the result of a course of radiotherapy has been derived from analyses of clinical data.44 Prolongation of a course of radiotherapy has been reported to result in the reduction of the probability of tumour cure at a number of sites, including uterine, cervix, breast and head and neck.45 The prolongation of overall duration of treatment for head and neck cancer by 1 week may reduce tumour control rates by 13 per cent.46,47** Most of this work is the result of retrospective analysis of consecutively treated patients, where treatment may have been prolonged for many reasons, including some that may be associated with unfavourable features of the tumour, but convincing data have been obtained from an

analysis of the results of a randomized trial of split-course therapy in head and neck cancer.48

Onset of repopulation In a range of different animal tumour models, the time to commencement of repopulation has shown a wide variation, with intervals ranging from 7 to 21 days. Withers et al.,40 following an analysis of the reported results of radiotherapy in head and neck cancer, found evidence that the repopulation of squamous cell cancer in the head and neck region begins after a lag period of 3–5 weeks after the first treatment. The influence of growth factors in determining the time of onset and extent of cellular repopulation has been studied and the influence of epidermal growth factor (EGF) has received much attention.49,50 Over-expression of the EGF receptor (EGFR) is now considered to be associated with decreased local tumour control after radiotherapy, particularly when overall treatment times have been long.49–51 A considerable research effort has been made to inhibit EGFR in combination with radiotherapy. The blocking antibody C225 with radiotherapy has been shown in animal tumour models to be more effective than either radiotherapy or C225 alone.52 In a randomized phase III trial in head and neck cancer, the addition of cetuximab (C225) gave significantly improved loco-regional tumour control and survival compared with radiotherapy alone.53** Some increase in acute skin reactions was noted in the experimental arm. Benefit has not been clearly achieved in other studies and it would seem that the EGFR mechanism is a complex one and much effort will be required to exploit this approach fully.49

Nutrition, environment and radiation response 47

TIME, FRACTIONATION AND THE IMPLICATIONS FOR CURRENT PROGRAMMING OF RADIOTHERAPY Unconventional fractionation in the head and neck site Knowledge concerning cellular division, the time course of repopulation and the implications of the LQ equation led to a questioning of conventional, five times weekly, 1.8–2.0 Gy doses to a total of 64–70 Gy as the standard best treatment when cure is the objective. Clinicians have been concerned about the possibility that towards the end of the standard course of radiotherapy there is much loss of effect because of tumour cell repopulation. The use of many small fractions to increase tolerance was attractive. Many trials have taken place, including a large number of randomized controlled studies. Squamous cell cancer of the upper aerodigestive tract has been the tumour most extensively studied (see Table 3.2).54–62** At least for such tumours, we can conclude the following: ●

●

●

The overall duration of time planned for the course of treatment should not be prolonged. Gaps will lead to a lowering of the expectation of tumour control. Shortening of the overall duration, other aspects remaining constant, will elevate tumour control. Acute reactions are likely to be enhanced by acceleration, but it is possible with hyperfractionation employing small doses per fraction and with adequate inter-fraction interval to achieve a higher total dose and with it a greater expectation of tumour control.

Unconventional fractionation in other sites The situation with regard to other tumours is less clear; however, it seems likely that squamous cell cancer at other sites such as lung, oesophagus and uterine cervix will benefit from the same approach. Experience with the CHART randomized controlled trial in lung cancer gives this support.63** There is evidence to suggest that it is the well-differentiated and moderately differentiated squamous tumours that show benefit from acceleration.64*,65** It would seem that such tumours have retained the characteristics of the parent normal tissue and its ability to respond with rapid proliferation after injury. It is possible that other tumours showing rapid proliferative characteristics, such as some malignant lymphomas, oat-cell carcinoma and some tumours occurring in children, may also benefit from acceleration; however, clear evidence is lacking.

The balance of tumour control and normal-tissue injury As in all applications of radiobiology to clinical practice, great care must be taken not to cause increase in normal-tissue

damage. Much can be learnt from laboratory study; however, the time course of clinical radiotherapy invariably differs from that in the laboratory, where the characteristics of both the tumour and of the host animal differ from those of the human. A high standard of clinical science is necessary to exploit the promise of benefit. The situation has been further complicated by the wide adoption of combined chemo-radiotherapy and the difficulties in interpretation of interactions between the elements of the treatment planned for the patient.

NUTRITION, ENVIRONMENT AND RADIATION RESPONSE The environment of tumour and normal tissues and the importance of oxygen All biological processes may be influenced by the nutritional support of the system. In determining radiation response, the dominant influence is that of the concentration of oxygen available at the time of treatment. The relationship between oxygen tension and radiation response has long been recognized in radiobiology. In 1935, Mottram gave a clear account of the importance of radioresistance due to hypoxia, and it was his colleague, Hal Gray, who gathered the evidence together and brought it to wide attention.66 There is good evidence to show that hypoxia commonly exists in human tumours and that hypoxic tumour cells are resistant to radiotherapy. A process of re-oxygenation has been shown to occur in tumours during a fractionated course of radiotherapy: as sensitive oxic tumour cells are destroyed, hypoxic ones move nearer to the blood supply released and so become sensitive. There is good circumstantial evidence, however, to suggest that this process is incomplete in some tumours, and that hypoxia is a cause for failure to achieve cure.67

Methods applied clinically to overcome hypoxia BREATHING OXYGEN OR CARBOGEN

Breathing 100 per cent oxygen or carbogen (95 per cent oxygen, 5 per cent carbon dioxide) has been the subject of phase I and II studies but has never reached phase III.67,68 HYPERBARIC OXYGEN AT 3 ATMOSPHERES ABSOLUTE

This technique, pioneered by Churchill Davidson in 1955, did proceed to randomized clinical trials and 15 have been reported in carcinoma of the cervix, bladder, lung and head and neck cancer. Some studies contained relatively fewer patients; however, margins of benefit were shown in nine, and statistical significance was reached in three.69

48 Clinical radiobiology

There was some increase in late normal-tissue effects. The difficulties of treating patients in hyperbaric chambers led to interest in simpler methods of achieving sensitization of hypoxic tumour cells. CHEMICAL SENSITIZING AGENTS

Chemical sensitizing agents such is misonidazole and etianidazole have been extensively studied in human tumours but nearly all showed no advantage.70,71** However, in a series of studies in oropharyngeal and supraglottic tumours performed by the Danish oncology centres (DAHANCA) a significant advantage was shown, first with misonidazole and then with nimorazole, which, unlike misonidazole, did not induce peripheral neuropathy.72**,73 Nimorazole is included in standard management for patients with such tumours in Denmark but its use in other countries has been limited. Despite demonstration of benefit in a large, well-conducted randomized controlled clinical trial, the report of so many other trials of chemical sensitizing agents that proved negative seems to have undermined its establishment and interest has moved to other methods to advance radiotherapy. AGENTS TO OVERCOME TRANSIENT HYPOXIA

In addition to chronic hypoxia, evidence has accumulated to show that acute hypoxia due to temporary occlusion of small vessels may be important during radiotherapy. Vasoactive drugs such as pentoxifylline and nicotinamide have been introduced to overcome this problem.74 It has not been felt that, used alone, sufficient numbers of patients would benefit and the application has been essentially in combination with other methods used to overcome chronic hypoxia.75 ARCON (ACCELERATED RADIOTHERAPY, CARBOGEN AND NICOTINAMIDE)

It was proposed by the late Juliana Denekamp that a tumour that is rapid in proliferation is also one that outgrows its vascular supply to become hypoxic.75 ARCON brought together carbogen to overcome chronic hypoxia, nicotinamide to overcome transient hypoxia, and acceleration to deal with cellular proliferation. In an extensive pilot study at Nijmegen, very promising results were reported and a margin of benefit was achieved with minimal increase in normal-tissue effects; a pilot study in bladder cancer performed at Mount Vernon Hospital has also given promise.76*,77* Randomized controlled clinical trials are underway in carcinoma of the bladder and in pharyngolaryngeal cancer. HYPOXIC CYTOTOXICITY

The work to develop hypoxic cell radiosensitizers has also produced compounds that are in themselves cytotoxic to hypoxic cells. A drug developed by the Stanford group,

tirapazamine has shown promise in phase I/II clinical trials.78 Such a drug needs to be given in combination with radiotherapy or cytotoxic chemotherapy, so that the oxic component of the tumour can be dealt with.79* The drug may also enhance the cytotoxic effect of cis-platinum, and remarkably good results have recently been reported from a pilot study of the combination in advanced head and neck cancer.79* Randomized trials of the use of tirapazamine are now underway and the results are awaited. COMBINATION OF VASCULAR-ACTING AGENTS WITH RADIOTHERAPY

The importance of the blood supply to the growth and advance of tumours led to the development of drugs that cause a shutdown of vascular supply and the induction of massive necrosis.80 Although promising agents have been developed that can achieve short-term palliation, a longer effect can only be expected when they are used in combination with either radiotherapy or cytotoxic chemotherapy so that the surviving tumour cells at the periphery of the tumour may be controlled.81,82 Efforts so far have concentrated on the combination with cytotoxic chemotherapeutic agents; however, studies are currently underway of the combination of combretastatin and radiotherapy.83–85

Overview Overgaard and his colleagues have performed an overview of trials of methods employed clinically to overcome the resistance associated with hypoxia, and have gathered data related to more than 10 600 patients. A margin of 5 per cent of improvement in loco-regional control (P  0.001) was demonstrated, and with it a 3 per cent improvement in survival (P  0.04).86** The overview is important in that it demonstrates that there is an oxygen effect and that methods of overcoming it can be successful. However, the margin is small and it is obvious that the normal process of re-oxygenation, which occurs during radiotherapy, is commonly successful. Before treatment is commenced, we need to identify those cases in which the process is unlikely to be successful and in which a method to overcome hypoxia should be employed.

Determining where hypoxia matters We know that once tumours have reached clinically detectable size hypoxia probably exists in practically all. Despite this, a large number of patients are cured and therefore the radiotherapy is successful in eradicating all tumour cells. Patients likely to benefit from methods to overcome hypoxia can therefore only comprise a proportion of those attending for treatment.86 The identification

The combination of chemotherapy with radiotherapy 49

of such patients continues to be a major area of research activity. Techniques employed have included measuring oxygen tension using sophisticated probes, radiolabelled nitroimidazoles to identify hypoxic areas, and measurements of vascular perfusion, often using magnetic resonance (MR) techniques, besides many other approaches.86,87 Among recent particularly promising lines of research has been the use of positron emission tomography (PET) with a range of molecules to allow for the imaging of hypoxia.88–91 All this research has been important for the development of our understanding of human tumours, but has not, so far, yielded a technique that can be readily applied to identify patients in whom hypoxia is a major problem and for whom a method to overcome it is indicated.

for women – levels in the lower range of normality.92 The demands on a blood transfusion service to achieve this in clinical practice may be considerable. Erythropoietin is effective in stimulating bone marrow function and can, in moderately anaemic patients, bring the haemoglobin concentration to within normal levels in 10–14 days. A randomized controlled clinical trial in patients undergoing radiotherapy for head and neck cancer demonstrated very satisfactory elevation of haemoglobin levels; however, there was no evidence of clinical benefit.94**,95** In this study, a margin in favour of the controls does raise the possibility of a direct adverse influence on tumour progression and the possibility that erythropoietin stimulates both bone marrow function and tumour growth.95** Considerable caution would seem appropriate for the use of erythropoietin in patients with potentially curable cancer undergoing treatment.

Hypoxia and future directions Molecular biology has now shown the importance of hypoxia in the regulation of tumour growth and progression. Hypoxia will induce genetic changes that stimulate tumour growth and facilitate dissemination of metastatic disease. There is thus a further stimulus to the understanding of the importance of hypoxia and its mechanism and the discovery of ways to overcome it to benefit the patient with cancer.

Anaemia In 25 papers reporting the clinical experience of radiation response and anaemia, 23 reported an adverse radiation response in anaemic patients. The interpretation of retrospectively derived data of this type must always be done with caution.92 There is no doubt that there is, in many tumour sites, an association between anaemia and advancement of disease. Even taking this into consideration, however, the evidence does suggest a real association between anaemia and response to radiation. A randomized controlled clinical trial of the use of blood transfusion in carcinoma of the cervix showed an improvement in primary tumour control when the haemoglobin was brought to 125 g/L or above, compared with the control group in which the haemoglobin level lay between 100 g/L and 125 g/L during therapy.93** However, in the DAHANCA head and neck cancer studies, a sub-randomization to test the value of transfusion showed only a small margin of advantage, which was not of statistical significance.86** Considering all the evidence, anaemia does seem of importance, and the implication for clinical practice is that in the curative situation the haemoglobin should be brought to normal levels before radiation therapy is commenced. It is noteworthy that in the Danish studies in which anaemia was associated with impaired response in head and neck tumours, the levels of haemoglobin chosen to divide the cases were 9 mmol (144 g/L) for men and 8 mmol (128 g/L)

Radioprotectors Radioprotectors were developed in the USA in an attempt to give some protection in atomic warfare; the compound that has reached clinical testing in oncology is amifostine. The initial work in the laboratory with amifostine suggested that the drug does not accumulate in tumours; however, the total reliability of this remains uncertain.96 The progress of this drug in clinical trial has been extremely slow,97 but its use in patients with head and neck cancer with a view to reducing late effects on salivary gland function has yielded a highly significant benefit,98** although the side effects can be troublesome.99 The drug is now marketed for this purpose and there may be further application for amifostine may have value in combination with cytotoxic drugs, such as cyclophosphamide, for the protection of bone marrow; evidence to support this has been demonstrated in clinical trials.100,101**,102**

THE COMBINATION OF CHEMOTHERAPY WITH RADIOTHERAPY To enhance tumour control within the irradiated volume The combination may be employed to enhance tumour control within the irradiated volume. The combination of local effect may be due to a simple addition of cell kill or to a true radiosensitization – processes often difficult to separate.103 Possible mechanisms of radiosensitization include the following: ●

●

Compounding of radiation-induced DNA breaks and so reducing repair. Drugs capable of doing this include cisplatin, bleomycin, adriamycin and hydroxyurea. Selective killing of cells in radioresistant phases of the cell cycle (late S and G1).

50 Clinical radiobiology

These mechanisms may be important to clinical practice, but so far there has been no way of scientifically directing inhibition of repair and selective cell cycle kill so as to maximize effect. ●

Selective killing of hypoxic cells. This promising approach has already been discussed above.

A simple addition of cell kill may in itself lead to advance in local tumour control. However, this relies on independent toxicities and no increase in radiation damage, otherwise a simple increase in radiation dose would achieve the same result.

Spatial co-operation Eradication of the primary tumour by radiotherapy and/or surgery can be complemented by chemotherapy for micrometastatic disease. In the management of the bulk of carcinomas, chemotherapy is most effective when used towards the achievement of cure by the eradication of micrometastases.103

Importance of time The giving of combined therapy concurrently, or with only a few days’ separation, does commonly lead to an enhancement of effect on the tumour. However, this may also be seen in the normal tissues. Reduction in total radiation dose may be necessary, and this complicates the interpretation of results. When chemotherapy and radiotherapy are separated, an increased effect in normal tissues is less commonly seen,103 but clinical experience now suggests that benefit is also lost.104*** With growing awareness that cellular repopulation may occur in gaps between treatments, whether they be surgery, radiotherapy or chemotherapy, the trend has been for concurrent radiotherapy and chemotherapy.

Debulking Preliminary (neoadjuvant) chemotherapy can be expected to reduce the tumour-cell number and so increase the possibility of cure, and may also allow a reduction in the volume of normal tissue to be irradiated as the tumour volume is smaller. Timing is critical: in order to minimize the morbidity of the use of two modalities and to see shrinkage of the tumour, a considerable separation is desirable. However, while shrinkage may be obviously visible, rapid cellular repopulation may already be underway and may negate the benefit. The approach is best established in the management of lymphomas.

Novel molecular targets Many of the cellular growth factors and signalling pathways for the control of proliferation, differentiation and angiogenesis may be activated in tumours and not in normal tissues, so giving rise to the possibility of drug targeting. Targets modifying radiosensitivity have been identified.10 Of great interest is the EGFR, which is highly expressed in many head and neck tumours and is associated with aggressive behaviour. This has already been discussed in the section dealing with repopulation.49,53** Other targets that are the subjects of current research include the ErbB-2 receptor in breast cancer and COX2 in colon cancer.4

Interactions between radiation and chemotherapy In addition to a potentiation or simple addition of the effects on tumour, there is, in some circumstances, the possibility of a reduction in radiotherapeutic response. As discussed, radiation response varies according to position in the cell cycle and it follows that if the chemotherapeutic agent significantly alters mitotic activity before the radiotherapy is given, the response may be reduced. Careful laboratory experiment can give some guidance, but as conditions for clinical application may differ considerably from those in the laboratory, careful planning and study in the clinic are essential. The potentiation of radiation effects in the normal tissues has already been discussed.

Current situation A vast clinical experience has now been recorded. The design of the studies has not come from laboratory work but from practical considerations related to programming and tolerance. There has been progression from phase I through to phase III, and with some tumours to adoption as ‘best practice’. Considerable margins of benefit have been demonstrated in the management of anal and oesophageal cancers, for which the combination therapies have become standard. In head and neck and non-small-cell lung cancer, margins have been smaller and overall results variable. Overviews and meta-analyses have demonstrated small but certainly significant gains, concurrent therapies appearing more successful.104***–107*** These have led to fairly wide adoption of combination chemotherapy in these conditions. There must, however, be concern, for in many of the individual studies, and certainly in the overviews and meta-analyses, data concerning morbidity, especially late morbidity, have not been included.104*** When consideration has been given to them, the data available have not been such as to be sensitive in evaluating morbidity. There is the necessity for large, randomized trials, where

The biological basis for special approaches in radiotherapy 51

tumour effects and those in normal tissues are given equal priority in order to assess the true therapeutic benefit.

THE COMBINATION OF SURGERY WITH RADIOTHERAPY Tumour cell kinetics in the postoperative field Advances in surgery have led to an increase in the number of patients with the more advanced tumours undergoing resection. Commonly the pathologist reports that tumour cells have reached the margin of the surgical specimen or that margins are narrow. Postoperative radiotherapy has been shown to reduce the high level of recurrence in subsequent months. In contrast to the situation when a late recurrence is managed in a surgically scarred neck, the tissues are very vascular.108** Tumour cells in the operated area are likely to proliferate rapidly and be stimulated by growth factors generated within the operative field. It is therefore important that the interval between surgery and onset of radiotherapy be as short as possible so as to allow the minimum time for the tumour cells to proliferate. The volumes of tissue at risk may be extensive. There is considerable risk of post-radiation morbidity being increased because of the recent surgery and any postoperative complication, together with the large volume commonly requiring treatment and the many vital structures in the area. The margin of benefit now demonstrated by the addition of chemotherapy suggests that it should now be incorporated, so the hazard of increased morbidity may be further accentuated.109**

Radiation dose required In the postoperative state, such as after lumpectomy for primary carcinoma of breast, where any nodule of residual tumour is likely to be truly microscopic, a total radiation dose of 46–50 Gy given in 2-Gy fractions may be adequate to achieve a high degree of probability of elimination of all tumour. However, after surgery for an advanced squamous cell carcinoma in the head and neck, the risk of residual disease is greater and the tumour-cell burden is likely to be higher. In those circumstances a dose of 60 Gy or greater may be indicated.

THE BIOLOGICAL BASIS FOR SPECIAL APPROACHES IN RADIOTHERAPY

with 250 kV X-rays. Values between 2 and 10 may be obtained, according to the energy of neutron beam and, importantly, the size of dose per fraction, for there is an inverse relationship between dose per fraction and RBE.110 The biological advantages rest upon a lessened influence of oxygen tension and the position in the mitotic cycle together with, in animal models and human tumour transplants, a more uniform response among tumour types.110 The results of phase II and phase III clinical trials have been difficult to interpret because of case selection, unusual dose fractionation regimes, a variable handling of morbidity and, in some trials, the use of a combination of photons and neutrons. A place was suggested in the management of squamous cancer in the head and neck region, but this was not confirmed in further trials. With evidence based on small numbers, there may be a particular advantage in advanced parotid and prostatic carcinoma.111 It can, however, be concluded that the considerable resources needed to pursue neutron therapy might give a greater benefit if employed in other ways to advance radiotherapy.

Charged particles The ion beams of charged particles increase their rate of energy emission as they slow down, finally stopping and releasing energy in an intense burst of ionization (the Bragg peak). The beam produced may be used to deliver high doses to small volumes and spare adjacent sensitive structures, so bringing advantages over photon therapy in certain situations, such as in the treatment of tumours in the base of the skull.112 When employed clinically, photon and helium ion beams have a Linear Energy Transfer (LET) similar to that of photons and 250 kV X-rays and present, therefore, no special biological advantage.110 If deeply placed tumours are to be treated with proton beams, high-energy cyclotrons are required. The cost and complexity of the apparatus required for the production of a heavy-ion beam are even greater than with neutrons.110 The advantage of proton ion beams has, however, been well demonstrated in the treatment of tumours closely related to the spinal cord and brainstem,113 and a strong justification has been made for the establishment of national centres where such therapy may be available for those patients likely to benefit.

Brachytherapy and the biological advantages of low dose rate

Neutrons The efficiency of any ionizing radiation increases with the density of the ionization along its track. X-rays and γ -rays are sparsely ionizing radiations, but neutron beams and heavy-ion beams have densities that may be several hundred times greater per unit length. The relative biological effectiveness (RBE) is normally determined by comparison

Interstitial and intra-cavitary applications of radioactive sources have an important place in radiotherapy. A high cure rate is obtained with accessible, well-defined tumours of small or moderate size, and such techniques may also be used to give a boost to the area of gross tumour after external-beam treatment. With the original low-activity sources, applications were for 1–7 days and the dose rates

52 Clinical radiobiology

were commonly less than 1 Gy/h. This can be compared with conventional external-beam therapy, in which 2 Gy may often be given in 1–2 minutes. Sublethal injury is important in determining the late effects of external-beam therapy using photons, but it has now been shown in the laboratory that there is complete recovery of all sublethal injury at the low dose rates used for brachytherapy.114 This does accord with the excellent normal tissue tolerance with limited late changes associated with brachytherapy. There is a further advantage in that with overall treatment times in brachytherapy ranging over 1–7 days, treatment is accelerated compared with conventional external-beam therapy and little or no time is allowed for repopulation. Finally, it has also been shown in the laboratory that the oxygen enhancement ratio is considerably reduced and that re-oxygenation appears to be very effective under low-dose therapy, even though overall times are relatively short. In addition to the considerable biological evidence to support the efficacy of brachytherapy, there is the well-localized dose distribution.

Afterloading and high dose rate The hazard of radiation exposure to staff has led to the introduction of hollow applicators and subsequent afterloading of the radioactive sources; this is most safely performed mechanically. However, the long period of exposure to radiation with traditional brachytherapy techniques is difficult to reproduce with machines for afterloading. With the advent of small, high-intensity sources, high-dose-rate techniques have been introduced and exposure times reduced from days to less than 30 minutes. The dose rate thus becomes similar to that of conventional external-beam therapy, and similar biological characteristics may be expected. As one or a few large doses are commonly given, there is not the benefit of multiple fractions usually associated with conventional externalbeam therapy. Reductions in dose have been made, but in some centres these were initially inadequate and morbidity was considerably increased. Fractionated brachytherapy is obviously a useful approach, easier to achieve with a boost rather than with definitive therapy. Treatment units have now been constructed to allow the introduction of very highactivity sources for a few minutes every hour. Calculations based on laboratory experiments have suggested that this approach will allow safe brachytherapy with biological effects similar to those of continuous low-dose-rate techniques.115

BIOLOGICAL FEATURES OF THE TUMOUR IMPORTANT TO MANAGEMENT Tumour volume and clonogenic tumour-cell number A ‘tumour mass’ will contain some normal tissue, stromal elements and necrotic tissue as well as tumour cells, therefore similar sized tumour masses may contain varying

numbers of viable tumour cells. There is, again, a variation in the proportion of those tumour cells that are clonogenic. In some neoplasms, such as the lymphomas, it is believed that clonogenic cells are relatively few in number, thus accounting, in part, for their relative radiosensitivity.41 The clonogenic tumour-cell burden is an important parameter in determining the response, and this has been clearly shown in laboratory experiments. We can expect in humans that in any one type of tumour, the number of clonogenic cells within a nodule 5 mm in diameter may be 1000 times fewer than the number within a mass 5 cm in diameter.41 In a range of clinical situations using standard programming of radiotherapy, very different total doses are required to achieve a 90 per cent probability of elimination of all tumour cells. In the postoperative state, as has already been discussed, doses may range from 46 Gy to 60 Gy according to the burden of risk. For a primary squamous cell carcinoma of 20 mm diameter in the head and neck region, the dose given in 2-Gy fractions may need to be elevated to 66–70 Gy to give an equal probability of loco-regional control of disease. However, with a big tumour mass of 5 cm diameter, 75 Gy may control at best only 50 per cent. Other factors, such as hypoxia, inherent radiosensitivity and proliferation characteristics, will all modify and complicate the situation. Nevertheless, the tumour-cell burden is, itself, an important biological parameter and justifies the use of a range of doses in clinical practice.

Precision in dosimetry and its biological significance Because of the steepness of the curve relating dose to tumour eradication, an elevation or depression of dose of 5 per cent at the 50 per cent control point can be expected to elevate or depress tumour control in the human situation by approximately 10 per cent. In clinical practice, there is commonly a 10 per cent variation in dose across the target volume at the centre of the fields of treatment, and when a three-dimensional view is taken, variations up to 15 per cent or even 20 per cent may be encountered. These dose variations within the area irradiated will also have important biological implications for the normal tissues. Where the total dose is lowered, normaltissue effects will be diminished further by the lower dose fraction. On the other hand, where the dose is elevated, the effect will be increased further by the higher dose per fraction. Using a conventional 2-Gy increment and a 66-Gy total dose, an increase of 10 per cent in part of the irradiated volume is likely to lead to a 13 per cent increase in biological effect, because of the increase in dose per fraction. This has been described by Rodney Withers as ‘double trouble’.116

SIGNIFICANT POINTS Laboratory and clinical research has greatly extended our knowledge of the processes that influence tumour control

References 53

and normal-tissue injury after radiotherapy. Brachytherapy and the fractionation of external-beam therapy, which were developed as a result of a continued process of clinical trial and observation, have now been given a firm scientific basis. Modification of the fractionation has now given guidance as to how the benefit of radiotherapy can be enhanced by programming treatment for the management of tumours in certain clinical situations. The complexity of the biology of human tumours, varying from site to site and within a site from tumour to tumour, combined with the many interacting factors that influence the result of a course of radiotherapy add to the clinicians’ burden as they attempt to give individual patients the most appropriate treatment. The complexity has to be recognized and tackled by high-standard research, which must be interpreted carefully and applied to the individual case. Finally, the chosen schedule will only be successful if biological knowledge is applied to good planning and delivery of treatment. In every aspect of clinical research designed to improve the results of treatment, the importance of observation of the normal-tissue effects, particularly in the long term, must be emphasized and is essential to the evaluation of any approach to improve the care of patients by radiotherapy. Morbidity must be measured not only by the incidence of severe episodes but also by the incidence of moderate or even mild effects together with its duration. The total burden to the patient must be measured and recognized. The established knowledge concerning the factors influencing radiation response in tumours and in the normal tissues is now being extended using new techniques developed from advances in molecular biology. There is great promise that this will lead to further improvement of radiotherapy. Clinical oncologists must keep in close contact with their laboratory colleagues and understand the tumour biology and radiobiology important to their work. A high standard of clinical science must then be brought to the bedside so that advances originating in the laboratory can be exploited to the benefit of the patient with cancer.

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4 Mathematical modelling and its application in oncology ROGER G. DALE AND BLEDDYN JONES

Introduction The basis and routine application of radiobiological models More advanced considerations

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INTRODUCTION Clinical experience and knowledge of the results of clinical trials can sometimes provide little more than tentative guidance on how to manage difficult clinical problems. It is useful for the treating physician to have a quantitative assessment of the likely clinical impact of more subtle changes in treatment, when dose per fraction, overall time, dose rate etc. are varied. Difficult cases can be formally assessed by using radiobiological models: from a numerical appraisal of the likely biological outcomes, the best available option can be selected or the radiation prescription can be modified in a direction compatible with safety of outcome. The amount of mathematics required for simple radiobiological assessments is well within the grasp of radiation oncologists, who should be aware of radiation effect models, their usefulness and limitations. Although computers and mathematical software packages are necessary for more advanced modelling, for a wide range of clinically relevant calculations the use of a pocket calculator is sufficient. Practice of these calculations is advised, as there are inherent subtleties. Radiation oncology is concerned with dose–effect relationships and their clinical optimization. With so many controllable variables (overall time, dose fractionation, choice of modalities, etc.) and inter-patient variations (in the biological and clinical parameters that influence outcomes), predictive models can sometimes be used to supplement clinical judgement, e.g. when an urgent decision is necessary. Randomized clinical trials can only provide

Conclusion Acknowledgement References

72 72 73

answers to situations in which the protocol is adhered to strictly and the information they provide only refers to those conditions. Modelling assessment can be used in the design of clinical trials, e.g. to define an equivalent radiotherapy fractionation schedule to be tested alongside a conventional schedule. Modelling assessments are already invaluable in special circumstances, e.g. treatment delivery errors (under-dosage or over-dosage) or if treatment is unintentionally interrupted, be this during external fractionated radiotherapy or brachytherapy. Where higher than usual doses of radiation are used, any local dose variations assume increased significance and modelling offers a valuable aid in the assessment of the resultant biological effect. Also, in the reporting of clinical data that comprise multiple different fractionation schedules, the quantification of the expected biological effect provides a method for inter-patient and inter-departmental comparisons. Modelling can be used to: ● ● ● ●

● ●

identify and modify dangerous treatment schedules, provide a standard way of reporting clinical data, optimize radiotherapy treatment outcomes, analyse clinical results from departments that use different fractionation or dose-rate schedules, aid in the design of better clinical trials, and test medico-legal issues.

This chapter examines the application of radiobiological models to a range of practical problems by means of many

The basis and routine application of radiobiological models 59

worked examples. The last part of the chapter considers more advanced examples that could improve the design of future radiotherapy schedules.

THE BASIS AND ROUTINE APPLICATION OF RADIOBIOLOGICAL MODELS

i.e.: E  αd  βd 2

(4.2)

For n such fractions, delivered several hours apart, both types of damage are n times greater, i.e.: E  nαd  nβd 2  n(αd  βd 2)

(4.3)

Types of model Earlier radiobiological models were based on logarithmic power-law models similar in form to those used in physics to predict the behaviour of gases under adiabatic conditions. Such formulations were empirical, and significant deviations from the predicted results were observed when they were applied at doses (or fractional doses) that lie outside the range of values from which the empirical relationships were originally derived. Thus, at very low and high doses per fraction, errors were found. Additionally, when power laws were first introduced, there was little awareness that acute-reacting tissues behaved differently from latereacting tissues, although tissue-specific line fitting did overcome this problem to a limited extent. No further discussion is required here about power-law models, but practising oncologists should be aware that until quite recently, many patients received treatments that had been calculated using the Ellis, cumulative radiation effect (CRE) or time–dose factor (TDF) formulations. Thames and Hendry (1987) have written a detailed history of these models.1 More reliable radiobiological models have been derived from consideration of the biophysical events that govern radiation effects. Mathematically awkward multi-target and multi-hit models were initially developed, but the target was undefined before DNA structure was discovered. Currently the best and most commonly used radiobiological model is the linear-quadratic (LQ) formulation, which can be derived from consideration of physical lesions in double-stranded DNA and their repair and mis-repair.2–4 In LQ methodology, lethal radiation damage consists of two components, A and B. Type A lethal damage is caused by a single ionizing event, the amount increasing linearly with dose with a proportionality constant of α (unit Gy1). Type A damage is not influenced by changes in the pattern of fractionation. Type B lethal damage is a consequence of there being an interaction between two sub-lethal damage components, each created in different ionizing events with a proportionality constant of β (unit Gy2). Unlike Type A damage, the amount of Type B damage is dependent on the pattern of fractionation and on the dose rate. For radiation fractions delivered in short irradiation times, the Type B damage is proportional to the square of the dose per fraction. Thus, for a single acute fractional dose of d (Gy), the total effect may be written as the summation of the Type A and Type B components: Effect (E)  Type A  Type B

(4.1)

It is clear from the dose-squared terms in Equations 4.2 and 4.3 that high doses per fraction create proportionately more effect than lower doses per fraction, the extent of this effect being governed by the relative magnitude of the β parameter compared to α. The LQ formulation is reliable over the range of dose per fraction encountered in conventional radiotherapy, but there are indications that it is less accurate at large (6 Gy) and low (1.8 Gy) values.

The concept of biologically effective dose The biologically effective dose (BED) is a useful measure of biological effect that allows comparison of different radiation schedules. The BED (in units of Gy) for a conventional course of fractionated radiotherapy is found by dividing both sides of Equation 4.3 by α and re-arranging, i.e.: BED 

⎛ E βd 2 ⎞⎟ ⎟⎟  n ⎜⎜ d  ⎜⎝ α α ⎟⎠

i.e. ⎡ d ⎤⎥ BED  nd ⎢1  ⎢ α /β ⎥⎦ ⎣

(4.4)

The bracketed term in Equation 4.4 is called the Relative Effectiveness (RE) per Unit Dose and essentially converts physical dose to biological dose. The α/β ratio (often called the fractionation sensitivity) is a measure of how a particular tissue will respond to changes in fractionation or dose rate. Consequently, any calculated BED is also tissue specific, and normally written with the α/β factor as a suffix to the dose unit, e.g. a BED of 100 Gy derived using α/β  3 Gy is written as 100 Gy3. As the product nd in Equation 4.4 is the total physical dose (TD) delivered by the treatment: biological dose (BED)  total physical dose(TD) relative effectiveness (RE) (4.5) The relationship summarized in Equation 4.5 applies also to radiotherapy that does not involve well-spaced fractions and to brachytherapy. In such cases, the form of the RE factor is more complex.

60 Mathematical modelling and its application in oncology

What does the BED represent? The BED is the (hypothetical) dose required for a given biological effect when delivered by the gentlest form of radiotherapy, i.e. using very small doses per fraction or, in the case of continuous irradiation, very low dose rates. To understand this, consider Equation 4.3 in situations in which d is progressively decreased, but with n correspondingly increased in order to maintain an iso-effect. The βd 2 term then becomes very small relative to αd and E 艑 nαd 艑 αD, where D is the total physical dose. Thus, the BED (i.e. E/α) corresponds to the iso-effective physical dose when delivered using very low dose per fraction or very low dose rate. The strength of the BED concept is that it can be calculated for any practical situation in radiotherapy, and a particular BED value may be achieved by a wide variety of schedules. It then follows that the biological effects of quite different schedules can be inter-compared using this single radiobiological yardstick. Also, because BED is tissue specific, it is a ‘one-number’ representation of either tumour or normaltissue response at the point of calculation. Caution is required in that a single value of BED cannot represent an entire volume of tissue unless further, more complex, calculations are made. Finally, it should be noted that BEDs are additive, thus a single BED can be used to represent a radiotherapy schedule consisting of two or more components (e.g. external radiotherapy plus brachytherapy) providing the doses are taken for the same point of interest.3 Two fractionation schedules of total doses D1 and D2 and dose per fractions of d1 and d2 respectively are said to be iso-effective on a particular tissue if: ⎡ ⎡ d ⎤ d ⎤ D1 ⎢1  1 ⎥  D2 ⎢1  2 ⎥ ⎢ ⎥ ⎢ α /β ⎦ α /β ⎥⎦ ⎣ ⎣

sometimes prudent to select lower values for situations in which normal-tissue tolerance may be compromised due to age, concomitant medical conditions, etc. A case in point is spinal cord, for which the fractionation sensitivity is around 1.7 Gy.5 Generic values of α/β derived from animal studies may not be representative for clinical use because of natural variation in α and β values in humans. Even for tumours of similar histology, radiosensitivity variations in heterogenous clinical data are a potentially significant factor affecting the reliability of BED-based predictions. It is clear that fractionation sensitivities need to be more accurately determined in a wider range of human tumours and normal tissues.

Worked example What are the tumour and late-responding BEDs associated with 45 Gy/25 fractions at the 100 per cent prescription surface and at a point where the iso-dose surface is given as 107 per cent? Using generic α/β values of 10 Gy for tumour and 3 Gy for late-responding normal tissue we have: ⎡ 1.8 ⎤ ⎥  53.1 Gy10 BEDtumour  45 ⎢1 ⎢⎣ 10 ⎥⎦

and: ⎡ 1.8 ⎤ ⎥  72 Gy 3 BEDlate  45 ⎢1 ⎢⎣ 3 ⎥⎦

(4.6)

Equation 4.6 may thus be utilized to design a fractionated treatment which is iso-effective to a first, or it may be used to estimate α/β ratios if parameters D1, D2 and d1 and d2 are already known from existing iso-effect treatments that are similar in their effects on a specific tissue. FRACTIONATION SENSITIVITIES: (α/β) RATIOS

These may be derived from data sets where different fractionation schedules have been used to achieve a common clinical endpoint. Typical α/β value ranges are 10–30 Gy for squamous-cell carcinomas and 4 Gy for breast cancer.5 There is a continuing debate about the value of α/β in prostate cancer; the value may be as low as 1.5 Gy.6 In the case of melanoma, it may also be small.1 A generic value of 10 Gy is often used for the tumour α/β when the exact value is not known, but a range of realistic values should be used wherever possible. Normal-tissue α/β ratios are generally smaller (1–4 Gy) than those for experimental cancers and many human tumours. A generic value of 3 Gy is often used, but it is

The fact that BEDlate is greater than BEDtumour does not mean that the late-responding tissue is receiving a greater biological dose than the tumour. Rather, the two numbers represent how much dose would be required for the same respective effects on the two tissues if a very gentle treatment (very low dose per fraction) could be used. For the 107 per cent surface we introduce a factor of 1.07 to the total dose and dose per fraction to give: ⎡ 1.8 1.07 ⎤ ⎥  57.4 Gy10 BEDtumour  45 1.07 ⎢1  ⎢⎣ ⎥⎦ 10

and ⎡ 1.8 1.07 ⎤ ⎥  79.1 Gy 3 BEDlate  45 1.07 ⎢1 ⎢⎣ ⎥⎦ 3 It can be seen that the relative increment in BED is greatest for the late reacting-tissue.

The basis and routine application of radiobiological models 61

Table 4.1 Fractionation schedules summarized and compared in terms of BED values (modified from Fowler (1989) with permission). Schedule (a) 68 fractions 1.2 Gy  81.6 Gy (b) 35 fractions 2 Gy  70 Gy (c) 30 fractions 2.0 Gy  60 Gy (d) 20 fractions 2.8 Gy  56 Gy (e) 36 fractions 1.5 Gy  54 Gy (f) 16 fractions 3.38 Gy  54 Gy

BED2

BED3

BED4

130.6 (3) 140.0 (2) 120.0 (5) 134.4 (4) 94.5 (6) 145.5 (1)

114.2 (3) 116.7 (1) 100.0 (5) 108.3 (4) 81.0 (6) 115.0 (2)

106.1 (1) 105.0 (2) 90.0 (5) 95.2 (4) 74.3 (6) 99.8 (3)

For explanation, see text.

Table 4.1 – modified from Fowler, 1989, with permission7 – gives some examples of how a selection of disparate fractionation schedules can be summarized and compared in terms of BED values. In the left-hand column the schedules are ranked in order of their total physical dose. In columns two, three and four are listed the respective later-responding BEDs corresponding to α/β values of 2, 3 and 4 Gy. The numbers in bold show, for each value of α/β, the BED lateeffect rankings of each of the schedules. The table illustrates two important points relating to radiobiological assessments. First, total dose alone is a poor predictor of radiobiological effect, as evidenced in particular by schedule f. Second, the ‘hotness’ ranking is influenced by the particular α/β selected to perform the BED calculation. Thus, where specific values are not known, it is prudent to use two or more α/β values in order to obtain a more balanced view. The occurrence of regions of high dose that exceeds the prescription dose can be a problem in radiotherapy. Although it may be beneficial within a tumour, if a critical volume of late-reacting normal tissue is included, increased toxicity may occur because small increments in dose per fraction will yield greater increments in effect due to the influence of the quadratic relationship. Withers coined the term ‘double trouble’ for this phenomenon. With further increases in the prescribed dose per fraction, i.e. as occurs in hypofractionated radiotherapy, a further increment in effect occurs when BED is estimated in high-dose regions. This additional penalty has been called ‘treble trouble’.8 The corollary of this is that additional care in treatment planning is necessary with hypofractionated radiotherapy of large volumes where dose homogeneity is common, as, for example, in breast radiotherapy.

The consequences of tumour repopulation Tumour cells originated during treatment reduce overall treatment efficacy and need to be accounted for in calculations. If repopulation occurs at a continuous (exponential) rate throughout treatment, the net effect depends on the treatment duration (T) and the effective tumour doubling

Worked example Compare the BEDs of (a) 50 Gy in 25 fractions and (b) an iso-effective dose given in 6 fractions to a volume of normal tissue (assumed α/β  2 Gy) that receives 120 per cent of the prescribed dose. What might the expected increase in complication rate be if the slope of the dose–response curve is approximately 1 per cent per Gy3? The iso-effective dose in 6 fractions is found from the solution of d in: ⎛ ⎛ 2⎞ d⎞ 50 ⎜⎜1 ⎟⎟⎟  6d ⎜⎜1  ⎟⎟⎟ ⎜⎝ ⎜⎝ 3 ⎟⎠ 3 ⎟⎠ d  5.13 Gy. The BEDs at 120 per cent will be: (a) 50 1.2(1  1.2 2/3)  108 Gy3 (b) 6 1.2 5.13(1  1.2 5.13/3)  112.7 Gy3. The increment in BED due to hypofractionation (treble trouble) is 112.7  108  4.7 Gy3. This would imply a 4–5 per cent increase in late tissue complications.

time teff (in units of days). The consequence of this is that the expression for biological effect (E) in Equation 4.3 is modified to: E  n(αd  βd 2 )  0.693

T t eff

(4.7)

To express this in terms of BED, it is necessary to divide E by α, as occurred in the derivation of Equation 4.4, i.e.: ⎡ d ⎤⎥ T BED  nd ⎢1   0.693 ⎢ ⎥ α / β α t eff ⎣ ⎦

(4.8)

62 Mathematical modelling and its application in oncology

If the subtractive repopulation factor in Equation 4.8 is simply referred to as RF, the aide-memoir for calculating BED [Equation 4.5] is then changed to: BED  TD RE  RF

detectable.9 To allow for this, a simple time time-delay factor (TK can be incorporated into the LQ equations, i.e. Equation 4.8 becomes: ⎡ (T  TK ) d ⎤⎥ BED  nd ⎢1   0.693 ⎢ ⎥ α / β αt eff ⎣ ⎦

(4.9)

where RF (units of Gy) is a measure of the biological dose ‘wasted’ in combating repopulation. It will be noted from Equation 4.8 that inclusion of an allowance for repopulation in the calculation of a tumour BED requires a value for α to be assumed. This potential disadvantage may be overcome by using clinically derived RF values, e.g. in head and neck squamous-cell cancers, the average daily repopulation may be equivalent to as much as 0.6 Gy/day, i.e. over a 6-week (42-day) treatment, the RF factor (i.e. the ‘wasted’ dose) is 42 0.6  25.2 Gy.

Worked example Comparison of tumour and late-normal tissue BEDs delivered by three schedules: (a) total dose of 60 Gy in 2-Gy fractions over 40 days (b) total dose of 50 Gy in 2.5-Gy fractions over 26 days (c) total dose of 52.5 Gy in 2.625-Gy fractions over 26 days. Assumed tumour parameters: α/β  10 Gy, α  0.35/Gy, teff  5 days. The assumed α/β for the normal tissue (which is assumed to receive the same dose schedule as the tumour) is 3 Gy. The results of applying Equations 4.5 and 4.8 are summarized in Table 4.2.

The table indicates how biological effects are governed by dose per fraction, treatment duration and total dose. Particularly noteworthy is the fact that schedules (a) and (c) are nearly identical in terms of their effects on both tumour and late-responding tissue, yet the total dose delivered in the latter schedule is 7.5 Gy (12.5 per cent) less than in the former.

Delayed repopulation For some tumours (squamous-cell cancers), there is an apparent time delay before significant repopulation is

and can be simplified as: ⎡ d ⎤⎥ BED  nd ⎢1   K (T  TK ) ⎢ α /β ⎥⎦ ⎣

(a) 60 Gy/30 fractions/40 days (b) 50 Gy/20 fractions/26 days (c) 52.5 Gy/20 fractions/26 days

(4.11)

where K is now the required dose equivalent of repopulation per day (units of BED Grays per day). Clearly the repopulation factor in Equation 4.11 is only required in cases where TK is less than T. TK values of 21–28 days are often recommended, although 21 days is probably most appropriate, as there is evidence of a time effect for tumour control beyond 3 weeks. For times that are less than TK, used in hypofractionated schedules, we advise that a smaller value of K be used, e.g. around 0.1–0.2 Gy10 per day. This is because it is more realistic to assume a slow rate of repopulation at short treatment times than to assume that there is no repopulation at all. The above considerations have also been applied to considering the implications of on-going tumour proliferation on overall tumour cure probability when there are delays in the initiation of treatment.10

Loss of control with extended treatment time: the effect of unscheduled treatment interruptions Tumour repopulation during treatment effectively wastes a significant amount of the delivered dose. It follows that for rapidly growing tumours, the presence of unintended gaps in the treatment schedule will have the effect of wasting even more dose. It has been estimated that for head and neck tumours, the loss of control amounts to 1–2 per cent per day of treatment extension.11 However, this figure is from data sets that included a wide range of parameter variations within the treated population and may seriously

Table 4.2 The results of applying equations 4.5 and 4.8.

Schedule

(4.10)

Tumour BED (Gy10) [via Equation 5.8]

Normal tissue BED (Gy3) [via Equation 5.5]

72.0  15.8  56.2 62.5  10.3  52.2 66.3  10.3  56.0

100.0 91.7 98.4

The basis and routine application of radiobiological models 63

underestimate the loss of control in individual patients. Tumour loss of control with increasing time depends on the expected tumour cure probability (TCP) and is most significant when the TCP is in the middle range, for example between 30 per cent and 60 per cent. In such situations, the values may be as high as 5 per cent per day for individuals. The potential seriousness of unscheduled gaps in treatment is such that the Royal College of Radiologists (RCR) has issued guidelines on how to deal with the issue.12,13 There are many technical, clinical and social reasons why individual patients might miss one or more fractions during a treatment course. It is important to appreciate that the treatment gap is less of a problem if the prescribed treatment can still be completed within the originally stipulated treatment time. More significant radiobiological problems arise if it is necessary to extend the overall treatment time, as may be the case for gaps occurring late during the treatment. There are essentially three methods that may be employed to offset the effects of an unscheduled treatment gap once it has occurred.14 1. Maintain the original prescription time by treating the ‘missing’ fractions at weekends and using the prescribed dose per fraction. 2. Maintain the original prescription time by employing twice-daily fractionation (using the prescribed dose per fraction) with a minimum of 6-hour intervals between daily fractions. 3. Devise a radiobiological compensation employing altered fractional doses. Methods 1 and 2 (either individually or in combination) are the preferred options, as they maintain the number of fractions and dose per fraction as originally prescribed. However, if the unscheduled gap occurs late in the schedule, it can be impossible to provide dose compensation without increasing the treatment time, so method 3 is used.

Worked example A patient prescribed a schedule of 66 Gy in 33 fractions over 6.5 weeks misses the whole of the second week of treatment (five fractions). How can this unscheduled gap be compensated for? Answer: After the gap, i.e. at the beginning of the third week of treatment, there are still 28 fractions to be delivered. If weekend working is possible then the ‘lost’ fractions can be treated on five of the six remaining weekend days, the rest of the treatment proceeding as prescribed. If treatment cannot be performed at weekends then, on five of the remaining treatment days, two fractions per day should be delivered, with a minimum 6h gap between those particular fractions.

Worked example A patient prescribed a schedule of 70 Gy in 35 fractions over 7 weeks misses the whole of the final 2 weeks’ treatment (10 fractions). How can this unscheduled gap be compensated for? Answer: This is a much more difficult case, as it is impossible to treat the ‘lost’ fractions without overrunning the original treatment time. If it is not possible to treat at weekends, then, in order to restrict the ‘over-run’ as much as possible, the only viable possibility is to treat twice daily on 5 days after the unscheduled break, taking the overall treatment time to 8 weeks (53 days). If the dose-equivalent of daily repopulation is 0.85 Gy per day and is operational after 25 days, the generic BEDs expected from the treatment as prescribed are: ⎡ 2⎤ BEDtumour  70 ⎢1 ⎥  0.85 (46  25) ⎢⎣ 10 ⎥⎦  66.2 Gy10 ⎡ 2⎤ BEDlate  70 ⎢1 ⎥  116.7 Gy 3 ⎢⎣ 3 ⎥⎦ The extra dose required to offset the repopulation in the 1-week extension of treatment time is 7 0.85  5.95 Gy, and this is the amount by which the tumour BED will be reduced if no compensation is made, i.e. BED10 will be 60.2 Gy10 rather than the expected 66.2 Gy10. Increasing the dose per fraction can restore the BED10, but at the cost of a BED3 that is greater than that prescribed. Delivery of more than 10 fractions, with a view to decrease dose per fraction, is a possible solution, but this extends treatment into the ninth week, which will require more dose to offset yet more repopulation. This is the essential dilemma involved in difficult cases, and the inevitable result is that there must be some compromise to the therapeutic ratio. The prescribed late BED can only be respected at the cost of a reduced tumour BED; achievement of a tumour BED that is close to that expected from the uninterrupted treatment can only be attained with some increase in the late BED. Usually it is necessary to consider several possible scenarios in order to identify the most acceptable compromise. For example, if we allow the late BED to increase by around, say, 3.5 Gy3, then if we give the remainder of the treatment in accelerated form using 12 b.i.d. fractions over 6 days (assuming that treatment can be completed on a Saturday), we find the late BED given at the time of interruption  50(1  2/3)  83.3 Gy3. To deliver a late BED of 116.7  3.5  120.2 Gy3, the remaining BED is 120.2  83.3  36.9 Gy3, and to find the

64 Mathematical modelling and its application in oncology

requisite dose per fraction (d ) to deliver this, we solve for d in: ⎛ d⎞ 12d ⎜⎜1  ⎟⎟⎟  36.9 , so that d  1.89 Gy. ⎜⎝ 3 ⎟⎠ The tumour BED for the entire course if completed in 54 days will then be 50(1  2/10)  1.89 12(1  1.89/10)  0.85(54  25)  62.3 Gy10. This is 66.2  62.3  3.9 Gy10 less than the original prescription. The alternative approach would be to calculate the full compensatory dose required to maintain equal tumour control but allow normal-tissue side effects to increase (the reader is left to calculate these). The patient may also have views on which is the best alternative. It must be remembered that normal-tissue dose–effect increment slopes are usually of the order of 1–3 per cent per Gy.

Worked example A treatment prescription for 60 Gy in 30 fractions includes the optic chiasm. Suppose there is an air cavity inhomogeneity that results in an 8 per cent increase in dose across a region of interest in the brain. What does this dose increase imply? For an α/β ratio of 2 Gy (applicable to the optic chiasm, a fractionation-sensitive structure), the prescribed BED is: ⎡ 2⎤ 60 ⎢1  ⎥  120 Gy2 ⎢⎣ 2 ⎥⎦

Because of the 8 per cent increase, the fractional dose is 2 1.08  2.16 Gy, instead of the prescribed 2 Gy. Over 30 fractions, the total dose will be 30 2.16  64.8 Gy. The true BED is then: ⎡ 2.16 ⎤ ⎥  134.8 Gy2 64.8 ⎢1  ⎢⎣ 2 ⎥⎦

Methods of presenting modelling results: the equivalent dose delivered in 2 Gy fractions Several methods exist for presenting the results of modelling assessments, e.g. comparison of BED values or their derived TCPs or normal-tissue complication probabilities (NTCPs). The results for routine clinical application can be summarized in a form that relates to the prescribing practice of the radiation oncologist. It is possible to stipulate any treatment in terms of a 2 Gy/fraction equivalent. This concept is easy for most clinicians: the calculated equivalent dose can be related to previous clinical experience of treating with 2 Gy fractions to form a judgement of both tumour control and normal-tissue complication risk.

Thus, although the dose increase is 8 per cent, the resultant increase in BED2 is 134.8  120  14.8 Gy2. What does this mean in clinical terms? This can be assessed by calculating how many 2 Gy fractions would give a similar increase in BED. To find the equivalent total dose given in n 2 Gy fractions, we solve for total dose D as if 2 Gy fractions had been given to the increased BED of 134.8 Gy2: ⎛ 2⎞ BED  134.78  D ⎜⎜1  ⎟⎟⎟ ⎜⎝ 2 ⎟⎠ from which D  67.4 Gy, the equivalent dose if given in 2-Gy fractions.

Brachytherapy For high-dose-rate brachytherapy, the LQ equations are essentially the same as those required for teletherapy. For low-dose-rate or medium-dose-rate continuous treatments, the delivery of a radiation dose is protracted such that it takes more than a few minutes, and thus there is an opportunity for sub-lethally damaged cells to repair during treatment delivery. The amount of lethal damage caused by interaction between sub-lethally damaged entities is thus reduced due to a smaller amount of Type B (βmediated) lethal damage than occurs in acute radiation delivery. For a given dose, the overall treatment time is determined by the dose rate, and the Type B damage calculation must include an allowance for this, together with the repair rate of sub-lethal damage. Type A damage, because it is caused only by instantaneous lethal events, is unaffected

by extension in irradiation time and is therefore independent of dose rate. A realistic radiobiological assessment of brachytherapy applications is always more difficult than in the case of teletherapy, principally because of the non-homogeneous doses and the rapid fall of dose with distance from the source(s).15 In particular it should be remembered that the critical normal tissue might receive a lower dose than that prescribed to the tumour, and this should be allowed for in the calculation of the normal-tissue BED. Also, the dose gradients within any tissue that contains sources causes the effective BED to that tissue volume to be higher than that calculated at the reference iso-dose surface. This point is returned to later in the chapter.

The basis and routine application of radiobiological models 65

be summed to obtain a measure of the total biological effect, i.e.:

BED calculations in brachytherapy For fractionated high-dose-rate (FHDR) brachytherapy, the BED is calculated using Equation 4.4 or 4.8, the latter being required in cases in which it is necessary to include an allowance for tumour repopulation. For continuous low-dose-rate (CLDR) brachytherapy, the required equation is: ⎡ 2 R ⎤⎥ BED  RT ⎢1  ⎢ μ(α /β) ⎥⎦ ⎣

(4.12)

where R is the dose rate (Gy/hour), T (hours) the duration of brachytherapy, and μ the DNA sub-lethal damage repair rate constant, related to the repair half-life via: μ

0.693 T1/ 2

Equation 4.12 is a simplified form of a more complex equation,3 but is nevertheless reliable in most cases where the CLDR treatment time is greater than about 12 hours. For shorter exposures, the longer equation should be used. In cases in which brachytherapy is combined with teletherapy the individual BEDs for each component may

Worked example A CLDR gynaecological treatment delivers 40 Gy in 48 hours to Point A. If an FHDR treatment involving six fractions is to be used instead, what total dose is required in order to maintain the normal tissue iso-effect? For α/β of 3 Gy and repair half-life of 1.5 hours, i.e. μ  0.693/1.5  0.46/hour. The dose rate (R) at Point A is 40/48  0.83 Gy/h. Therefore, from Equation 4.11:

BED (total)  BED (external beam)  BED (brachytherapy) (4.13)

Worked example A pelvic teletherapy regime of 45 Gy/25 fractions is combined with an FHDR brachytherapy regime of 2 7 Gy prescribed to Point A. The bladder and rectum each receive 100 per cent of both the teletherapy dose and the brachytherapy dose. What is the BED for the bladder/rectum, assuming an α/β value of 3 Gy? ⎡ ⎡ 1.8 ⎤ 7⎤ ⎥  14 ⎢1  ⎥  118.7 Gy 3 BED  45 ⎢1  ⎢⎣ ⎥ ⎢ 3 ⎦ 3 ⎥⎦ ⎣ If geometrical sparing of the bladder/rectum during brachytherapy achieves 80 per cent of the prescribed Point A dose, what is the new BED in these tissues? ⎡ ⎡ 1.8 ⎤ 7 0.8 ⎤ ⎥  14 0.8 ⎢1  ⎥ BED  45 ⎢1  ⎢⎣ ⎥ ⎢ 3 ⎦ 3 ⎥⎦ ⎣  104 .1 Gy 3 In general, the severe side effects associated with pelvic radiotherapy manifest after BED values that significantly exceed 110 Gy3. This example therefore demonstrates how, in principle, a modest reduction of the brachytherapy dose and dose per fraction to the critical organ can bring about a reduction in the likelihood of serious toxicity.

⎡ 2 0.83 ⎤ ⎥  88.1 Gy 3 BED3  40 ⎢1  ⎢⎣ 0.46 3 ⎥⎦ To match this BED value with six FHDR fractions requires a dose per fraction of d Gy, where: ⎡ d⎤ 6 d ⎢1  ⎥  88.1 ⎢⎣ 3 ⎥⎦ i.e.: 2d2  6d  264.3  0 i.e. the required dose per fraction (d) is 5.3 Gy.

Amelioration of an incorrectly delivered radiotherapy treatment It is sometimes said that no amount of radiobiological manipulation will correct a treatment that is incorrectly prescribed or executed. Whilst this is correct in cases involving a geometrical miss or significant over/under-dosing, there are occasions when changes in time–dose-fractionation may significantly ameliorate the potential damage, although it may be necessary to accept a reduction in control probability if total dosage has to be reduced. The problem is essentially one of obtaining the best benefit: risk ratio in a particular set of circumstances.

66 Mathematical modelling and its application in oncology

Worked example During the first four fractions of a treatment, a 30 per cent overdose to the spinal cord occurred due to the use of an incorrect wedge filter. The prescribed cord dose was 46 Gy in 23 fractions. How can the overdose be corrected over the remaining treatment course if it is decided to complete the treatment in a further 20 fractions rather than 19? The spinal cord α/β is assumed to be 2 Gy. The intended spinal cord BED was to be: ⎡ 2⎤ 46 ⎢1  ⎥  92 Gy 2 ⎢⎣ 2 ⎥⎦ In the first four fractions, the BED actually delivered is: ⎡ 2 1.3 ⎤ ⎥  23.9Gy2 4 2 1.3 ⎢1  ⎢⎣ 2 ⎥⎦ The remainder of the treatment course should give a BED2 and not exceed 92.0  23.9  68.1 Gy2. For a further 20 fractions, allowing one extra fraction to be given beyond that originally prescribed, the required dose per fraction (d ) is given by the solution of d in: ⎡ d⎤ 20 d ⎢1  ⎥  68.1 ⎢⎣ 2 ⎥⎦ from which d  1.79 Gy. It is therefore decided to give 20 fractions of 1.79 Gy. If the tumour receives the same dose as the spinal cord and possesses an α/β value of 15 Gy, how is the tumour BED affected by the change to the schedule? The prescribed tumour BED was: ⎡ 2⎤ 46 ⎢1  ⎥  52.1 Gy15 ⎢⎣ 15 ⎥⎦

The addition of conventional external-beam and focal methods Worked example A patient is treated to a tolerance dose equivalent to 70 Gy in 35 fractions to a small volume by: 1. initial wide-field radiotherapy to 40 Gy in 22 fractions followed by 2. reduced field sizes to a further 16 Gy in eight fractions and then 3. focal radiotherapy given in four fractions. Calculate the dose per fraction of the focal therapy (assume α/β  2 Gy). The total BED will be: ⎡ 2⎤ 70 ⎢1  ⎥  140 Gy2 ⎢⎣ 2 ⎥⎦ We know that the following condition must hold: BEDphase1  BEDphase2  BEDphase3  140 Gy2 So that: i.e.: ⎡ ⎡ ⎡ 1 .8 ⎤ 2⎤ d⎤ ⎥  16 ⎢1  ⎥  4 d ⎢1  ⎥  140 40 ⎢1  ⎢⎣ ⎥ ⎢ ⎥ ⎢ 2 ⎦ 2⎦ 2 ⎥⎦ ⎣ ⎣ d2  2d  15.8 76  32  4d  2d2  140 d  3.1 Gy. The above equations and examples are sufficient for most practical clinical problems.

whereas the true value will be: ⎡ ⎡ 2 1 .3 ⎤ 1 .79 ⎤ ⎥  20 1 .79 ⎢1  ⎥ 4 2 1 .3 ⎢1  ⎢⎣ ⎢⎣ 15 ⎥⎦ 15 ⎥⎦  52.3 Gy15

which is scarcely different from that prescribed. However, an extra fraction would have involved an extra treatment day, with possible loss of tumour control, depending on the operative tumour repopulation dose equivalent per day. Thus, the treatment error has been effectively overcome by the altered fractionation and use of a lower – more forgiving – dose per fraction.

MORE ADVANCED CONSIDERATIONS The discussion and examples have so far focused on what might be called general modelling: the parameters used are intrinsically assumed to apply throughout individual tumour volumes and throughout whole patient populations. For example, use of the radiosensitivity factor α assumes a uniform radiosensitivity throughout the tumour, i.e. in hypoxic and oxic zones, and is also inclusive of clones that show variation in intrinsic radiosensitivity. Likewise, the Teff value is generalized, being a one-figure representation of a more complex pattern of repopulation

More advanced considerations 67

throughout very heterogeneous tumours. Even the ubiquitous α/β ratios are averages, which probably incorporate the effects of multiple radiobiological processes such as reoxygenation (in the case of tumours), cell-cycle redistribution and repopulation. Thus, although the LQ model has a sound individual biophysical basis, the variations inherent in the critical parameters place a limit on how accurate modelling can be in individual cases. The alternative approach is to attempt to model the processes in greater detail whilst accepting the associated drawback that multiple parameter assumptions are necessary. Some more advanced approaches are briefly discussed below.

If the number (C) of clonogenic cells is known, the Poisson model may be used to estimate TCP: (4.14)

The slope of the dose response generated by the Poisson distribution (i.e. TCP plotted against BED or total dose) is much steeper than found in data sets obtained from large numbers of patients. This is to be expected because, as the Poisson distribution reflects the probability of achieving a cure from the elimination of all cells in a single tumour, it is essentially useful only for individual tumours. The alternative logistic function is applicable to population data and has a less steep dose–response curve.

⎡ 2⎤ BED  60 ⎢1  ⎥  0.5 39  52.5 Gy10 ⎢⎣ 10 ⎥⎦

TCP  exp[108 exp(0 .35 52 .5)]  0 .35(35 %)

If the tumour is treated without weekend breaks, i.e. is treated with 2 Gy fractions on 7 days of each week, the overall time falls to 29 days. The BED then increases to: ⎡ 2⎤ BED  60 ⎢1  ⎥  0.5 29  57.5 Gy10 ⎢⎣ 10 ⎥⎦ For this BED, the associated TCP is:

TCP  exp[108 exp(0 .35 57 .5)]  0 .83 (83 %)

Optimization Clinically effective radiotherapy requires a balance to be maintained between several potentially conflicting requirements. For example, use of small fractional doses is more likely to minimize NTCP, but this may require the use of so many fractions that treatment time is greatly extended, thereby allowing more tumour repopulation, and thus a reduced TCP. As the LQ model includes these effects, the model can be extended to identify schedules that are optimized for a given set of circumstances. By consideration of how tumour cell kill varies with changes in dose per fraction, overall time and the mean inter-fraction interval (f ), calculus may be used to derive an optimum dose per fraction that maximizes the TCP whilst respecting any given normal-tissue effect.15–17 Essentially, the optimum tumour dose per fraction (z) is given by the solution for z of: ⎞ ⎛ ⎜⎜ g  LATE (α /β) ⎟⎟ ⋅ z 2  2 ⋅ f ⋅ g ⋅ k ⋅ z  ⎟⎟ ⎜⎜ ⎝ TUM (α /β) ⎠ LATE (α /β) ⋅ f ⋅ k  0

A particular tumour has a dose equivalent of repopulation of 0.5 Gy/day and consists of 108 clonogens. It is treated with 60 Gy/30 fractions over 6 weeks (39 days). What is the expected TCP? (Assume α/β  10 Gy.) The repopulation dose equivalent is subtracted from the given BED:

In order to calculate TCP from Equation 4.12 it is necessary to assume a value for α. If this is taken to be 0.35/Gy:

Estimation of tumour cure probabilities from BEDs

TCP  exp[Cexp(αBED)]

Worked example

(4.15)

This example clearly demonstrates how overall treatment time can have a strong influence on TCP in individual patients.

where g is the normal-tissue sparing factor such that d  gz, where d is the dose per fraction actually received by the normal tissue and K is the tumour repopulation factor. The suffixes LATE and TUM apply to the α/β ratios of late-reacting normal tissues and tumour respectively. The term f is the mean inter-fraction interval (days), which is approximated by seven days divided by the number of treatments given per week. Where there is a delayed onset to the initiation of tumour repopulation during treatment, it may be necessary to use non-analytical, reiterative techniques to determine the optimum fraction size.18 In conjunction with accurate predictive assays, or with better information as to the averaged values of the key parameters during radiotherapy for specific cancers,

68 Mathematical modelling and its application in oncology

Estimate the optimum fraction size for treating a tumour with average repopulation rate during treatment of 0.5 Gy/day, assuming treatment is to be given five times per week and the critical normal tissue receives 80 per cent of the full dose. Assume α/β  10 Gy (tumour) and 3 Gy (normal tissue). In this case, f  7/5  1.4 and g  0.8. Using Equation 4.15, optimum dose per fraction  ( 0.8 3/10)z 2  2 1.4 0.8 0.5 z  3 1.4 0.5. The solution for z is 3.46 Gy per fraction. This is the fractional dose to be prescribed to the tumour; the normal tissue would receive 3.46 0.8  2.77 Gy per fraction. In this case the model is predicting the use of a relatively large fraction size and this is therefore an example of where the decision over whether to use that or a reduced value needs to be additionally guided by clinical experience.

the developments described could be an important step towards ‘tailored’ radiotherapy.

Incorporation of cell-loss factors An alternative explanation for the apparent appearance of delayed acceleration is that tumour repopulation rates are initially slow but may progressively increase during the course of treatment. When analysing the effect in a range of data sets, such a phenomenon could easily be mistaken for a two-component process (Fig. 4.1). An explanation for an asymptotically increasing repopulation rate may be developed from consideration of the role of the potential doubling time (Tpot) and the cell-loss factor θ, which is the probability that newly born cells will die due to causes such as hypoxia and insufficiency of nutrients and growth factors. The cell-loss factor is likely to decrease during radiotherapy due to improved tumour microvascular perfusion. The probability that newborn cells will survive can be represented by 1  θ, and this term can be used for BED assessments when there is a slow exponential reduction in θ (at a rate constant v) due to improved blood perfusion during treatment.19 Relatively rapid changes in cell-loss factor are then effectively followed by a delayed elevation in repopulation rate. The formulation is applicable at any time duration, including ultra-short schedules.

The problem with closely spaced fractions The delivery of an acute dose of radiation results in the creation of both lethal and sublethal damage. By definition, the lethal damage is unrepairable, but the sub-lethal damage component is able to repair pseudo-exponentially with

Clonogen repopulation rate

Worked example

Treatment duration

Figure 4.1 A schematic representation demonstrating how a continuously increasing repopulation process (solid line) can be mistakenly interpreted as a two-component linear process with accelerated repopulation beginning part-way through treatment (dashed line).

a repair half-time typically in the range 0.5–3 hours. When the fractional doses are well spaced (e.g. as 24-hour gaps), the residual sublethal damage after any particular fraction is effectively fully repaired before delivery of the next fraction. If the fractions are delivered at much closer intervals, any unrepaired sublethal damage remaining after any one fraction can be compounded to extra lethal damage by fractions delivered later in the schedule. The amount of extra damage created depends on several factors, but the inter-fraction intervals and the repair rates are of prime importance and, within the LQ formulation, the extra damage due to closely spaced fractions appears in the form of a modified β term in Equation 4.2. Any increased damage due to this effect is obviously beneficial in a tumour, but will be of major concern if it occurs in a critical normal tissue. The equations for dealing with closely spaced fractions are complex, but, using published tables,1,5 a simpler alternative may be used. The tables provide tabulated values of an incomplete-repair factor, hM, which allows for different numbers of treatments per day, repair half-times and inter-fraction intervals. When hM is incorporated into the basic BED equation, the latter is modified to: ⎡ d(1  hM ) ⎤ ⎥ BED  nd ⎢1  ⎢ α /β ⎥⎦ ⎣

(4.16)

More advanced considerations 69

Worked example A dose of 60 Gy is to be delivered in 30 fractions (2 Gy per fraction) over 10 consecutive days by treating three fractions per day at 4-hour intervals. Assuming T1/2  1.5 hours and α/β  3 Gy, what is the lateresponding BED? From Table 6.3 of Thames and Hendry (1987),1 hM  0.2265. Therefore, from Equation 4.16: ⎡ 2 (1  0.2265) ⎤ ⎥  109.1 Gy 3 BED  30 2 ⎢1  ⎢⎣ ⎥⎦ 3 The BED3 for 60 Gy delivered as daily fractionation is 100 Gy3. Therefore three fractions per day increases this figure by approximately 9 per cent.

New repair models Most radiobiological models assume that sublethal damage repair is a mono-exponential or multi-exponential process, the latter being required when there is the apparent presence of separate fast and slow repair rates. Fowler (1999) suggested a different description of repair.20 In-vitro DNA repair data are consistently better fitted by assuming that the fraction of unrepaired breaks decreases in proportion to the reciprocal of the time elapsed (t) since their production, i.e. proportional to 1/(1  zt), where z is an appropriate constant. This postulation of a ‘reciprocal-time’ pattern of repair is consistent with the view that there is total saturation of repair enzymes at clinically relevant doses. The practical advantage is that the observed presence of separate components of fast and slow repair in some cell lines can be covered by an equation involving only one rate constant (z), rather than several exponential rate constants. The reciprocal-time model may be incorporated into the LQ model,21 where it predicts the breakdown in tissue tolerance when the central nervous system is irradiated by three fractions per day. This is in contrast with monoexponential models of repair, which cannot satisfactorily explain the clinical problems observed in the early continuous hyper-fractionated and accelerated radiotherapy CHART trials. This alternative model of repair predicts the following: ●

●

Repair in normal tissues may remain incomplete at much longer intervals of time, such as at 18–24 hours, than had previously been thought. It is only over a weekend ‘gap’ that late-reacting normaltissue repair may be complete.

●

For long exposures, as occur in low-dose-rate brachytherapy, the apparent rate of repair after irradiation appears to be slower for longer irradiation times.

Limitation in the scope of BED inter-comparisons The earlier worked examples demonstrate how the BED parameter may be used to inter-compare existing treatments or to design a new treatment that is iso-effective to an existing treatment. It is nevertheless important to appreciate that, as conventionally used, BED is a measure of radiobiological effect at one particular point within the treated volume. BED inter-comparisons thus lose much of their usefulness if they are used to compare treatments in which the geometrical details (e.g. field shapes, number of applied fields, irradiated volumes, etc.) are not held constant. Indeed, the application of LQ methodology in cases in which these conditions are not met may produce some very misleading results. This point also needs to be borne in mind when using BED calculations retrospectively to assess the results of clinical trials for which the various treatment schedules do not share common geometrical field arrangements, or where there are significant dose inhomogeneities. In such cases, the concept of a radiobiologically derived equivalent uniform dose (EUD) is of major interest.22

The particular problem caused by brachytherapy dose gradients For brachytherapy, the above observations are all the more important, principally because of the non-homogeneous doses and the rapid fall of dose with distance from the source(s).15 The full radiobiological significance of brachytherapy dose gradients is discussed elsewhere,23 from which some general guidelines have been established. In cases in which there is a continuous dose gradient from the reference (or prescription) surface (at which the dose is prescribed) to the sources, as occurs in most gynaecological treatments and line-source applications, the effective BED throughout the volume enclosed by that surface can be derived using tabulated multiplying factors (MFs). The BED at the surface is first calculated using the simple equations outlined above and then corrected by an MF appropriate to the particular treatment set-up. In the case of an FHDR brachytherapy application, the MF value will be mostly dependent on the number of fractions and the dose per fraction, but only marginally so on the radiobiological factors (α, α/β, etc.). The treatment geometry (e.g. line source, point source) also has little influence. For CLDR applications, the MFs are mostly influenced by total dose and dose rate.

70 Mathematical modelling and its application in oncology

Worked example An FHDR gynaecological treatment involves delivering 6 5 Gy to Point A. What is the effective BED to the tissues within the iso-dose surface that contains Point A? First, the BED3 is calculated in the usual manner: ⎡ 5⎤ BED3  6 5 ⎢1  ⎥  80 Gy 3 ⎢⎣ 3 ⎥⎦

Inter-comparison of treatment alternatives on the basis of their net costs

From the table look-up data given by Dale et al. (1997) (21a), the appropriate MF value for this particular combination of dose per fraction and fraction number is 1.185. Therefore the true effective BED throughout the enclosed volume is 80 1.185  94.8 Gy3.

Tumour volume changes during radiotherapy Tumour regression generally follows a negative exponential function. In such cases, if V0 and Vt are the tumour volumes at times 0 and t respectively: Vt  V0 ezt

treatment volume are often modelled empirically using clinical dose–response data of limited usefulness. The result is that most of the existing NTCP models have little biological basis; thus the use of simpler BED iso-effect calculations backed by clinical judgement remains reasonable until better predictive models are found.

(4.17)

where z is the regression rate coefficient. Consequently, if the regression rate is accurately measured, one can predict the volume at a future time point. This information may be used to plan additional treatment, such as conformal therapy, where the reduced volume allows a higher radiation dose to be delivered.

Worked example Serial imaging during the first part of a course of radiotherapy shows that a tumour, originally of volume 95 cm3, has a volume regression rate of 3 per cent per day. Estimate the volume of tumour 28 days after completion of a 35-day course of treatment. From Equation 4.17: Vt  95 ⋅ e 0.03 63  14.4 cm3

The volume effect and difficulties in relation to normal tissues Whilst it is clinically well established that large volumes of normal tissue will tolerate less radiation than small volumes (the so-called volume effect), accurate modelling of the effect is a difficult and controversial issue. The volume effect is strongly influenced by variations in tissue physiology and anatomical location, yet attempts at formulating the phenomenon tend to concentrate almost exclusively on physical and radiobiological considerations. A further difficulty is that the changes in radiation tolerance with

The net costs of treatment can be estimated by inclusion of the fixed costs (treatment planning, treatment delivery, etc.) together with the notional costs associated with treatment failure. The former costs can take account of the treatment complexity, whilst the latter are based on the cost of additional medical/surgical care in the event of failure to control the primary tumour. For a given set of radiobiological parameters, cost-optimized treatments will often differ from radiobiologically optimized treatments, this being especially true of those more complex treatments that offer relatively small gains in TCP. Such modelling may have a useful role to play in identifying the situations in which the more complicated (and hence more costly) methods of treatment can be most effectively employed.24

Radiotherapy combined with chemotherapy, surgery and other molecular-based treatments For concomitant chemo-radiotherapy or the use of chemotherapy in close temporal approximation to radiotherapy, the equivalent BED of the chemotherapy can be estimated from some clinical data sets, particularly from randomized control trials.25 For normal-tissue sensitization, similar concepts apply.26 The distinction between cytotoxic and cytostatic adjuvant therapies can also be accommodated in calculations that estimate the changes in TCP by the use of adjuvant therapies.27 Pure dose sensitization of the radiotherapy is another method, whereby the dose per fraction is enhanced by factor s, which is 1.06 for the effect of the widely used CMF (cyclophosphamide, methotrexate and 5-fluorouracil) chemotherapy regime, in causing subcutaneous fibrosis in breast cancer and is equivalent to a BED3 value of approximately 6.5 Gy3 extra dose; the effect of age in increasing shoulder fibrosis after breast and gland field radiotherapy is approximately 3.6 Gy3, and when laparotomy is used in intra-abdominal lymphoma, the subsequent bowel radiation tolerance is reduced by approximately 17.7 Gy3. There are also several literature discussions on how to model gene and other novel molecular-based therapies in association with radiotherapy.27–32

Palliative radiotherapy In principle, radiation-induced growth delay is amenable to BED quantification, providing the α/β and repopulation

More advanced considerations 71

dose equivalents (K) are known for a particular tumour type. Interestingly, the average K values can also be derived from re-growth delay times. For example, if a slow-growing adenocarcinoma (α/β  4 Gy assumed) has recurred to its previous dimensions with recurrence of symptoms following a remission period of 300 days after 20 Gy in five fractions was given, for restoration of the original tumour volume, the given BED should equate with the total BED equivalent of repopulation over the observed re-growth time (TR), i.e. the average K value is determined from: ⎛ 4⎞ 20 ⎜⎜1  ⎟⎟⎟  KTR ⎜⎝ 4 ⎟⎠ i.e. K

40  0.13 Gy 4 per day. 300

⎡ RBE 2 ⎢ MIN .d BED  D ⎢ RBE MAX  α /β ⎢ ⎣⎢

Serum tumour markers The serum marker concentration is assumed to reflect the total number of cells present, and although marker levels fall during or after therapy, the absolute levels during a period of such change do not reflect the absolute number of cells. If the half-life (T1/2) of the marker is known, the tumour marker production rate (TMP), which will better represent the absolute number of cells, can be calculated as in the equation of Price (1989):33 TMP  C2  C1 ⋅ e



0.693(t 2 t1 ) T1/ 2

(4.18)

where C1 and C2 are the marker concentrations at times t1 and t2 respectively.

Worked example Consider a pre-treatment situation in which the marker is slowly rising, so that in 14 days the level changes from 95 units to 100 units, and T1/2 is 12 hours (0.5 days). From Equation 4.18, the average TMP, expressed as units per day, in this period is: TMP  100  95 ⋅ e



0.693(14 ) 0.5

 100  0  100 day1

Now, if in a 2-day interval near to the completion of radiotherapy the levels fall from 75 to 60 units, the new marker production rate falls to: TMP  60  75 ⋅ e



0.693(2) 0.5

particles or ions (e.g. protons and carbon ions). The increased biological effects of high-LET radiations are found mainly at the Bragg peaks and have usually been quantified as a relative biological effect (RBE), where, RBE  doseLOW/doseHIGH, where LOW and HIGH refer to the radiation LET quality. Experimental studies in vitro and in vivo have confirmed that there is an inverse relationship between RBE and dose per fraction in the case of radiations with high LET, although the effect is difficult to find in proton beam experiments since the RBE is relatively small, being of the order of 1.1. For neutrons, and ions, larger RBEs are operative and here the BED equations can be modified to account for the very high RBEs of around 8 (the RBEMAX) at very low dose to values of 1–1.3 at very high doses per fraction (the RBEMIN). It can be shown that:34

 60  4.69  55 .3 day1

High linear energy transfer radiations There is increasing clinical interest in high linear energy transfer (LET) radiations delivered by high-energy atomic

⎤ ⎥ ⎥ ⎥ ⎥⎦

(4.19)

It must be noted that the α/β used is that of the low LET, and the RBE factors essentially convert this to the fraction sensitivity of the high-LET radiation.35 The use of this equation allows the overall RBE, when high-LET and low-LET radiations are inter-compared, to vary between its maximum and minimum values. This then avoids underestimation of dose at low dose per fraction and overestimation of dose at high dose per fraction in comparison to the use of a fixed RBE, which is the present international method. A comparison of the two methods is shown in Figure 4.2.

Worked example A carbon-ion beam delivers a physical dose of 12 Gy to a small squamous-cell cancer. What would be the true equivalent dose using X-rays (RBE  1) assuming that, for the carbon ions, RBEMAX  8 and RBEMIN  1.2? From Equation 4.19, this physical dose would deliver a tumour BED of: 12

8  (1.22 12)  116.7 Gy10 10

The equivalent single dose (d) of X-rays required to provide the same BED is given as the solution for d in: d

1 d  116.7 10

the solution for which is d  29.53 Gy.

It can also be shown that low-LET repopulation factors can be used with the above equation.36 Essentially, the dosecorrection factor for compensation for missed treatments for high-LET radiation is close to K (the low-LET dose equivalent repopulation factor) divided by RBEmax.

72 Mathematical modelling and its application in oncology

RBEmax8, RBEmin1.25, Generic RBE3

Relative biological effect

10 Variable RBE

8

Generic RBE

6 4 2

2.5

5

7.5

10

12.5

15

17.5

20

High LET physical dose per #(Gy)

Figure 4.2 Relationship between RBD and dose per fraction of a high LET radiation using Eq. (18). It can be seen that use of a fixed (generic) RBE value of 3 will underestimate the RBE at low dose per fraction and overestimate the RBE at high dose per fraction.

Relative biological effects may also be highly significant in the biological dosimetry of radionuclides used for permanent implant brachytherapy and for targeted radiotherapy.37,38 In such cases, the enhancing effect of using a high-LET radionuclide needs to be assessed alongside a number of other significant physical and biological considerations (radionuclide half-life, biological half-life, shrinkage rates, repopulation rates, etc.), and the associated methodology may become complex.39–42

Commercial software packages for radiobiological bio-effect planning Despite the advances in radiobiological understanding, treatment planning in radiotherapy continues to be based on the computation and assessment of physical dose distributions. Where radiobiological features are available on commercial systems, two approaches have been adopted. The first is to transform physical dose distribution to a BED distribution, a method that, in principle, allows the biological effects of various radiation treatments, e.g. external-beam therapy and brachytherapy, to be graphically added. The second approach is to produce estimates of TCP and NTCP in specific volumes of interest. The TCP calculations are based on clonogenic cell survival and may take into account non-uniform dose delivery. The NTCP calculations are based on models of normaltissue functional organization in which the sub-units are not regarded as independent for response purposes. Despite the growing acceptance of the potential importance of bio-effect planning, progress in this area remains slow because of difficulties in identifying user requirements, limitations of the models (particularly in relation to normal-tissue biology) and concerns relating to the clinical interpretation of results.

CONCLUSION Radiobiological models can provide a useful complement to clinical judgement in a variety of circumstances. In the

routine practice of radiotherapy there are many situations (e.g. geometrical difficulties, dosimetric errors, treatment interruptions, etc.) in which modelling can allow compensatory treatment schedules to be estimated. With the necessary caveats already mentioned, modelling can often guide or inform clinical judgement by means of ranking a series of alternative treatments in order to reject the less satisfactory options. For radiation oncologists in training, familiarity with the simpler methods of quantifying radiobiological effect should not be underestimated, because even the simplest radiobiological estimates can provide a useful assessment of disparate treatments. In research and development, quantitative appraisal of proposed new techniques or clinical trials should always be the subject of a modelling review. Similarly, in order to allow quantitative comparisons between new and existing treatment schedules, all published works should record at least the generic BEDs associated with the reported treatments. Technological developments presently abound in radiation oncology. However, whilst some technological advances (e.g. the ability to reduce irradiated normal-tissue volumes through the use of conformal techniques) provide seemingly obvious benefits, the full potential of modern radiotherapy will be realized only if commensurate attention is given to the radiobiological aspects that determine treatment outcome. Radiation oncology thus faces an interesting future, with radiobiological modelling providing more pivotal guidance on how to make optimal use of the emerging technology.

ACKNOWLEDGEMENT The authors wish to thank Elena Antoniou for her excellent help in updating this manuscript.

KEY LEARNING POINTS ●

●

●

●

●

●

Biological effect is not related solely to the total physical dose delivered in a radiotherapy treatment – factors such as dose per fraction and dose rate are also fundamentally important. Modern radiobiological models take account of a range of practical and radiobiological factors that are known to influence treatment outcome. Simple radiobiological assessments can provide a useful supplement to clinical judgement in a variety of ways. More advanced modelling ideas, when coupled with the results of reliable predictive assays, will allow more appropriate use of the emerging technologies. Radiobiological models already have an important role to play in the teaching and understanding of clinical radiotherapy. In order to facilitate easier comparison between clinical studies, reports and publications should routinely record the BEDs.

References 73

REFERENCES ◆1

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Thames HD, Hendry JH. Fractionation in Radiotherapy. London: Taylor and Francis,1987. Barendsen GW. Dose fractionation, dose rate and iso-effect relationships for normal tissue responses. Int J Radiat Oncol Biol Phys 1982; 8:1981–97. Dale RG. The application of the linear quadratic dose–effect equation to fractionated and protracted radiotherapy. Br J Radiol 1985; 58:515–28. Thames HD. An ‘incomplete-repair’ model for survival after fractionated and continuous irradiations Int J Radiat Biol 1985; 47:319–39. Joiner MJ, Van der Kogel AJ. The linear-quadratic approach to fractionation and calculation of isoeffect relationships. In: Steel GG (ed.) Basic Clinical Radiobiology. London: Arnold, 1997, 106–22. Fowler JF. The radiobiology of prostate cancer including new aspects of fractionated radiotherapy. Acta Oncol 2005; 44:265–76. Fowler JF. The linear quadratic formula and progress in fractionated radiotherapy. Br J Radiol 1989; 62: 679–94. Jones B, Dale RG, Deehan C, Hopkins KI, Morgan DAL. The role of biologically effective dose (BED) in clinical oncology. Clin Oncol 2001; 13:71–81. Withers HR, Taylor JMG, Maciejewski B. The hazard of accelerated tumour clonogen repopulation during radiotherapy. Acta Oncol 1988; 27:131–46. Wyatt RM, Beddoe AH, Dale RG. The effect of delays in radiotherapy treatment on tumour control. Phys Med Biol 2003; 48:139–55. Fowler JF, Lindstrom MJ. Loss of local control with prolongation in radiotherapy. Int J Radiat Oncol Biol Phys 1992; 23:457–67. Guidelines for the Management of the Unscheduled Interruption or Prolongation of a Radical Course of Radiotherapy. Document BFCO(96)4. London: Royal College of Radiologists, 1996. Guidelines for the Management of the Unscheduled Interruption or Prolongation of a Radical Course of Radiotherapy. Document BFCO(02)5. London: Royal College of Radiologists, 2002. Dale RG, Hendry JH, Jones B, Deehan C, Sinclair J, Robertson G. Practical methods for compensating for missed treatment days in radiotherapy, with particular reference to head and neck schedules. Clin Oncol 2002; 14: 382–93. Dale RG, Jones B. The radiobiology of brachytherapy (Review). Br J Radiol 1998; 71:465–83. Jones B, Tan LT, Dale RG. Derivation of the optimum dose per fraction from the linear quadratic model. Br J Radiol 1995; 68:894–902. Jones B, Dale RG. Estimation of optimum dose per fraction for high-LET radiations: implications for proton radiotherapy. Int J Radiat Oncol Biol Phys 2000; 48:1549–57. Armpilia CI, Dale RG, Jones B. Determination of the optimum dose per fraction in fractionated radiotherapy

when there is delayed onset of tumour repopulation during treatment. Br J Radiol 2004; 77:765–7. 19 Jones B, Dale RG. Cell loss factors and the linear quadratic model. Radiother Oncol 1995; 37:136–9. ●20 Fowler JF. Is repair of DNA strand break damage from ionizing radiation second-order rather than first-order? A simpler explanation of apparently multiexponential repair. Radiat Res 1999; 152:124–36. 21 Dale RG, Fowler JF, Jones B. A new incomplete-repair model based on a ‘reciprocal-time’ pattern of sub-lethal damage repair. Acta Oncol 1999; 38:919–29. 21a Dale RG, Coles IP, Deehan C, O`Donoghue JA. Calculation of integrated biological response in brachytherapy. Int J Radiat Oncol Biol & Physics, 1997; 38, 633–42 ●22 Niemierko A. Reporting and analysing dose distributions: a concept of equivalent uniform dose. Med Phys 1997; 24:103–10. ●23 Dale RG, Coles IP, Deehan C, O’Donoghue JA. Calculation of integrated biological response in brachytherapy. Int J Radiat Oncol Biol Phys 1997; 38:633–42. 24 Jones B, Dale RG. Radiobiologically based assessments of the net costs of fractionated focal radiotherapy. Int J Radiat Oncol Biol Phys 1998; 41:1139–48. ●25 Jones B, Dale RG. The potential for mathematical modelling in the assessment of the radiation dose equivalent of cytotoxic chemotherapy given concomitantly with radiotherapy. Br J Radiol 2005; 78:939–44. 26 Jones B, Gaya A, Dale RG. Linear quadratic modelling of increased late normal tissue effects in special clinical situations. Int J Radiat Oncol Biol Phys 2006; (in press). ●27 Jones B, Dale RG. Inclusion of molecular biotherapies with radical radiotherapy: modelling of combined modality treatment schedules. Int J Radiat Oncol Biol Phys 1999; 45:1025–34. 28 Tucker SL, Geara FB, Peters LJ, et al. How much could the radiotherapy dose be altered for individual patients based on a predictive assay of normal tissue radiosensitivity? Radiother Oncol 1996; 38:103–14. 29 Wheldon TE, Mairs RJ, Rampling RP, Barrett A. Modelling the enhancement of fractionated radiotherapy by gene transfer to sensitize tumour cells to radiation. Radiother Oncol 1998; 48:5–13. ●30 Jones B, Dale RG. Mathematical models of tumour and normal tissue response. Acta Oncol 1999; 38:883–93. 31 Keall PJ, Lammering G, Lin PS, et al. Tumor control probability predictions for genetic radiotherapy. Int J Radiat Oncol Biol Phys 2003; 57:255–63. 32 Jones B, Cominos M, Dale RG. Application of Biological Effective Dose (BED) to estimate the duration of symptomatic relief and repopulation dose equivalent in palliative radiotherapy and chemotherapy. Int J Radiat Oncol Biol Phys 2003; 55:736–42. 33 Price PM. Individualisation of cancer treatment by predicting response to therapy. MD Thesis, University of Cambridge, 1989. 34 Carabe-Fernandez A, Dale RG, Jones B. The incorporation of the concept of minimum RBE (RBEmin) into the linearquadratic model and the potential for improved radiobiological analysis of high-LET treatments. Int J Radiat Oncol Biol Phys 2007; 83:27–39.

74 Mathematical modelling and its application in oncology

●35

36

37

38

●39

Dale RG, Jones B. The assessment of RBE effects using the concept of biologically effective dose. Int J Radiat Oncol Biol Phys 1999; 68:894–902. Jones B, Carabe-Fernandez A, Dale RG. Calculation of highLET radiotherapy dose required for compensation of overall treatment time extensions. Br J Radiol 2006; 79:245–57. Ling CC, Li WX, Anderson LL. The relative biological effectiveness of 125I and 103Pd brachytherapy sources. Int J Radiat Oncol Biol Phys 1995; 32:373–8. Dale RG. Use of the linear-quadratic radiobiological model for quantifying kidney response in targeted radiotherapy. Cancer Ther Radiopharm 2004; 19:363–70. Dale RG. Radiobiological assessment of permanent implants using tumour repopulation factors in the linear-quadratic model. Br J Radiol 1989; 62:241–4.

40 Antipas V, Dale RG, Coles IP. A theoretical investigation into the role of tumour radiosensitivity, clonogen repopulation, tumour shrinkage and radionuclide RBE in permanent brachytherapy implants of 125I and 103Pd. Phys Med Biol 2001; 46:2557–69. ●41 Armpilia CI, Dale RG, Coles IP, Jones B, Antipas V. The determination of radiobiologically optimized half-lives for radionuclides used in permanent brachytherapy implants. Int J Radiat Oncol Biol Phys 2003; 55:378–85. 42 Abou-Jaoud W, Dale RG. A theoretical radiobiological assessment of the influence of radionuclide half-life on tumour response in targeted radiotherapy when a constant kidney toxicity is maintained. Cancer Ther Radiopharm 2004; 19:308–21.

5 Principles of chemotherapy and drug development JEFFRY EVANS, MEENALI M. CHITNIS AND DENIS C. TALBOT

Basic principles Principles of treatment Drug development Classification of cytotoxic drugs, mode of action, toxicities and clinical utility

75 77 79

Drug resistance Novel anti-cancer therapies References

90 97 105

81

BASIC PRINCIPLES Chemotherapy drugs are developed for their potential to cause a greater proportion of cell death among neoplastic as opposed to normal cells. Differences exist between normal and malignant cells that result in the latter being more susceptible to anti-cancer drugs by virtue of their biological and proliferation characteristics.

Cancer cell kinetics CHARACTERISTICS OF THE TUMOUR CELL

The proliferation of tumour cells is not entirely autonomous and there is increasing evidence of local control by autocrine and paracrine factors produced by the tumour cells and the stroma. The rate of proliferation during the lifetime of a tumour is not constant. In experimental tumours in the early stages, growth is exponential and the growth fraction is high. As the tumour enlarges, the growth rate slows and the growth fraction falls. A decreased rate of growth is commonly observed for transplantable tumours in animals and probably results, in part, from decreasing tumour vascularity and cellular nutrition leading to slowing of cell proliferation, and also from cell loss due to death or differentiation. The smallest tumour that is likely to be clinically detectable (either by physical or radiological assessments) will be approximately 1 cm in diameter and will contain 108–109 tumour cells, depending on the contribution of

stroma and other elements to tumour bulk; growth of these small, clinically detectable tumours follows a Gompertzian pattern. Such a tumour will have undergone approximately 30 doublings in cell number if it is clonally derived from a single transformed cell, and will usually weigh about 1 g. Growth to a potentially lethal mass of 1 kg of tumour requires only a further 10 doublings of cell number. Thus the period of tumour growth that is clinically apparent is only a relatively short period in the total life history of a tumour, and clearly the potential exists for micro-metastases to develop before detection of the primary tumour. The effect of chemotherapy on a tumour is influenced by some of the features of its growth pattern: ●

●

●

●

Response to chemotherapy is proportional to the number of cells synthesizing DNA. The shorter the doubling time at the onset of treatment (i.e. the more rapid is tumour growth), the better the response to chemotherapy, since more cells will be synthesizing DNA. As the tumour grows, the disease becomes less easy to cure. As the tumour shrinks with treatment, the growth rate increases because of the Gompertzian growth pattern.

CELL CYCLE

All proliferating cells go through a series of events that comprise the cell cycle. The division of the cell cycle into

76 Principles of chemotherapy and drug development

discrete phases followed the demonstration that DNA synthesis took place during a defined time interval, rather than continuously during interphase. After mitosis (M), the cell spends a variable resting period (G1) during which DNA synthesis does not occur but RNA and protein are produced. Entry to the S phase is heralded by an increase in RNA synthesis followed by doubling of the DNA content. The G2 phase follows as DNA synthesis ceases, and is followed by mitosis. The total duration of the cell cycle depends mainly on the duration of the G1 phase, which may be 0–30 hours. The durations of the S phase (6–8 hours), M phase (less than 1 hour) and G2 phase (2–4 hours) are fairly constant both in normal and malignant cells. Consequently, the cycle of a malignant cell may last between 9 and 43 hours. For aggressive, highly proliferative tumours, the cell cycle will be at the shorter end of the time span, but for more indolent, low-grade tumours, the cell cycle will be significantly longer. The mean cycle time of cells within human tumours is typically much shorter than the mean volumedoubling time of the tumours for two main reasons: a high rate of cell death, and a high proportion of non-proliferating cells. The term G0 is applied to cells that are out of cycle. The proportion of cells within a population that is undergoing active proliferation in the cycle is termed the growth fraction. Estimates of growth fraction calculated by comparing the measured proportion of cells in S phase with that predicted from the phase distribution of cycling cells are consistently of the order of 20–30 per cent. This is particularly relevant, as most anti-cancer drugs do not cause cell death during the G0 phase. Furthermore, although higher proportions of S-phase cells are found in some rapidly growing tumours such as high-grade lymphomas, most tumours do not have a higher proportion of S-phase cells than some normal highly proliferative tissue such as bone marrow and intestinal crypt cells. Mathematical models have been developed to describe the interaction of cytotoxic chemotherapy and tumour growth kinetics and may be used to evaluate hypothetical strategies for cancer treatment.1

ANTI-CANCER DRUGS AND THE CELL CYCLE

Cytotoxic chemotherapy agents have traditionally been classified as phase or non-phase specific, depending on the effect on the cell cycle (Table 5.1). In-vitro models demonstrate that phase-dependent drugs kill cells exponentially at lower doses but reach a plateau when given at a higher dose because they are only able to kill cells in a specific part of the cell cycle. Non-phase-dependent drugs kill cells exponentially with increasing dose and are equally toxic both for cycling cells and those in G0. The practical value of this classification is somewhat limited in that chemotherapy regimens designed on kinetic principles have so far shown no advantage over those derived empirically.

Table 5.1 Cytotoxic drugs and the cell cycle Predominantly non-phase-specific agents Nitrogen mustards Cyclophosphamide Melphalan Chlorambucil Busulphan Thiotepa 5-Fluorouracil Doxorubicin Mitomycin-C Dacarbazine Actinomycin-D

Predominantly phase-specific agents Methotrexate Cytosine arabinoside 6-Mercaptopurine 6-Thioguanine Vincristine Vinblastine Bleomycin Etoposide Procarbazine

SKIPPER HYPOTHESIS FOR CELL KILL BY CYTOTOXIC AGENTS

In the early 1960s, Skipper et al.2 formulated some principles of tumour cell kill on the basis of experiments using the L1210 murine leukaemia model: ●

●

●

●

The survival of an animal is inversely related to the tumour burden. A single leukaemic cell is capable of multiplying to kill the host. For most drugs there is a clear relationship between dose of drug and eradication of tumour cells. Cell destruction by anti-cancer drugs follows log kill kinetics. That is, a given dose of drug kills a constant fraction of cells and not a constant number. Thus if a particular dose of an individual drug kills 3 logs of cells and reduces the tumour burden from 1010 to 107 cells, the same dose used at a tumour burden of 105 will reduce the tumour burden to 102 cells. The cell kill is therefore proportional regardless of tumour burden.

These principles established that there is an inverse relationship between cell number and curability and imply that tumours are best treated when they are small in volume. Furthermore, if drug treatment is discontinued as soon as the tumour is no longer clinically detectable, at least 109 tumour cells remain and relapse is inevitable. However, these observations should be considered in the context of the growth differences between this murine leukaemia model and human cancers. For example, L1210 leukaemia is a rapidly growing tumour, with a high percentage of cells in S phase and a growth fraction of 100 per cent, giving a consistent and predictable cell cycle. In contrast, the cell cycles of human tumours are heterogeneous, prolonged and with a smaller growth fraction. Overall, the evidence favours a Gompertzian growth pattern with a growth fraction that is not constant and with an exponential decrease in growth rate as the tumour enlarges.

Basic principles 77

Nevertheless, Gompertzian kinetics also support the notion that chemotherapy is more likely to be effective in eradicating a small tumour burden. When the tumour burden is small (such as when no longer clinically detectable), its growth fraction would be at its largest, and the proportional cell kill would be larger. This is one of the principles that form the basis of adjuvant chemotherapy strategies. NORTON–SIMON HYPOTHESIS

In tumours that show Gompertzian-type growth curves, the rate of re-growth increases as the tumour shrinks with therapy. Thus the level of treatment necessary to initiate a regression may be insufficient to maintain the regression and produce cure. Norton and Simon3 hypothesized that to overcome the slowing rate of regression in a tumour responding to therapy it was necessary to increase the intensity of treatment as the tumour became smaller. This can be achieved in one of two ways: 1. increase the dose intensity of the chemotherapy agents used to induce remission; 2. switch to alternative cytotoxic agents in an aggressive schedule. Dose intensity is commonly used in leukaemia, for which agents such as cytosine arabinoside are used in highdose pulses after the induction of remission. In addition, high-dose chemotherapy with bone-marrow transplantation or peripheral blood stem-cell harvesting with growth factor support is another means of achieving dose intensity. The concept of dose intensity is discussed more fully later in this chapter. Alternatively, the use of other cytotoxic agents in hybrid regimens such as MOPP-ABVD for Hodgkin’s disease4 not only exposes the tumour to drugs that are different from those used to achieve induction or remission, but also attacks residual populations of cells that are biochemically resistant to the initial combination of drugs. GOLDIE–COLDMAN MODEL

Spontaneous mutation is a basic property of DNA. There is also evidence that tumour cells may be more genetically unstable than normal cells. In 1979, Goldie and Coldman proposed a model to explain the genetically determined resistance to cancer chemotherapy based on this principle.5 They proposed that populations of cells within a tumour are capable of randomly mutating and becoming resistant to the cytotoxic agents. These spontaneous mutations occur at population sizes of less than 106 tumour cells, which is less than the clinically detectable level. As such mutations occur at frequencies of 106 or higher, a clinically detectable tumour of 109 cells is likely to have several drug-resistant clones. However, the absolute number of resistant cells would be relatively small and these tumours would probably respond initially to treatment with a

complete or partial remission, only to relapse and reappear when the resistant clone(s) expand, a clinical picture that is familiar in oncology practice. Some tumours are resistant to cytotoxic chemotherapy agents even when they present with a relatively small tumour volume. However, such slow-growing tumours may have considerable cell loss through cell death – up to 90 per cent of the tumour volume. Therefore what appears to be an early tumour may have gone through many more cell doublings than expected in order to compensate for cell loss in achieving that size. Consequently these cells may have undergone a higher frequency of spontaneous mutations, leading to a tumour that consists predominantly of drugresistant clones. However, there are many other mechanisms of drug resistance, including decreased uptake due to changes in drug-specific transport mechanisms, decreased activation of pro-drugs, alterations in cellular metabolism and repair mechanisms, increased inactivation of drugs, target alterations and acquisition of a multi-drug-resistance phenotype. Drug resistance is discussed more fully in a later section of this chapter.

Principles of treatment ROUTE OF ADMINISTRATION

The route of administration of a cytotoxic drug is determined by the stability, size, molecular charge and sclerosant characteristics of that drug. Traditionally, the oral route has been used infrequently because of the unpredictability of patient compliance and variable absorption of the drug. However, the desire to move cancer treatment from a predominantly hospital-based, inpatient system into the ambulatory setting, together with a growing body of information showing higher anti-tumour activity, or lower systemic toxicity, with dosing regimens that produce prolonged exposure to some cancer agents suggest that oral cancer chemotherapy may be increasingly of interest in the future. This has already led to the evaluation of oral administration of anti-cancer drugs that have been available for many years (e.g. etoposide, idarubicin) as well as strategies for oral use of anti-cancer drugs traditionally given intravenously, for example the oral fluoropyrimidines.6 Subcutaneous and intramuscular routes are rarely employed because large volumes of diluent are frequently required to dissolve the drug, or because, once dissolved, they are often highly toxic to tissues in the extravascular compartments. For the majority of cytotoxic drugs, the intravenous route is the optimal means of delivery for most indications, and the drug can be administered by bolus injection, short infusions or protracted venous infusion, usually through an indwelling central venous catheter in the last case. Other routes that can be used for specific indications include the intrathecal administration of non-sclerosant water-soluble

78 Principles of chemotherapy and drug development

drugs such as methotrexate or cytosine arabinoside to palliate or prevent meningeal disease; intra-arterial administration of drugs via the hepatic artery to achieve high doses of drug to be delivered locally or in chemo-embolization strategies; intra-arterial administration in isolated limb perfusion in melanoma or sarcoma; intravesical administration in reducing recurrence rates of superficial bladder cancers; and intraperitoneal administration to small tumour nodules on the peritoneal surface.

COMBINATION CHEMOTHERAPY

Based on the cancer cell kinetics data, it is reasonable to assume that even small tumours, when clinically detectable, already have resistant clone(s) of cells. The use of cytotoxic agents of different groups in combination should give a broader range of cover of resistant cell clones in a heterogeneous tumour population, and prevent or slow the development of new resistant cell clones, thereby giving maximum cell kill that is not possible with a singleagent regimen. There are four general principles that guide the selection of drugs for use in effective combination chemotherapy regimens: 1. Each drug should have activity against the tumour when used alone, those drugs with maximal efficacy being most preferable. 2. Drugs should have different mechanisms of action. 3. Drugs should have minimal overlapping toxicities. When several drugs of a class are available, a drug should be selected with minimal overlapping toxicity, which, although leading to a greater range of side effects, decreases the risk of potentially life-threatening cumulative toxicity to the same organ system. 4. Each drug in a combination should be used in its optimal dose and schedule. However, it should also be noted that omission of a drug from an effective combination may allow overgrowth of a cell clone that is sensitive to that drug alone and resistant to the other drugs in the combination. Conversely, adding too many drugs to a regimen with the aim of increasing efficacy may reduce the doses of some, or all, of the component drugs of the combination below the threshold of efficacy, thereby decreasing activity of the regimen. THE DOSE-RESPONSE RELATIONSHIP

Within experimental systems, it is easy to demonstrate the dose–response effect of anti-cancer drugs on cancer cells. This relationship is more difficult to demonstrate and quantify in patients due to the heterogeneity of tumour responses and also because of the variability of drug absorption, binding, distribution, metabolism, excretion and delivery of the drug to the tumour. Nevertheless, a positive dose–response

relationship has been demonstrated in retrospective studies,7 and also in prospective studies in advanced ovarian, breast and colon cancers, and in the lymphomas.8**,9–11 In experimental models, the dose–response relationship is steep and linear and the principles of chemotherapy include exploiting the differences between the dose– response curves of normal and tumour tissue. Reduction of doses in this linear phase of the dose–response curve in experimental models results in a decreased cure rate before there is a reduction in the response rate. Although complete remissions are still observed in these animal tumours, a few residual cells will not be killed and will ultimately repopulate, leading to relapse. It has been suggested that in these experimental models, a dose reduction of 20 per cent will lead to a loss in the cure rate in excess of 50 per cent.9,12 Conversely, in high growth fraction tumours, a two-fold increase in dose often leads to a ten-fold increase (1 log) in tumour cell kill. This not only re-enforces the desire to minimize the reductions in recommended doses, but also justifies efforts to increase dose to aim for increased cure rates in chemosensitive tumours. The principal restriction to dose escalation is toxicity of normal tissues. When myelosuppression is the dose-limiting toxicity, this can be overcome by the use of recombinant bone-marrow growth factors such as G-CSF, by bone-marrow transplantation, or by haemopoietic support using peripheral blood progenitor cells. Ultimately, dose escalation of these agents (and those agents that have non-bone-marrow dose-limiting toxicities) will be restricted by toxicities to tissues such as the myocardium, lungs and kidneys, for which there is no currently available means to overcome toxicity. Consequently, the drugs that can be used in dose-escalation strategies are few in number, as are the tumour types that demonstrate a dose response to these agents. SCHEDULING OF CYTOTOXIC CHEMOTHERAPY

The concentration of a cytotoxic agent in plasma or in tissue does not depend on total dose alone, but also on the schedule of administration; that is, it is believed that ‘drug exposure’ as measured by the area under the concentration–time curve (AUC) is a crucial determinant of drug activity in many situations. In a series of classical experiments with the L1210 murine leukaemia model, Goldin and Schabel13 demonstrated that methotrexate was more effective and less toxic when administered to mice in an intermittent rather than a daily regimen, and this observation has also been noted in clinical practice. Scheduling is also a determinant of achieving dose intensity. Dose intensity has been defined as the amount of drug delivered per unit time, expressed as mg/m2 per week. Relative dose intensity is the amount of drug delivered per unit time relative to an arbitrarily chosen standard single drug, or, for a combination regimen, the fraction of the ratio of the test regimen to the standard regimen. In this way, treatment delays are given equal consideration to dose reductions when calculating dose intensity. Clearly if the

Drug development 79

time interval between successive courses of chemotherapy is too prolonged, this can allow repopulation of cancer cells, which may well have acquired resistance to the cytotoxic agents to which they have been exposed. If the time interval is too short, toxicity in normal tissues may be unacceptable. Consequently, scheduling may influence outcome by affecting toxicity, allowing greater doses to be administered over the same time frame. In this regard, accurate scheduling is also required to rescue normal tissues from the toxic side effects of certain chemotherapy drugs; for example higher doses of methotrexate can be administered to patients during 24 hours when a sufficient flow of alkaline urine is maintained and by rescue of normal tissues by giving folinic acid titrated to the plasma concentration of methotrexate. Similarly, scheduling of individual cytotoxic agents can enhance response rates, e.g. when 5-fluorouracil (5-FU) is given as a continuous intravenous infusion rather than by intermittent boluses,13**,14 and also in exploiting potential interactions between cytotoxic drugs to achieve optimal synergistic effects.

DRUG DEVELOPMENT Although many of the agents currently in use were developed by a combination of science and serendipity, the acquisition and evolution of novel agents are generally the result of both carefully thought-out screening processes and our increasing knowledge of the molecular basis of cancer development and progression, and cellular metabolism. Criteria for selecting new anti-cancer drugs can include: ● ● ● ● ● ●

novel chemical entity novel mechanism of action selective for solid tumours in-vivo activity in solid tumour models evidence for a positive therapeutic index feasibility of supply.

The serendipitous discovery of active anti-cancer agents has resulted in the development of many important drugs. In the mid-1960s, Rosenberg was studying the effects of electric currents on the growth of bacterial cultures and noted that the application of an alternating voltage reduced the growth rate of the bacteria, and that this effect was due to the formation of platinum complexes in the growth medium resulting from dissolution of platinum from the electrodes. Neutral platinum complexes exhibited a relatively selective effect on rapidly dividing bacterial cells, and therefore these compounds were tested as anticancer agents. Platinum was thus found to have significant anti-tumour activity in these tests and subsequently also in a wide variety of animal models. Another way in which new agents are appropriated is by chemically modifying an existing active agent that may otherwise have restricted utility because of toxicity. The

term ‘structure–activity relationship’ describes the link between varying specific chemical substructures on the parent compound and differential anti-tumour activity. Analogue development is aimed primarily at producing: ●

● ●

a drug as effective as the parent compound, with significantly less toxicity, a more potent drug, or a drug with a different spectrum of anti-tumour activity.

Examples of successful analogues are epirubicin (from doxorubicin), carboplatin (from cisplatin) and topotecan or CPT-11 (from camptothecin). It is expected that more active agents will be developed as a result of the increasing understanding of the biochemical and biological behaviour of cancer cells. Certainly, focusing on a defined molecular target and using computers to design and construct molecules that would interact and antagonize these targets would increase the potential selectivity for such an agent. However, empirical drug screening for novel agents will continue to play a major role in the twenty-first century.

Acquisition of drugs SCREENING

Large-scale, empirical screening for the discovery of new anti-cancer agents was initiated by the National Cancer Institute (NCI) of the USA in 1955. During the next 20 years, nearly half a million potential anti-cancer agents of natural or synthetic origin were screened, producing more than 50 per cent of all clinically useful agents. This screen used a tumour panel with two models being involved primarily – murine leukaemia L1210 and P388. In the mid1980s it was decided to change this leukaemia-based strategy because: ●

●

●

not many drugs were discovered with broad activity against common solid tumours, agents inactive against P388 were often active in other pre-clinical models, and vice versa, many active agents, e.g. bleomycin, were inactive against P388.

The NCI disease-oriented in-vitro screen has been used regularly since 1991. Here, human tumour cell lines derived from seven common cancers have been selected and maintained for use as a test-bed for novel-agent sensitivity. Such a screen could theoretically speed up the process of clinical development for agents found to be differentially sensitive to a particular tumour type. Secondary in-vitro studies may be used in order to examine the effects of schedule, exposure and potential mechanisms of action. Finally, in-vivo testing is carried out, generally using the most sensitive human tumour cell line as a subcutaneous xenograft in a nude mouse.

80 Principles of chemotherapy and drug development

FORMULATION

An intravenous formulation is generally preferred for preclinical studies, in order to exclude variations in bioavailability and to enable promising drugs to be used at their maximum tolerated dose (MTD). Solubility is also very important, as limited solubility is regularly a reason to discontinue overall development of an agent. Various approaches and experimental methods for solubilization are being used, in addition to techniques such as liposomal encapsulation, conjugation to polymers and other delivery systems that could empower the clinical evaluation of a promising agent. However, these means of solubilizing the drug may alter the toxicity profile and/or the anti-tumour efficacy. TOXICOLOGICAL AND PHARMACOLOGICAL TESTING

Unlike other drugs in clinical use, cytotoxic agents have very narrow therapeutic windows, i.e. the most biologically active doses are often close to the lethal doses. It is therefore necessary to try to predict the potential toxic effects, and also to define a safe (but still potentially active) starting dose prior to human studies. Animal studies are often performed using two species. In Europe, an accepted method for obtaining the safe dose for human clinical trials is defined as one-tenth the dose that is lethal to 10 per cent of mice (called the LD10), providing this dose is safe in another species, e.g. rat. However, it is important to note that animal toxicities do not always predict similar toxicity in humans. It is rarely necessary to perform additional tests on larger animals (e.g. dogs, monkeys), although some data suggest that tests in these species are more able to predict certain human toxicities. Additional toxicological studies are undertaken in order to evaluate more fully any organ toxicity demonstrated in the animals, and to investigate any relationships with dose, schedule and whether any documented effects are potentially reversible. Single-dose and multiple-dose studies are undertaken in order to mimic more accurately the anticipated human trial protocols. Finally, pharmacological studies derive knowledge about bioavailability, metabolism, route of excretion etc. and allow rational schedule design for the clinical testing of the agent.

Clinical testing For many anti-cancer drugs, a dose–response relationship is observed in pre-clinical studies, and this knowledge is subsequently integrated into the design of the initial clinical studies. There are three stages (phases) of clinical studies used for the evaluation of a novel compound. PHASE I TRIALS

Phase I studies are concerned with the first exposure of a novel agent to humans. The primary objective is to establish

the MTD by an escalating dose protocol, and to document the toxicity profile of the agent at the chosen dose, schedule and route of administration. However, one of the goals of pre-clinical studies is to try to predict a phase I starting dose close to the agent’s therapeutic window. Despite this, it has been noted that clinical response rates in phase I trials are less than 5 per cent overall. This raises ethical dilemmas, particularly with respect to informed consent. However, these studies are conducted in a patient population deemed to have disease that is refractory to standard chemotherapy, or disease for which there is no known effective treatment. Anti-cancer efficacy is therefore necessarily a secondary endpoint, and unfortunately the first patients are often treated at sub-therapeutic doses. Research on study designs that decrease the number of patients treated at sub-therapeutic doses is ongoing, and includes the accelerated titration design and continual reassessment method (CRM).15 The former design allows for one patient per dose level in the early stages, provided no significant toxicity is encountered. The CRM allows for intra-patient dose escalation. Both designs may be useful, provided that data on toxicity are always as up to date as possible. In most trials, however, patients (generally three) are treated at the first dose level and monitored for toxicity. Subsequent patients are entered at the next dose level (cohort) and so on, until significant toxicity is encountered. Historically, the degree of dose escalation is based on a modified Fibonacci scheme (e.g. dose level 2 is twice dose level 1; level 3, 167 per cent of level 2; level 4, 150 per cent of level 3). Some studies have used a pharmacokinetically guided scheme, involving target AUCs. All studies incorporate pharmacokinetic and pharmacodynamic aspects, and assessments of biological endpoints are often included (e.g. inhibition of a target enzyme). Dose-limiting toxicities (DLTs) are defined, and once the MTD has been reached at a particular dose level, the previous lower dose level is generally expanded to a larger cohort of patients and becomes the recommended dose for further studies. Any anti-tumour activity documented may also be useful in planning subsequent phase II studies.

PHASE II TRIALS

These studies are conducted using the dose and schedules from phase I studies considered to be optimal in terms of pharmacology and therapeutic index (i.e. near to the MTD). The stated objective of phase II trials is to determine a level of efficacy for the drug in question, and therefore patients with measurable disease are selected. In addition, patients are less heavily pre-treated in order to select a patient population with the best chance of demonstrating anti-tumour activity, if it exists. Phase II studies may be directed towards specific tumour types, based on any responses seen in phase I studies, or towards a well-defined spectrum of pre-clinical activity. Further information on drug toxicity is gathered, and specific data on cumulative toxicity are acquired, because more patients

Classification of cytotoxic drugs, mode of action, toxicities and clinical utility 81

are likely to receive multiple cycles of treatment. Phase II trials are designed to allow early study termination if a drug has no, or minimal, efficacy. Designs such as the Gehan two-stage model allow a number of patients to be accrued (generally 14), and if one or more response is documented, recruitment proceeds to a total of 25 patients. If no responses are documented in these first 14 patients, the trial terminates. A response rate of 20 per cent may be considered worthy of further evaluation; however, this should relate to the patient population being tested. If performed in patients with a relatively chemoresistant malignancy, pre-treated with ‘standard’ chemotherapy, the likelihood of detecting activity may be prejudiced. Another design is to randomize patients to the experimental treatment and a drug with known activity in the disease (e.g. the parent compound of a novel analogue), or even to another experimental agent. Such studies will not allow the determination of efficacy differences, but may give a baseline response rate for the patient population being selected. Finally, new active agents are often subsequently added to other standard therapies in two-drug or three-drug combination regimens. These need to be piloted as feasibility/phase I type studies to ensure that toxicity is neither additive nor synergistic. PHASE III TRIALS

The next stage of testing for a novel agent is to compare against the existing standard therapy. The most scientifically valid method is by a prospective, randomized clinical trial, in which patients eligible for the protocol are randomly assigned to one of the treatment arms. Suitable endpoints for a phase III study include progression-free survival (PFS), overall survival (OS) and overall response rate (ORR). Data on quality of life and comparative toxicities are also collected in order to determine the overall clinical benefit of a treatment. Stratification for known prognostic factors is carried out to ensure that the arms of the study are statistically balanced. Such procedures do not ensure that the study will include a representative sample of the general population with the disease, but can provide evaluation of the relative merits of the treatments being compared. Variations on the simple randomized study format include: ●

●

the crossover design, which allows patients relapsing on one treatment to receive the other drug, therefore using the patient as his/her own control, the 2 2 factorial design, wherein the first factor may be a comparison between two treatments (e.g. the novel agent versus standard therapy), and the second factor interventions consequent on the first factor (e.g. maintenance treatment or not).

Phase III trials are generally large, consisting of hundreds of patients, because the differences between treatments may be small and therefore increasing sample size increases the

chance of small differences in outcome being statistically significant.

CLASSIFICATION OF CYTOTOXIC DRUGS, MODE OF ACTION, TOXICITIES AND CLINICAL UTILITY Historically, anti-cancer agents have been divided into groups according to the mechanism of cytotoxicity. However, the increasing number of new drugs, and their diverse and novel mechanisms of action, make such divisions increasingly difficult and arbitrary.

DNA alkylators The alkylating agents were the first compounds identified to have activity against neoplastic diseases, and have been in use now for more than 50 years. Early studies used the nitrogen mustard mechlorethamine, following observations from the mustard gas chemical warfare programme that soldiers exposed to this agent developed aplasia of the bone marrow. Mechlorethamine was subsequently found to induce significant tumour regression in patients with lymphoma in clinical trials. Mechlorethamine is ideally suited to illustrate the chemistry of alkylation, having the simplest structure of the class. The CH2CH2Cl linked to nitrogen is labelled the mustard group, and in the case of mechlorethamine there are two such groups, thus giving the term ‘bifunctional nitrogen mustard’. Following administration, the drug undergoes an internal cyclization reaction and loses a chloride ion to form an electron-deficient, positively charged aziridinium ion. These highly reactive species are able to react and form covalent bonds (adducts) with electronrich (nucleophilic) sites in DNA, such as the 7-nitrogen group of guanine on the major groove. Other biological macromolecules, e.g. proteins, are also targeted, but it is the reactions involving the nitrogenous bases in DNA that are critical for the anti-cancer action of the alkylating agents. Adduct formation with two separate bases on the DNA, especially across the two anti-parallel strands – the inter-strand crosslink – is thought to be the most lethal interaction. The results of DNA alkylation involve interference with the fidelity of replication and transcription by abrogating the functions of DNA and RNA polymerases. It follows that alkylating agents are most toxic to rapidly cycling cells; tumours with a high fraction of cells in S phase are more vulnerable, possibly as they have less damagerepair time. In addition, adduct formation leads to structural lesions, which include ring opening and base deletions. Cellular repair processes attempt to restore the integrity of the DNA, but if incomplete can result in further damage, such as the creation of apurinic sites or strand breaks. Furthermore, it appears that these repair processes can be saturated by higher doses of alkylating agents, thus providing

82 Principles of chemotherapy and drug development

a rationale for extending the use of these agents into highdose chemotherapy techniques. MECHLORETHAMINE (NITROGEN MUSTARD, MUSTINE)

Mechlorethamine is administered intravenously, and has a half-life of approximately 3 minutes due to rapid hydrolysation. It has extremely vesicant properties, and can also cause severe phlebitis and sclerosis of the vein used. The major use is in the treatment of Hodgkin’s disease, as part of the combination MOPP (nitrogen mustard, vincristine, procarbazine and prednisolone). It is also occasionally administered by direct intra-cavity infusion for the treatment of malignant effusions. MELPHALAN

Melphalan is another bifunctional alkylating agent, and is a phenylalanine derivative of mechlorethamine. It is active against a broad cross-section of tumours (lymphomas, breast and ovarian cancers, multiple myeloma) and can be administered orally, intravenously or intraperitoneally. Although the oral bioavailability is variable, with 20–50 per cent being excreted in the stool, the ease of oral administration makes this the most common route employed. It routinely causes myelosuppression, with nadir counts occurring at 4–5 weeks following a short, 7-day, oral course. Doses require to be adjusted according to the level of myelosuppression. It is also used in high-dose chemotherapy regimens for haematological malignancies and multiple myeloma, due to exponential cell killing demonstrated in cell culture. Occasionally, it is used intraperitoneally for relapsed ovarian cancer, although efficacy data are not well established. CHLORAMBUCIL

This bifunctional alkylating agent is a benzene butanoic derivative of mechlorethamine, and is also a close structural congener of melphalan. It is almost completely absorbed when given by the oral route, and is used either continuously or intermittently for long periods in lowgrade lymphoma, chronic lymphocytic leukaemia and multiple myeloma. It can also be given to elderly patients with ovarian cancer who are unable to tolerate more aggressive chemotherapy. The toxicity is predictable myelosuppression, which makes dose adjustments fairly straightforward. However, stem-cell damage is cumulative and irreversible, leading to problems of severe myelosuppression with subsequent cytotoxic drug use. Longer-term use (e.g. 1 year) has been associated with pulmonary toxicity and the development of second malignancies.

to develop cytotoxicity. It undergoes a complex multi-step activation process, initially being metabolized by the cytochrome P450 system in the liver and eventually converted to a variety of active metabolites, of which phosphoramide mustard is thought to be the major cytotoxic derivative. One of the main metabolites, acrolein, is excreted in the urine and can cause a chemical (haemorrhagic) cystitis in up to 10 per cent of patients. Adequate hydration and the concurrent administration of sodium-2-mercaptoethane (MESNA), which inactivates acrolein in the urine, can prevent this toxicity. Cyclophosphamide has good oral bioavailability of around 90 per cent and therefore is often utilized by this route. The main toxicity is myelosuppression, with the nadir occurring 10–21 days after intravenous administration. Doses of 750 mg/m2 are common in regimens such as intravenous CMF (cyclophosphamide, methotrexate and 5-FU), whereas higher doses may be given as part of high-dose stem-cell transplantation. Such high doses can lead to problems such as hyponatraemia, haemorrhagic carditis, cardiomyopathy and pulmonary fibrosis. Like all alkylating agents, there is a risk of developing second malignancies. The major use of cyclophosphamide is as a component of combination regimens for cancers of the breast, small-cell lung and haematological malignancies. The CMF regimen is still one of the mainstays of chemotherapy for breast cancer, with variations existing that deliver different dose intensity and toxicity. It has recently fallen out of favour in ovarian cancer treatment, with the introduction of newer, more active combinations. Ifosfamide is a structural analogue of cyclophosphamide, which exhibits a similar spectrum of activity but different pharmacological properties and toxicity profile. It is generally administered as prolonged infusions, with concurrent MESNA and hydration, due to a higher incidence of urothelial toxicity. In addition, ifosfamide can cause a severe but reversible neurological syndrome, characterized by altered mental state, cerebellar dysfunction, cranial neuropathies and epileptiform seizures. Risk factors for the development of neurotoxicity are impaired renal or hepatic function. Both ifosfamide and cyclophosphamide can cause impairment of gonadal function. The usefulness of ifosfamide is evidenced by its incorporation into chemotherapy regimens that have been shown to be curative in germ-cell malignancies. It is also used in the treatment of sarcomas and lymphomas and has demonstrated activity in ovarian cancer. As part of the ICE regimen (ifosfamide, carboplatin and etoposide) or combined with vincristine, VICE, it has been used in the treatment of small-cell lung cancer. NITROSOUREAS (BU, CU)

OXAZAPHOSPHORINES (CYCLOPHOSPHAMIDE AND IFOSFAMIDE)

Cyclophosphamide differs from the previously described alkylating agents in that it is a pro-drug, requiring activation

BU (1,3-bis-(2-chloroethyl)-1-nitrosourea,carmustine) and CU (1-(2-chlorothyl)-3-cyclohexyl-1-nitrosourea, lomustine) are important agents in that they exhibit only partial cross-resistance with the other alkylating agents. They are

Classification of cytotoxic drugs, mode of action, toxicities and clinical utility 83

highly lipid soluble and easily cross the blood–brain barrier. Clinical activity has been observed in lymphoma, melanoma, myeloma and malignant glioma. Major toxicities are emesis and delayed myelosuppression, which can be severe. BU is given intravenously, whereas CU can be administered orally. ALKYLAKLANE SULPHONATES (BUSULFAN, TREOSULFAN)

Busulfan is an orally available bifunctional alkylating agent which, when hydrolysed, binds extensively to nucleophilic sites on DNA to form crosslinks. It is used mainly in haematological malignancies, and is an integral component of many high-dose chemotherapy regimens preceding stem-cell transplantation. Myelosuppression can be severe and long lasting after excessive dosing. Other notable toxicities include ‘busulfan lung’, a form of interstitial pulmonary fibrosis, and increased pigmentation in an Addisonian distribution. Treosulfan was synthesized in 1961 as dihydroxybusulphan and is a bifunctional alkylator, structurally related to busulfan. It is a pro-drug, activated to the reactive epoxide in a non-enzymatic, first-order, pH-dependent process. It has demonstrated specific activity in ovarian cancer and is available in intravenous and oral form. The predominant toxicity is mildto-moderate myelosuppression. AZIRIDINYL DRUGS (THIOTEPA, MITOMYCIN C)

Thiotepa (N,N,N-triethylenethiophosphoramide) is a complex drug that acts as a monofunctional DNA-alkylating agent. It is thought to act as a pro-drug, being metabolized to highly reactive aziridine moieties via hydrolysis, following diffusion into the cell. It is delivered by the intravenous or intra-cavity route and readily crosses the blood–brain barrier. It has a role in the palliation of refractory ovarian cancer as an intraperitoneal agent, and recently there has been a resurgence of interest in its use as part of high-dose chemotherapy due to its relative lack of non-myelogenous toxicity. Mitomycin C is related to the anthracycline anti-tumour antibiotics, being derived from Streptomyces species, but differs substantially in that it is the prototype bioreductive agent, undergoing preferential activation in the hypoxic environment found in solid cancers. Once activated, mitomycin C performs bifunctional alkylation, crosslinking DNA with the adduct in the minor groove and causing strand breaks. The utility of mitomycin C is limited by delayed myelosuppression, similar to that of the nitrosureas. Other notable toxicities include renal failure and cardiomyopathy, both related to the total cumulative dose of mitomycin C administered. The elucidation of the mechanism of action of mitomycin C has evoked great interest due to the potential of tumour selectivity through preferential reductive activation in hypoxic solid tumour masses. A range of aziridinyl agents, including E09, has been developed and is undergoing clinical evaluation.

N-METHYLTRIAZINES AND MELAMINES

Dacarbazine (DTIC) was initially thought to function as an anti-metabolite, given that its genesis was as an analogue of 5-amino-imidazole-4-carboxamide, a purine precursor. However, it is now thought to be hepatically activated to function as an alkylating agent. It is decomposed by exposure to light and is administered by intravenous infusion. It is active against a broad spectrum of tumours, but the main clinical utility is in the treatment of malignant melanoma, lymphoma and sarcomas. Hexamethylmelamine has an uncertain mechanism of action, but is likely to act as a DNA-methylating agent, with crosslink formation. However, it is incompletely cross-resistant with classical alkylating agents such as cyclophosphamide. It is administered by the oral route, but bioavailability is erratic due to variable first-pass metabolism. It is used in the treatment of ovarian cancer, but emesis can be problematic. In addition, it can produce neurological toxicity in some patients. Procarbazine is metabolically activated in the liver microsomes into a DNA-methylating species. It is generally administered orally in the treatment of Hodgkin’s disease and is also useful in the treatment of brain tumours due to its ability to penetrate well into the cerebrospinal fluid. Side effects are usually not severe, but care should be taken with co-administration of other drugs, due to the inhibitory effect of procarbazine on monoamine oxidase.

Platinum analogues Platinum, transition metal, possesses eight electrons in its outer d shell, which are highly polarizable and able to form covalent bonds. Cisplatin is a square planar molecule, which has two chloride and two ammonia ligands in the cis-configuration. This stearic conformation is important for anti-tumour effect, as the trans-isomer has no activity. The pharmacological behaviour and activation to a cytotoxic species are determined by the aquation reaction, in which a chloride ion is replaced by a water molecule. This reaction mainly occurs in the cellular cytoplasm, as the low chloride-ion concentration favours driving the formation of the active species. Once in the cell, platinum complexes are able to react with nucleophiles, such as DNA bases, RNA and proteins, to form adducts. These adducts can bridge the strands of DNA in a similar way to the crosslinks formed by melphalan and chlorambucil. The actual pathway from DNA damage to cell death has not been fully elucidated, but involves many steps, resulting ultimately in apoptosis or programmed cell death. Cisplatin is generally given intravenously and has an initial half-life of 40 minutes and a terminal half-life of greater than 24 hours. It is highly protein bound, and renally excreted, resulting in nephrotoxicity due to a

84 Principles of chemotherapy and drug development

mechanism thought to be related to persisting adducts in renal tissue DNA. Large volumes of fluid are required to ameliorate this renal damage, but significant cumulative doses of cisplatin invariably lead to an irreversible reduction in glomerular filtration rate. Renal wasting of magnesium and potassium can occur, and therefore supplementation is provided during the hydration phases. In addition, cumulative cisplatin dosing produces neurotoxicity, which usually manifests as a sensory peripheral neuropathy or hearing loss. No interventions are known to abrogate this toxicity, and when present it is thought to be only partially reversible over many months or years. Other significant toxicities include emesis, which is routinely managed by prophylactic use of 5-HT3 antagonists in addition to corticosteroids. Myelosuppression is mild to moderate. Cisplatin has a wide spectrum of activity against solid tumours, and is an integral component of curative regimens for testicular and ovarian cancer. It is also used in the treatment of upper gastrointestinal cancers, head and neck cancer, cervical and endometrial cancer, lung cancer (nonsmall cell and small cell), bladder cancer and osteosarcomas. Intraperitoneal cisplatin has been utilized in malignancies such as ovarian cancer and gastrointestinal cancer, with demonstrated activity and a decreased frequency of systemic toxicity. However, optimal pharmacokinetic and pharmacodynamic considerations mean that intraperitoneal tumour masses of 1 cm are required to ensure adequate delivery of drug to target. Carboplatin is a cisplatin analogue that is less potent but more stable, with a longer half-life. Mechanistically, the ultimate reaction products of carboplatin are thought to be chemically identical to those of cisplatin, and the drugs have similar, if not identical, spectra of activity. However, toxicity profiles are different, with carboplatin being much less nephrotoxic and neurotoxic, but causing more bonemarrow suppression. Clearance of carboplatin is also renal, with the majority of the administered dose appearing in the urine during the first 24 hours. Dosing is most accurately performed using the Calvert formula, wherein the required AUC is chosen and the dose in milligrams is calculated by: (glomerular filtration rate  25) desired AUC. Carboplatin has virtually replaced cisplatin in combination chemotherapy for ovarian cancer, having demonstrated equivalent efficacy in prospective, randomized trials. However, carboplatin has been shown to be less effective than cisplatin in testicular cancer; therefore cytotoxic equivalency extrapolations between tumour types is not recommended. Oxaliplatin is a third-generation platinum analogue, from the 1,2-diaminocyclohexane (DACH) platinum family. Pre-clinical studies have demonstrated at least equivalent potency when compared with cisplatin but, more interestingly, a degree of non-cross-resistance with other platinum compounds. In addition, data from the US NCI COMPARE programme – a screen for functional families of cytotoxics – identified DACH platinum compounds as

mechanistically different from cisplatin and carboplatin. Although oxaliplatin engages DNA in a similar way to the other platinum compounds, it seems likely that the specific cellular target and exact mechanism of action are different. Tumour types sensitive to oxaliplatin include ovarian cancer and colorectal cancer, and there is evidence for synergy with 5-FU. An unusual type of peripheral neurotoxicity has been documented, mainly characterized by reversible paraesthesias or cold-related dysaesthesias. Haematological toxicity is mild.

Anti-metabolites Anti-metabolites interfere with key steps in normal cellular metabolism due to their similarity of structure to certain RNA and DNA precursors. They can act as substrates for key enzymes, or inhibit enzymic reactions crucial to the synthesis of RNA and DNA, and are therefore S-phase specific.

ANTI-FOLATES

Methotrexate primarily inhibits dihydrofolate reductase (DHFR), an enzyme that functions to catalyse the conversion of dihydrofolate to tetrahydrofolate, which, in turn, is converted to a variety of co-enzymes involved in reactions in which the carbon atom is transferred in the synthesis of thymidylate, purines, methionine and glycine. By abrogating thymidylate monophosphate synthesis, methotrexate inhibits RNA and DNA synthesis. Folic acid (also known as leucovorin), given orally or intravenously, is converted to the tetrahydrofolate co-enzymes that are needed for the function of thymidylate synthase (TS). This is able to bypass the blocking activity of methotrexate to prevent systemic toxicity. It can also be given locally as a mouthwash or as eye drops. Methotrexate is well absorbed orally at low doses, but higher doses are given parenterally. An initial fast half-life is followed by a prolonged phase of renal excretion and a long terminal half-life. This is responsible for methotrexate toxicity to the bone marrow, mucous membranes and gastrointestinal tract – areas of high cell turnover and active DNA synthesis. Because methotrexate can accumulate in third spaces and be slowly released into the circulation, its use should be avoided in patients with effusions because of the risk of severe toxicity. Methotrexate also penetrates the blood–brain barrier at high doses, and can be given intrathecally for meningeal disease. With high doses, adequate diuresis should be obtained. It is also 50 per cent albumin bound and can be displaced by other protein-bound drugs, leading to higher systemic levels of free methotrexate and increased toxicity. However, it is generally well tolerated, with few side effects unless the risk factors are not taken

Classification of cytotoxic drugs, mode of action, toxicities and clinical utility 85

into account. Severe toxicity is manifested by myelosuppression, oropharyngeal ulceration and diarrhoea, with renal and hepatic failure and pneumonitis seen less commonly. Indications for use are as part of combination regimens in breast cancer, haematological malignancies, osteosarcoma and choriocarcinoma. Methotrexate is also known to act partly through inhibition of TS, which catalyses the methylation of deoxyuridylate (dUMP) to thymidylate, which is then incorporated into DNA. More specific inhibitors of TS have been developed, which target the folate-binding site of the enzyme. Raltitrexed (Tomudex) acts as a direct and specific TS inhibitor which, once transported into cells, is extensively polyglutamated to chemical entities that are even more potent inhibitors of TS. Such polyglutamation increases the duration of TS inhibition, which in theory could improve anti-tumour activity. Pemetrexed targets TS, but also inhibits dihydrofolate reductase and glycinamide ribonucleotide formyl transferase (GARFT), folatedependent enzymes involved in purine synthesis. Again, once inside the cell, pemetrexed is an excellent substrate for folylpolyglutamate synthase. FLUOROPYRIMIDINES

5-Fluorouracil (5–FU) is an analogue of uracil that is converted by multiple alternative biochemical pathways to several cytotoxic forms. It is converted to 5-fluoro-2deoxyuridine (FUDR) by the enzyme thymidine phosphorylase, and subsequent phosphorylation by thymidine kinase results in the formation of 5-fluoro-deoxyuridine monophosphate (FdUMP). In the presence of reduced folate, FdUMP forms a stable covalent complex with TS, which is also a key enzyme in the de-novo synthesis of the pyrimidine deoxynucleotide, deoxythymidine triphosphate (dTTP), a direct precursor for the synthesis of DNA. This inhibition of TS is considered to be the main mechanism for the action of 5-FU, although nucleotides of 5-FU can also be incorporated directly into both DNA (5-fluoro2-deoxyuridine-5-triphosphate, FdUTP) and RNA (fluorouridine triphosphate, FUTP). The TS–FdUMP complex is slowly dissociable, with a half-life of 6 hours, and the expression of TS is cell-cycle dependent, with high activity during the S phase. Also, as the presence of reduced folate is critical for TS–FdUMP complex formation, depletion of intracellular reduced folates impairs the maintenance of TS inhibition. Co-administration of leucovorin has been shown to increase the duration of TS inhibition and enhance the cytotoxic effect of 5-FU. The pharmacology of 5-FU is complex and characterized by erratic oral bioavailability, non-linear elimination pharmacokinetics and significant intra/inter-patient variability. Clearance is rapid, especially when given by bolus injection, with a half-life of 15 minutes. Several randomized trials have demonstrated the advantage of continuous infusion over bolus injection, but this is at the expense of considerable patient inconvenience (with the requirement

of an indwelling central venous catheter) and increased cost. The main uses are in the treatment of breast and gastrointestinal cancers. Toxic effects include nausea, diarrhoea, mucosal inflammation and moderate myelosuppression. Infusional schedules also increase the incidence of plantar–palmar erythrodysaesthesia (hand–foot syndrome). The development of oral fluoropyrimidines is proceeding apace, with the aim to deliver optimal 5-FU to the tumour in a convenient and controlled fashion while minimizing the variability and clearance. Capecitabine is an orally available tumour-selective fluoropyrimidine carbamate. Following administration, it is bioactivated to 5-FU by a cascade of three enzymatic reactions. After oral administration it passes unchanged through the gastrointestinal tract and is metabolized in the liver by carboxylesterase to 5-deoxy-5-fluorocytidine (5-DFCR). Then it is converted to 5-deoxy-5-fluorouridine (5-DFUR) by cytidine deaminase in liver and also tumour tissues. Further metabolism of 5-DFUR occurs selectively within tumours by thymidine phosphorylase (dThdPase) to 5-FU, thus minimizing the exposure of normal tissues to systemic 5-FU. Side effects resemble those seen with infusional 5-FU and are reversible; severe (grade III/IV) toxicities were shown to be infrequent and manageable with subsequent dose modification. The events observed most often were diarrhoea, nausea, hand–foot syndrome, vomiting, fatigue and stomatitis. Capecitabine is used in gastrointestinal and breast cancers. The enzyme dihydropyrimidine dehydrogenase (DPD) is the rate-limiting step for the catabolism of 5-FU, and converts more than 85 per cent of clinically administered 5-FU into inactive metabolites. It is primarily responsible for the high systemic clearance and short half-life of this drug, and therefore limits the amount of 5-FU available for conversion to the most active cytotoxic metabolite, 5-FUTP. DPD is found in many human tumours, but also in normal tissues, including the liver and the intestines, where it is largely responsible for the erratic bioavailability of 5-FU. Pharmacological inhibition of DPD may therefore increase the therapeutic index and efficacy of oral 5-FU, by allowing consistent dose delivery, eliminating hepatic clearance and producing more predictable drug clearance through the renal tract. In addition, over-expression of DPD in tumour cells may result in rapid intracellular fluoropyrimidine destruction and increased resistance to 5-FU. It is theoretically possible that the oral administration of fluoropyrimidines together with DPD inhibitors may overcome clinical drug resistance. In contrast to capecitabine, which is absorbed as an inactive pro-drug, other novel oral fluoropyrimidine formulations are co-administered with inhibitors of DPD in order to produce an improved pharmacokinetic profile for 5-FU. These compounds include UFT (uracil/Tegafur), eniluracil, S-1 and BOF-A2. These novel agents all deliver a therapeutic advantage from DPD modulation, and permit safe and effective 5-FU administration.

86 Principles of chemotherapy and drug development

PURINE ANALOGUES

6-Mercaptopurine (6-MP) is an analogue of the natural purine base hypoxanthine. It is converted by the enzyme hypothine-guanine phosphoribosyl transferase to the active nucleotide 6-mercaptopurine ribose phosphate, which inhibits de-novo purine synthesis. The triphosphate nucleotides also incorporate into DNA, causing strand breakage. 6-MP is absorbed well orally, and broken down by hepatic xanthine oxidase to inactive metabolites, with half the dose excreted within 24 hours. Allopurinol can inhibit this enzyme, and therefore if both drugs are co-administered, care is needed in order to reduce the risk of increased toxicity. Toxicity includes emesis, myelosuppression and a hepatic toxicity characterized by cholestatic jaundice. 6-Thioguanine (6-TG) is an analogue of guanine and has a similar mechanism of action to 6-MP. However, xanthine oxidase is not involved in its metabolism, and therefore there is no interaction with allopurinol. Again, oral administration is used, and the main indications are in haematological cancers.

PYRIMIDINE ANALOGUES

Cytarabine (cytosine arabinoside; Ara-C) is an analogue of deoxycytidine isolated from the sponge Cryptothethya crypta. It follows the same metabolic pathways of its physiological counterpart, and thus requires to be transported to the cell for activation. Cytarabine triphosphate (araCTP) is the cytotoxic metabolite of cytarabine, and acts via inhibition of DNA replication and repair and by incorporation into the DNA. Because of this, it is considered as an S-phase-specific drug, although it is active at other phases of the cycle. The main use is in the treatment of lymphoma and leukaemia, and it is given by intravenous injection because it is affected by first-pass metabolism if given orally. Intrathecal cytarabine is administered in the treatment of meningeal leukaemia and carcinomatosis. Toxicities include myelosuppression, emesis and diarrhoea. Syndromes of pulmonary toxicity and neurological toxicity occur rarely. Gemcitabine (2,2-difluorodeoxycytidine) is a pyrimidine analogue structurally similar to cytarabine. The metabolism differs in that accumulation of its active cytotoxic metabolite is higher than ara-CTP, and its elimination is much more prolonged. The mechanism of activity is similar, consisting of incorporation into DNA and inhibition of DNA synthesis. However, gemcitabine can also be incorporated into RNA. Toxicity is relatively low, consisting of myelosuppression, lethargy, flu-like symptoms and a skin rash. A rare pulmonary toxicity is also thought to be implicated. Gemcitabine is active in many pre-clinical solid-tumour models, and has demonstrated clinical activity against ovarian, gastrointestinal, breast, bladder and nonsmall-cell lung cancers. Furthermore, pre-clinical evidence for synergism has been demonstrated with several other cytotoxic agents, including cisplatin, etoposide and mitomycin C.

Anti-tumour antibiotics ANTHRACYCLINES

Doxorubicin hydrochloride is one of the most widely used anti-cancer drugs and has the broadest spectrum of activity of all chemotherapeutic agents. Daunorubicin was first isolated from Streptomyces in the 1960s, and was found to have activity against a variety of cancers. Mutations of Streptomyces led to a new strain from which doxorubicin was isolated. These two first-generation anthracyclines differ structurally by a single hydroxyl group, which results in a considerable difference in their anti-tumour activity. The mechanism of action has not been completely determined, but seems to involve DNA intercalation, free-radical formation, covalent DNA binding and inhibition of the enzyme topoisomerase II. Daunorubicin is mainly used for the treatment of acute non-lymphocytic leukaemia, whereas doxorubicin has a much wider spectrum of activity and is particularly used in the treatment of lymphomas, small-cell lung cancer, breast cancer, upper gastrointestinal cancer, sarcomas and ovarian cancer. Doxorubicin is administered by the intravenous route and is rapidly metabolized by the liver, to be excreted in bile. Caution must be used in hepatic dysfunction, and it (and all anthracyclines) is highly vesicant. Other toxicities include emesis, myelosuppression, oropharyngeal ulceration, diarrhoea and alopecia. The major long-term complication is a cumulative, dose-limiting cardiotoxicity, which is irreversible and may be fatal. Doses are usually up to 75 mg/m2 as a single agent every 3 weeks, but cardiotoxicity becomes increasingly frequent at cumulative doses of 450 mg/m2. ‘Cardioprotectors’ such as bisdioxopiperazine have been developed in an attempt to circumvent this cardiotoxicity, and are thought to work by chelating iron required by doxorubicin to produce the free radicals proposed to initiate the membrane damage evident in cardiac cells. Developmental chemistry has produced more than 1000 structural anthracycline analogues in an attempt either to increase activity of the drug or decrease toxicity, especially cardiac. Most do not proceed to clinical testing, and many get to trials only to demonstrate no clear advantage over doxorubicin or different toxicities. Epirubicin was synthesized in 1975 and has a similar spectrum of activity to doxorubicin while exhibiting less chronic cardiotoxicity. Idarubicin was shown to have a high affinity for lipids, and therefore can be administered effectively by the oral route. Liposomal drug-delivery systems (e.g. daunorubicin encapsulated by distearoylphosphatidylcholine/cholesterol, DaunoXome, and polyethylene glycol (PEG)-coated liposomal encapsulation of doxorubicin, Caelyx) have been extensively investigated as carriers for anti-cancer agents. Both DaunoXome and Caelyx have longer half-lives, higher AUCs and lower clearances than either free daunorubicin or doxorubicin, and also appear to be free of significant cardiotoxicity, and generally have decreased anthracycline-like

Classification of cytotoxic drugs, mode of action, toxicities and clinical utility 87

toxicities. However, myelosuppression is still an important feature of both formulations at recommended doses, with neutropenia occurring at grade III/IV in 50–60 per cent of patients. In addition, plantar–palmar erythrodysaesthesia was noted to be dose limiting at higher cumulative doses of Caelyx. Liposomal drug-delivery systems have been found to be especially useful in the treatment of autoimmune deficiency syndrome-associated Kaposi’s sarcoma (AIDS-KS), as conventional treatment with anthracyclines tends to be limited by cumulative toxicities (especially cardiac) preventing prolonged courses of chemotherapy.

Kaposi’s sarcoma. The main toxicities are myelosuppression, mucositis, diarrhoea and alopecia. In addition, drug extravasation can lead to severe tissue necrosis. Actinomycin D appears to inhibit DNA repair after radiation damage, and therefore the combination of both modalities enhances the risk of toxicity.

Plant-derived agents Many of the anti-cancer drugs that are used in clinical medicine are of natural origin.

MITOXANTRONE

Mitoxantrone is based on the anthracenedione structure. It is completely synthetic and was designed with the aim of retaining anthracycline anti-tumour activity with less toxicity. It undergoes DNA intercalation, in a similar fashion, and also inhibits topoisomerase II. It is given by intravenous injection and has a long terminal half-life of up to 40 hours. It is used in leukaemia, breast cancer and in combination regimens for the treatment of lymphomas. The reduced toxicity profile makes it an attractive drug to use in the elderly breast cancer patient. In addition, cardiac toxicity is less than that due to doxorubicin, probably as a result of its decreased free-radical production. BLEOMYCIN

Bleomycin is a mixture of low-molecular-weight glycopeptides isolated from the fungus Streptomyces verticullus and has both anti-bacterial and anti-cancer activity. The mechanism of cytotoxicity appears to relate to DNA binding and the production of strand breakage, with ferrous iron being essential to this mechanism. It is administered by parenteral injection and is renally excreted, with an initial half-life of 30 minutes and a later elimination phase of 2–9 hours. It is generally administered either by intravenous infusion or intramuscular injection, and also has utility via the intra-cavity route to control pleural or pericardial effusions. It has virtually no myelosuppressive toxicity or gastrointestinal side effects. Chronic administration can produce pneumonitis, which can lead to an irreversible and occasionally fatal interstitial fibrosis. Fevers, chills and flu-like symptoms are common, and prolonged administration also leads to skin pigmentation. It is used mainly in combination regimens for the treatment of germ-cell tumours and lymphomas. ACTINOMYCIN D

This compound is also isolated from Streptomyces and acts in a similar fashion, by DNA intercalation and the induction of strand breaks. It is eliminated almost unchanged in the bile and urine. Actinomycin D is usually administered intravenously. It is active against choriocarcinoma, Wilms’ tumour, Ewing’s sarcoma, embryonal rhabdomyosarcoma and, to a lesser extent, testicular cancer, lymphoma and

VINCA ALKALOIDS

Compounds with marked anti-tumour activity have been extracted from the periwinkle plant. Vinblastine and vincristine have been widely used, both as single agents and in combination with other drugs. Vinca alkaloid analogues have been prepared either by functional transformation (vindesine, desacetylvinblastine-amide) or, more recently, by hemisynthesis (vinorelbine, 5-noranhydrovinblastine). Although these compounds are all chemically related, differences have been observed in anti-tumour activity and toxicity. The mode of action of vinca alkaloids is yet to be completely understood, but they act as mitotic spindle poisons, which impair chromosomal segregation during mitosis. Microtubules are essential for normal cellular function and are involved in the maintenance of cell shape, mobility, adhesion and intracellular integrity, as well as having a role in the formation of the mitotic spindle during proliferation. Vinblastine is active in haematological cancers and in testicular and breast cancer. Vincristine is also active in these tumours, in addition to Wilm’s tumour, Ewing’s sarcoma, neuroblastoma, hepatoblastoma and embryonal rhabdomyosarcoma. The anti-tumour activity of vindesine is similar to that of vinblastine and vincristine, whereas vinorelbine is particularly active in non-small-cell lung cancer, breast cancer, ovarian cancer and Hodgkin’s disease. Vincristine and vindesine administration can cause neurological toxicity characterized by a decrease in the deep tendon reflexes, paraesthesias, constipation, myalgias, muscle weakness and paralytic ileus. Vinblastine generally produces haematological toxicities. Vinorelbine neurotoxicity is usually very mild, with only rare cases of paraesthesia or paralytic ileus being reported. Experimental evidence suggests that this may be due to the capacity of vinorelbine to bind to mitotic microtubules, rather than axonal microtubules. Clinical pharmacokinetics of vinca alkaloids are characterized by large distribution volume, high systemic clearance and long terminal half-life, although there are significant differences between analogues. TAXANES

Paclitaxel (Taxol) is a chemically complex molecule first isolated from the bark of the Pacific Yew tree Taxus brevifolia in

88 Principles of chemotherapy and drug development

the early 1970s. Its unique mechanism of action was not elicited for almost a decade and its importance as a major advance in the treatment of malignant disease was not recognized until 1989. Paclitaxel interferes with cell division by manipulating the molecular regulation of the cell cycle. In the presence of paclitaxel, polymerization of subunits of tubulin occurs, and the formed microtubules resist disassembly, thus shifting the equilibrium towards microtubule formation. Disruption of this equilibrium interferes with cell division and normal cellular activities involving microtubules. The pharmacokinetic behaviour of paclitaxel was studied during the early-phase trials in the 1980s. These studies used infusional schedules of between 1 and 24 hours and optimally modelled the concentration/time profile using a triphasic model. In general, administered dose was proportional to the area under the time/concentration curve (AUC). However, shorter infusions of paclitaxel (3 hours) seem to demonstrate non-linearity, and the important implication for this feature is that small dose de-escalations may result in a disproportionate lowering of the AUC, with subsequently decreased anti-tumour activity. Paclitaxel is 90 per cent bound to plasma proteins, but this is readily reversible and results in rapid elimination of the drug. Renal excretion is negligible, and no renal metabolites have been identified. There may be significant hepatic metabolism, and various studies are in progress to look at the effects that other drugs that use the cytochrome P450 pathway may have on the pharmacological behaviour of paclitaxel. Administration of paclitaxel is associated with allergic hypersensitive reactions ranging from acute anaphylaxis and hypotension to flushing, rashes and urticaria. Indeed, development of this agent was almost halted in the early stages due to the severity of these reactions. However, the instigation of a premedication regimen consisting of corticosteroids and H1/H2 blockers has significantly reduced the incidence of allergic reactions from 20 per cent to 3 per cent. Although the formulation of paclitaxel in Cremophor EL® (due to its limited aqueous solubility) may be responsible for the hypersensitivity phenomena, some contribution of paclitaxel itself is possible, as hypersensitivity reactions also occur with the semisynthetic analogue docetaxel formulated in Tween-80. Leukopenia is the dose-limiting toxicity, and thrombocytopenia is rare. Myelosuppression occurs early and is associated with a rapid recovery, allowing treatment to proceed on a 3-week cycle. Neurotoxicity occurs with higher cumulative doses of paclitaxel, and with higher doses per course. This is mainly a sensory neuropathy and manifests in a ‘glove and stocking’-type distribution. It is at least partially reversible with time. Many cardiac arrhythmias have been reported with paclitaxel administration, ranging from asymptomatic bradycardia to various degrees of heart block and atrial/ventricular tachyarrhythmias. Other frequently reported toxicities include alopecia (universal), fatigue and arthralgia/myalgia. Indications for use

include breast cancer (anthracycline-pretreated), ovarian cancer, and non-small-cell lung cancer. Docetaxel (Taxotere) is another member of the taxoid family. There is pre-clinical evidence to suggest that docetaxel may be superior to paclitaxel. Docetaxel has been shown to be more potent (up to five-fold) in vitro than paclitaxel with regard to the promotion of tubulin polymerization and inhibition of depolymerization. In a direct comparison with paclitaxel in a large number of freshly explanted tumours (including breast, ovarian, lung and colorectal tumours), docetaxel was found to have at least equivalent cytotoxicity, but with incomplete crossresistance. Docetaxel also had a longer residence time, accumulated at higher concentrations within cells and demonstrated a superior therapeutic index in vivo. Clinical studies have confirmed the presence of incomplete crossresistance with paclitaxel, reporting activity for docetaxel in paclitaxel-resistant metastatic breast cancer. Docetaxel pharmacokinetics following a 1-hour infusion demonstrate that the plasma elimination at the highest doses follows a triphasic decay, with a terminal half-life of 13.5 hours and a plasma clearance of approximately 21 L/h per m2. The AUC increases linearly with the dose and correlates with the percentage decrease of neutrophils. Less than 10 per cent of the administered dose is excreted unchanged in the urine. The recommended dose as a single agent is 100 mg/m2 given as a 1-hour intravenous infusion. Patients that have been heavily pretreated or have abnormal hepatic function should receive a reduced dose. The most frequent toxicity is an early, reversible, noncumulative neutropenia, which may be associated with concurrent infections. Anaemia has also been observed. Hypersensitivity reactions occurred in 25 per cent of patients who were unpremedicated with corticosteroids, and these generally occurred on the first course, within a few minutes of the start of the infusion. Premedication with corticosteroids has reduced the incidence of hypersensitivity reactions to less than 5 per cent. Cutaneous reactions occur, characterized by a rash, mainly on the extremities (but also localized eruptions on arms, face or thorax), and are occasionally associated with pruritus. These are usually transient and resolve prior to the next course of treatment. Less frequently, desquamation is observed. Nail changes (onycholysis, hypo/hyperpigmentation) are also seen. A fluid-retention syndrome, characterized by asymptomatic weight gain and/or oedema (and, less often, pleural, peritoneal or pericardial effusions), has been observed. This generally starts in the lower extremities and at cumulative doses of 400 mg/m2. The pathogenesis of this condition is incompletely understood, but appears reversible on cessation of docetaxel treatment and can be significantly reduced by premedication with dexamethasone. Mild degrees of this syndrome can be treated adequately by diuretic therapy, but it is recommended that patients with severe oedema should not continue with docetaxel. Clinically significant cardiac events occurred in less than 2 per cent of all patients treated, and are not clearly

Classification of cytotoxic drugs, mode of action, toxicities and clinical utility 89

related to docetaxel administration. Other significant toxicities encountered are alopecia, hepatotoxicity (mild, reversible transaminase elevations), mucositis, diarrhoea, arthralgia/myalgia and peripheral neuropathy (sensory and motor). Emesis is generally mild and easily treated with 5HT3 antagonists.

Topoisomerase I and II inhibitors DNA topoisomerase I and II are enzymes that bind to supercoiled DNA, forming a ‘cleavable complex’ and, through strand breakage, passage and re-ligation, allow a wide variety of essential DNA metabolic reactions, including replication and repair, to take place. These enzymes are functionally related, work together and appear to be essential to maintain cellular viability throughout the cell cycle. Since it was shown in the 1980s that the cleavable complex could be stabilized by known cytotoxic drugs such as doxorubicin, etoposide and camptothecin, resulting in interference with the strand breakage–re-ligation catalytic cycle and subsequent cell death, much research has taken place into the development of agents that exploit this novel nuclear target. Established inhibitors of topoisomerase II include the anthracycline antibiotics (e.g. doxorubicin) and the epipodophyllotoxins (etoposide), which were not developed on the basis of rational drug design against this specific cellular target, and are in fact not ‘pure’ topoisomerase II inhibitors. Specific topoisomerase I inhibitors with antitumour activity include the heterocyclic alkaloid camptothecin and its analogues. Isolated in 1966 from the tree Camptotheca acuminata, early studies with camptothecin demonstrated unpredictable and severe toxicity with limited efficacy. However, the development of water-soluble synthetic/semi-synthetic analogues of camptothecin, such as irinotecan (CPT-11) and topotecan, and the discovery that topoisomerase I levels were higher in some tumours compared to normal tissues have led to renewed interest in the topoisomerases as important targets for anti-cancer agents. Topotecan exerts its cytotoxic effects by stabilizing the covalent DNA–topoisomerase I cleavable complex, thus blocking DNA repair. When DNA replicates in the presence of this complex, double-strand breaks occur and the resulting DNA fragmentation causes cell death. The major side effect of topotecan is myelosuppression, which can be severe, is schedule dependent and may be associated with infectious complications. Thrombocytopenia and anaemia are also common, and non-haematological toxicities are otherwise mild – emesis, diarrhoea, oropharangeal ulceration and alopecia. Significant activity has been observed in refractory ovarian cancer, small-cell lung cancer, breast cancer, lymphoma, and head and neck cancer. It has only modest activity against gastrointestinal tumours, unlike CPT-11 (irinotecan). Combination studies of topotecan with other cytotoxic agents, including

platinum and paclitaxel, demonstrate dose-limiting myelosuppression, generally requiring dose reductions of both agents. CPT-11 was developed in Japan and is used for the treatment of 5-FU-relapsed colorectal cancer. In addition to colorectal cancer, activity has been observed in ovarian cancer, lung cancer (small cell and non-small cell), gastric cancer, oesophageal cancer and cervical cancer. It is converted by hepatic carboxylesterases to a major metabolite, SN-38, which is up to 2000-fold more effective at topoisomerase I inhibition than the parent compound. Like topotecan, the formation of a cleavable complex effects damage to the DNA through double-strand breaks. After intravenous infusion, CPT-11 concentrations decline in a multi-exponential manner, with a mean terminal half-life of 6 hours, whereas the equivalent SN-38 half-life is 10 hours. SN-38 is much more highly protein bound than CPT-11. The main toxicities are myelosuppression, which can be severe, and diarrhoea. CPT-11 can induce both early and late diarrhoea, which appears to be mediated by different mechanisms. Early diarrhoea (within 24 hours) is cholinergic in nature and can be avoided by atropine administration. Late diarrhoea can be prolonged and severe and requires prompt instigation of loperamide as it can quickly lead to dehydration and electrolyte imbalance. ETOPOSIDE

Podophyllin and podophyllotoxin are derived from the mandrake root, and act as mitotic poisons in a similar fashion to vinca alkaloids. Early clinical trials were stopped because of significant toxicities, and researchers looked at analogue development as a way of proceeding. VP-16 (etoposide) is an epipodophyllotoxin analogue that is not only less toxic, but also has a different mechanism of action from the parent compound. It interferes with the re-ligation of topoisomerase II, causing stabilization of DNA–topoisomerase II complexes that are cleavable and result in DNA strand breaks. Another possible contributory mechanism of cytotoxicity is the generation of free radicals. Oral VP-16 bioavailability is approximately 50 per cent (range 17–100 per cent), and approximately 50 per cent of the VP-16 dose is eliminated as unchanged drug or glucuronide within 24 hours of administration. Protein binding is approximately 90 per cent. VP-16 clearance appears to be related to renal clearance, and therefore increased toxicity may be expected in patients with poor renal function. Bone-marrow and gastrointestinal toxicity dominate the side effect profile, but other common side effects include alopecia, nausea, vomiting and diarrhoea. VP-16 is active in small-cell lung cancer, germ-cell tumours, ovarian cancer, choriocarcinoma and haematological cancers. Dosing schedules may involve intravenous administration, but many studies have demonstrated that chronic oral dosing is feasible and safe.

90 Principles of chemotherapy and drug development

Miscellaneous agents AGENTS DERIVED FROM MARINE ORGANISMS

Marine organisms have survived for up to 700 million years through natural selection and the release of potent chemicals that offer protection in a hostile milieu without the need for bioactivation. It follows that there is extraordinary potential among these toxic chemicals for antitumour specificity. Over the past 10–15 years, a wide range of potent chemicals with different cellular targets has been isolated. Many have been evaluated in clinical trials, and some are listed briefly here. Bryostatin 1 is the prototype of a novel class of structurally related compounds isolated from the marine bryozoan Bugula neritina. It is a macrocyclic lactone, which exhibits many biological effects mediated through modulation of protein kinase C, a family of enzymes crucial in cellular signalling pathways controlling proliferation and differentiation. It has demonstrated broad-spectrum preclinical anti-tumour activity, and has also been shown to induce differentiation, enhance the immune response and inhibit the production of members of the matrix metalloproteinase family thought to be essential for angiogenesis. Dolastatin 10 was isolated from a herbivorous mollusc in the Indian Ocean, and acts by halting microtubule assembly. Exceptional potency has been described in preclinical models, and it is rapidly and extensively metabolized, with high protein binding. Ecteinascidin 743 (ET-743; Yondelis) was isolated from a Caribbean tunicate in 1990 and forms covalent adducts with DNA in the minor groove, with sequence specificity. In addition, effects on the microtubular spindle are postulated, and down-regulation of transcription factors. A broad spectrum of pre-clinical anti-cancer activity has been demonstrated, in addition to a lack of cross-resistance with other agents, including anthracyclines, taxoids and platinum. Target organs for toxicity are the liver and bone marrow. This agent has been evaluated extensively in clinical trials, with activity in soft-tissue sarcoma.16* Aplidine is a potent cyclic depsipeptide isolated from a Mediterranean marine tunicate, Aplidium albicans. The mechanism of action is not completely understood, but studies are in progress to identify the potentially unique target involved in its anti-tumour activity.

DRUG RESISTANCE Resistance to chemotherapeutic agents remains one of the predominant reasons for cancer treatment failure. Tumours can be intrinsically resistant, showing no significant response to first-line agents; resistance may also be induced such that, after an initial response to drug therapy, the tumour acquires drug resistance to initial and/or subsequent therapy. A defining feature of all cancer types is the presence of an unstable genome. The high mutation rate of

cancer cells results in the characteristic phenotype of uncontrolled cell growth and enhanced survival seen in tumours. By the time the cancer becomes clinically detectable, the original clone of cells has diversified into a multi-clonal tumour capable of adapting to environmental stresses such as anti-tumour agents. The Goldie and Coldman hypothesis proposes that numerous subpopulations of cells within a tumour are likely to possess mutations that render certain cells resistant to treatment. Although chemotherapy-sensitive clones are destroyed, resistant clones continue to evolve. The rationale behind the use of combination chemotherapy lies in this inherent genetic diversity that the tumour possesses. Mechanisms of drug resistance are multiple and diverse. In any given tumour type, it is usual for combinations of different mechanisms to contribute to the overall resistance pattern seen. The major advances in the field of drug resistance have been in the understanding of the molecular pathways by which tumour cells acquire this resistance. As our knowledge of the intracellular pathways of cell survival, division and cell death broadens, the importance of cell-cycle-specific mechanisms of drug resistance is being increasingly recognized. Ways in which this might occur are varied and complex and by no means completely elucidated. This section of the chapter highlights some important and clinically relevant examples of how drug resistance may occur and current therapeutic advances that are designed to overcome this obstacle (Fig. 5.1).

Cytokinetic drug resistance Various models have been proposed to predict cell kill in the presence of cytotoxic agents, as outlined earlier in the chapter. There exists a broad relationship between the rate of cellular proliferation within a tumour and subsequent response to chemotherapy. The difference between curable tumours such as lymphomas and the common solid tumours is the higher proportion of cycling cells in lymphomas compared with the relatively small percentage (2–3 per cent) of proliferating cells in the latter. The proportion of cycling cells may vary considerably, even within tumours of the same histological type, due to genetic heterogeneity and tumour microenvironment.17 Certain cytotoxic agents are cell-cycle specific, having anti-tumour effects only on cells in cycle. Of this group of drugs, some only have activity in cells within certain stages of the cell cycle, for example 5-FU and the anthracyclines targeting cells in the S phase. It follows that in cells proliferating slowly, a short period of exposure to an S-phase-specific drug will result in a smaller proportion of cell kill than for rapidly proliferating cells. In order to overcome ‘cytokinetic resistance’ to a cellcycle-phase-specific agent, a prolonged dosing schedule can prove more effective than bolus regimens. This enables a higher proportion of cells in the vulnerable phase of their cell cycle to be exposed to the chemotherapeutic agent (Fig. 5.2).

Drug resistance 91

Reduced delivery of cytotoxic agent Tumour angiogenesis

Decreased drug uptake

Increased drug efflux

Decreased drug activation Inhibition of apoptosis

Increased DNA repair

Alteration in target protein

Increased metabolism Alteration in target protein

Figure 5.1 Cellular mechanisms of drug resistance. Original tumour mass

Cells entering S-phase of cell cycle Cells not proliferating

Tumour mass after short exposure to S-phase agent

Tumour mass decreases further as result of prolonged exposure to S-phase agent

Figure 5.2 Prolonged exposure to cell-cycle-phase-specific agents may allow cytokinetic resistance to be overcome.

For example, several randomized trials have shown the superiority in tumour response rates and overall survival in colorectal cancer with the use of a prolonged infusion of 5FU compared with bolus regimens.18***,19**

resistance. There is also the potential to exploit tumour microenvironment to enhance the targeting of cancer therapy. HYPOXIA

Tumour microenvironment Cells in normal tissues exist in a homeostatically controlled environment. A wide variation exists, however, in the physiological microenvironment of tumour cells, even between different regions of a single solid tumour. Such differences in the microenvironment between tumour cells and normal cells, as outlined below, may account for drug

Rapid tumour proliferation results in tumour cells outgrowing their existing blood supply, with resultant lack of nutrients, hypoxia and eventual necrosis. Hypoxia is one of the characteristic features of cancer, and is a cause of resistance to chemotherapy and radiotherapy. A key reason for this effect is that hypoxia reduces the rate of cell proliferation, decreasing the effectiveness of cell-cycle-specific drugs. A second factor is that hypoxic cells are those often

92 Principles of chemotherapy and drug development

furthest away from an adequate blood supply and therefore exposed to a lower concentration of the drug. Tumour hypoxia may be used to direct therapy towards cancer cells while sparing normal, aerobic tissues. Drugs that undergo reductive activation under hypoxic conditions can be used as pro-drugs of cytotoxic agents. Once activated, these agents act as cytotoxins of tumour cells by direct or indirect (bystander) mechanisms, and are specifically targeting those hypoxic cells that would normally be resistant to traditional cytotoxins. A clinical example of how this can be applied is the use of tirapazamine, a benzotriazine-di-N-oxide, which is selectively activated under hypoxic conditions to DNA-damaging reactive radicals that synergize with cisplatin and radiation. A phase III trial has shown a survival benefit of patients with advanced non-small-cell lung cancer treated with tirapazamine and cisplatin compared with cisplatin alone,20** and comparison of tirapazamine and cisplatin with cisplatin and etoposide in a second phase III trial21** has shown similar response rates between the two groups. Several other hypoxically activated drugs are under investigation, including AQ4N, an anthraquinone-di-N-oxide, that is activated intra-tumorally by CYP3A, a member of the cytochrome P450 family of enzymes, to the topoisomerase II inhibitor AQ4. Tumour expression of CYP3A is thought to be upregulated under hypoxic conditions22 and may enhance the selectivity of AQ4N. Clinical studies of AQ4N are currently underway.

therapy.23 In combination with traditional cytotoxic agents, anti-angiogenic agents have been shown to behave synergistically. For example, the use of bevacizumab (Avastin) in combination with standard platinum-based chemotherapy for non-small-cell lung cancer has proved effective in enhancing tumour response to chemotherapy and resulted in a statistically and clinically significant survival advantage in a phase III evaluation.24**

Control of intracellular drug concentrations Cell membranes are biological barriers composed of proteins embedded in a cholesterol and phospholipid bimolecular matrix, which selectively inhibit the passage of drug molecules. Drugs may cross this biological barrier by passive diffusion, facilitated passive diffusion, active transport or pinocytosis (Fig. 5.3). Pinocytosis probably plays a minor role in drug transport, except for protein drugs. It follows that any alterations to the structure or function of

ANGIOGENESIS

Once tumours have outgrown their existing blood supply, in order to continue to grow they must develop their own blood supply by means of neovascularization or angiogenesis. Angiogenesis is stimulated by hypoxia and tumour secretion of angiogenic factors. The resultant tumour ‘neovasculature’ possesses characteristic structural and physiological differences to the normal cellular micro-environement. Vessels are generally more tortuous, with increased vascular permeability. The process of neo-angiogenesis can result in drug resistance in a number of ways. Whereas traditional cytotoxic agents will be effective against sensitive clones of tumour cells, drug-resistant tumour populations supported by a new blood supply will continue to grow. Increased vascular permeability accompanied by reduced lymphatic clearance within the tumour environment results in an increased interstitial pressure and hence reduced delivery of cytotoxic therapy to the tumour. The mechanisms and implications of angiogenesis are covered in detail in a separate chapter (Chapter 12). The use of anti-angiogenic agents directed against vascular endothelial cells can result in regression of tumour blood vessels, blood supply and tumour size. The relative genetic stability of endothelial cells compared with tumour cells renders them far less prone to the development of drug resistance with repeated courses of anti-angiogenic

ATP

A

B

C

Cell membrane

Carrier component of membrane

Drug molecule

Transport protein

Figure 5.3 (A) Passive diffusion: transport across a cell membrane depends primarily on the concentration gradient of the solute, but also on the molecule’s lipid solubility, degree of ionization and size, and on the area of the absorptive surface. (B) Facilitated passive diffusion: a carrier component is thought to combine reversibly at the cell membrane exterior with a selective substrate molecule of a relatively specific molecular configuration. This results in rapid diffusion of the carrier–substrate complex across the membrane, releasing the substrate at the interior surface. The process does not require energy expenditure, and transport against a concentration gradient does not occur. (C) Active transport involves membrane transport proteins, of which the ATP-binding cassette family is the most extensively studied. Active transport is characterized by selectivity and saturability, requires energy expenditure by the cell, and may result in accumulation of substrates intracellularly against a concentration gradient.

Drug resistance 93

proteins involved in drug transport will affect the amount of the drug reaching its intracellular target, and hence lead to increased drug resistance. DECREASED DRUG UPTAKE

Folates are critical in DNA and RNA synthesis by acting as co-factors in a number of reactions, including the synthesis of purines and thymidylate de novo. Drugs targeting the folate-dependent enzymes, such as the dihydrofolate reductase inhibitor methotrexate and the thymidylate synthetase inhibitor 5-FU, are widely used as cytotoxics in the treatment of cancer. The passage of anti-folate agents across the cell membrane occurs predominantly via the widely expressed reduced folate carrier (RFC) system. In cell lines in which a defective RFC protein is present, 250fold higher concentrations of methotrexate are required for equivalent cell kill as compared with cell lines in which the transport protein has retained normal function. In the clinical setting, decreased transport of methotrexate across the cell and resistance to methotrexate were demonstrated in children with acute lymphoblastic leukaemia (ALL), in whom the presence of a particular polymorphism in the RFC gene (RFC1A80) resulted in higher levels of methotrexate in the plasma and a shorter event-free survival.25 One strategy to overcome this form of drug resistance is the use of anti-folate agents selectively targeted to folate transport proteins other than the RFC, such as the α-folate receptor (α-FR). The α-FR is often over-expressed in ovarian and other epithelial malignancies.26 Conventional antifolate agents such as methotrexate have a low affinity for the α-FR. Novel anti-folate inhibitors of thymidylate synthetase have been synthesized with low affinity for the RFC and high affinity for the α-FR. For example, BGC 945 has been studied in vitro in α-FR over-expressing tumour cell lines and has been identified as a potential candidate for phase I studies.27 FPGS (folylpoly-γ-glutamate synthetase) catalyses the attachment of glutamate residues to all naturally occurring folates and folate analogues such as methotrexate. Absence, decreased expression and mutations resulting in decreased activity of FPGS may all result in impaired polyglutamylation and the inability of cells to retain folates and their analogues after cell-membrane transport.28 This may lead to an intrinsic resistance to anti-folates such as methotrexate. Evidence of defective polyglutamylation resulting in resistance has been seen in rodent tumour cell lines and in human leukaemia, breast and other tumour types.29–31 In ‘good-risk’ subgroups of children with ALL, the ability of blast cells to accumulate methotrexate and form long-chain methotrexate polyglutamates is an important determinant of outcome, with the accumulation of higher levels of methotrexate and its polyglutamates correlating with a more favourable event-free survival outcome.32 Defective polyglutamylation as a mechanism of resistance can be overcome by the development of newer anti-folates that may not require polyglutamylation for

retention and efficacy. For example, trimetrexate, an analogue of methotrexate, is retained in cells in high concentrations despite its inability to be polyglutamylated, although limited activity as a single agent in phase II studies in cancer and dose-limiting toxicities have restricted its clinical use.33 ZD9331, which does not require polyglutamylation for its activity, has been the subject of numerous phase I and II studies, as monotherapy and in combination, and promising activity has been seen in platinum-refractory relapsed ovarian, pancreatic and gastric cancers.34 INCREASED DRUG EFFLUX AND MULTI-DRUG RESISTANCE

Tumour cells exposed to one chemotherapeutic agent may often demonstrate resistance to other structurally unrelated agents with differing mechanisms of action, a phenomenon known as multi-drug resistance (MDR). One proposed mechanism to account for this is the presence of transport proteins that actively pump drugs out of cells. This is of particular relevance to hydrophobic agents such as the taxanes, anthracyclines and vinca alkaloids that enter cells by means of passive diffusion. One such protein is a member of the ATP-binding cassette family of membrane transporters, P-glycoprotein (P-gp), which is expressed at high levels in several normal tissues and over-expressed in certain solid tumours and haematological malignancies. P-gp knockout mice have increased sensitivity to chemotherapeutic agents, as drug elimination is decreased and cellular levels of the cytotoxic agent are increased.35 Alterations in drug efflux secondary to expression of P-gp have also been demonstrated in vitro. In clinical practice, data exist that would support a role for P-gp in mediating MDR. In soft-tissue sarcoma of childhood, detectable levels of P-gp appear to be an important adverse prognostic factor. The probability of a longer relapse-free and overall survival was significantly greater in chemotherapy-treated patients with P-gp-negative tumours than in those whose tumours contained detectable levels of P-gp.36 In acute myeloid leukaemia or breast cancer, patients with P-gp activity at presentation were significantly more likely to have chemotherapyresistant disease.37***,38 Clinical trials of agents that inhibit proteins such as P-gp (cyclosporine, verapamil) have been disappointing, and these agents are not routinely employed in clinical practice. Their contribution to clarifying the clinical relevance of P-gp and other proteins potentially implicated in MDR, such as the MDR-associated protein (MRP) family, thus remains limited. Phase II trials of more specific third-generation P-gp inhibitors such as Tariquidar in conjunction with chemotherapy are ongoing.39* If P-gp plays a direct role in mediating MDR, one would expect to see improved, prolonged or even restored drug sensitivity in these patients as a result of effective inhib-ition of P-gp.

94 Principles of chemotherapy and drug development

Drug metabolism DECREASED DRUG ACTIVATION

Many anti-cancer agents are pro-drugs, agents that require metabolic activation by key enzymes prior to exerting cytotoxic effects. Consequently, any structural or functional abnormalities in these key enzymes could result in resistance to the effects of the drug, as a result of a decrease in the level of enzymatic activity and consequent decrease in the amount of active drug metabolite within the cell. Examples of this method of drug resistance include the absence or reduction in expression of salvage enzymes in the activation of the pyrimidine and purine anti-metabolites cytosine arabinoside and 6-mercaptopurine respectively. Ara-C requires activation by deoxycytidine kinase to ara-CTP, a competitive inhibitor of DNA polymerase-α. The rate of formation of ara-CTP is a critical factor in the response of acute leukaemia to ara-C therapy. Similarly, 6-MP and 6-TG require activation to their monophosphates by hypoxanthine-guanine phosphoribosyl transferase (HGPRT) before they are able to exert anti-tumour activity (inhibition of synthesis of purine nucleosides de novo). Reduced expression of, or decreased affinity for, 6MP or 6-TG by HGPRT results in drug resistance. The enzyme carboxylesterase is responsible for the conversion of irinotecan to its active metabolite SN-38, and reduced tumour expression of the enzyme may be responsible for inducing resistance. Strategies for overcoming resistance to irinotecan include gene therapy to transfer the carboxylesterase gene directly into tumour tissue prior to the administration of irinotecan. This approach has been used in cell lines and mouse models with some success.40,41

INCREASED DRUG METABOLISM OR DETOXIFICATION

Pathways of drug metabolism are traditionally classified as either phase I reactions (e.g. oxidation, reduction and hydrolysis) or phase II, conjugation reactions (e.g. acetylation, glucuronidation, sulphation and methylation). Most drugs are metabolized by several different enzymes. Enzymes of the cytochrome P450 super-family of drugmetabolizing enzymes are the most important enzymes that catalyze phase I drug metabolism. Agents responsible for the induction of these enzymes can result in striking variations in the pharmacokinetics and physiological effects of individual chemotherapeutic drugs. For example, the use of the anticonvulsant phenytoin in patients with central nervous system tumours resulted in increased clearance of irinotecan due to the induction of hepatic cytochrome P450 enzymes.42* Similarly, polymorphisms in the CYP enzymes can result in resistance to cytotoxic agents. Inhibition of CYP1B1 has recently been the focus of targeted drug therapy because this member of the CYP family is over-expressed in ovarian, breast and testicular tumours but not in normal tissues.43 CYP1B1 is involved

in the metabolism of various anti-cancer agents, resulting in reduced efficacy. Inhibition of this enzyme is therefore an attractive proposition for attempting to reverse drug resistance.44 Rapid drug detoxification within a cell can result in a decreased amount of active product available to bind to its intracellular target. Glutathione, an anti-oxidant, binds to highly reactive chemical groups generated by anthracyclines and platinum agents, and promotes drug efflux through ABC transporter proteins in the cell membrane. In tumour cell lines, the level of glutathione itself, as well as levels of other enzymes involved in the process of glutathione conjugation, correlates with the degree of resistance observed to platinum agents.45–47

Altered expression of target proteins Many chemotherapeutic agents ultimately exert their effect by interacting with one or more key target proteins. Mutations in target proteins may result in the inability of the drug to bind to its target and exert its effect; they may also result in a lower affinity of binding. This is exemplified by the taxanes, which exert their effects on the cellular microtubule apparatus during mitosis. Microtubule depolymerization to tubulin monomers is an important step in the restructuring of the microtubule apparatus for mitosis. The taxanes bind to and stabilize the protein tubulin, thus blocking the process of mitosis and eventually triggering cell death via apoptosis. Resistance to taxanes is seen in cell lines expressing mutations in β-tubulin that interfere with tubulin stabilization (48). Of clinical relevance, in a study sequencing β-tubulin genes in non-small-cell lung carcinoma patients treated with singleagent paclitaxel, the presence of β-tubulin mutations was found to be a predictor of paclitaxel resistance.49 If a drug exerts its effect by inhibition of a target protein, over-expression of the target proteins may confer resistance, simply due to the greater amount of target requiring inhibition for the same concentration of active drug. For example, the anti-folate agent 5-FU inhibits the enzyme TS. A high level of TS has been associated with a significantly poorer survival in Duke’s stage A–D colorectal cancers50 and appears to be a powerful prognostic indicator independent of disease stage.51 In-vitro studies have demonstrated that high levels of TS expression are associated with resistance to 5-FU.52 In the clinical setting, a statistically significant association has been demonstrated between the degree of TS expression in colorectal cancer metastases and response to infusional 5-FU,53 although the response appears to vary according to the particular schedule of 5-FU used. Specific TS inhibitors currently in development, either alone or in combination with traditional anti-folate agents, may prove effective in enhancing response to treatment in tumours with high levels of expression of TS. Agents such as irinotecan exert their cytotoxic effects by inhibiting the enzyme topoisomerase I involved in the

Drug resistance 95

relaxation and re-ligation of supercoiled DNA during DNA replication. This results in S-phase-specific cell kill. Human cancer cell lines that are resistant to irinotecan have been shown to exhibit increased levels of topoisomerase I, topoisomerase I mutations, or down-regulation and reduced activity of the enzyme. The true relevance of these changes to the mechanism of irinotecan resistance remains unclear due to the lack of well-designed prospective clinical studies. A combination chemotherapeutic approach has been shown to be of some benefit in overcoming resistance to irinotecan. Mitomycin C has been shown to increase topoisomerase I catalytic activity and, not surprisingly, has synergistic effects with irinotecan in pre-clinical studies. Sequential administration of this combination chemotherapy has shown promising activity in phase I studies in heavily pre-treated gastric, oesophageal, breast and non-small-cell lung cancer patients, with major responders showing a greater induction of topoisomerase I when compared with non-responders.54 Phase II studies continue to evaluate this combination regime.55* Alterations in target proteins conferring resistance are also demonstrated by the epidermal growth factor receptor (EGFR) family of transmembrane receptors, which include EGFR, HER-2, HER-3 and HER-4. The receptors exist as monomers spanning the plasma membrane, and require dimerization in response to the appropriate ligand in order to become functional. They play a critical role in tumour proliferation and survival by virtue of possessing tyrosine kinase activity. Abnormal signal transduction or ligandindependent activation of the EGFR receptor, often caused by mutation in the receptor extracellular domain, is thought to correlate with increased resistance to conventional chemotherapy and a poorer prognosis.56,57 The use of agents that interfere with EGFR signalling, such as the HER-2 inhibitor traztuzumab, and the EGFR tyrosine kinase inhibitors gefitinib and erlotinib, has provided a method to overcome resistance to cytotoxic therapy. The EGFR inhibitors exert their effect by binding the ATP pocket within the catalytic domain of the receptor. Traztuzumab has shown synergism with cytotoxic agents such as the anthracyclines. The co-localization of the topoisomerase II-α gene (the target of the anthracyclines) and the HER-2 gene on the same chromosomal region and potential co-amplification in tumours might be one explanation for this synergism.58 Similarly, the EGFR inhibitor cetuximab demonstrates synergism with irinotecan in colorectal carcinomas.59**

Tumour cell apoptosis A large number of chemotherapeutic agents act by the induction of programmed cell death, or apoptosis. A variety of enzymes, namely the caspases (intracellular cysteine proteases), mediate apoptosis in a cascade that leads to the systematic de-structuring and death of the cell. There are two main apoptotic pathways that activate the effector

caspases: an extrinsic apoptotic pathway involving the triggering of cell-surface death receptors, including tumour necrosis factor-α (TNF-α ) receptor and CD-95 (Fas), and an intrinsic pathway involving increased mitochondrial permeability and disruption of function. There is extensive cross-talk between the pathways. Two families of proteins are involved in apoptotic regulation. The Bcl-2 family of proteins act at the mitochondrial level and include promoters of apoptosis such as Bax and Bak, and inhibitors of apoptosis such as Bcl-2 and BclXL. A second family comprise the IAP (inhibitors of apoptosis proteins), survivin being one such example, which act as endogenous caspase inhibitors. The relative proportion of these proteins within a cell determines whether apoptosis is triggered in that individual cell. In cells undergoing DNA damage, the p53 family of proteins play a key role in triggering apoptosis, partly by regulating levels of Bax protein, as is seen in DNA damage occurring secondary to platinum drugs such as cisplatin. Drugs such as the taxanes that do not result in direct DNA damage are also able to trigger apoptosis by inducing phosphorylation of Bcl-2, reducing its binding and thus resulting in a higher proportion of pro-apoptotic proteins within the cell. It follows that accumulation of mutations resulting in the absence or under-expression of pro-apoptotic proteins, or over-expression of anti-apoptotic proteins, will not only result in tumorigenesis, but can also play a part in clinical drug resistance as a result of reduced apoptosis and cell death in response to drug-induced cellular damage. Invitro studies have shown Bcl-2 over-expression increases chemo-resistance, whereas Bax over-expression increases chemosensitivity.60,61 Ways of manipulating the process of apoptosis in order to overcome drug resistance have included the development of small-molecule inhibitors. For example, ABT-737, an inhibitor of the anti-apoptotic proteins Bcl-2, Bcl-XL and Bcl-w, has shown promise in animal models, cell lines and primary patient-derived cells.62 The use of techniques such as gene therapy in trying to restore p53 expression and of antisense oligonucleotides in attempting to reduce Bcl-2 expression, survivin expression or any specific gene of interest has also been investigated. Although some promising results have been seen in early trials, these techniques need continued development and refinement. More recently, attention has been paid to the importance of the protein ubiquitin in targeting cellular proteins for proteosomal degradation. Ubiquitin is a 76-aminoacid protein that, in conjunction with a three-enzyme ubiquitination complex, forms a polyubiquitin chain on a target protein. This in turn targets the protein for degradation via the 26S proteasome.63 With the knowledge that a number of tumour suppressor genes and oncogenes are integral to or degraded via the ubiquitin–proteasome pathway comes the realization that disruptions to this pathway may lead to alterations in the balance between proteins signalling cell death and those signalling survival. Examples include von Hippel Lindau (VHL) gene mutations in renal

96 Principles of chemotherapy and drug development

cell carcinoma resulting in altered function of the VHL ubiquitin–ligase complex. This results in reduced degradation of hypoxia-inducible factors and increased angiogenesis.63 Mutations in the adenomatous polyposis coli (APC) gene in colorectal carcinoma leads to reduced phosphorylation, ubiquitination and degradation of β-catenin, which is a transcription factor for genes such as cyclin D1, and MYC.63 Similarly, increased proteosomal degradation of the inhibitor I-κB results in increased levels of the transcription factor NF-κB and hence increased expression of the anti-apoptotic protein Bcl-2. The end result in all these cases is the inhibition of apoptosis and the potential for resistance to chemotherapeutic agents that are inherently relying on apoptosis for therapeutic effect. Inhibition of the 26S proteosome may be a mechanism to overcome drug resistance by allowing the process of DNA damage and apoptosis initiated by other chemotherapeutic agents to proceed. A number of agents have been identified and have been shown to overcome drug resistance in vitro in myeloma, prostate and ovarian cancer cells.64,65 One such agent is bortezomib, which has now been approved for use in the treatment of relapsed multiple myeloma. The effects of bortezomib appear to be related to reduced proteasomal degradation of the inhibitor I-κB, with subsequent decreased levels of the transcription factor NF-κB and hence reduced expression of the anti-apoptotic protein Bcl-2,66–68 as illustrated in Figure 5.4. There are initial data supporting a role for bortezomib in sensitizing cells to chemotherapy-induced apoptosis in solid tumours such as non-small-cell lung carcinoma.69

3) I-κB stabilises NF-κB and prevents nuclear translocation and transcription

1) Unbound NF-κB is a nuclear transcription factor

BORTEZOMIB can also reduce efficiency of DNA repair mechanisms following DNA damage

Enhanced DNA repair The majority of chemotherapeutic agents act by causing either direct or indirect damage to cellular DNA. There are cellular mechanisms in place for detecting DNA damage and initiating one of a number of potential responses, including apoptosis, modulation of cell-cycle progression via DNA damage checkpoints, and initiation of DNA repair. DNA damage can occur in many different ways, and multiple DNA-repair pathways exist involving a series of enzymatic steps. If chemotherapeutic agents act by causing DNA damage, an important mechanism of drug resistance is the efficiency of DNA-repair mechanisms within a cell. Genetic mutations within the DNA of repair genes can alter the efficiency of repair. Recently, increasing attention is being paid to the role of single nucleotide polymorphisms (SNPs) of DNA repair genes in predicting prognosis and response to chemotherapy. The SNPs are single base differences in the DNA between individuals, and when present in certain genes, such as those involved in DNA-repair cascades, they may alter the efficiency of those genes. Novel therapeutic agents targeting DNA-repair mechanisms may be effective treatment strategies to overcome resistance. Cisplatin induces cellular damage primarily by the formation of bulky intra-strand platinum–DNA adducts. Removal of these adducts is mediated by the nucleotide excision repair (NER) pathway, a crucial element of which is the excision cross-complementing 1 (ERCC1) gene. It has previously been shown that over-expression of the ERCC1 gene is associated with increased removal of platinum–DNA adducts

4) I-κB targeted for degradation BORTEZOMIB inhibits 26S proteasome

26S proteasome

2) Expression of anti-apoptotic proteins such as Bcl-2 and suppression of apoptotic cascade induced by chemotherapy

Figure 5.4 Proposed mechanism of action of NF-κB and its inhibitor I-κB in inhibiting apoptosis. Bortezomib inhibits this process by inhibiting the 26S proteasome. Bortezomib may also have some direct action on altering DNA-repair mechanisms within the damaged cell.

Novel anti-cancer therapies 97

and relative platinum resistance, as seen in human ovarian and gastric tumours.70,71 There are known SNPs of the ERCC1 gene conferring differences in the levels of ERCC1 mRNA synthesis, and stability of the ERCC1 protein. Polymorphism C8092A is shown to affect overall survival negatively in patients with non-small-cell lung cancer previously treated with platinum-based chemotherapy (13.4 months median survival versus 22.3 months, p  0.006).72 Although predicting survival, it remains to be determined whether these polymorphisms directly impact on response to platinum-based chemotherapy. The ability of tumour cells to utilize an alternative repair pathway where the normal pathway of repair is deficient can account for some of the resistance patterns observed with chemotherapeutic regimes. However, if the cells were to be prevented from utilizing the alternative DNA-repair pathway, by targeted inhibition, this might prove an effective way of overcoming drug resistance. PARP (poly [ADP-ribose] polymerase) is involved in the base excision repair (BER) pathway for repair of singlestrand DNA breaks. Where PARP is deficient or lost, it is thought that accumulating defects in DNA that would normally be repaired by BER are alternatively repaired by homologous recombination (HR). As BRCA1 and BRCA2 are essential components of DNA repair by HR, inhibition of PARP in carriers of BRCA1 and BRCA 2 mutations, i.e. in cells already deficient in the HR repair pathway, has been shown to result in continued accumulation of DNA defects, chromosomal instability, cell-cycle arrest and apoptosis.73

Future directions in drug resistance The Human Genome Project and the resultant progress in the field of gene expression profiling of human tumours have opened the door to the concept of individualized cancer therapy. Traditional approaches have relied on grouping tumours into histopathological categories to make treatment decisions, usually resulting in patients receiving a standard combination chemotherapy regimen. However, it is increasingly obvious that two patients with the same pathological grouping can have remarkably different clinical outcomes to standard treatment. This is likely to be determined by the individual gene expression profile of that particular tumour. It is hoped that gene profiling will allow for a more individualized molecular approach to tumour staging, determination of molecular predictors of outcome and predicting response/resistance patterns to therapies. Similarly, with an increase in the understanding of the complex and varied mechanisms by which a tumour cell can become resistant to chemotherapeutic agents will come newer, more targeted and less toxic alternatives to traditional chemotherapeutic agents. Some advances in these areas have been highlighted in this chapter. In order to translate gene expression signatures of individual tumours into reliable clinical benefit we will need to evaluate prospectively, using

validated methods, in randomized clinical trials. Only then will we be able to progress to a stage at which clinicians can reliably identify a group of patients for whom treatment can be tailored for optimum efficacy and with the prospect of avoiding drug resistance.

NOVEL ANTI-CANCER THERAPIES The development of the current generation of novel anticancer therapies is based on exploiting our increasing understanding of the molecular basis of cancer. The identification of putative molecular targets, allied to high through-put screening strategies of potential lead compounds, and utilizing the advances in biotechnology (particularly in the field of drug delivery) give rise to the exciting possibility of a number of novel therapies, many of which are already undergoing clinical evaluation. However, the preclinical and early clinical evaluation of these novel therapeutic strategies targeted to specific molecular pathways presents new challenges that will require an integrated approach from both laboratory and clinical scientists. Preclinical evaluation will require the demonstration of reproducible biological effects in experimental systems at concentrations of drug comparable to those that can be achieved in the clinic. In addition to the conventional endpoints of toxicity and pharmacokinetics, early clinical evaluation will also require the demonstration of desired biological activity, which is likely to be particularly pertinent with those agents that are likely to have a cytostatic effect, in order to determine the optimal biologically active dose for subsequent clinical trials. Furthermore, these agents may not have objective evidence of anti-tumour activity by classical tumour response criteria in patients with bulk disease, which usually make up the patient population in whom new agents are evaluated. Consequently, evaluation of these agents will require identification of appropriate candidate patients (e.g. the presence of molecular target in biopsy material), demonstration of desired biological effect (usually in tumour biopsy material or by assessment of surrogate biological endpoints) and identification of the appropriate clinical scenario for evaluation (e.g. as maintenance therapy after ‘debulking’ chemotherapy, or as adjuvant therapy for agents with a proposed cytostatic effect).

Signal transduction inhibitors The processes of normal cell growth, proliferation, differentiation and death are controlled by signals that balance their activation and inhibition. Disruption of normal cellular signalling enables malignant cells to proliferate and/or survive when normal cells would not. The process of signal transduction typically involves ligand binding to, and activation of, a specific receptor. This, in turn, initiates a cascade of enzymatic and biochemical reactions that

98 Principles of chemotherapy and drug development

allow proliferation signals to be transmitted from the cell surface, through the cytoplasm, to the nucleus.74,75 Several signal transduction pathways have been proposed as potential targets for cancer therapy, and among the most prominent examples are the tyrosine kinase inhibitors. INHIBITORS OF TYROSINE KINASE

Tyrosine kinases are a family of enzymes that catalyse the phosphorylation of the phenolic moiety of tyrosine residues.76 Abnormal constitutive ‘activation’ of this group of signalling proteins has been implicated in malignant growth and progression.77 Common to the structure of all tyrosine kinases are a substrate-binding domain, an ATP-binding domain and a catalytic or kinase domain. Furthermore, there are two classes of tyrosine kinase – receptor (RTK) and nonreceptor. The RTKs are further organized into three distinct sections: an extracellular ligand-binding region, a hydrophobic transmembrane portion, and a cytoplasmic domain containing the active tyrosine kinase site.78 The various types of RTK include the EGFR, platelet-derived growth factor receptor (PDGFR), vascular endothelial growth factor receptor (VEGFR) and the fibroblast growth factor receptor (FGFR). The mechanisms by which RTKs and non-RTKs activate downstream signalling pathways have been extensively reviewed.79 Several strategies have been proposed to inhibit tyrosine kinases, including inhibiting receptor–ligand interactions, inhibiting the tyrosine kinase domain of RTKs, inhibiting non-receptor tyrosine kinases, and antisense oligonucleodies against RTK mRNA. The most striking example of the potential use of these approaches in clinical practice is the use of imatinib in chronic myeloid leukaemia (CML). The Philadelphia chromosome is the result of a t(9;22) reciprocal translocation; it is present in more than 90 per cent of patients with CML and results in the juxtaposition of DNA sequences from the BCR and ABL genes. BCR-ABL encodes a protein, p210BCR-ABL, with dysregulated tyrosine kinase activity, which is necessary and sufficient for leukaemogenesis. Imatinib mesylate (Glivec) is a potent competitive inhibitor of the tyrosine kinases associated with ABL and impedes the interaction of ATP with these proteins and thereby inhibits their ability to phosphorylate and activate proteins downstream. Initial phase I and phase II studies with imatinib in CML showed that it was well tolerated, and 60 per cent of the patients had a major cytogenetic response (defined by the finding that no more than 35 per cent of cells in metaphase were Ph-positive), with 41 per cent having a complete cytogenetic response and 95 per cent of the patients still alive after a median follow-up of 18 months.83**,84** Imatinib was subsequently compared with interferon-alpha combined with lowdose cytarabine in newly diagnosed chronic-phase CML [n  1106].85** After a median follow-up of 19 months, the estimated rate of a major cytogenetic response at 18 months was 87 per cent in the imatinib group, compared with 35 per cent in the interferon-α plus cytarabine group

(p  0.001). The estimated rates of complete cytogenetic response were 76 per cent and 15 per cent respectively (p  0.001). Furthermore, imatinib was also better tolerated than combination therapy, and had a significantly superior progression-free rate (p  0.001) than combination therapy.85** Imatinib mesylate is also active in inhibiting other tyrosine kinases, including the transmembrane receptor KIT. Gastrointestinal stromal tumours are mesenchymal neoplasms that express the cell-surface transmembrane receptor KIT, which is the product of the KIT proto-oncogene. These tumours have frequent gain-of-function mutations of KIT, and KIT activation occurs in almost all cases of gastrointestinal stromal tumour, regardless of the mutational status of KIT.86,87 Gastrointestinal stromal tumour is a universally fatal disease that is resistant to most conventional cytotoxic chemotherapy agents, with a response rate of less than 5 per cent with single-agent doxorubicin. Imatinib induced a sustained objective response in 53 per cent of patients in a multi-centre trial [n  147].88* Interestingly, early resistance to imatinib was noted in 13 per cent of patients, and this is likely to be the next major challenge in this disease. The role of imatinib in the management of gastrointestinal stromal tumours is discussed more fully in Chapter 40.

MONOCLONAL ANTIBODIES

One example of an approach to inhibit receptor–ligand interactions of RTKs is to use monoclonal antibodies against the RTK. The most prominent example of this approach is trastuzumab (herceptin), a highly purified, recombinant, DNA-derived, humanized monoclonal antibody that binds with high affinity and specificity to the extracellular domain of the erbB-2 receptor. Amplification of erbB-2, which occurs in approximately 30 per cent of breast cancers, is associated with poor prognosis and has been linked to resistance to both tamoxifen and alkylating agent chemotherapy drugs.89 Although the precise function of erbB-2 is unclear, its over-expression is associated with constitutive tyrosine kinase activity and may play a role in unregulated cell growth. Trastuzumab can downregulate HER-2 and angiogenic proteins, such as VEGF, and induce antibody-dependent cellular cytotoxicity. The rates of response to trastuzumab given as a single agent range from 12 per cent to 40 per cent, depending in part on the method used to determine the HER-2 status and the prior treatment received.80*,91,92* Furthermore, the combination of chemotherapy with trastuzumab produces higher response rates and increased survival compared with chemotherapy alone in patients with advanced breast cancer.93** More recently, it has been demonstrated that the addition of trastuzumab to standard adjuvant chemotherapy regimens for patients with HER-2-positive early breast cancer can improve disease-free survival, and can reduce the risk of death by 33 per cent.94**,95**

Novel anti-cancer therapies 99

Antibodies have also been developed to target other signal transduction pathways, including bevacizumab and cetuximab. Bevacizumab is a humanized antibody that targets VEGFR, one of the most important pro-angiogenic growth factors, and has proven efficacy in phase III studies in advanced colon cancer and also promising activity in renal cancer, non-small-cell lung cancer and a range of other tumour types.96 This agent is discussed more fully in the chapter on angiogenesis (Chapter 12). Similarly, cetuximab is one of the agents that targets the EGFR pathway.97 KINASE INHIBITORS (e.g. EGFR TYROSINE KINASE INHIBITORS)

A further strategy for inhibiting RTKs is to target the kinase domain directly, either by competitive substrate inhibitors or by competitive inhibition of the ATP-binding site. Several inhibitors of the RTK kinase domain have entered clinical trials, including agents that target the EGFR signalling pathway. EGFR is a transmembrane receptor tyrosine kinase of the Erb (also known as HER) family that is abnormally activated in many epithelial tumours. Several mechanisms lead to aberrant receptor activation, including receptor over-expression, gene amplification, activating mutations, over-expression of receptor ligands and/or loss of their regulatory mechanisms. Receptor activation leads to recruitment and phosphorylation of several intracellular substrates, which, in turn, engage mitogenic signalling and other tumour-promoting activities. In addition to monoclonal antibodies directed to the extracellular domain of the receptor, a second class of anti-EGFR agents are those that compete with ATP binding to the tyrosine kinase domain of the receptor, which then inhibits tyrosine kinase activation and subsequently leads to blockade of EGFR signalling pathways. There are a number of this class of agents currently undergoing clinical development, including gefitinib (Iressa, ZD1839), erlotinib (Tarceva, OSI774) and lapatinib.98 The clinical development of some of these agents highlights the opportunities and challenges in the development of kinase inhibitor therapy for cancer. The failure of gefitinib, when combined with chemotherapy, to show superiority to standard treatment in advanced non-small-cell lung cancer demonstrates some of the pitfalls in the clinical evaluation of novel agents. In pre-clinical studies, gefitinib showed activity against a broad panel of tumour cell lines expressing EGFR, either when given alone or in combination with chemotherapy or radiation. Consequently, early studies were not restricted to including patients with a specific molecular abnormality, and clinical activity was observed in lung and colonic cancers.99*,100* Subsequently, significant responses, including complete remissions, were observed in patients with late-stage lung cancer, but only in a small number.112** However, the combination of gefitinib with chemotherapy showed no survival advantage over chemotherapy alone in two large, randomised, phase III lung cancer trials.102**,103**

There has been renewed interest in the field following the results of a placebo-controlled, randomized study of single-agent erlotinib in patients with non-small-cell lung cancer after first-line or second-line chemotherapy. Statistically significant and clinically relevant differences were observed for both progression-free and overall survival.98 In all of these studies, there was a strong indication that there was a subset of patients with non-small-cell lung cancer who seemed to benefit from treatment with erlotinib or gefitinib. Patients with bronchioalveolar carcinoma, never-smokers, females and Japanese patients seemed to have a higher response rate and clinical benefit. These clinical findings have now been followed by the discovery of somatic mutations in exons 18 through 21 encoding the tyrosine kinase domain of the EGFR, and the close association between these mutations and clinical responses to these agents.104,105 Current research strategies are directed at selecting the optimal dose and schedule and identifying factors of response and resistance beyond EGFR gene mutations and/or amplifications, and also to integrate inhibitors of EGFR signalling with conventional therapies and with other molecular targeted therapies, including other antireceptor therapies, receptor-downstream signalling inhibitors and targeted approaches interfering with other essential drivers of cancer such as angiogenesis. INHIBITION OF RAS, RAF, MET AND OTHER SIGNALLING PATHWAYS

The ras family of oncogenes is one of the most frequently activated groups of dominant transforming genes in both human and experimental cancers.106 The ras family of genes encodes highly similar proteins with molecular weights of 21 kDa which are thought to play a key role in signal transduction. One strategy for regulating ras gene expression is by the use of an antisense oligonucleotide directed against H-ras expression. An alternative approach is by inhibiting protein farnesylation. Ras proteins carry an essential lipid moiety – a farnesyl group – at theirCOOH termini. Inhibition of ras farnesylation blocks ras localization to the plasma membrane and, as a consequence, ras fails to interact with regulatory and effector molecules.107 Inhibition of this step alone may be sufficient to stop the cell-signalling and transforming function of constitutively activated ras in tumour cells. Therefore, farnesyl transferase (FT), the enzyme that catalyses this reaction, has become an interesting target for the design of anti-cancer drugs. Initially, inhibitors of FT were regarded as specific and sensitive inhibitors of ras-mediated cellular proliferation.108,109 However, it has become apparent that the critical target of FT inhibitors may not be ras proteins or may include other polypeptides in addition to ras.110 More than 100 proteins have been identified that possess a ‘CAAX’ sequence that can potentially be farnesylated,110 and up to 20 of these have been shown to undergo farnesylation, including rho B, laminins A and B, transducin,

100 Principles of chemotherapy and drug development

CENP-E and CENP-F. Currently, at least three proteins have been identified, inhibition of which may be implicated in the cytotoxic actions of FT inhibitors, and these include rho B, which regulates cytoskeleton re-organization,111 the centromeric proteins CENP-E and EP-F, which interact with microtubules,112 and proteins associated with the phosphoinositide 3-OH kinase AKT pathway.113 Thus, the molecular targets of FT inhibitors remain unclear, but are likely to include several key proteins and possibly some or all of the ras isoforms. Several FT inhibitors have entered clinical trials, including R115777 (Zarnestra), SCH-66336 (Sarasar), L-778,123 and BMS-214662,114 either as single agents or in combination with standard therapies. Promising results have been observed in single-agent studies in breast cancer,115* CML116 and recurrent malignant glioma.117 Pre-clinical experiments have suggested that FT inhibition may have synergistic antitumour effects when administered in combin-ation with several chemotherapy, hormone therapy or targeted therapy agents.114 Furthermore, the combination of SCH-66336 with paclitaxel has demonstrated responses in patients whose disease was refractory to taxanes.114 However, in phase III studies, the addition of Zarnestra to gemcitabine has no bene-fit in patients with advanced pancreatic cancer,118** and further studies are awaited to define the role of FT inhibitors in cancer therapy. One strategy to overcome the challenge inherent in developing therapeutics against signalling elements situated in redundant pathways is to target downstream of convergence points of critical signalling modules. The MAPK pathway integrates a wide array of proliferative signals initiated by RTKs and G protein-coupled receptors. Therapeutic strategies directed at the MAPK pathway are targeting the cascade of downstream effector proteins including raf, MAPK kinase (also called MEK or ERK kinase) and ERK. The raf/MEK/ERK module of the MAPK pathway, which is immediately downstream of ras, may be less redundant and innately resistant to therapeutic manipu-lation than ras. The potential of raf as a therapeutic target has been comprehensively reviewed.119 In brief, the raf family consists of three genes: A-raf, B-raf and C-raf. All the raf proteins are serine/threonine kinases capable of activating the MAPK cascade, but with distinct downstream phosphorylation targets and with unique roles in signalling. Raf activation occurs immediately downstream of membrane and cytoplasmic receptors that relay mitogenic signals.120 Although principally activated by ras, raf may also be activated by ras-independent elements, including the soluble non-RTK Src, protein kinase C, retinoids, anti-apoptotic proteins (e.g. bcl-2) and interferon-beta. The activation status of raf depends on the integration of both activating and inhibitory stimuli, the net result of which determines the downstream messages. Initial efforts at identifying raf mutations in human cancer focused on C-raf, but it would appear that activating B-raf mutations are the predominant genetic aberrations. Most

B-raf mutations are caused by thymidine-to-adenine transversions at nucleotide position 1796 in exon 11 or 15, which encode a valine-to-glutamic acid substitution at amino acid 599 in the kinase domain of the protein. B-raf mutations have been discovered in 60–70 per cent of malignant melanomas and are essentially mutually exclusive with ras mutations in melanoma. There have been many attempts to develop therapeutics against raf, including antisense oligonucleotides, small-molecule kinase inhibitors and dominant interfering DNA constructs. However, most have been directed at C-raf rather than B-raf. The most prominent example of a potential therapeutic against raf is sorafenib, which is a potent competitive inhibitor of ATP binding in the catalytic domains of C-raf, wild-type B-raf and B-raf mutant.121 Sorafenib is also a potent inhibitor of RTKs involved in tumour progression and angiogenesis, including VEGFR-2, VEGFR-3, PDGFR, flt-3, c-KIT and FGFR-1. Sorafenib has been evaluated in the clinic through to phase III studies. It improved the progression-free survival from 12 weeks to 24 weeks compared with placebo (p  0.0000001) in patients with advanced renal cancer who had received at least one prior systemic therapy.122** In contrast, sorafenib has little anti-tumour activity in patients with melanoma in the studies reported so far.123*,124* The results of additional studies of sorafenib, including combination studies with other anti-cancer agents, are awaited. The proto-oncogene C-met is also an interesting target for cancer therapy. C-met encodes the high-affinity receptor for hepatocyte growth factor (HGF) or scatter factor (SF). C-met and HGF are each required for normal mammalian development and are important in cell migration, morphogenic differentiation, cell growth and angiogenesis.125 Both C-met and HGF have been shown to be deregu-lated, and to correlate with poor prognosis, in a number of human cancers. A number of approaches to the therapeutic inhibition of C-met and HGF are currently undergoing evaluation.125 Other signalling pathways currently being investigated as potential targets for cancer therapies are the Src family kinases and the P13K/Akt/mTOR pathway. Src was one of the first proto-oncogenes to be identified and plays an important role in cellular proliferation, adhesion and motility, and is also involved in cell survival and intracellular trafficking in various specialized cell types.126 Several inhibitors are currently in early-phase clinical trials. The downstream effector of phosphatidylinositol 3-kinase (PI3K), AKt, is frequently hyperactivated in human cancers. A critical downstream effector of AKt, which contributes to tumorigenesis, is mTOR. In the P13K/Akt/mTOR pathway, AKt is flanked by two tumour suppressors: PTEN activating as a brake upstream of AKt, and TSC1/TSC2 heterodimer, acting as a brake downstream of AKt and upstream of mTOR.127 The rapamycin derivatives CCl-779, RAD001 and AP23573 are currently being investigated in clinical trials as cancer therapies.128 Finally, angiogenesis is one of the most attractive targets in developing cancer

Novel anti-cancer therapies 101

therapies. The mechanisms of new blood vessel formation and its role in malignant transform-ation, tumour growth, metastasis and its inhibition are discussed in Chapter 12.

Targeting the cell cycle Dysregulation of the cell cycle is a hallmark of malignancy. The biochemical events involved in cell-cycle progression have been reviewed in detail.129,130 Cyclin-dependent kinases (CDKs) regulate the transition from one cell-cycle phase to the next by phosphorylating key structural and regulatory substrate molecules. This activity is regulated by the orderly appearance of cyclins, prompted by environmental factors and by post-translational modification of CDKs through phosphorylation of key stimulating and inhibitory sites in the catalytic subunit. Altered expression of CDK components has been demonstrated in malignant cells with consequent loss of regulation of cell-cycle progression, and as such are targets for developing novel therapeutic strategies. Many different strategies for targeting the cell cycle have been described. Potential strategies have included targeting mitosis (by targeting tubulin or mitotic kinases such as Aurora kinases); chemical inhibitors of CDK catalytic activity; inhibition of the interaction between cyclins and cdks; decreasing cyclin expression; promoting the degradation of cyclins by increasing their phosphorylation; and restoration of endogenous cdk inhibitor function. The first generation of cdk inhibitors lacked specificity, with flavopiridol, staurosporine and its analogue U-01, and E7070 being non-selective inhibitors of not only cdks but also many other targets. Second-generation inhibitors are more selective, with many of the compounds developed to target selected cdks. Flavopiridol has several mechanisms of anti-cancer activity131 and is a broad-spectrum cdk inhibitor targeting cdks 1, 2, 4, 6 and 7, and also inhibits the cdk9–cyclin T complex, repressing transcription and decreasing cyclin D1 mRNA expression. A number of schedules of flavopiridol have been evaluated in phase I and phase II studies, with some indication of anti-tumour activity in patients with advanced mantle-cell lymphoma.132* The use of flavopiridol in combination studies is also being pursued. U-01 also has several mechanisms of action, including CDK1 and CDK2 inhibition, induction of cell-cycle arrest and apoptosis, abrogation of the G2 checkpoint in response to DNA damage and the induction of p53-independent apoptosis.133–135 This agent has also been evaluated in a phase I clinical trial.136* E7070, a chloroindolyl sulphonamide, has been evaluated in phase I and phase II trials, and the purine analogue R-roscovitine (CYC202) and 2-aminothiazole BMS387032 are also in early-phase clinical trials.137 Aurora is the name given to a family of serine/threonine protein kinases that regulate many processes during cell

division. Aurora kinases are involved in the control of the centrosome and nuclear cycles, and have essential functions in mitotic processes such as chromosome condensation, spindle dynamics, kinetochore–microtubule interactions, chromosome orientation and establishment of the metaphase plate. They are also required for the proper completion of cytokinesis.138 The family members have been designated Aurora A, B and C and have very distinct localizations and functions. Aurora A over-expression is correlated with tumour progression, is mutated in certain cancers and behaves, at least in certain circumstances, as an oncogene. Survivin, part of the Aurora B complex, may be a key protector against apoptosis and/or mitotic catastrophe.139 Given these observations, and the known roles of Aurora A and B kinases in so many fundamentally important aspects of a range of cell-cycle events, these kinases are likely to be relevant targets for designing novel anti-cancer drugs. Information on at least three Aurora kinase inhibitors have been fully published, including ZM447439,140 hesperadin,141 and VX-680.142 The results of clinical studies are awaited.

Apoptotic pathways – targets for drug design Apoptosis (programmed cell death) is a set of ordered events that enables the selective removal of cells from tissue and is essential for homeostasis and proper function of multi-cellular organisms. Components of this signalling network, which includes ligands such as CD45, TNF and TNF-related apoptosis-inducing ligand (TRAIL), as well as downstream molecules such as caspases, bcl-2 family members and inhibitor-of-apoptosis proteins, which trigger and regulate apoptosis, are crucial targets for anti-cancer drug development.143 The cloning of the human TNF cDNA, as reported in 1984, allowed the generation of recombinant soluble protein for pre-clinical and clinical studies. In these trials, it was found that TNF was unsuitable for systemic administration at clinically relevant doses due to toxicity associated with its strong pro-inflammatory activity, including fever, lung or liver failure, hypotension and coagulopathy.144* Subsequent studies have shown that TNF can be administered safely and effectively by isolated limb perfusion, for example in melanoma, in which the protein does not enter the systemic blood circulation.145 Another death-ligand family member, TRAIL, has been cloned and characterized.146 TRAIL can induce apoptosis in transformed cells with little detectable cytotoxic effect in normal and non-transformed cells. Several receptors for TRAIL have been identified, including two death receptors (DR4 and DR5, also called TRAIL-R1 and TRAIL-R2) and two decoy receptors (TRAIL-R3, TRAIL-R4).147 Monoclonal antibodies that functionally engage DR4 or DR5 have demonstrated anti-tumour activity in pre-clinical models,148 and the results of clinical evaluation are awaited.

102 Principles of chemotherapy and drug development

MANIPULATION OF THE TUMOUR SUPPRESSOR P53

P53 is a transcription factor that plays a critical role in the cellular response to stress. Functional p53 is vital for tumour growth suppression in vivo,149 and this function is lost by mutation in more than 50 per cent of cancers, the remainder appearing to have defective p53 signalling pathways.150 Under normal, non-stress conditions, p53 is maintained at very low levels. However, on exposure to the stress of DNA damage, hypoxia, alterations in redox potential and deregulated oncogene expression, p53 is stabilized and activated through post-translational modification.151 Activated p53 induces growth arrest and/or apoptosis through the induction or repression of specific target genes. P53-directed pathways of apoptosis involve both transcriptional regulation of multiple p53 target genes as well as transcription-independent mechanisms. P53 targets have been identified in both the extrinsic (death receptor) and intrinsic (mitochondrial) pathways of apoptosis.152 Through these mechanisms, p53 eliminates cells with damage that cannot be repaired. Several strategies have been proposed in the manipulation of p53 in cancer therapy,151 including relieving p53 from inhibition by Mdm2; accumulating p53 by proteosome inhibitors; targeted eradication of mutant p53 by HSP90 inhibitors; reactivation of p53 by small molecules or adaptor proteins; and genetic therapies, by either re-expressing wildtype p53 or selectively eradicating cells with a mutant p53 using an oncolytic virus [Onyx-015].153 Heat shock protein 90 (HspP90) is a molecular chaperone whose association is required for the stability and function of multiple mutated, chimeric and over-expressed signalling proteins that promote the growth and/or survival of cancer cells. Hsp90 client proteins include mutated p53, bcr-abl, raf-1, Akt, erbB2, and HIF-1α. Hsp90 inhibitors, by interacting specifically with a single molecular target, cause the destabilization and eventual degradation of Hsp90 client proteins, and have shown promising anti-tumour activity in pre-clinical models.154 The Hsp90 inhibitor 17-allylaminogeldanamycin (17AAG) has been evaluated in early-phase clinical studies.155* Myelosuppression was not a dose-limiting toxicity, supporting the notion that this agent may be combined with other anti-cancer agents in combination studies. The ubiquitin–proteosome system also plays a critical role in protein homeostasis and in regulating normal and cancerrelated cellular processes. Ubiquitin-mediated degradation is a complex process that comprises of well-defined steps involving ubiquitin-activating enzymes, ubiquitin-conjugating enzymes and ubiquitin ligases, and is a rich source of potential molecular targets for therapeutic intervention.156 The first in class proteosome inhibitor bortezomib (Velcade) inhibits NF-κB, and can overcome conventional drug resistance in both in-vitro and in-vivo models of human myeloma in the bone-marrow microenvironment.157,158 Following promising results in initial studies, bortezomib was compared with high-dose dexamethasone in patients

with relapsed multiple myeloma who had received one to three previous therapies. Bortezomib had a statistically significant superior response rate, time to progression and median overall survival compared to high-dose dexamethasone in these patients with previously treated multiple myeloma, and the results of combination therapy studies are awaited.159**

Differentiation agents Included amongst the newer strategies in oncology practice is the evaluation of a number of agents designed to induce differentiation in tumour cells, thereby leading to inhibition of cellular proliferation and apoptosis. The most prominent of these so-called differentiation agents are the retinoids and vitamin D analogues. RETINOIDS

Vitamin A and its biologically active derivatives retinal and retinoic acid together with a large repertoire of synthetic analogues are collectively referred to as retinoids. Naturally occurring retinoids regulate the growth and differentiation of a wide variety of cell types and play a crucial role in the physiology of vision and as morphogenic agents during embryonic development. Retinoids exert most of their effects by binding to specific receptors and modulating gene expression. The nuclear retinoid receptors are members of the steroid/thyroid hormone superfamily of receptors,160 with which they share common structural and functional properties. The diversity of retinoid-induced signalling pathways is mediated by at least six retinoid receptors, which fall into two subfamilies, retinoic acid receptors (RARs) α, β and γ, and the retinoid X receptors (RXRs) α, β and γ.161 The mechanism of action of retinoid receptors and the cellular consequences of retinoid stimulation have been extensively reviewed.162 Briefly, the RARs bind all-trans retinoic acid (ATRA) with high affinity,163 whereas the stereoisomer 9-cis retinoic acid is a bifunctional ligand that can bind to and activate both RARs and RXRs.164 Despite these similarities, the RXRs belong to a subgroup of nuclear receptors distinct from the RARs, suggesting that these two groups of retinoid receptors have distinct roles in retinoid signalling. Both negative and positive effects on transcription can occur in the absence of ligand, and these bimodal transcriptional properties of retinoid receptors are mediated, in part, by the ability of these receptors to associate with various co-activators and co-repressors such as SMRT and N-CoR.165 Transcriptional regulation by receptors would therefore seem to be controlled by selective recruitment of co-activators and co-repressors in response to hormone and, in turn, control of activity of a target promoter. It may be that the role of ligand binding is to cause a conformational change in the receptor, and as a result of this a co-repressor protein is dissociated from the receptor

Novel anti-cancer therapies 103

and a co-activator binds to the receptor, thereby initiating transcription.166 The diversity of dimer complexes that can occur increases the complexity of retinoid signalling mechanisms. Both RARs and RXRs can bind response elements as homodimers, albeit at high concentrations, although heterodimerization of RARs and RXRs enables high-affinity binding of RARs to response elements. Furthermore, RXRs also serve as promiscuous partners in a multitude of other hormonal response systems, including vitamin D signalling pathways. Therefore a large number of different receptor complexes can be formed, controlling distinct pathways.167 Consequently, a range of possible effects is possible by disruption of these pathways by pharmacological agents. At the cellular level, activation of the retinoid receptors can inhibit cell proliferation, induce differentiation and induce apoptosis in normal and transformed cells in tissue culture. Although there is a difference between various cellline models in the receptor which mediates these processes, it appears in some models that activation of RARs alone is sufficient to induce differentiation, but activation of RXRs is essential for the induction of apoptosis.168 Numerous putative mechanisms have been proposed for the induction of apoptosis by retinoids, including activation of the AP-1 complex, for which activation of the receptors is not necessary,169 but the exact mechanisms remains unknown. However, retinoids can cause growth regression in in-vivo xenograft models of experimental cancer169 as well as having anti-promotion activity in several animal models of carcinogenesis.170 Most of the clinical trials of retinoids as chemoprevention agents focus on individuals at an increased risk of developing cancer, such as patients with pre-malignant lesions or patients who have been successfully treated for an early-stage carcinoma and have a high risk of developing a second primary cancer. None of these studies has as yet demonstrated significant chemopreventive effect with acceptable toxicity, that can be maintained after retinoid withdrawal, and which could justify routine use in clinical practice.162 The most prominent example of retinoids as differentiating agents in oncology practice is the remarkable activity of ATRA in patients with acute promyelocytic leukaemias (APLs). Numerous phase II studies have confirmed that ATRA induces complete remission in the vast majority of patients, with rapid resolution of the characteristic life-threatening coagulopathy. The duration of remission with ATRA alone is usually brief, and post-remission chemotherapy is required to diminish the likelihood of relapse. A randomized study has confirmed that ATRA as induction or maintenance treatment improves disease-free and overall survival as compared with chemotherapy alone and should be included in the treatment of APL.171** The increasing understanding of retinoid-induced signalling pathway should lead to the design of combination therapies with other agents acting on steroid hormone receptors, agents which inhibit intracellular signalling pathways, and raises the intriguing possibility of enhancing the sensitivity

of tumours to cytotoxic agents and of overcoming drug resistance by adjusting the apoptotic set point.162 VITAMIN D ANALOGUES

In addition to its role in calcium homeostasis, vitamin D can also promote cellular differentiation, inhibit proliferation and induce apoptosis in cancer cells as well as inhibiting tumour-induced angiogenesis172 and the invasive potential of breast cancer cells in vitro.173 The vitamin D hormone mediates its action through the activation of the vitamin D receptor, where the receptor–ligand complex functions as a transcription factor, and binds with DNA by interacting with vitamin D response elements leading to either activation or suppression of target gene transcription. Vitamin D3 is limited in its potential clinical application because of the induction of hypercalcaemia at therapeutic doses. A number of analogues have been synthesized with the aim of decreasing this calcaemic effect and enhancing its anti-proliferative actions. MC903, as a topical application, can stabilize locally advanced and cutaneous metastatic breast cancer.174 EB1089 can induce regression of colon and breast cancers in animal models without causing significant hypercalcaemia and has been evaluated in a phase I study in these two types of cancer.175* EB1089 has also subsequently been evaluated in phase II studies in pancreatic176* and hepatocellular177* cancers. In both studies, the most commonly observed toxicity was dose-related hypercalcaemia that resolved with dose interruption. Although stable disease was seen at the first disease assessment (12 weeks of treatment) in a small number of patients with pancreatic cancer,176* there were no objective responses. In contrast, objective responses were observed in a small number of patients with hepatocellular cancer (3–5 per cent). Another novel vitamin D analogue, ILX23-7553, has also entered phase I clinical trials.178*

Epigenetic therapies Epigenetic mechanisms regulate the expression of genetic information. Epigenetic modifications of DNA and histones are stable and heritable, but also reversible.179 They include covalent modifications of bases in the DNA and of amino-acid residues in the histones. DNA methyltransferases are a family of enzymes that methylate DNA at the carbon-5 position of cytosine residues.180 Methylated DNA can then be bound by methyl-binding proteins that function as adaptors between methylated DNA and chromatinmodifying enzymes (e.g. histone deacetylases and histone methyltransferases) by recruiting histone-modifying enzymes to stretches of methylated DNA.181 Histone-modifying enzymes then covalently modify the amino-terminal residues of histones to induce the formation of chromatin structures that repress gene transcription.182 DNA methylation is a crucial mechanism associated with epigenetic regulation. It has a comparatively simple binary

104 Principles of chemotherapy and drug development

pattern (i.e. methylated versus non-methylated bases) compared with the highly complex pattern of histone modifications. Changes in the pattern of DNA methylation, either increased (hypermethylation) or decreased (hypomethylation), have been identified in all types of cancer cells examined so far. Genomic tumour DNA is characterized by distinct methylation changes, termed epimutations. At the global level, the DNA is often hypomethylated, particularly at centromeric repeat sequences, and this hypomethylation has been linked to genomic instability. Local hypomethylation of individual genes may also occur, and has been associated with aberrant gene silencing.183 The reversibility of epigenetic modifications makes them attractive targets for possible therapeutic intervention. Epigenetic mutations must be actively maintained, and so inhibition of certain epigenetic modifications could lead to a change in gene expression patterns and consequently in cellular characteristics. DNA METHYLTRANSFERASE INHIBITORS

DNA methyltransferase inhibitors have been tested in phase I–III clinical trials, and include both nucleoside and non-nucleoside inhibitors. The DNA methyltransferase inhibitor 5-azacytidine is a derivative of the nucleoside cytidine. It is incorporated into DNA and leads to methyltransferase being trapped and inactivated in the form of a covalent protein–DNA adduct. Consequently, cellular DNA methyltransferase is depleted and genomic DNA is demethylated as a result of continued DNA replication. 5azacytidine is a ribose nucleoside and must be modified to a deoxyribonucleoside triphosphate to be incorporated into DNA. In contrast, 5-aza-2 -deoxycytidine (decitabine) is a deoxyribose analogue of 5-azacytidine which does not need to be modified to a deoxy form and can be directly incorporated into DNA. Decitabine has greater inhibition of DNA methylation and anti-tumour activity than 5-azacytidine in experimental models. Decitabine has single-agent activity in myeloid malignancies and myelodysplastic syndrome.184,185 However, it also has significant haematological toxicity.186* Another derivative of 5-azacytidine, zebularine,187 has not yet been evaluated in the clinic. Its mechanism of action is similar to that of the aza-nucleoside inhibitors, and so the demethylating activity of zebularine may be difficult to separate from the toxic effects of DNA methyl-transferase depletion that result from covalent enzyme trapping. Some non-nucleoside agents can also inhibit DNA methyltransferase activity. These compounds include ECGC, the main polyphenol component in green tea,188 RG108,189 4-aminobenzoic acid derivatives, psammaplins, and oligonucleotides such as MG98.190 Of these, MG98 is currently in clinical trials. HISTONE-DEACETYLASE (HDAC) INHIBITION

Gene expression can be regulated by the remodelling of chromatin and altered chromatin conformation. In an open

state, chromatin is conducive to transcriptional activation, whereas closed chromatin confirms transcriptional repression. Chromatin consists of nucleosomes comprising DNA wound around a histone octomer. Post-translational modifications of the N-terminal ‘tails’ of histones, through acetylation, methylation, phosphorylation and ubiquitination, can result in chromatin remodelling, altered chromatin conformation and regulated transcription.182 The opposing activities of histone acetyltransferases (HATs) and histone deacetylases (HDACs) are potent regulators of gene expression.191,192 HDACs counteract the activity of HATs and catalyse the removal of acetyl groups from lysine residues in histone N-termini, leading to chromatin condensation and transcriptional repression.191,192 To date, 18 HDACs have been identified in humans.192 HDACs are over-expressed, or associated with oncogenic transcription factors due to chromosomal translocations or aberrant physical associations, in a number of cancers, making them attractive targets for anti-cancer therapies.192 A number of HDAC inhibitors have been developed, and can be subdivided into five groups: 1. hydroxamic acid-derived compounds, including trichostatin A, PXD101, suberoylanilide hydroxamic acid (SAHA); 2. cyclic peptides, e.g. depsipeptide; 3. short-chain fatty acids, such as valproic acid; 4. benzamides, e.g. MS-275 and CI-994; 5. ketones.194 HDAC inhibitors show selective cytotoxicity against tumour cells, and can activate a number of molecular pathways to mediate a range of biological events that can influence tumour-cell development, growth and survival.194 At least nine different HDAC inhibitors are currently in earlyphase clinical trials, either as single-agent therapy or as part of combination therapy with other agents.195

Senescence, the telomere structure and the telomerase enzyme Telomerase is an enzyme which, although thought to be required during development, is largely repressed in adult somatic tissues.196 Telomerase replicates the terminal sequences of eukaryotic chromosomes, namely the telomere.197 The absence of telomerase activity from normal somatic cells has led to the proposal that telomere shortening may be a molecular clock that contributes to the onset of cellular senescence in normal cells.198 Conversely, the reactivation or expression of telomerase may be a major mechanism by which cancer cells overcome normal cellular senescence.199 Indeed, telomerase activity may be present in more than 80 per cent of tumour biopsies, yet absent or reduced in normal somatic tissues.200 The realization that activation of telomerase can co-operate with a limited

References 105

number of other ‘genetic hits’ leading to malignant transformation, allied to the high levels of expression of the telomerase enzyme in specific cancers, reinforces the notion that the telomerase enzyme and the telomeric structure are exciting targets as potential anti-cancer strategies. Numerous potential therapeutic strategies have been proposed, including telomerase-interactive compounds (peptide nucleic acids, antisense oligonucleotides, ribozymes, reverse transcriptase inhibitors) and telomere-interactive compounds, such as the G-quartet interactive agents.201 One potential drawback of these strategies is the ‘phenotype lag’, i.e. the number of cell divisions necessary before inhibition of telomerase leads to sufficient shortening of the telomere to give rise to a phenotypic effect, suggesting that these agents are likely to be active in minimal disease states. However, the most successful approaches that have been evaluated in pre-clinical studies have exploited the selectively of telomerase gene expression within cancer cells to develop gene therapy strategies.202

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Smaller tumours have more rapid growth rates and are more likely to be responsive to chemotherapy; cure rates are likely to be higher with a small tumour burden. The route to administration of a cytotoxic drug is determined by the stability, size, molecular change and sclerosant characteristics of the drug. Combination chemotherapy aims to prevent or slow the development of resistant tumours; drugs used in such regimens have activity as single agents, different mechanisms of action and minimal overlapping toxicities. Drug resistance is the most important reason for cancer treatment failure. Genetic instability and the multi-clonal nature of tumours enable them to adapt to environmental changes. Hypoxia reduces the sensitivity of tumour cells to many drugs. Tumours often have mutations that make them resistant to chemotherapy-induced programmed cell death. DNA-damage repair is important in resistance to many alkylating agents. Understanding the biological mechanisms of drug resistance allows the design of strategies to overcome drug resistance, with potential to improve the efficacy of cytotoxic drugs. Novel anti-cancer agents are being developed based on exploiting our increasing understanding of the molecular and cellular bases of cancer development and progression.

Genes, vaccines and drug delivery Strategies to target the underlying genetic lesions of the cancer cell are often considered under the umbrella of ‘gene therapy’, and include antisense oligonucleotides, recombinant vaccines as immunotherapy, transducing a drug-resistance gene into bone-marrow stem cells to protect the bone marrow during chemotherapy, and the use of expression vectors to convert inactive pro-drugs into active drugs. These approaches are discussed more fully in Chapters 8 and 13. Many of the existing vectors for gene delivery and expression have limitations, and improvement in drug delivery mechanisms and vector design remains a crucial area in order to increase the efficiency of expression and the precision of targeting and to reduce toxicity. The possibility of specific gene targeting and possible synergy with other, existing, cancer therapeutics is a promising goal for future development.

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189 Brueckner B, Garcia BR, Siedlecki P, et al. Epigenetic reactivation of tumor suppressor genes by a novel smallmolecule inhibitor of human DNA methyltransferases. Cancer Res 2005; 65:6305–6311. ◆190 Lyko F, Brown R. DNA methyltransferase inhibitors and the development of epigenetic cancer therapies. J Natl Cancer Inst 2005; 97:1498–1506. ◆191 Roth SY, Denu JM, Allis CD. Histone acetyltransferases. Ann Rev Biochem 2001; 70:81–120. ◆192 Thiagalingam S, Cheng KH, Lee HJ, et al. Histone deacetylases: unique players in shaping the epigenetic histone code. Ann NY Acad Sci 2003; 983:84–100. ◆193 Johnstone RW. Histone-decaetylase inhibitors: Novel drugs for the treatment of cancer. Nat Rev Drug Discov 2002; 1:287–299. ◆194 Lindemann RK, Gabrielli B, Johnstone RW. Histonedeacetylase inhibitors for the treatment of cancer. Cell Cycle 2004; 3:779–788. ◆195 Kelly WK, O’Connor OA, Marks PA. Histone deacetylase inhibitors: from target to clinical trials. Expert Opin Investig Drugs 2002; 11:1695–1713. ◆196 Harley CB, Villeponteau B. Telomeres and telomerase in ageing and cancer. Curr Opin Gen Dev 1995; 5:249–255. 197 Morin SG The implication of telomerase biochemistry for human disease. Eur J Cancer 1997; 33:750–760. ◆198 Hurley CB, Sherwood SW. Telomerase, checkpoints and cancer. Cancer Surv 1997; 29:263–284. ◆199 Parkinson EK, Newbold RF, Keith WN. The genetic basis of human keratinocyte immortalization in squamous cell carcinoma development: the role of telomerase reactivation. Eur J Cancer 1997; 33:727–734. 200 Shay JW, Bacchetti S. A survey of telomerase activity in human cancer. Eur J Cancer 1997; 33:781–791. ◆201 Sharma S, Raymond E, Soda H, et al. Preclinical and clinical strategies for development of telomerase and telomere inhibitors. Ann Oncol 1979; 8:1063–1074. ◆202 Keith WN, Bilsland A, Hardie M, Evans TRJ. Drug Insight: cancer cell immortality – telomerase as a target for novel cancer gene therapies. Nat Clin Practice Oncol 2004; 1:88–96.

6 Tumour imaging in oncology ANJU SAHDEV AND RODNEY H. REZNEK

Introduction Imaging modalities Clinical application of imaging techniques to specific tumours

112 112

Imaging treatment response References

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124

INTRODUCTION Imaging plays an integral and diverse role in oncology, including in diagnosis, staging, planning treatment, surveillance, assessing response to treatment and its complications and identifying recurrent disease. It also helps to target therapies such as radiofrequency/thermal/cryotherapy ablation and embolization of tumours. It plays a vital part in monitoring response to treatment, often acting as a surrogate endpoint for drug trials. Recent advances in functional and molecular imaging have widened the scope and application of imaging by combining the exquisite anatomical detail provided by cross-sectional imaging with information concerning tissue and cellular activity obtained by scintigraphy and molecular imaging. The role of imaging is specific to each cancer type and site. Radiologists with a special interest in imaging patients with cancer need to develop a detailed knowledge of its natural history and response to treatment while keeping abreast of new developments in imaging. For all these reasons, imaging now has a central role in the practice of multidisciplinary teams caring for cancer patients. This chapter provides a brief description of basic principles and recent advances in commonly used imaging modalities. It discusses the optimal use of imaging as applicable to individual cancer types, with particular emphasis on detection (including screening and characterization), staging, planning and monitoring treatment and identifying recurrent disease.

IMAGING MODALITIES Conventional radiographic techniques The basic principle used in medical imaging is that the degree of X-ray absorption (attenuation) of a beam is based

on the atomic density and thickness of material through which it is passed. Dense materials like bone and contrast agents (iodine and barium) attenuate most, whereas air attenuates few of the X-rays within the applied beam. Once X-rays have travelled through the material they are ‘collected’ by X-ray film. X-ray film is photographic film consisting of a photographically active or radiosensitive emulsion coated by plastic. It contains silver halide, that on exposure to light or X-rays, is converted to silver, which appears black. Therefore, in conventional radiographs, less dense materials such as air appear black, as most X-rays travel through, exposing the film and converting silver halide to black silver. The converse is true for dense materials, which will appear white, as fewer X-rays are available to expose the film. Conventional techniques include plain films, fluoroscopy, intravenous urograms (IVUs) and barium studies.1 The main advantage of these techniques is their availability worldwide. The techniques require minimal technical training, support or expertise and can often provide adequate diagnostic information. For example, the International Federation of Gynaecology and Obstetrics (FIGO) staging of cervical cancer includes an IVU and barium enema for the assessment of bladder and rectal invasion respectively.2 Intravenous urograms are also important in the detection of transitional cell carcinomas (TCCs) of the urinary tract. The main disadvantage of plain films is poor sensitivity, as the inherent contrast resolution is too poor to allow separation of soft-tissue structures; they perform well at sites where the tumour lies against air or bone. However, here too, lesions have to be significantly larger in size for detection on plain films compared to cross-sectional imaging. Due to good contrast between fat, calcification and tumour, conventional X-rays in the form of mammography play an important role in breast cancer. Barium studies, particularly double-contrast barium studies, utilize the contrast between

Imaging modalities 113

barium-coated mucosa and air within the bowel lumen for the detection of upper and lower gastrointestinal tumours. These are increasingly being replaced by endoscopy, endoscopic ultrasound (EUS) and computed tomography (CT). DIGITAL RADIOGRAPHY

The basic principle of digital imaging is the same as that of conventional radiography, but it utilizes digital apparatus. For digital radiography, the radiograph is produced on a special phosphor screen and then read by laser, converting the image either onto laser film or displayed on television monitors. This can be done in real time as in fluoroscopy, or the images can be stored in local digital networks or PACS systems by modified digital converters. The benefits of digital radiography are clearly the varied forms of image output that can be achieved and the long-term storage and distribution of images. As digital images can be manipulated and post-processed, technically poor images do not require repeat X-rays, thus saving patients unnecessary radiation exposure. Post-processing also allows threedimensional and multi-planar reconstruction, image subtraction, as in digital subtraction angiography, and dual energy subtraction techniques used for screening and characterizing lung masses.3–4

Ultrasound Sound waves are longitudinal waves which once generated continue in their original direction until they are reflected, refracted or absorbed. In medical imaging, ultrasound waves (US) – sound frequencies between 2.5 and 20 Megahertz (MHz) – are generated by transducers that can convert an electrical signal into US and, once reflected from tissues, back into electrical signal. A thin layer of acoustic jelly is placed over the area to be scanned in order to obtain effective acoustic coupling between the skin and transducer. The most important component of the transducer is a thin (approximately 0.5 mm) piezoelectric crystal element located near the surface of the transducer. When the transducer is in contact with a skin surface and a voltage pulse is applied across the transducer, the piezoelectric crystal vibrates, generating sound waves that are transmitted through the body. A backing block dampens the vibrations to prime the transducer for its second function, which is to detect reflected sound waves from the body. The returning sound waves induce a voltage in the transducer and are converted into a grey-scale image. The reflection of sound waves is greatest where there is a large difference in acoustic impedance (density and elasticity) of two tissues. Soft tissues reflect more echoes than fluid and appear brighter (or hyperechoic), whereas fluid appears dark (or hypoechoic). The elapsed time for the wave to return allows estimation of distance or depth, providing spatial information in the construction of the image. Bone and air reflect all sound and therefore structures beyond them cannot be imaged.

The Doppler effect is the shift in frequency of a wave when the source moves relative to the receiver, e.g. blood flow in vessels. When blood flows towards the transducer, the reflected sound wave has a higher frequency than the transmitted frequency. Conversely, when blood flows away, the reflected wave has a lower frequency. This frequency shift can be measured and blood-flow velocity and direction can be calculated. When pulsed Doppler is applied, the transducer emits bursts of sound, between which it remains quiet to receive reflected sound. This allows the combination of an US image and a Doppler trace (duplex scan), providing depth, site and velocity information, which is accomplished by transmitting a sound beam and recording the returning waves. The difference in frequencies of the emitted and returning waves usually falls in the audible range. Spectral analysis of the returning Doppler signal allows evaluation of blood flow in normal and stenotic vessels.5 INTRACAVITY ULTRASOUND

Intracavity US is performed using small transducers that can be introduced into body cavities. The commonest clinical applications are transvaginal (TVUS), transrectal (TRUS), transoesophageal and endoscopic US (EUS). Intracavity US utilizes ultra-small curved transducers that have a small field of view (a few centimetres only) but provide high-resolution images. Endoscopic US was introduced in the early 1980s. Its uses have since expanded to evaluate upper and lower gastrointestinal tracts, pancreato-biliary tumours, diagnosis and staging oesophageal and gastric tumours and evaluation of mediastinal nodes in lung cancer. Although this has limitations and is greatly dependent on the skill of the operator, one of its main advantages over other cross-sectional techniques is that it allows simultaneous tissue biopsy of detected lesions and offers the potential of localized treatment options. ULTRASOUND CONTRAST AGENTS

Ultrasound contrast agents (UCAs) are micro-gas bubbles that when exposed to an US beam reflect sound several times more than blood. The UCAs currently used in diagnostic US have a micro-bubble structure consisting of inner gas bubbles stabilized by an outer protein shell. They remain within the intravascular space and are therefore blood-pool agents that enable the display of parenchymal microvasculature with real-time enhancement. There are currently three approved agents, one micro-air bubble and two lowsolubility gas bubbles. The contrast agents are administered to the patient via a peripheral vein and US of the target organ is performed immediately and/or at timed intervals. After injection, they traverse even the smallest capillaries and therefore can be used to detect lesions not seen on conventional US (Fig. 6.1). The assessment of micro-bubble enhancement requires contrast-specific US imaging mode software, which is generally available and compatible with newer US machines. Normal tissues produce linear signals,

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metastases within the homogeneously enhanced background liver parenchyma can improve their detection and also improve differentiation from hepatocellular carcinoma or benign focal lesions. All malignant lesions generally show negative enhancement or washout during the extended portal venous phase, and this pattern is useful to differentiate them from benign lesions.6 HIGH-INTENSITY FOCUSED ULTRASOUND

(a)

High-intensity focused ultrasound (HIFU) is a completely non-invasive treatment technique that utilizes a highly focused US beam to coagulate a well-defined tissue volume by heating it to above 50°C. This temperature is maintained for 1–2 seconds, resulting in cell death. A single treatment results in cell death of 0.5 mL of tissue. There is a linear demarcation between coagulated and normal tissue. This method has been used to treat small malignant lesions of the prostate, breast, liver and kidneys. Treatment efficiency is monitored by magnetic resonance imaging (MRI), as US cannot differentiate between treated and untreated tumour or between coagulated and normal tissue. Improvements in technique and technology will make this a promising technique in the future.8

Computed tomography

(b)

Figure 6.1 Contrast enhanced ultrasound. (a) 49-year-old woman with breast cancer. Conventional ultrasound of the liver showing a diffuse heterogenous echotexture of the liver detected during staging for breast cancer. No definite local lesions can be appreciated. (b) After administration of Sonovue™ (Bracco, Milan, Italy) multiple focal hypoechoeic lesions consistent with multiple liver metastases are seen. The normal liver is hyperechoeic and enhances after contrast administration.

but micro-bubbles produce a non-linear signal. The specific US imaging modes are based on separation of the linear from the non-linear signal enhancing the tissue images containing micro-bubble contrast agents.6,7 Most benign liver masses show characteristic features on contrast enhanced US (CEUS), allowing an accurate diagnosis. Hepatocellular carcinoma is typically characterized by increased arterial flow with frequent dysmorphic tumour vessels and decreased portal venous flow. However, negative enhancement in the portal phase is often not obvious until late (2 minutes). On the other hand, metastasis shows prompt brief arterial hypervascularity, with either a rim or diffuse pattern and rapid washout, seen as perfusion defects during the portal venous phase. This pattern of complete rapid washout of

Computed tomography was first described by G.N. Hounsfield, a research scientist at EMI Limited, England, in 1972 at the Annual Congress of the British Institute of Radiology. It is currently the most commonly used imaging tool in oncology. Computed tomography is similar to conventional radiography in that the image is based on differential X-ray absorption within the body. The amount of X-ray absorption is dependent on the tissue atomic density and thickness. The difference is that the X-ray beam is narrow and passes through a thin section of the body at a time. The attenuated beam is collected at the other side by detectors that are capable of differentiating very subtle differences in tissue density. Therefore CT has much greater contrast resolution than plain radiography; it has the ability to separate 2000 or more densities, compared to about 20 on plain films. The CT images are generated by computers from information collected by the detectors. The images are a grey-scale representation of anatomy, and the computer allocates electronic CT values to all structures within the scanned area and arranges them as a spatial image. These CT numbers, called attenuation values, are measured in Hounsfield units (HU) and are calculated based on the linear X-ray absorption coefficient of tissues compared to water. To generate a grey scale, water has a standardized Hounsfield number of 0 HU, air 1000 HU, and bone 1000 HU. Fat has between 80 and 100 HU. The normal pre-contrast liver measures between 40–60 HU, but this decreases with increasing fatty replacement in the liver. Blood density varies with the age of the blood; acute

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haematomas measure 50–60 HU, with a fall in the density value as the blood ages. Although the tissue contrast of CT is good, it can be improved further by the use of oral and intravenous contrast media. Oral contrast outlines the lumen of bowel, allowing better separation of normal bowel from mesenteric, serosal or peritoneal disease. Intravenous contrast medium is usually administered into a large peripheral vein, usually the antecubital fossa, at variable rates. Intravenous contrast is used for angiographic detail and characterization at different phases of the circulation. Traditionally, the term ‘enhancement’ refers to the appearance following intravenous injection of contrast media. Post-processing and manipulation of the grey-scale images allow optimal visualization of different tissues of interest to detect focal lesions. This is done by selecting the mean value closest to the attenuation value of the tissue of interest (window level) and selecting a narrow range of attenuation values around the mean value (window width). Tissue densities outside this range will not be visualized and will be either white or black. For example, optimized settings for the routine visualization of soft tissues will be best performed at a window width (WW) of 350 HU and a window level (WL) of 40 HU. For the lung parenchyma, the WW is 1500 HU and the WL is 700 HU, for bone the WW is 2000 HU and the WL is 500 HU, for liver the WW is 250 HU and the WL is 40 HU. Post-processing also allows the direct measurement of tissue attenuation values on CT, useful when characterization of masses is required. This is done by placing an elliptical or circular electronic cursor over the region of interest (ROI) and the computer measures the mean attenuation value in the ROI. On unenhanced scans (non-contrast), this allows characterization, as the attenuation values of soft tissue, fat, water and blood will vary. Measurements of ROI values before and after the administration of intravenous contrast media allow interrogation of the enhancement properties of tissues, providing information on their vascularity. This has a wide application in tumour imaging, as enhancement properties of liver lesions allow characterization of haemangiomas, hepatocellular carcinomas and metastases. Adrenal lesions are characterized by their CT attenuation values and contrast washout properties. Tumour angiogenesis evaluation also relies on measurements before and after different phases of contrast enhancement. The major advantage of CT is that it provides very high quality images of different organ systems with little or no overlap. It separates normal from abnormal tissues and can provide limited physiological information by means of quantitative measurements of perfusion, blood volume and vessel permeability using intravenous contrast agents. It is cost effective, widely available and an easily reproducible technique. Its major disadvantages are the radiation burden – CT accounting for the greatest proportion of medical radiation exposure in the Western world – and the fact that intravenous iodine-based contrast agents are nephrotoxic and can cause mild to fatal anaphylactic reactions.9

Figure 6.2 The principle of spiral CT. The patient on the CT table travels through the scanner at a pre-determined rate. The CT gantry containing the x-ray tube and detectors rotates continuously around the patient from the beginning to the end of the scan area, thereby obtaining a volume acquisition of information. The movement of the gantry forms a spiral or helix providing the term ‘spiral CT’.

CONVENTIONAL SINGLE-SLICE CT

Conventional scanners acquire data on a ‘slice-by-slice’ method, the X-ray tube rotating around the patient and providing information from a single slice; the X-ray stops and the patient moves into position for the next scan. This continues until all the slices in the ROI are obtained. The slice thickness is set at the start of the scan and, to minimize the radiation burden to the patient, a gap between the slices is introduced. Slice-by-slice scanning is time consuming and prone to respiratory and motion artefacts, as patients are required to be still and in suspended respiration during each slice acquisition. During image generation, the computer has to average the densities at tissue and slice interfaces, introducing the partial volume effect, which may appear as false lesions. SPIRAL (HELICAL) CT

Since its introduction, spiral CT has dramatically altered the approach to CT scanning. The most direct impact has been in the increased speed of scanning. The revolutionary difference lies in the introduction of a slip-ring gantry mechanism that no longer requires a delay between scans. In contrast to conventional CT, in which the gantry rotates around a stationary patient, in helical CT the patient moves through a continuously rotating gantry that continuously produces X-rays. The gantry consists of multiple parallel rings of X-ray detectors and the X-ray tube. Whereas conventional CT requires multiple views of precisely the same structure through at least 180° (slice-by-slice technique), spiral CT relies on a 360° segment of the patient associated with one gantry rotation and is therefore volume acquisition (Fig. 6.2). After mathematical interpolation, the data from the detectors are displayed as axial images, similar to conventional CT.10 The most important clinical advantage of spiral CT is the speed of data acquisition, which allows the chest and abdomen to be scanned in a single breath hold, compared to several minutes on conventional CT. Rapid scanning

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image reconstruction, virtual endoscopic procedures (virtual CT colonography, bronchoscopy, cystoscopy) and angiography (Fig. 6.4). This additional information assists in providing more accurate and early lesion detection and localization and aids pre-surgical and radiotherapy treatment planning for patents with cancer.12,13 FUSION/CO-REGISTRATION TECHNIQUES

Figure 6.3 The principle of multidetector CT. The CT gantry and the patient movement of multidetector scanners are similar to the principle of single row detector spiral scanners shown in figure 6.2. In multidetector CTs the detectors form up to 128 rows. This allows data from more than one slice position to be collected, simultaneously dramatically reducing the scan times.

Developments in CT software have allowed co-registration of other imaging modalities onto CT images. This is particularly useful in providing functional images when co-registered with nuclear medicine techniques and positron emission tomography (PET). In oncology, this provides useful information in treated lymphoma and teratoma patients with residual masses in the chest and retroperitoneum by differentiating active from sterile residual masses.14 Fusion of CT and MRI is particularly useful in mapping gynaecological, particularly cervical, cancer and prostate tumours that are best demonstrated on MRI but receive CT-guided radiotherapy. Accurate co-registration allows targeted radiotherapy and avoids side effects of radiotherapy to the bowel, bladder and other pelvic structures.15 COMPUTER-AIDED DIAGNOSIS

allows organs to be scanned at differing phases of contrast enhancement, which in turn is very important in characterizing lesions. In the liver, hypervascular lesions may not be detected at all in the equilibrium phase on conventional CT, but may be detected on arterial spiral scanning.11 Rapid scanning also reduces cardiac pulsation artefacts, improving lesion detection on chest CT. The reduction in respiratory artefact allows improved three-dimensional image reconstruction and two-dimensional multi-planar image reformatting. Post-processing of the acquired data allows reconstruction of scan slices thinner than the original acquired scan thickness. This clearly has a benefit of lower radiation burden for the patient and improves spatial resolution.

MULTI-DETECTOR CT

Recently, the ability to acquire data from more than one slice simultaneously has been developed using parallel rows of detectors. Scanners are now capable of obtaining 4–128 slices in a single X-ray-tube rotation (Fig. 6.3). Data are therefore obtained much faster than with a single-slice spiral scanner. The advantages of multi-detector CT include fast scanning times, which are particularly useful in the paediatric patient, for whom sedation or general anaesthesia may be avoided or used for significantly less time. The entire chest, abdomen and pelvis can be scanned in less than 2 minutes. Much thinner slices can be obtained, providing greater spatial and temporal resolution and a reduction in partial volume effects. Post-processing of the data allows exquisite three-dimensional reconstruction, multi-planar

Computer-aided diagnosis (CAD) can be defined as diagnosis made by a radiologist using computer-aided image analysis. The computer acts as a ‘second reader’ of the images and lists the detected abnormalities. It helps increase the sensitivity by detecting lesions that may be missed by the radiologists. The main clinical applications are in reporting screening mammography in the detection of breast cancer, identifying pulmonary nodules, and CT pneumocolonography for the detection of small polyps. The CAD systems are especially helpful where a large volume of low-incidence examinations needs to be screened rapidly.16 FUNCTIONAL CT AND TUMOUR ANGIOGENESIS

The combination of fast CT scanning techniques using helical and multi-detector computed tomography (MDCT) and commercially available CT perfusion software has allowed CT to explore tumour vasculature and tumour biology. Computed tomography assesses vascular tumour physiology by measuring the temporal changes in X-ray attenuation occurring in major vessels and tissues after intravenous iodine contrast administration. It is possible to derive timeattenuation curves that depict changes in attenuation and iodine concentration and hence measure perfusion, relative blood volume, vascular permeability and relative extravascular space. The term functional CT (fCT) is applied to the measurement of these values using CT.17 Tumour angiogenesis is characterized by increased numbers of small blood vessels. This increased vessel density increases tumour perfusion and blood volume. The vessels also have defective basement membranes that allow

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(a)

(d)

(c)

(b)

Figure 6.4 Multidetector CT and post-processing and reconstruction images. (a) Coronal oblique reformatted image demonstrating a left renal carcinoma (arrow) and an adjacent simple cyst (arrow head). (b) Surface volume rendered image showing the relationship of the ribs and underlying kidney and tumour. (c) Surface volume rendered image with the ribs removed demonstrating renal surface and the relationship of the renal cyst and carcinoma. (d) CT angiogram demonstrating the renal artery and vein.

macromolecules to leak and increase the extravascular space. Thus values obtained by fCT can be correlated with microvascular changes in tumour angiogenesis. Clinical applications of fCT include assessment of liver perfusion to detect metastases in colorectal cancer, and characterization of pulmonary nodules where the microvasculature density in malignant lesions is much higher than in benign nodules. Tumour angiogenesis has also been studied with contrast enhanced US, dynamic MRI and PET, but fCT maintains the best and most direct correlation between tumour angiogenesis and functional measurements. The main disadvantages of fCT are the limited area that can be interrogated and the high radiation exposure.18

Magnetic resonance imaging Magnetic resonance imaging is a non-ionizing-radiationbased, cross-sectional imaging modality that utilizes weak signals emitted by body tissues when the body is placed in a strong magnetic field and radiofrequency (RF) pulses are applied. These emitted signals are then converted into greyscale images. The signals are predominantly associated with protons from water and, to a lesser extent, fat. The principle underlying MRI is the weak magnetic property of hydrogen protons in water. Within very strong magnetic fields (such as large circular MRI magnets), the spinning hydrogen protons align themselves with the external magnetic field. When a short RF pulse with the same frequency as hydrogen protons is applied, the magnetization direction is

altered and all the protons align themselves in the same direction (in-phase). A weak signal is emitted by the aligned protons, and is detected and amplified by a receiver coil (antenna) placed around the patient. As soon as the RF pulse is stopped, the signal begins to decay. This loss of signal depends on two factors: (a) the protons return to their original alignment in the static magnetic filed (spin–lattice relaxation), and (b) interactions of nearby protons disrupt local proton magnetic fields (spin–spin relaxation). The spin–lattice and spin–spin relaxation signals are converted into T1 and T2 relaxation times respectively by means of a mathematical conversion. The strength of the signals depends on the T1 and T2 relaxation properties of the tissue, the number of free protons (proton density) and the number of moving protons, especially flowing blood or cerebrospinal fluid. T1 relaxation is short in heavy molecules such as fat and protein, whereas smaller molecules with more free protons have long T1 relaxation. T2 relaxation depends on the dissipation of magnetic energy into the local environment. Solids, bone and large rigid molecules do not move and have very short T2 relaxation times, unlike free water protons, which have a long T2 relaxation. Image generation relies on varying the time of applied RF pulses and the time to collect returning signals. Signals can be obtained at times when the T1 or the T2 effects predominate (T1/T2 weighted). Electromagnetic signals emitted by the body tissues decay rapidly. They can be prolonged sufficiently to allow capture by applying spin-echo (SE) or gradient-echo (GRE) RF pulses for image generation. In SE systems the signal is flipped by 90° or 180° several times

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Table 6.1 MRI tissue characteristics on T1-weighted and T2-weighted images Tissue

T1 signal intensity

T2 signal intensity

Bone and calcium

Low

Low

Air Flowing blood Flowing blood Fat

Low Low High High

Water Blood Deoxyhaemoglobin (acute blood) Methaemoglobin (subacute blood) Haemosiderin (chronic blood) Gadolinium-based contrast agents

Low Mildly low High

Low Low High Intermediate High High Very low Low

High Intermediate to low High

Calcium in some states may be bright on T1 sequences

High, with thin, hypointense rim Low with thick, very low signal rim Reflect host tissue signal

(time of repeat (TR)) and the returning signal echoes are collected at variable times (time to echo (TE)). In GRE, the applied RF pulses flip the pulse signal by less than 90° by variable angles (flip angles). In general, GRE sequences are faster to acquire than SE sequences. SE sequences with a short TR and TE produce images where the T1 effect of tissues is dominant (T1W). A long TR and long TE result in images where the T2 effects are pronounced (T2W). Long TR and short TE produce proton density images that are influenced by T1, T2 and proton density effects of the tissue.19 Recent advances in receiver coil technology and rapid sequences in both SE and GRE have allowed faster imaging times and improved image quality. The major advantages of MRI are its lack of radiation, lack of iodine-based contrast media and its superior tissue contrast resolution. Its multi-planar imaging abilities were an advantage, but this importance has diminished with the advent of multidetector CT, which also provides very good multi-planar imaging. Magnetic resonance imaging has the ability to provide functional information (fMRI), echoplanar imaging, MR perfusion and spectroscopy. These are important, mainly in neuroradiology where correlation of anatomical and functional information assists in planning surgical resection and radiation of brain tumours aiming to preserve vital sensory and motor areas.20 The main disadvantages of MRI include longer imaging times than CT, less widespread availability and a need for specialist training. The combination of a long period in a closed space and noise generated by loud radiofrequency pulses can result in claustrophobia in adults and the studies are difficult for children to tolerate. The performance of MRI is also highly protocol and technique dependent. To achieve reproducibility, imaging protocols need to be standardized.

Spin-echo sequences Gradient-echo sequences Spin echo sequences Fast spin-echo sequences

Intracellular (early subacute blood) Extracellular (late subacute blood)

TISSUE CHARACTERISTICS

On T1W images, fat, complex proteins, heavy metals (gadolinium) and melanin have high T1 signal intensity. Water, air and bone (calcium) have low signal intensity. On T2W images, water has high signal intensity. Fat has low signal intensity on SE T2W images but high signal intensity on fast SE and some GRE sequences. Air and bone have low signal T2W sequences. Blood has very complex appearances on MRI. A summary of the tissue characteristics is provided in Table 6.1. PERFUSION IMAGING

Perfusion MRI measures blood flow through an organ or tissue. Gadolinium contrast agents are intravenously injected rapidly (5 mL/s) and the MRI signals are acquired rapidly. This is done using T2* and echoplanar imaging and analysing the images pixel by pixel. The increase in signal intensity is related to the rate of passage and amount of gadolinium passing through the tissue of interest. Signal intensity–time curves are used to derive blood-flow volumes, mean transit time and overall blood flow. These reflect tissue perfusion, microvessel permeability and extracellular leakage. The clinical applications include characterization of brain and breast tumour vascularity, follow-up of treatment response and study of stroke. At present, there are limited clinical data related to the application of these techniques.21

DIFFUSION-WEIGHTED IMAGING

Diffusion-weighted imaging (DWI) is more sensitive than conventional MRI sequences in discriminating tissues. The

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(a)

(b)

(c)

Figure 6.5 Diffusion weighted imaging (DWI) of thick walled cystic intracranial mass. 32-year-old woman presenting with fever, headaches and focal neurology. Previous history of cervical cancer stage 2B treated with radiotherapy 3 years ago. (a) Axial T2-weighted image showing a large right sided cystic mass with mass effect and surrounding oedema (arrow). (b) Coronal T1-weighted post gadolinium image showing a thick irregular enhancing wall with no central enhancement (arrow). This appearance may represent either a cerebral abscess or cystic metastases. (c) DWI shows central low signal intensity suggesting no restriction of diffusion (arrow). The central tissue therefore does not contain long molecules seen in abscesses and the mass was a cystic metastasis on biopsy and treated by radiotherapy.

degree of mobility of water molecules is dependent on the surrounding tissue characteristics. The motion of water molecules is restricted by high viscosity fluids and limited by cell membranes. Water molecules that are restricted will not respond to gradient pulses applied during the diffusion-weighted scan and thereby retain signal on DWI images. Tissues with highly diffusing water molecules will quickly lose signal (low signal intensity on DWI images) with the application of gradient pulses. The loss of signal as a function of diffusion gradient can be quantified by the apparent diffusion coefficient (ADC) of water and presented as a ‘map’ or MRI image. On ADC maps, areas of high diffusion have high signal intensity and areas of low diffusion have low signal intensity. Although DWI and ADC maps are most commonly applied to stroke imaging, they have been used for differentiating tumours from cerebral abscesses and for monitoring tumour response after treatment (Fig. 6.5). Abscesses and untreated tumours have bound water molecules, and therefore have low diffusion (high signal intensity), whereas treated tumours, due to cellular necrosis, have more free water molecules with more diffusion (lower signal intensity).22 MAGNETIC RESONANCE SPECTROSCOPY

Magnetic resonance spectroscopy (MRS) differs from MRI in that it detects signals from chemical compounds rather than water to evaluate in-vivo biochemistry. A conventional MRI signal is obtained from water and fat. By selecting signals from other metabolites and measuring these

relative to water, a spectrum can be generated that provides important clinical information. This provides a twodimensional spectral trace with the plot of frequency on the horizontal axis and intensity of resonance on the vertical axis, which can be presented as a colour-coded trace or superimposed onto conventional images (MRS imaging or chemical shift imaging). The spectral trace is obtained from a small region of interest by placing a rectangular block over the tissues to be studied within a conventional image. The signals are obtained at variable echo times and can be altered to obtain signals from molecules of interest. Only certain atomic nuclei have biological significance (1H, 31P, 13 C, 19F, as they are constituents of biological molecules. 1H spectroscopy is the most frequently utilized, as the atomic nucleus provides the strongest signal and its detection does not require additional hardware.23 In the brain, N-acetyl acetate (NAA) and choline are molecules of particular interest, as NAA is a structural component of intact neural tissue and choline is a component of cell membranes that results in increased cell turnover. In tumours, NAA decreases and choline increases in concentration. The ratio of NAA:choline confers prognostic information, with a lower NAA:choline ratio being related to a worse prognosis (Fig. 6.6).24 The presence of lactate and lipids in a spectral trace is always pathological but not specific for tumours. Normal prostate tissue contains choline, creatinine and citrate. Citrate is produced by normal glandular tissue, but in prostate cancer the normal production of citrate ceases, thereby elevating the choline:citrate ratio. This is useful in separating benign from malignant processes in the prostate.

120 Tumour imaging in oncology

(a)

(b)

Figure 6.6 50-year-old woman with a glioma in the left frontal lobe. (a) Axial T2-weighted image showing the large glioma with surrounding oedema (arrow). A small square voxel is placed on the mass to acquire a spectral trace of the mass. (b) Spectral trace of the mass demonstrates an elevated choline and N-acetyl-acetate peak but has a high NAA/choline peak in keeping with a low grade glioma.

In patients treated by radiotherapy or anti-androgens, normal tissue production of citrate stops and there is a spurious elevation of the choline:citrate ratio. Magnetic resonance spectroscopy cannot reliably discriminate between recurrent disease and normal treated prostatic tissue.25

Tissue-specific contrast agents MAGNETIC RESONANCE LYMPHOGRAPHY (LYMPH-NODE-SPECIFIC AGENTS)

Nodal metastases have a significant negative prognostic impact in patients with cancer. Although 18F-fluorodeoxyglucose (FDG)-PET has been shown to have high sensitivity and specificity in the detection of nodal metastases in thoracic malignancies, its application in pelvic and abdominal cancers is limited. Cross-sectional imaging modalities have low sensitivities in detecting lymph-node metastases in normal-sized nodes. High-resolution MRI (scan thickness 3 mm) using ultra-small particles of iron oxide (USPIO), which act as lymph-node-specific agents, allows the detection of small lymph-node metastases in patients with primary pelvic cancer. The use of lymph node-specific agents involves conventional imaging of the pelvic tumour and high-resolution GRE T2* sequences in sagittal and coronal oblique planes (parallel to the psoas muscles) prior to administration of USPIO. The USPIO is then administered as an intravenous injection and is taken up by normal macrophages and transported to lymph nodes. Deposited USPIO reduces the signal intensity within normal nodes (Fig. 6.7). In nodes or parts of nodes replaced by tumour metastases, the signal intensity is not reduced, as there is no

normal uptake and deposition of USPIO. Twenty-four hours after contrast administration, normal nodes and malignant tissues have different signal intensities, normal nodes appearing dark and malignant tissue appearing bright on GRE T2* images. Hence MR lymphography requires two scans, the first prior to and the second 24 hours after the administration of intravenous USPIO.26–28 The accuracy of USPIO MR lymphography has been best evaluated in prostate, endometrial and cervical cancers. The threshold for detecting metastases is 2–3 mm in 5–10-mm diameter nodes. The sensitivity and specificity of USPIO for the detection of metastases are 90.5 per cent and 97.8 per cent respectively in prostate cancer. In endometrial and cervical cancers, the sensitivity and specificity are 93 per cent and 97 per cent respectively. For the detection of nodal metastases, the use of USPIO increases the sensitivity without loss of specificity. These results show the excellent potential of MR lymphography as a non-invasive technique in diagnosing nodal metastases not only in pelvic cancers but also in other anatomical sites.29 LIVER-SPECIFIC AGENTS

Liver-specific contrast agents comprise a heterogeneous group that can be divided with respect to their target tissues into hepatocyte-selective or Kupffer-cell-selective (reticuloendothelial system, RES) agents. Hepatocyte-specific agents are ionic metal chelates with weak protein binding (manganese-DPDP, gadolinium-BOPTA, gadoliniumEOB-DTPA. After an intravenous injection, the contrast agents distribute in the extracellular space and are transported to the liver, where they are taken up by hepatocytes or Kupffer cells. On the basis of the paramagnetic properties of gadolinium and manganese, all hepatocyte-specific

Imaging modalities 121

(a)

(b)

Figure 6.7 24-year-old woman with Stage IB2 cervical cancer. (a) Magnified T2*-weighted MRI of the right pelvic side wall showing two small lymph nodes measuring 6 mm and 2 mm in their short axis with high signal before administration of USPIO contrast agents. (b) T2*-weighted image acquired 24 hours after intravenous administration of USPIO. The lymph nodes have uniformly lost signal intensity indicating normal lymph nodes filled with macrophages and with no metastastic deposits.

contrast agents increase the T1 signal intensity of the liver. In contrast, the Kupffer cell-selective agents, which are iron based, cause a strong reduction in signal intensity on T2-weighted images and increase signal intensity on T1weighted images.30,31 Mangafadipir trisodium (Mn-DPDP) reaches peak liver enhancement in 10–15 minutes, with an imaging window of several hours. By increasing the signal intensity of the normal liver on T1-weighted sequences, it increases the conspicuousness of liver lesions that do not contain normal hepatocytes and therefore do not take up the contrast

agent. On post-contrast images, cysts, haemangiomas and most metastatic lesions appear of low signal intensity compared to the surrounding liver. Benign and malignant hepatocellular lesions have a variable appearance depending on the hepatocyte cellular differentiation and content. Mn-DPDP improves the detection rate of liver lesions compared to contrast-enhanced CT and gadolinium-enhanced MRI. Although it offers reliable differentiation between hepatocellular and non-hepatocellular lesions, in clinical practice the differentiation between benign and malignant lesions is of greater importance. This is particularly relevant in hepatocellular lesions, where uptake is demonstrated in regenerating nodules, hepatocellular carcinomas, adenomas and focal nodular hyperplasia. Similar uptake has also been demonstrated in metastases from neuroendocrine tumours.32 Gadobenate dimeglumine (Gd-BOPTA) demonstrates both perfusion properties and hepatocellular selectivity. This enables MR angiography and dynamic perfusion imaging after intravenous administration of Gd-BOPTA. It reaches peak liver enhancement after 10 minutes, followed by a plateau phase of 120 minutes. In this phase the differential uptake into hepatocytes and non-hepatocyte lesions is maximal. The combination of dynamic contrastenhanced MRI and delayed imaging has been shown to increase lesion conspicuity and detectability. Again, differentiation between hepatocyte-predominant benign and malignant lesions is limited.33 Gadoxetate (Gd-EOB-DTPA) differs from Gd-BOPTA in its time to reach peak enhancement in the liver. This takes 10–25 minutes after intravenous injection, and maximum liver-to-lesion contrast is achieved in 20–45 minutes, compared to 60–120 minutes with Gd-BOPTA. The other pharmokinetic properties are similar. Care should be taken with hepatocyte-specific agents, as delayed images alone will miss hepatocyte-predominant lesions, which have signal intensity similar to that of the normal liver. Optimal imaging should include sequential information from dynamic contrast-enhanced and delayed images.34 Kupffer-cell-specific contrast agents are colloidal compounds composed of an iron-oxide core. The core iron particles are typically between 3 nm and 10 nm in size, but the whole particle with the outer protein coat is 50–150 nm. After intravenous administration, the agents are taken up by the RES in the liver (80 per cent) and the spleen (12 per cent). The particles are eliminated in lymph nodes and bone marrow. Although the half-lives are in minutes, the paramagnetic effects persist for several days. Optimal imaging is performed several hours after administration. The molecules are degraded within the macrophages of the RES, and free iron is incorporated into the cellular iron metabolic pathways. The presence of iron in Kupffer cells results in pronounced reduction in signal intensity of normal liver on T2-weighted images (fast spin echo (FSE) and T2* images). This results in an ‘inverse’ contrast effect, lesions not containing Kupffer cells retaining their normal signal but the surrounding normal liver becoming of very low signal intensity on T2 images.35

122 Tumour imaging in oncology

Kupffer cells are present in lesions of focal nodular hyperplasia, hepatocellular adenomas, regenerating nodules and well-differentiated hepatocellular carcinomas and adenomatosis hyperplasia. Hence these lesions lose signal intensity to varying degrees along with normal liver tissue. As with hepatocyte-specific agents, Kupffer-cell agents increase lesion conspicuity and detection rate, but complete characterization remains elusive and there are currently not enough data and experience to eliminate the need for a diagnostic biopsy for certain liver lesions.36 Metastatic deposits in the liver do not contain normal liver hepatocytes and Kupffer cells (except for HCC metastases). Therefore metastases remain of low signal intensity with hepatocyte-specific agents and of high signal intensity with Kupffer-cell agents. The blood-pool phases usually reveal some peripheral increase in contrast uptake due to the variable angiogenesis in liver metastases. Characterization of metastases in patients with a known primary cancer is relatively simple, and the use of liver-specific contrast agents has been shown to increase the number of detected metastases compared to CT and gadolinium-enhanced MRI.30,33,35

surgical clips up to 6 weeks after surgery. Joint prostheses are fixed and generally acceptable but may cause susceptibility artefacts in the images, and occasionally patients may experience discomfort due to heating of the metallic prosthesis. Pregnancy, particularly the first trimester, is a relative contraindication, as there are no studies demonstrating the safety of MRI in vivo in the human fetus. Intravenous administration of gadolinium is also avoided, and its safety in pregnancy has not been confirmed. However, no fetal developmental adverse effects have been reported. The most significant side effect in pregnancy can occur at any magnetic field strength. Supine scanning of a pregnant woman, particularly in the third trimester, may result in aorto-caval compression by the fetus and reduce maternal blood flow resulting in dizziness in the mother and a reduction in placental blood flow to the fetus. At higher field strengths (higher than 2T), in-vitro experiments have demonstrated a small increase in amniotic fluid temperature; the significance of this has not been evaluated in humans. Despite these limitations, MRI and US are the preferred imaging modalities, rather than ionizing radiation (CT), in all stages of pregnancy.40,41

ENDOLUMINAL MRI

Endoluminal MRI has been used most extensively in rectal, prostatic and cervical cancers. It involves placing transmitter/receiver MRI coils in the rectum and vagina. The use of endoluminal coils allows very high-resolution images of the organ of interest. The baseline sequences are T2-weighted images in several planes. In early cervical cancer it provides detailed information about the size and extent of cervical lesions and parametrial spread, optimizing the surgical approach to treatment. Patients with small-volume invasive disease without deep cervical stromal invasion can be treated successfully by radical removal of the cervix, thereby conserving their fertility. In prostate cancer, transrectal MRI offers better loco-regional staging than transabdominal MRI. This is used in patients suitable for radical treatment or localized tumour treatment such as cryotherapy or thermal ablation. The reported accuracies of transrectal MRI staging in prostatic cancer are variable, between 51 and 85 per cent, the results being highly dependent on local radiology and histopathology expertise. Transrectal MRI has been used in benign (inflammatory bowel disease, diverticulitis and adenomatous disease) and malignant lesions of the rectum. In rectal carcinoma it has been used to delineate the tumour and assess invasion into the surrounding mesorectal fascia prior to total mesorectal excision (TME) surgery. In rectal, prostatic and cervical cancers, concurrent imaging of the pelvis is recommended using pelvic phase-array coils to image the pelvic sidewalls for nodal disease.37–39 SAFETY OF MRI

Magnetic resonance imaging is contraindicated in patients with metallic intra-ocular foreign bodies, non-MRIcompatible cerebral aneurysm clips, cardiac pacemakers, neurostimulator devices, cochlear implants and metallic

Nuclear medicine Nuclear medicine imaging has contributed significantly to the diagnosis, treatment planning and evaluation of response to treatment in patients with cancer since the development of modern techniques. It utilizes the body’s own normal and abnormal biochemical and physiological pathways, making it a form of functional imaging. The patient is injected with a gamma-emitting labelled tracer and the distribution of tracer after a period of time is detected by modified gamma cameras containing scintillation crystals that are read by photomultiplier tubes. The patient lies under the gamma detector system (camera) for 20–60 minutes and the whole-body distribution of the tracer is mapped into an image by applying mathematical algorithms. The image is most commonly a planar image, but if tomographic techniques are applied, single-photon emission CT (SPECT) and PET images can be obtained. Table 6.2 summarizes the current common uses of nuclear medicine tests and tracers in oncology.42 POSITRON EMISSION TOMOGRAPHY

Positron emission tomography is a nuclear medicine modality that provides quantitative tomographic images allowing non-invasive functional imaging. It has taken on an increasingly important role in oncology for diagnosis, staging during and after completion of treatment, and detection of recurrent disease. It utilizes biochemical metabolites (the commonest being 2-deoxy-D-glucose), labelled with beta-emitting radiotracers (18FDG), which are injected intravenously. Both glucose and deoxyglucose enter cells via the cell glucose transporters and undergo phosphorylation, but whereas glucose undergoes further

Imaging modalities 123

Table 6.2 Current nuclear medicine tests and tracers in oncology Test

Tracer

Indication

Bone scan

99m

Gallium scan MIBG scan Octreotide scan

67

Thallium scan Monoclonal antibodies

201

Staging bone disease in prostate, breast, lung cancers; detecting symptomatic bone disease in other cancers Staging and treatment response in lymphoma Localization and staging of neuroendocrine tumours Localizes and stages tumours with somatostatin receptors (pancreas, carcinoids, medullary thyroid cancer, neuroblastoma) Brain tumours and osteosarcoma To stage and detect tumour containing tumour antigen (lung, colorectal, ovarian and prostate cancers)

Tc-methylenediphosphate

Ga-chloride I-labelled or 123I-labelled MIBG 111 In-octreotide 131

TI-chloride In-labelled or 99mTc-labelled tumour antibodies

111

enzymatic breakdown, deoxyglucose becomes trapped in the intracellular compartment. Cancer cells over-express glucose membrane transporters and intracellular phosphorylation enzymes, thereby taking up and trapping more glucose and deoxyglucose than normal cells. It must be remembered that FDG is not a specific marker for cancer cells, and activated macrophages are also known to exhibit high tracer uptake. This has significant implications in the analysis of PET studies, as active infection and cancer can behave similarly. The 18F component undergoes beta decay in the body and produces a positron and a neutrino. Once a positron is slowed down, it produces two gamma-rays, which are emitted back-to-back and have energy of 511 KeV each. These decay events are detected by coincidence registration of gamma quanta. Therefore it is not the position of positron emission but the position of annihilation into gamma-rays that is detected by PET. As the positron only travels small distances, in clinical practice the locations of positron emission and annihilation are close together. However, this explains the ‘flare’ effect, in which the tissue source appears to have ill-distinct margins. This is registered by two opposing external detector units, and images are constructed after applying mathematical algorithms (18FDG PET imaging). Detectors for PET imaging are similar to those for conventional nuclear medicine, consisting of scintillation crystals (the commonest is bismuth germinate), which are read out by photo-multiplier tubes. The images created represent the metabolic activity of underlying tissues.42 Positron emission tomography has an advantage over conventional nuclear medicine in that it is possible to measure the effects of attenuation of photons within the body, providing image correction for better qualitative images. It also allows measurement of tracer concentrations within tissues, providing the most commonly used clinical measurement index, the standard uptake value (SUV), which compares lesion activity concentration to average activity concentration of the whole body. The SUV values have been utilized to differentiate between benign and malignant lesions and to prognosticate survival in lung cancer and head and neck squamous cell cancers – in general, the

higher the SUV, the poorer the outcome. Changes in SUV before and after chemotherapy have been compared to assess the effectiveness of the chemotherapy agent.43,44 18 F-Fluorodeoxyglucose-PET does not reliably distinguish between inflammation/infection and malignancy, as FDG accumulates in granulocytes and macrophages. This can lead to limitations in clinical practice, as differentiation between residual or recurrent disease and post-radiation inflammatory changes may be difficult. There are, however, several established clinical applications of PET, including the pre-surgical work-up of patients with small-cell lung cancer, oesophageal cancer, colorectal cancer and metastatic melanoma, for which the addition of PET has been shown to decrease surgical procedures in patients with CT-occult metastases. 18F-Fluorodeoxyglucose-PET has also been used to improve radiation treatment planning by defining more accurate biological target volume, especially in intensitymodulated radiotherapy (IMRT). Its use is also being investigated to predict response to chemotherapy both during and at the completion of treatment.45–47 PET-CT

In clinical oncology, the diagnosis and staging of cancer are traditionally based on CT imaging that relies on detecting anatomical alteration of normal tissues. However, cancer originates as a functional change that precedes anatomical alteration. Positron emission tomography has a high sensitivity for the detection of this functional change, but its spatial resolution for anatomical localization is limited. Over the past decade, software-based algorithms have been developed that allow the fusion and combined display of CT and PET images. However, this requires the superimposition of data acquired retrospectively, and normal variations in the position and activity of bowel, respiration and cardiac function contribute to correlation difficulties.48 The alternative solution of hardware fusion has created PET-CT. This allows the acquisition of CT and PET in a single session without re-positioning the patient between scans. In clinical practice, this involves injecting patients with 18F-FDG-PET tracers at least 1 hour prior to the start

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of the combined PET-CT. A topogram is then acquired to define the area of interest. Contiguous helical CT scans are acquired through the area of interest. After completion of the last helical CT image, the patient is advanced for the PET emission scan acquired in a caudal–cranial direction and taking up to 1 hour. Unlike conventional CT, due to the long duration of the combined acquisition, patients have their arms by their sides and are allowed to breathe shallowly during the scan. Once the collection of CT data is complete, they are sent to the PET console for attenuation and scatter correction. Once corrected, the emission and CT data can be viewed separately, side by side or fused with the PET images superimposed on the CT images. Early results show that combined PET-CT improves diagnostic accuracy compared with CT and PET alone. At present, even with the best PET technology, imaging is slow and the hardware expensive.49 Future developments in PET include hardware improvements that will allow combined use with multi-detector CT by increasing the acquisition rate of emission data. Faster acquisition would overcome respiratory and cardiac limitations, increasing its application in cardiac viability imaging. In oncology, PET has been used to evaluate gene expression and offer prognostic information. It can be used in combination with numerous tracers that image key molecules and molecular based events. Other tracers, particularly labelled chemotherapeutic agents, have been used to predict the uptake of the agent into primary and metastatic lesions, thereby predicting the effectiveness of the chemotherapeutic agent.50

lesions, tumoral calcification and bony destruction, which help to characterize the lesions.52 Although CT is sufficient for diagnosis in most cases, MRI is without doubt a more sensitive technique, visualizing the posterior cranial fossa and leptomeningeal space better than CT. It is the imaging modality of choice in the diagnosis and pre-surgical planning of brain tumours. It has a higher spatial (2 mm) and tissue contrast resolution and delineates and separates tumour from surrounding oedema better than CT. The presence and degree of necrosis detected on MRI have been shown to be associated with higher-grade tumours.53 The MRI technique is variable, but usually includes T2-weighted, T1-weighted, fluid-attenuated inversion recovery (FLAIR) sequence and gadolinium-enhanced T1 sequences. The imaging planes are also variable, but should include axial and coronal images, ensuring the complete cranial fossa is included. Both CT and MRI have high sensitivities but lack specificity for differentiating tumours from other infective and inflammatory masses and predicting tumour grade. Fluorodeoxyglucose-PET is rarely helpful, as it lacks the sensitivity and spatial resolution to challenge MRI as the investigation of choice. SURVEILLANCE AND RECURRENCE

Tumours of the brain account for 1.6 per cent of all cancers in England and Wales and are the twelfth and fifteenth commonest type of cancer in men and women respectively. Between 1995 and 1997, 2170 new tumours were reported in men and 1780 in women.51 Improvements in detection have probably led to the observed increase in incidence of brain tumours in both men and women, particularly in the 55–64-year age group. The brain is also a common site for metastatic disease from other tumours. However, this discussion focuses on primary brain tumours.

Magnetic resonance imaging is the modality of choice for postoperative surveillance and for the detection of recurrent disease. A routine postoperative study is performed 4–6 weeks after initial surgery.54 If radiotherapy is also administered to the patient, differentiating radiotherapy changes from recurrent disease can be difficult. Both radiation necrosis and recurrent disease occur at the postoperative bed and both can demonstrate similar appearances on conventional and contrast-enhanced MRI. Magnetic resonance spectroscopy is most commonly used to differentiate between tumour recurrence and radiation effects: there is marked elevation of choline in tumour recurrence, whereas marked reduction of choline levels is observed in radiation necrosis. Positron emission tomography demonstrates a reduction of FDG uptake in areas of radiation necrosis and an increase in uptake in recurrent disease. It has a reported accuracy of 85 per cent for detecting tumour recurrence.55 Thallium, SPECT and perfusion weighted imaging (PWI)201 have also been suggested for detecting tumour recurrence; the ultimate diagnosis still requires a brain biopsy.56,57

DIAGNOSIS AND STAGING

RECENT ADVANCES

The introduction of CT 30 years ago revolutionized the detection of brain tumours. It still remains the most frequently used imaging modality to detect space-occupying lesions in the brain. The CT technique should include images acquired before and after the administration of intravenous contrast. The advantages of CT over plain radiography and MRI include better assessment of bone-based

To improve the specificity of CT and MRI in characterizing intracranial masses, newer MRI sequences, MRS, fCT and fMRI, MRI perfusion (PWI) and MRI DWI, have been applied. Diffusion-weighted imaging has been used for lesion characterization and can usually differentiate between abscesses and necrotic tumours, which is not possible by conventional CT and MRI (see Fig. 6.5). It distinguishes between

CLINICAL APPLICATION OF IMAGING TECHNIQUES TO SPECIFIC TUMOURS Brain tumours

Clinical application of imaging techniques to specific tumours 125

Squamous cell carcinomas of the nasopharynx, oropharynx and larynx account for 80–90 per cent of all head and neck cancers.

main advantage is the ability to examine lymph nodes in the neck and, combined with fine-needle aspiration (FNA) of suspicious nodes, to provide cytology. It has a sensitivity of 73 per cent and a specificity of 100 per cent in the detection of nodal metastases in normal-sized nodes, significantly better than for CT and MRI.61 Nodal staging with FDG-PET has also been shown to be more sensitive and accurate than CT or MRI. FDG-PET has a sensitivity of 90 per cent and a specificity of 94 per cent, compared to 82 per cent and 85 per cent respectively for CT and 88 per cent and 79 per cent respectively for MRI.62 It can detect nodal metastases in lymph nodes down to 4 mm, but has the propensity to miss smaller disease. In a small minority of patients (5 per cent), lymph-node metastases are noted in the neck without a known primary source. In this group, FDG-PET (in association with CT) has been shown to identify the occult primary in 40 per cent of the patients (Fig. 6.8).63

DIAGNOSIS AND STAGING

SURVEILLANCE AND RECURRENT DISEASE

Most cancers at presentation are mucosal lesions and undetected on cross-sectional imaging. They are diagnosed and characterized on direct visualization and biopsy. These tumours have the tendency to submucosal spread, and assessment of their extension to the skull base, infratemporal and pterygopalantine fossa cannot be evaluated clinically and requires cross-sectional imaging. Metastatic lymph-node involvement is the most important prognostic factor affecting patient survival, and loco-regional node involvement decreases the 5-year survival to nearly 50 per cent.59 Imaging is used to identify subclinical, retropharyngeal and paratracheal lymph-node involvement. Other clinically important nodal groups are the submandibular, submental, lateral cervical, posterior triangle and supraclavicular chains. Both CT and MRI have similar performance in staging head and neck tumours and should be regarded as complementary tools. On the whole, for high tumours (nasopharyngeal and paranasal) with suspected involvement of the skull base, MRI detects early intracranial extension, perineural spread and marrow involvement better than CT. Computed tomography demonstrates nodal involvement and early cortical bone invasion of the skull base, orbits and nasal sinuses better than MRI.60 Both modalities require thin-section scans (2–3 mm) through the head and neck. Computed tomography has the advantages of performing additional scans during the modified Valsalva manoeuvre and obtaining three-dimensional volumetric data sets that can be reconstructed for planning treatment. Contrast enhancement is essential for both CT and MRI. A significant disadvantage of MRI is its long scanning time, which introduces significant motion artefacts from coughing and prolonged swallowing, frequent in these patients. Ultrasound is commonly used in the examination of the neck and its main contribution is in the detection of primary cancers of the salivary glands and thyroid. Its role in the detection of oral and pharyngeal tumours is limited. Its

After radiotherapy, tissue changes become evident on CT and MRI within 2 weeks and are most pronounced during the first few months, resolving slowly over time. These changes include symmetric thickening of the skin, subcutaneous tissue and platysma, oedema in the retropharyngeal space, symmetric thickening and enhancement of the laryngeal and pharyngeal walls, atrophy of nodes in the Waldeyer’s ring, and atrophy and sialadenitis of the salivary glands. The post-surgical changes include the introduction of reconstructive tissue and material grafts. Immediately after surgery, muscle grafts appear as normal muscle but, gradually undergoing atrophy and fatty replacement due to denervation. Areas of residual fibre-like muscle tissues can be confused with recurrent disease. Due to these post-radiation and post-surgery changes, baseline post-treatment imaging is suggested 3–6 months after completion of treatment.64 Studies using CT have shown that baseline scans can be used to predict long-term outcomes and patients, who demonstrate expected post-radiotherapy changes only, with complete resolution of primary tumour have the best prognosis. CT features of a residual mass 1 cm in maximum diameter and post-radiotherapy reduction of tumour volume by 50%, are predictive of future local disease recurrence.65,66 Fluorodeoxyglucose-PET has been shown to have better sensitivity and significantly better specificity than CT and MRI in detecting residual and recurrent disease. The sensitivity and specificity of FDG-PET are between 88 and 100 per cent and 75 and 100 per cent respectively, compared with 70 and 92 per cent and 50 and 57 per cent for CT and MRI.67 Recommendations have been made to assist in the selection of imaging modalities in patients being investigated for residual or recurrent disease. FluorodeoxyglucosePET should be used when no clinically obvious mass is palpable in patients with non-specific symptoms of recurrence or in patients with a low clinical suspicion of recurrence with advanced cancer at presentation. Computed

densely cellular tumours such as lymphoma and gliomas, but it cannot separate tumour infiltration from oedema, and the appearances of high-grade and low-grade tumours overlap. Perfusion-weight imaging provides information concerning tissue vascularity and can be used to grade tumours into low and high grades. Low-grade tumours have low perfusion, whereas high-grade tumours have increased perfusion. Functional MRI is increasingly used to maximize surgical margins whilst attempting to conserve unaffected brain tissue to retain normal function.58

Head and neck tumours

126 Tumour imaging in oncology

(a)

(b)

(c)

Figure 6.8 67-year-old male patient presenting with cervical lymphadenopathy. (a) Non-contrast enhanced image of the neck demonstrating large volume left sided cervical lymphadenopathy (arrow). On CT alone the primary tumour is not clearly visualised. (b) 18F-FDG PET image showing tracer uptake in the left sided lymphadenopathy and the left oro-pharynx (arrow). (c) CT-PET fusion image accurately delineates the primary tumour lying in the left Waldeyer’s fossa (arrow) (See Plate Section.).

tomography or MRI is advocated when there is a positive or equivocal FDG-PET or to image the extent of disease in biopsy-proven recurrence or a suspicious palpable mass. Early-stage disease with low clinical suspicion precludes imaging studies.68 RECENT ADVANCES

Improvements in imaging have concentrated on differentiating malignant from non-malignant nodal disease in an attempt to improve surgical outcomes but also to avoid extensive neck dissection in NO disease. Dynamic contrast enhancement in MRI and functional imaging techniques in CT and MRI have been evaluated but are not currently in routine clinical use. Early experience with USPIO MRI lymphography suggests that this technique will improve the diagnostic accuracy in the detection of nodal metastases. Colour Doppler ultrasound (DUS) is another method investigated in the diagnosis of cervical metastatic lymphadenopathy that enhances the predictive value of conventional B-mode US. The presence of cortical thickening, structural inhomogeneity, compressed, displaced or nonvisualized hilum and high-resistance arterial flow in the nodal hilum increases the likelihood of metastatic involvement of nodes. Extracapsular extension, which is a significant negative prognostic feature, can also be detected on DUS. There is currently a limited number of studies evaluating DUS and no studies comparing DUS with FDG-PET.69,70

Lung cancer Lung cancer was a relatively rare disease at the beginning of the twentieth century but is currently the commonest cancer

in the world; nearly 90 per cent of cases are caused by tobacco smoking. In 1997, in the UK, there were 21 000 new cases of lung cancer in men, in whom it was the most common cancer, and 13 200 new cases in women, in whom it was the third commonest cancer.51 Imaging provides information about disease extent by defining the extent of local invasion as well determining mediastinal and distant spread. Lung cancers are divided into small-cell (SCLC) and non-small-cell lung cancer (NSCLC), reflecting the marked difference in natural history, therapeutic strategies and response to treatment between the two groups. DIAGNOSIS AND STAGING

Small-cell lung cancer is usually disseminated at presentation in 60–80 per cent of patients.71 Plain radiographs and contrast-enhanced CT of the chest and abdomen are the standard imaging tests.72 In SCLC, staging divides tumours into limited (involving one hemithorax, unilateral or contralateral mediastinal and supraclavicular nodes) or extensive disease (metastatic thoracic and extrathoracic disease). Patients with limited disease receive radiotherapy, whereas extensive disease is treated with systemic chemotherapy. Staging of NSCLC is more complex. Involvement of hilar, mediastinal lymph nodes, chest wall invasion and fissural extension and extra-thoracic disease are crucial features to stratify patients for surgery, radiotherapy or systemic chemotherapy. Despite discrepancies between CT and surgical TNM staging in up to 40 per cent of cases, CT is widely used as a guide for the use of EUS-guided biopsy, mediastinoscopy, MRI and exploratory thorocotomy (Fig. 6.9).73 Both CT and MRI show extensive mediastinal tumour extension and chest-wall invasion equally well, but lesser

Clinical application of imaging techniques to specific tumours 127

(a)

(b)

Figure 6.9 45-year-old male smoker with NSCLC. (a) Non-contrast enhanced CT of the mediastinum demonstrating lymph nodes at the upper limit of normal size in the sub-carinal site (arrow). This is a difficult site to access at mediastinoscopy. (b) Trans-oesophageal ultrasound demonstrates the lymph nodes (arrow) and offers the ability to biopsy these nodes aiding management of the patient.

degrees of invasion are less reliably diagnosed or excluded.74 No other imaging modality, including FDGPET, has proved superior to CT for diagnosing mediastinal invasion.75 For chest-wall invasion, MRI was shown to have a sensitivity of 85 per cent and a specificity of 100 per cent, but when compared to CT in a prospective study, no significant difference was seen.76 The one exception, where MRI is superior to CT, is in the detection of brachial plexus and chest wall involvement in superior sulcus or Pancoast tumours.77 Nodal involvement on CT is based on increase in size. The normal sizes of nodes in the mediastinum are 10–11 mm in the subcarinal and lower paratracheal regions and 7 mm in the upper paratracheal regions. Using 10 mm as the upper limit of normal nodes, CT has a sensitivity and specificity of 50–65 per cent for metastatic involvement;78 MRI does not perform better than CT. The most comprehensive comparative study demonstrated sensitivity and specificity of CT as 52 per cent and 69 per cent respectively, compared to 48 per cent and 64 per cent respectively for MRI.76 Fluorodeoxyglucose-PET is being increasingly used for staging lung cancer; it consistently shows better sensitivity (79 per cent) and specificity (91 per cent) for detecting nodal involvement.79 Optimal staging is achieved by the combined use of FDG-PET and CT, which confirms tumour involvement of enlarged nodes and detects metastases in unenlarged nodes and unsuspected extra-thoracic disease (Figs 6.10 and 6.11). Combined use has a negative predictive value between 92 and 100 per cent and is therefore advised.80 More than 50 per cent of all patients with lung cancer present with distant metastases, with the probability increasing with advancing local stage. Currently the most common strategy to detect extra-thoracic disease is additional CT of the brain and abdomen at the same time as the staging thoracic CT. This is performed with intravenous

contrast enhancement to identify brain, liver and adrenal metastases. With increasing availability of FDG-PET, this is likely to change, as PET has been shown to have higher sensitivity and specificity and is cost effective compared to CT in the detection of all extra-thoracic disease except for in the brain. It has been shown to alter management in 24–65 per cent of patients staged by CT, and prevents unnecessary thorocotomy in 20 per cent. Fluorodeoxyglucose-PET has also been shown to have performance superior to that of 99m Tc bone scans, with sensitivity and specificity of 92 per cent and 99 per cent respectively, compared to 92 per cent and 50 per cent respectively for 99mTc bone scans.81,82 SURVEILLANCE AND RECURRENT DISEASE

There is limited literature and no generally accepted guidelines on imaging for local recurrence in lung cancer. For asymptomatic patients, the routine work-up is a plain chest radiograph only, although CT has been shown to be significantly more sensitive.83 The only imaging modality to have acceptable sensitivity and specificity for the detection of recurrent disease is FDG-PET performed 3–6 months after treatment.84 The false-positive rate is as high as 40 per cent if the imaging is performed close to treatment, due to scarring, fibrosis and radiation changes.82 Recurrent tumour is almost never amenable to cure, and the survival benefit of routine imaging has not been demonstrated.

RECENT ADVANCES

Population screening for lung cancer The use of low-dose CT has been advocated to screen an at-risk population. The initial results demonstrate a diagnostic yield of lung cancer of 2.7 per cent on the first round of screening. Most cancers detected are stage IA, fulfilling

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(a)

(b)

(c)

Figure 6.10 56-year-old male smoker presenting with a large cavitating central NSCLC. (a) Coronal reformatted non-contrast enhanced CT demonstrating the left sided lung cancer and a right sided supraclavicular enlarged lymph node (arrow). (b) 18F-PET image shows tracer uptake centrally in the lung cancer within viable tissue, in the right supraclavicular lymph node and also in an unsuspected right humeral metastasis (arrow). (c) PET-CT fusion provided anatomical and functional correlation of the active tumour sites (See Plate Section.).

the screening criteria of diagnosing asymptomatic earlystage disease. However, 90 per cent of all detected lung nodules are benign and therefore imaging protocols have been suggested to minimize false-positive thoracotomies. In subsequent rounds of screening, the false-positive rate and the true-positive rate are lower, but remain significant. The implementation of screening is currently being debated and its long-term benefit of reducing mortality and morbidity from lung cancer is still undecided.85,86

Breast Breast cancer is the commonest female cancer in the West. In the UK, there are approximately 41 000 new cases annually.51 Imaging plays an important role in the detection of primary breast cancer, in the characterization of palpable breast masses and in the detection of recurrent disease.

DIAGNOSIS AND STAGING

Breast-cancer screening programmes exist in many countries. Mammography is the screening modality of choice. The screening programmes have shown a significant reduction in mortality of around 25–30 per cent among screened groups compared to non-screened populations.87 However,

the age at which screening commences, the screening interval and the age at which it ceases all vary in different countries and there is currently no consensus as to the optimal strategy. In the UK, screening commences at the age 50 years and is performed every 3 years up to the age of 70 years. The most common mammographic manifestations of carcinoma are stellate breast mass, poorly defined irregular mass, and clustered, multiple, polymorphic and branching breast calcification. Screen-read mammograms are categorized into seven categories: 0  needs additional imaging, 1  normal, 2  benign, 3  probably benign, 4  suspicious, 5  highly suggestive of malignancy, and 6  proven malignancy. Carcinomas are present in 23–34 per cent of category 4 and 81–97 per cent of category 5 mammograms.88,89 Mammography is supplemented by US, biopsy and MRI in difficult cases. Ultrasound is useful to separate benign cystic from malignant solid lesions, and FNA or biopsy can be performed in non-palpable masses. Magnetic resonance imaging is also emerging as a useful tool in the detection of breast cancer. It is especially useful in patients with previous breast cancer and post-treatment distorted breast tissue, in patients with breast prosthesis and in young high-risk women below the national screening age.90 The staging of breast cancer is based on the TNM classification. It is largely clinical, but imaging is increasingly used to delineate the tumour. Ultrasound is more readily available in UK for this purpose, but has been shown to

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sequences has been advocated as the most accurate technique for the measurement of primary tumour.92 Computed tomograhy is used to look for lymph-node involvement (in the axilla, internal mammary, supraclavicular and mediastinal nodes) and to identify pulmonary metastases. A liver US is performed to exclude liver metastases. Radioisotope bone scans are performed to exclude bony metastases preoperatively in patients with clinical stage III disease.

SURVEILLANCE AND RECURRENT DISEASE (a)

(b)

Mammography is the standard modality for the follow-up of patients after breast surgery. It identifies microcalcification and in the long term can detect non-palpable ipsilateral or contralateral breast cancers. The Royal College of Radiologists recommends mammography should be performed every 2 years after surgery, whereas The British Association of Surgical Oncology recommends a baseline at 6 months followed by annual mammography for 5 years after surgery. Localized recurrence occurs at 1 per cent per year.93 Magnetic resonance imaging has been used for surveillance, particularly in patients with breast prosthesis and post-surgical scarring.94 Metastatic breast cancer is unusual at the time of presentation in early-stage disease, but can present between 2 and 5 years after diagnosis. Metastatic disease can involve any organ, with nodal disease, bone, liver and lung deposits being the most common. No clinical advantage has been demonstrated in imaging distant disease in asymptomatic patients, and the choice of imaging is dictated by the patient’s presenting symptoms. RECENT ADVANCES

(c)

Figure 6.11 54-year-old male smoker with SCLC. (a) Noncontrast CT of the chest demonstrating left upper lobe collapse (arrow). A separate mass is difficult to define. 5-7 mm lymph nodes are also noted in the left paratracheal and pre tracheal sites (arrow). (b) 18F-PET image demonstrates tracer uptake in a central tumour without uptake in the distal collapsed lung (arrow). (c) The PET-CT fusion image provides anatomical correlation and demonstrates that the lymph nodes have no increased tracer uptake, thus excluding mediastinal metastases (See Plate Section.).

underestimate size due to the irregular margins of the tumour.91 Magnetic resonance imaging has been shown to delineate tumour margins accurately, assess the contralateral breast and detect multi-focal disease not appreciated clinically or by mammography. Magnetic resonance imaging with gadolinium enhancement and fat-suppressed

Over the past few years there has been a marked increase in the use of MRI and 18F-FDG-PET imaging of the breast. Their use covers the spectrum of cancer detection, staging, response to treatment and detecting recurrent disease. In 2004 the International Breast MRI Multicenter Consortium published a large study (n  821) evaluating the role of MRI in patients recommended for biopsy based on mammographic, clinical or US findings. This demonstrated that despite the inclusion of dynamic enhancement techniques, MRI missed 12 per cent of cancers (particularly well-differentiated ductal and lobular carcinomas) detected by other modalities.94 The study concluded that MRI cannot substitute for biopsies in patients with palpable or imagingdetected abnormalities. The main role of MRI is in assessing the extent of disease, multi-centricity and bilaterality of breast cancers at the time of detection. It has also been shown to detect occult breast cancer in 75–85 per cent of patients presenting with axillary lymphadenopathy with an unknown source.95 In screening high-risk patients, although MRI has a higher sensitivity than clinical examination and mammography (80 per cent versus 18 per cent and 33 per cent respectively), its specificity is highly variable.

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Magnetic resonance imaging has not been tested for screening the general population. In detecting breast cancer, FDG-PET has no advantage over MRI and has a lower sensitivity than mammography for lobular carcinoma, small carcinomas and carcinomas with low metabolic activity.96 The lack of evidence to demonstrate a clear advantage over other techniques and its high cost have limited the use of FDG-PET in the routine diagnosis of primary breast cancer. Early studies reported very high sensitivities (79–100 per cent) and accuracy of more than 90 per cent of FGD-PET in detecting axillary nodal metastases, but more recent prospective studies are less convincing (sensitivities between 20 per cent and 61 per cent).97,98 The current data therefore do not support the routine use of FDG-PET to predict axillary metastases. The main strength of FDG-PET lies in the detection of recurrent breast cancer and distinguishing it from post-radiation and post-surgical changes.99 It has a higher sensitivity than bone scans for the detection of bone metastases. New radio-pharmaceuticals in PET which bind to oestrogen receptors (ER) have been utilized to assess metastatic disease. As the ER status is almost always known from the histopathology specimen, early studies indicate that the potential role of these ligands is to assess recurrent breast cancer in women with ER-positive primary tumour and potentially predict response to second-line chemotherapy.100 Fluorine-18 fluorothymidine (18F-FLT) is a new PET agent that measures cellular proliferation and has been used for the assessment of therapeutic effectiveness. A single available study concludes that this tracer seems to be suitable for the diagnosis of primary breast cancer and loco-regional metastases, but clearly further studies are required.101

Colorectal cancer Colorectal cancer accounts for 13 per cent of all cancer in the UK and is the second most common cancer in women and the third most common cancer in men. In 1997, there were 28 900 new cases, of which two-thirds were in the colon and a third in the rectum.51 Imaging has an established role in detecting, staging, surveillance, identifying recurrent disease and, more recently, in screening for colorectal carcinomas.

DIAGNOSIS AND STAGING

The mode of detection of colorectal carcinomas is determined by the clinical risk factors. Patients with moderate/ high risk usually undergo colonoscopy, whereas those with low risk undergo barium-enema studies. In the elderly who are unable to tolerate a barium enema, CT of the abdomen and pelvis will exclude large lesions only. The technique of CT pneumocolon, which involves prior bowel preparation similar to that for barium enemas and rectal air insufflation at the time of CT, has been proposed as a substitute for

barium enemas for screening in colorectal cancer. Its role is discussed below. The usefulness of CT in local tumour staging of both the colon and rectum is limited.102 The spatial resolution of CT cannot separate the layers of the bowel wall, and the limits of the mesorectal fascia are also not well demonstrated on CT. Nonetheless, preoperative CT of the chest, abdomen and pelvis is performed to assess nodal and distant metastases and to identify surgically significant complications of the primary tumour. These complications include intestinal obstruction, local tumour perforation, pericolic abscess, intussusception and acute appendicitis, the presence of which confers an unfavourable prognosis.103,104 The performance of CT for the detection of nodal metastases is also poor. The sensitivity, specificity and accuracy are 38 per cent (rectal), 56 per cent (colon), 88 per cent and 62 per cent respectively.105 Distant metastases from colorectal cancer are most commonly to the liver, lungs and bone. The sensitivity and specificity of intravenous contrast-enhanced CT in the detection of liver metastases are 77 per cent and 94 per cent respectively.106 Computed tomography arterioportography – which involves rapid scanning of the liver in arterial and portal phases whilst contrast is administered directly into the hepatic circulation via a previously placed catheter in the superior mesenteric artery or splenic artery – has been shown to have better sensitivity and specificity than conventional CT. However, this technique is invasive, and recent CT advances, particularly multi-detector CT, are likely to improve the results of conventional CT. Magnetic resonance imaging has also been shown to perform as well as CT arterioportography; particularly with the use of hepatocyte-specific agents, it has higher sensitivity and specificity than CT in the demonstration of lesions below 1 cm in size.107,108 Magnetic resonance imaging now has a central role in the local tumour staging of rectal cancers for patients being considered for TME surgery. High-resolution, thin-slice (2–3 mm) pelvic MRI can be used to measure accurately the depth of extramural spread (Fig. 6.12). It has been shown to predict accurately the histological status of the circumferential resection margin, with a positive predictive value of 92 per cent, and to identify negative prognostic features such as extramural venous invasion and peritoneal invasion.109,110 For nodal staging, however, MRI, like CT, relies mainly on size criteria and only provides limited morphological information. Its sensitivity for detecting nodal metastases is similar to that of CT. It may be possible to overcome this in the future with the use of MRI lymphnode-specific agents. Currently FDG-PET is not used routinely in the staging of colorectal carcinoma. Small studies have compared histology, sensitivity, specificity and CT and FDG-PET showing a accuracy for detection of tumour of 90 per cent, 66 per cent and 87 per cent with FDG-PET, compared to 60 per cent, 100 per cent and 65 per cent with CT.111 Its main role is in the identification of occult liver metastases in

Clinical application of imaging techniques to specific tumours 131

(a)

(b)

Figure 6.12 67-year-old female patient with stage T3 rectal carcinoma. (a) Sagittal T2-weighted image demonstrating a large circumferential mid rectal carcinoma (arrow). The exact site, length of the tumour and anterior bladder and posterior sacral involvement can be assessed on the sagittal images. (b) Axial-oblique T2-weighted image obtained perpendicular to the long axis of the tumour provides a true cross-section of the tumour. This allows evaluation of the depth of tumour invasion and the extent of mesorectal fascial invasion. Lymph nodes in the mesorectum are also evaluated (arrow).

patients being considered for hepatic resection. There is evidence that FDG-PET loses sensitivity when the lesion size is below 1 cm, and combined use with multi-detector CT may result in improved accuracy.112

soon after surgery or radiotherapy is useful, but a positive scan may be due to recurrent disease or treatment changes.111 In patients with a rising CEA and a negative CT, FDG-PET is able to locate recurrence accurately in about 67 per cent of cases.115

SURVEILLANCE AND RECURRENT DISEASE

The total incidence of recurrence in colorectal cancer is 15–50 per cent of which 75 per cent recur within 5 years.113 As surveillance, patients undergo clinical assessment and carcinoembryonic antigen (CEA) measurements, with colonoscopy at regular intervals. Imaging is of vital importance in surveillance and currently consists of CT of the chest, abdomen and pelvis at 3 months after surgery for baseline postoperative appearances, followed by 3-monthly CT examinations for 3 years and annually thereafter.114 It is important to detect early recurrent disease, as salvage surgery may be possible. Magnetic resonance imaging performs as well as CT, but both are unable to differentiate between postoperative scar tissue and radiation fibrosis and necrosis. Also, MRI does not routinely image the chest, and therefore metastases in the lung, a common site of recurrent disease, are undetected. Currently, MRI is not superior to CT in the surveillance of colorectal cancer. 18 F-Fluorodeoxyglucose-PET is evolving as an important problem-solving tool, and as many as 70 per cent of cases that are equivocal on CT may be resolved on FDG-PET.111 One weakness of FDG-PET is the uptake of tracer in postsurgical scar tissue and radiation fibrosis up to 6 months after primary therapy, with appearances indistinguishable from those of recurrent disease. Negative FDG-PET imaging

RECENT ADVANCES

Screening Screening programmes are currently being evaluated in the USA and Europe. The American Cancer Society guidelines recommend screening for men and women over the age of 50 years; high-risk groups enter the screening programme earlier. High-risk groups include individuals with (a) a strong family history of colorectal cancer or polyps, (b) a family with hereditary colorectal cancer syndromes, (c) a previous history of polyps or colorectal cancer, and (d) a history of chronic inflammatory bowel disease. There are five possible screening protocols that are in use: annual testing for faecal occult blood (alone or in association with 5-yearly flexible sigmoidoscopy); 5-yearly flexible sigmoidoscopy alone; colonoscopy every 10 years; and double contrast barium enema every 5 years. A positive result for faecal occult blood, sigmoidoscopy or barium enema should be followed by colonoscopy.116 Computed tomography colonography has been evaluated in the role of screening and has been shown to be accurate in the detection of polyps down to 10 mm.117,118 The potential benefits and limitations of screening are currently being debated and it is too early to assess the difference it makes to the mortality rates from colorectal cancer.

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Prostate cancer Prostate cancer is now the second commonest cancer in men in the UK. There were 18 300 new cases in 1997 in England and Wales, with the peak age distribution in men in their seventies.51 The combination of digital rectal examination (DRE), serum prostate-specific antigen (PSA) level and prostatic biopsy forms a very effective means of detecting prostate cancer. Appropriate imaging is highly controversial and continually evolving as treatments for early disease unfold. There is currently little evidence to support imaging of low-risk (clinically stage I or II), Gleason score 7, PSA 10 ng/mL) patients prior to radical treatment by surgery or radiotherapy, but imaging is appropriate in patients with intermediate (stage I-II), Gleason score 5–7, PSA 10–20 ng/mL) and high risk of extra-prostatic (clinically stage T3 or higher, Gleason score 8 and PSA 20 ng/mL) disease.

DIAGNOSIS AND STAGING

Imaging has no role in detecting prostate cancer except for guiding transrectal prostatic biopsies.118 It is widely used in staging to stratify patients into organ-confined (stage I and II) and non-organ-confined (stage III and IV) disease for the purpose of treatment selection. Digital rectal examination is simple, inexpensive and central in staging prostate cancer, but is highly subjective and underestimates local extent of disease in 30–60 per cent of patients.119 Transrectal ultrasound of the prostate examines the prostate in a transverse and sagittal plane. Its most important role is in guiding prostate biopsies and measuring prostate size prior to brachytherapy and cryotherapy. The tumours of the peripheral prostate gland appear as hypoechogenic foci, but these appearances are non-specific and mimicked by inflammatory and infective processes of the prostate. TRUS also has a low positive predictive value (18–52 per cent) for the diagnosis of cancer.120 For extracapsular extension, the sensitivity and specificity of TRUS are equivalent to those of DRE and are between 50 and 92 per cent and 46 and 91 per cent respectively.121 For seminal vesicle involvement, the sensitivity and specificity of TRUS are highly variable, ranging between 20 and 92 per cent and 65 and 100 per cent respectively.122 In patients at high risk of seminal vesicle involvement, seminal vesicle biopsies can be performed on TRUS. Computed tomography does not confer any information concerning the local organ-confined tumour. In asymptomatic patients with PSA 20 ngmL, CT is not recommended due to the low probability of a positive study. Advanced extracapsular extension into the peri-prostatic fat and presacral space can be demonstrated. Its main role is in nodal staging, where using a cut-off value of 7 mm as the upper limit for normal nodes, CT has sensitivity and specificity of 78 per cent and 100 per cent respectively.123

Figure 6.13 82-year-old male with clinically T2b prostate cancer. The Axial T2-weighted image demonstrates the low signal intensity tumour centrally in both right and left peripheral zones at the bases (arrow heads). On the right there is tumour extension through the capsule into the peri-prostatic fat (arrow) indicating a T3a tumour.

Magnetic resonance imaging provides the best visualization of tumour in the prostate gland, the prostatic capsule, peri-prostatic tissue and the seminal vesicles. The performance of MRI in the available studies has been highly variable. A meta-analysis of several studies shows maximum sensitivity and specificity of MRI for extracapsular extension of 64 per cent and 69 per cent respectively, and for seminal vesicle involvement of 82 per cent and 80 per cent respectively (Fig. 6.13).124 As for CT, conventional MRI relies on nodal enlargement to detect metastases. Using the criterion of rounded nodes larger than 8 mm in the pelvis, MRI has a reported maximum accuracy of 90 per cent and a positive predictive value of 94 per cent in the detection of nodal metastases.125 Distant metastases are seen in less than 1 per cent of lowrisk patients. Imaging for distant metastases is recommended in patients with high-risk disease. Bone is the commonest site for metastases. Radioisotope 99mTc bone scans and plain films are used to detect bony metastases. Magnetic resonance imaging is helpful in equivocal cases and in patients with known bony metastases and symptoms suggestive of cord compression to guide radiotherapy. Metastases to liver, spleen and lungs are detected during the staging CT examinations. SURVEILLANCE AND RECURRENT DISEASE

Routine imaging of asymptomatic patients is not recommended. For patients who have undergone radical prostatectomy or radiotherapy, imaging is performed if the

Clinical application of imaging techniques to specific tumours 133

serum PSA is greater than 2 ng/mL. Local recurrence is best imaged by MRI, whereas distant nodal and metastatic disease is best assessed by CT and 99mTc bone scans.126 RECENT ADVANCES

Magnetic resonance spectroscopy has recently been evaluated in prostate cancer. In prostate cancer there is an elevation of choline and a reduction in citrate when compared to normal peripheral zone tissue of the prostate. The combination of MRI and MRS improves the localization, specificity and detection of extracapsular extension. There is an increase in accuracy from 53 per cent to 75 per cent in detecting prostatic cancer. The high specificity of MRS aids in the distinction of post-biopsy haemorrhage and other benign abnormalities from tumour.127

73–96 per cent.130 Magnetic resonance imaging is superior to CT in demonstrating peri-vesical extension, due to the high inherent tissue contrast of the bladder wall and peri-vesical fat. Overall, when early tumours are included in the staging accuracy, no significant difference is demonstrated between the performance of CT and MRI.131 For nodal metastases, MRI relies on the same criteria as CT, and both are equally accurate in the detection of nodal metastases. Distant organ metastases occur in advanced invasive local disease, with liver, lung and bone metastases occurring most frequently. Computed tomography of the chest and abdomen is included in the staging investigations of invasive bladder cancer. Technetium-99m bone scans are not used in routine staging, but are reserved for patients with bone pain. SURVEILLANCE AND RECURRENT DISEASE

Bladder cancer Bladder cancer is the fourth commonest cancer in men and the ninth commonest cancer in women in the UK, with 12 100 new cases reported in 1997.51 Cystoscopy is the main mode of tumour detection and staging, and is highly accurate in the evaluation of superficial tumours. However, in invasive tumours, clinical staging is inaccurate in 25–50 per cent of cases, and CT and MRI are used for staging. DIAGNOSIS AND STAGING

For local tumour staging, the key issue is whether the tumour is confined to the bladder wall or whether there is extension beyond into perivesical fat, adjacent structures or pelvic and abdominal walls. Cystectomy is offered to patients with invasive disease confined to the bladder, and very early T3 disease may be down-staged by radiotherapy prior to surgery. Advanced extravesical disease receives palliative chemoradiotherapy. For optimal CT technique, the patient should have a full bladder during the time of imaging; intravenous contrast enhancement is mandatory and oral contrast may be helpful. With optimal CT technique the local tumour staging accuracy of CT has been reported to be between 72 and 89 per cent.128 The best accuracy is achieved in early superficial tumours and advanced invasive disease. Distinction between stage T2a and T2b is not possible. Under-staging on CT results from its inability to detect early peri-vesical invasion. In the detection of nodal metastatic disease using an increase in size, rounded shape and enhancement after contrast administration, CT has sensitivity, specificity and accuracy of 75 per cent, 90 per cent and 90 per cent respectively for nodal metastases.129 The optimal MRI technique includes axial T1, axial, coronal and sagittal T2 images, and T1 images with dynamic contrast enhancement and fat saturation. Using these optimal techniques, the accuracy of MRI in staging bladder cancer is

Surveillance CT of the abdomen and pelvis is controversial, although there is evidence that CT can detect up to 30 per cent of recurrent disease prior to the development of symptoms.132 It is currently unclear whether it should be offered to all patients who have undergone radical treatment or should be reserved for patients at high risk (highgrade, high-stage, extra-vesical tumour, nodal metastases, lymphatic and vascular invasion prior to treatment). The frequency of the CT imaging has been proposed at 6, 12 and 24 months, as 70 per cent of all recurrent disease occurs within 2 years of completion of treatment.133 Imaging has an important role in detecting and defining sites of recurrent disease. Pelvic soft-tissue masses, nodal disease at the common iliac and internal iliac groups and retroperitoneal nodal disease are the commonest manifestations of relapse. Computed tomography of the chest, abdomen and pelvis is the imaging modality of choice, with MRI used for imaging the vertebral column in suspected cord compression. Both CT and MRI also have a role in monitoring treatment response in patients offered chemoradiotherapy to identify progression and assess response. This may be offered to down-stage patients prior to surgery or as palliative treatment. With both modalities there may be difficulty in differentiating radiotherapy changes from residual or recurrent tumour. The bladder wall is thickened and enhances in the presence of tumour and inflammatory changes secondary to radiation. Fluorodeoxyglucose-PET cannot be used to assess local bladder disease, as normal excretion of the tracer into the bladder lumen masks abnormalities of the bladder wall and immediate perivesical tissue.

Ovarian cancer Ovarian cancer is the fourth commonest cancer in women in England and Wales, with 6100 new cases registered in 1997.51 Imaging performs poorly in accurate detection,

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pre-treatment diagnosis and staging, and thus ovarian cancer remains a major challenge in oncological imaging. These tumours often present late with widespread dissemination throughout the abdomen and pelvis. Imaging has an important role at presentation for diagnosis, preoperative assessment of extent of disease, postoperative assessment of residual disease and assessing response to adjuvant chemotherapy.

DIAGNOSIS AND STAGING

Ultrasound, particularly transvaginal ultrasound (TVUS), is the commonest modality used to identify and characterize pelvic ovarian masses at presentation. TVUS is usually performed during investigations for pelvic pain, menstrual disturbances, as part of investigations of a raised serum CA125 level or in patients with ascites and a palpable pelvic mass. Criteria for characterizing malignant masses on US have been described and include masses larger than 10 cm, the presence of soft-tissue nodules (soft-tissue components) and vegetations, thickened, irregular walls, thickened nodular septae, presence of ascites and peritoneal nodules. The sensitivity and specificity of US, including the addition of DUS, have been reported as between 85 and 97 per cent and 56 and 95 per cent respectively.134 Contrastenhanced CT relies on the same criteria as TVUS and has an accuracy of detection of ovarian masses of up to 95 per cent and in distinguishing benign from malignant disease of between 66 and 94 per cent.135 Magnetic resonance imaging with Gd enhancement has also been shown to have a high sensitivity (95 per cent) and an overall better specificity (60–93 per cent) and accuracy (91 per cent) than US for malignancy in ovarian masses.136 In the presence of a suspicious ovarian mass, elevated CA125 and a high clinical suspicion of ovarian carcinoma, FIGO-based staging is performed. This is based on a formal staging laparotomy sampling the omentum and peritoneal reflections, chest radiograph, intravenous urogram and barium enema. Surgery includes hysterectomy and bilateral salpingooopherectomy, providing local staging and tissue for histology. Surgical staging is the gold standard, but is inaccurate in 30–40 per cent of cases, with upper abdominal disease being the most common site of occult disease.137,138 Intravenous and oral contrast-enhanced CT of the abdomen and pelvis is the commonest imaging modality used for radiological preoperative staging or as baseline imaging prior to chemotherapy after debulking surgery. Computed tomography is useful in detecting ascites, pleural effusions, tumour involvement of intra-abdominal viscera, mesentery, peritoneal reflections and omentum (Fig. 6.14). The major limitation of CT is its inability to detect peritoneal deposits below 1 cm; the staging accuracy of CT is between 70 and 90 per cent.139 Magnetic resonance imaging with Gd enhancement has similar accuracy to CT in detecting peritoneal disease and does not improve the detection of peritoneal disease below 1 cm. It has better

Figure 6.14 56-year-old female with Stage 3 ovarian cancer. The contrast enhanced CT image demonstrates ascites, omental thickening (short arrow) and peritoneal nodules (arrows) in keeping with stage 3 disease. Note the calcified peritoneal nodule (arrowhead).

accuracy detecting implants on bowel serosa, and invasion of the sigmoid colon, bladder and rectum.140 Although cross-sectional imaging cannot replace surgical staging, it is valuable in patients with unresectable tumour and can identify disease missed at laparotomy. SURVEILLANCE AND RECURRENT DISEASE

Response to treatment may be assessed by non-invasive imaging such as CT and MRI, by invasive laproscopy or laparotomy or serum CA125 levels. Computed tomography is most commonly used to document treatment response. Localized disease in the pelvis at the vaginal vault and the pouch of Douglas is better assessed by MRI. Both imaging modalities miss small (1 cm) peritoneal, omental and serosal nodules. Although more sensitive (62–91 per cent versus 40–67 per cent), MRI has a significantly lower specificity (40–93 per cent versus 93–100 per cent) than CT in the restaging of recurrent disease.141 RECENT ADVANCES

Radionuclide imaging Indium-111-labelled monoclonal antibodies binding to tumour cell-surface antigens have been used experimentally to improve the detection of peritoneal and omental disease that is missed by other techniques. The site of antibody uptake is detected by SPECT or intra-operatively using handheld gamma cameras. This technique has a reported sensitivity of 68 per cent for detecting primary and recurrent disease.142 Its main strength is identification of tracer uptake in peritoneal seedlings 2–5 mm in size. However, the poor

Clinical application of imaging techniques to specific tumours 135

spatial resolution of SPECT does not allow accurate localization of the disease. This technique is currently not in routine clinical use and its role is poorly defined. 18

F-FDG-PET

Fluorodeoxyglucose-PET has recently been used in staging primary disease and detecting recurrent disease. The literature reports no improved sensitivity of FDG-PET alone or in conjunction with CT compared to conventional CT alone. In fact, FDG-PET is inferior to CT in the demonstration of small peritoneal deposits. False-negative FDGPET results have also been reported early after completion of chemotherapy.143 Population screening for ovarian carcinoma Ovarian cancer can be detected in asymptomatic patients using several methods, of which pelvic clinical examination, serum CA125 and TVUS are the most commonly used. The effectiveness of screening the general population of postmenopausal women using the above methods is currently under investigation by two randomized control trials: the UK-based UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS) and the USA-based National Institute of Health Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial (NIH PLCO) study. The UKCTOCS is a 7-year prospective study measuring ovarian cancer mortality rates in controls, patients screened by TVUS alone and patients undergoing multi-modality screening. The results from these studies are currently awaited.

Endometrial cancer In the UK, endometrial cancer is the fifth commonest female malignancy and 5600 new cases and 1200 deaths were reported in 2002.51 Carcinoma of the endometrium is primarily a disease of the elderly, but 25 per cent of cases occur in pre-menopausal women; 90 per cent are histologically adenocarcinomas. Conventional treatment is by hysterectomy and as 75 per cent of tumours are confined to the uterus at presentation, this is a curative procedure. Although the mainstay of treatment is hysterectomy with bilateral salpingo-oopherectomy, pelvic lymphnode sampling or lymphadenectomy is required in a subset of patients who have a higher risk of nodal metastases. The Gynaecologic Oncology Group (GOG)144 has identified those groups of patients in whom it recommends paraaortic and pelvic lymph nodes should be sampled: ●

● ● ● ●

myometrial invasion greater than 50 per cent, regardless of tumour grade; extension of tumour into the internal os or cervical stroma; adnexal or other extra-uterine metastases; visibly enlarged lymph nodes; serous, undifferentiated, clear cell or squamous histology.

A significant number of women with endometrial cancer have various co-morbidity factors increasing the risks

of anaesthesia and surgery. These factors include obesity, diabetes mellitus, hypertension, ischaemic heart disease and AIDS. It is prudent therefore to perform the most appropriate and expeditious procedure after consultation between the surgeon and anaesthetist. Preoperative imaging will allow staging and planning so that a straightforward hysterectomy and salpingo-oopherectomy is performed without other surgical planning prolonging the procedure. FIGO recommends pre-treatment imaging evaluation of endometrial cancer with conventional imaging including barium enema, chest X-ray and intravenous urography. Recently, TVUS for endometrial cancer, CT, MRI and FDG-PET have expanded the role of imaging in the management of endometrial cancer. Imaging has become an important adjuvant to clinical evaluation in tumour staging, treatment planning, assessing treatment response, monitoring complications and during surveillance. DIAGNOSIS AND STAGING

Transvaginal ultrasound and endometrial biopsy establish the diagnosis of endometrial cancer. In endometrial cancer, TVUS shows an increase in endometrial width, heterogeneous echotexture and an irregular, poorly defined edge. As part of staging, TVUS has been used to evaluate the depth of myometrial and cervical invasion in endometrial cancer. The depth of myometrial invasion is an important prognostic factor, the incidence of nodal metastases increasing sharply from 3 per cent for stage IB tumours to 40 per cent for stage 1C tumours.145 Transvaginal ultrasound, CT and MRI have all been used to assess myometrial invasion. The performance of TVUS is variable and operator dependent. The reported accuracies for myometrial invasion vary between 77 per cent and 91 per cent.146–148 Computed tomography, including newer multi-detector CT, has poor sensitivity and specificity for myometrial and cervical invasion. The sensitivity and specificity are 83 per cent and 42 per cent respectively for the detection of deep myometrial invasion, and 25 per cent and 70 per cent respectively for the detection of cervical invasion.149 The overall staging accuracy of CT is between 58 and 76 per cent.150,151 Computed tomography is therefore of limited value for local staging and unlikely to affect management in early endometrial cancer. In more advanced disease with parametrial and pelvic sidewall disease, CT is highly accurate in detecting local spread beyond the uterus.152 Due to its excellent tissue contrast resolution, MRI has established its role in identifying deep myometrial invasion, and thereby contributes to the preoperative decision regarding the need for lymphadenectomy (Fig. 6.15). It is highly accurate in local staging and is recommended for patients in whom there is clinical suspicion of advanced disease and in select histological subtypes, listed earlier. With regards to myometrial invasion, the reported sensitivity and specificity are between 84 and 87 per cent and 91and 94 per cent respectively. The positive predictive value (PPV) is 87 per cent and the negative predictive value (NPV) is 91 per cent for the identification of myometrial invasion greater

136 Tumour imaging in oncology

with overall accuracy, sensitivity and specificity of 92 per cent, 92 per cent and 80 per cent respectively.158 Fluorodeoxyglucose-PET has been evaluated in small studies, which report promisingly high sensitivity of 96 per cent and specificity of 57 per cent. Correlation of FDG-PET with tumour markers and CT minimizes false-positive rates, resulting in a higher specificity of 88 per cent.159 As FDGPET is a whole-body imaging technique, all comparative studies report a higher accuracy than for both CT and MRI in the detection of para-aortic disease and lung metastases. RECENT ADVANCES

Figure 6.15 70-year-old woman with Endometriod Stage 1A carcinoma of the endometrium. Sagittal T2-weighted image demonstrating the large tumour in the endometrial cavity with intermediate signal intensity (star) and complete preservation of the underlying junctional zone which indicates no myometrial invasion (arrow). The endocervical canal and cervical stroma are normal. A synchronous ovarian carcinoma is also noted (arrowhead).

than 50 per cent.153,154 The use of Gd improves the ability to assess depth of myometrial invasion with MRI. Magnetic resonance imaging also performs particularly well in the detection of cervical invasion, for which its sensitivity, specificity, accuracy, PPV and NPV are 80 per cent, 96 per cent, 92 per cent, 89 per cent and 93 per cent respectively.155 Several investigators have reported that macroscopic cervical invasion, detectable on MRI, imparts a worse prognosis than microscopic invasion. Therefore preoperative assessment for cervical involvement may help in planning surgery and radiotherapy. For the detection of cervical invasion, FSE T2-weighted images are well suited. The detection of cervical invasion utilizes the natural contrast between the low T2 signal intensity of normal cervical stroma and the hyperintense T2 signal intensity of the invading endometrial carcinoma. Also as part of staging, extra-uterine disease, including peritoneal deposits in the pouch of Douglas, omental disease and pelvic or retroperitoneal lymphadenopathy, is also readily detected on MRI. SURVEILLANCE AND RECURRENT DISEASE

Magnetic resonance imaging has also been advocated in the detection of recurrent disease to evaluate surgical resectibility.151 Recurrent endometrial cancer may present as a pelvic mass in the hysterectomy bed or as pelvic or retroperitoneal lymphadenopathy. Less commonly, it may manifest as peritoneal carcinomatosis. Distant metastases and early recurrent disease are usually associated with high-grade tumours and advanced stage at presentation.156,157 Computed tomography performs well in the detection of recurrent pelvic disease,

Although endometrial cancer is primarily a disease of postmenopausal women, 25 per cent of tumours occur in younger pre-menopausal women, with 3–5 per cent under 40 years of age. In this subset of patients, the issue of fertility preservation poses a therapeutic dilemma both for patients and surgeons. Recent studies have shown grade 1, stage 1A tumours can be safely treated conservatively with hormonal therapy. Patients are treated with a high-dose progesterone regimen, with endometrial sampling every 3 months until complete regression of the tumour is documented. In these patients, MRI is performed during initial staging to exclude myometrial and cervical invasion, during surveillance, and after completion of treatment.160–162 Magnetic resonance imaging lymphography with USPIOs has been used to improve the detection of lymph-node metastases from gynaecological malignancies independent of node size. The sensitivity, specificity, PPV and NPV by size criteria were 27 per cent, 94 per cent, 60 per cent and 79 per cent respectively, and by USPIO criteria were 100 per cent, 94 per cent, 82 per cent and 100 per cent respectively.29 The USPIOs increase the sensitivity of MRI in the prediction of lymph-node metastases without loss of specificity. This will greatly improve preoperative treatment planning in endometrial carcinoma.

Non-Hodgkin’s lymphoma Non-Hodgkin’s lymphoma (NHL) is the commonest of the leukaemias and lymphomas. It is a collection of malignancies whose clinical behaviour, prognosis and management vary according to the subtype. The International Prognostic Index was developed by the International Collaborative Group to compare the efficiency of treatment regimens by implementing a standardized prognostic system.163 Imaging plays an important role in staging NHL, and in particular stage III and IV disease, and in identifying sites of extranodal disease, which are poor prognostic features, surveillance and detecting disease relapse. High-risk groups are treated with more aggressive therapies. DIAGNOSIS AND STAGING

The objectives of imaging are to define the extent of symptomatic disease and to detect occult disease. Non-Hodgkin’s

Clinical application of imaging techniques to specific tumours 137

lymphoma is commonly disseminated at presentation and although the majority of patients present with superficial lymphadenopathy, visceral involvement is common. The ability of CT to demonstrate enlarged lymph nodes throughout the body and to detect visceral pathology together with its easy availability and reproducibility have made it the imaging modality of choice for staging NHL. Patients undergo routine intravenous contrast-enhanced CT of the neck, chest, abdomen and pelvis. In the neck, lymph nodes larger than 1 cm with minimal or contrast enhancement and a rounded shape are considered to be involved. Nodal involvement in the mediastinum is seen in 25–40 per cent of cases of NHL, and the commonest sites are the superior mediastinum, subcarinal and hilar nodes. The nodes may be discrete (1 cm in short axis), matted together, have cystic changes or fine calcification. Other important sites of nodal disease in the chest are the paracardiac, intramammary, diaphragmatic, axillary, posterior mediastinal and the bronchopulmonary nodes.164,165 Within the abdomen and pelvis, mesenteric nodes are involved in 50 per cent, retroperitoneal nodes in 45–55 per cent and pelvic nodes in 40–45 per cent of patients.166 Other important sites of disease that may be overlooked are celiac, hepatic porta, splenic hilum and the porto-caval node (node of Winslow). In NHL, nodal involvement is non-contiguous, bulky and often associated with extra-nodal disease. About 40 per cent of NHL arises in extra-nodal sites. Secondary involvement may occur by direct invasion from adjacent nodal disease. The presence of extra-nodal disease is an adverse prognostic feature.167 As for nodal disease, CT is excellent for the depiction of extra-nodal disease, particularly in the lungs and abdomen. In NHL, pulmonary infiltrates may be present without thoracic lymphadenopathy in up to 50 per cent of patients. Pulmonary involvement occurs as nodules, rounded or segmental consolidation, ill-defined alveolar shadowing and cavitation.168 Pleural effusions may occur due to pleural involvement or to lymphatic obstruction resulting in a chylothorax. Chest-wall involvement is uncommon in NHL, but large masses may occur in the soft tissues of the chest wall. The margins and extent of the chestwall disease are better demonstrated on MRI than CT, as the former is more sensitive to bone-marrow infiltration and has better soft-tissue contrast than CT. Similarly, breast and cardiac involvement is also better assessed on MRI.169 Thymic infiltration may be indistinguishable from the frequently co-existent superior mediastinal lymphadenopathy. Thymic hyperplasia occurs in response to treatment and can be difficult to distinguish from recurrent disease on CT, MRI, gallium-67 (Ga-67) and FDG-PET, and follow-up studies may be necessary.170 Within the abdomen, the spleen is involved in up to 40 per cent of patients, but the detection of the disease is poor with CT, as the spleen may be of normal size and the disease in the form of lesions less than 1 cm in size.171 When lesions are larger than 1 cm, they are seen on CT and MRI and detection is improved by the administration of intravenous contrast media and multi-detector CT.

Splenomegaly indicates disease involvement; MRI does not perform better than CT in the detection of lesions smaller than 1 cm. The addition of USPIOs may improve sensitivity, and recent FDG-PET studies have demonstrated better sensitivity for the detection of splenic infiltration than CT and gallium-67.171,172 The liver is involved in 15 per cent of cases of NHL, with a higher predilection in children and recurrent disease. As for the spleen, the disease is usually microscopic, confined to the portal triad and consequently difficult to detect on CT and MRI. Non-Hodgkin’s lymphoma of the gastrointestinal tract is the most common site of primary extra-nodal NHL (stomach 51 per cent, small bowel 33 per cent, large bowel 16 per cent and oesophagus 1 per cent). As the disease is submucosal, EUS and barium contrast studies (barium meal, small-bowel follow-through and enemas) along with CT are particularly valuable. Local staging is best performed by EUS, but the frequently co-existing distant disease is best staged on CT.173 Although involvement of the genitourinary tract is rare at presentation, it is involved in more than 50 per cent of end-stage NHL. Histologically, more than 90 per cent are high-grade NHL, 40 per cent at recurrence, and renal function is usually normal. Multiple masses occur in 60 per cent of cases and solitary masses in 10–20 per cent; no associated retroperitoneal lymphadenopathy is present in 50 per cent. In 25 per cent there is direct invasion by retroperitoneal nodal disease and in a minority a peri-renal soft-tissue mass encasing the kidney without CT evidence of parenchymal invasion is seen (Figs 6.16 and 6.17).174 Extra-nodal disease of the central nervous system (particularly leptomeningeal disease), musculoskeletal system, bone marrow and head and neck lymphomas are poorly demonstrated and staged on CT. With its better tissue contrast, MRI improves both the detection and depiction of extent of disease. In the central nervous system, MRI is also very useful in detecting spinal extension of retroperitoneal or pre-sacral nodal disease and to exclude spinal cord compression in vertebral marrow disease.175 Bonemarrow disease occurs in 20–40 per cent of NHL and is considered stage IV disease and confers a poor prognosis. The involvement of the marrow is patchy but disseminated and, not surprisingly, imaging modalities such as wholebody MRI and FDG-PET are more sensitive than bonemarrow aspiration and biopsy for the detection of bone-marrow involvement. Although their exact role in staging bone-marrow disease is as yet undefined, they can be used to guide and increase the positive yield of bonemarrow aspiration for cytology.176,177 SURVEILLANCE AND RECURRENT DISEASE

Imaging is important in monitoring response to treatment and, once completed, regular periodic surveillance studies detect relapse early, allowing salvage treatment. Computed tomography is used for chest, abdominal and pelvic disease, but localized central nervous system, bone marrow, musculoskeletal system and head and neck disease is monitored

138 Tumour imaging in oncology

Figure 6.16 45-year-old woman presenting with an incidental left renal mass. Coronal reformatted contrast enhanced CT in the arterial phase demonstrates a mass associated with the inferior pole of the left kidney (arrows). The mass encases the renal parenchyma without invading or distorting the renal parenchyma. These appearances are typical of primary renal lymphoma.

Figure 6.17 32-year-old woman presenting with NHL. Sagittal T2-weighted mass involving the perineum, vulva, urethra, vagina and cervix (arrows). The mass enlarges all the affected tissues but no destruction of the tissue planes is present.

Table 6.3 Radiological criteria for diagnosing response in lymphoma Response

Features

Complete remission (CR)

1. No residual abnormality at original sites of disease 2. Nodes and nodal masses regressed to 1.5 cm in greatest transverse diameter for nodes 1.5 cm before therapy 3. Nodes regressed to 1 cm in greatest transverse diameter for nodes 1.1–1.5 cm before therapy 4. Spleen if enlarged by CT criteria must have regressed

Complete remission, unconfirmed (CRu)

Residual nodal mass 1.5 cm maximum diameter that has regressed by 75% of sum of products of greatest diameters (SPD)

Partial remission (PR)

1. 50% decrease in SPD of largest nodes/masses 2. No increase in size of liver, spleen and lymph nodes 3. Hepatic and splenic nodules decreased by 50%

Stable disease (SD)

Less than PR and no evidence of progressive disease

Progressive disease (PD)

1. 50% increase from nadir in SPD of previous abnormal nodes for PRs 2. Appearance of any new lesion during or at the end of treatment

Relapse (from CR or CRu)

1. Appearance of any new lesion 2. Increase by 50% in size of previous disease 3. Increase by 50% in greatest diameter of any previously identified node 1 cm in short axis or in SPD of more than one node

on MRI. The criteria for diagnosing radiological response are listed in Table 6.3.178 The optimal imaging intervals for assessing treatment response and for surveillance are not established. Strategies for surveillance vary according to the extent of primary disease, presence of residual masses, site of disease and grade of NHL. For patients who attain complete remission, functional imaging with Ga-67 and FDG-PET have been shown to have high sensitivity for

detecting recurrent disease prior to the development of symptoms.178 Ga-67 has been shown to detect relapse an average of 7 months prior to the onset of symptoms. Routine CT surveillance has limited value, as relapse can occur at sites distant from the primary disease and there is a significant time lag between microscopic relapse and the development of a mass detectable on cross-sectional imaging.

Imaging treatment response 139

Table 6.4 Definition of response based on World Health Organization (WHO) and Response Evaluation Criteria in Solid Tumours (RECIST) criteria WHO

RECIST

Response

Change in sum of the products of two longest perpendicular diameters

Change in sum of the longest diameter of each target lesion

Complete response at 4 weeks

Disappearance of all lesions with no residual disease

Disappearance of all target lesions

Partial response at 4 weeks

50% decrease in tumour area (product of the two longest perpendicular diameters) in single lesion or 50% decrease in the sum of the product of perpendicular diameters in multiple lesions, without 25% increase in size of one or more measurable lesions

30% decrease in the sum of the longest diameter of target lesions (using baseline sum of the longest diameters as the reference)

Stable disease

Absence of criteria of partial response or progressive disease

Absence of criteria of partial response or progressive disease

Progressive disease

25% increase in tumour area or appearance of new lesions

20% increase in sum of the longest diameter of target lesions (compared to smallest sum of the longest diameter recorded since start of treatment) or appearance of one or more new lesions

RECENT ADVANCES

Fluorodeoxyglucose-PET has been extensively investigated in lymphoma. It has a higher sensitivity than cross-sectional imaging and Ga-67 in staging lymphoma at presentation. Its strengths lie in detecting active disease in normal-sized lymph nodes and extra-nodal disease, particularly the liver and spleen, and detecting bone-marrow and skeletal involvement indicating tumour burden. It has been shown to upstage 10–20 per cent of patients compared to CT and Ga-67. Fluorodeoxyglucose-PET has also been evaluated in detecting relapse and restaging; it has a higher PPV for relapse than CT and Ga-67.179,180 A positive FDG-PET study at the end of therapy is strongly associated with an early relapse in NHL.181

IMAGING TREATMENT RESPONSE Imaging treated cancer is an expanding role of radiology. Imaging plays an increasingly central role in monitoring tumour response to treatment after standard therapies. It is increasingly used as a surrogate marker for treatment response, particularly in cancer treatment trials, which require more frequent follow-up and strict adherence to protocols. The choice of the most appropriate technique depends on the cancer type, cost, local availability of the imaging equipment and expertise. To assess response, a baseline study should be available prior to commencing treatment using the most appropriate imaging technique for follow-up. The frequency and

duration of follow-up differ for each type of cancer, when assessing patients for radical or palliative treatments, for type and interval of radiotherapy or chemotherapy, and for drug trials. Generally, CT remains the major modality for assessing treatment response for most solid cancers and lymphoma, although conventional techniques such as US and plain radiography can be used. Newer imaging techniques such as dynamic MRI, FDG-PET and MRS are under evaluation for the assessment of tumour response. Response to treatment can be measured objectively using the World Health Organization (WHO) criteria and the Response Evaluation Criteria in Solid Tumours (RECIST).182,183 The RECIST were developed specifically to standardize the evaluation of response in drug trials. A measurable lesion is a solid lesion whose limits can be clearly visualized due to the contrast with surrounding tissues. Target lesions chosen under the RECIST should be more than 2 cm in longest diameter or longer than 1 cm on spiral CT. Lesions smaller than 2 cm, bone disease, pericardial effusions, ascites, pleural disease, leptomeningeal disease, inflammatory breast lesions, cystic disease, and lymphangitis and carcinomatosis have been declared non-measurable diseases. Table 6.4 summarizes the definitions of response in WHO and RECIST terms. There are many problems with the application of these criteria, including the variability of methodologies, quality of reproducibility of the radiological examination, choice of target lesions and operator dependence. Despite these limitations, the WHO and RECIST are the most widely used assessment criteria in treatment response.

140 Tumour imaging in oncology

KEY LEARNING POINTS ●

●

●

●

●

Plain film radiography, mammography, IVU, barium studies, CT, nuclear scintigraphy, PET and PET-CT are ionising radiation based imaging modalities. Ultrasound and MRI are non-ionising imaging modalities. Imaging is part of the management of all patients with cancer. Cross-sectional imaging is important in diagnosis and staging of many cancers, assessing treatment options, surveillance and diagnosing recurrent disease. CT, including MDCT, is the most widely used cross-sectional imaging modality. It is the technique of choice in the evaluation of lung parenchyma, mediastinal, abdominal and pelvic pathology. It is widely used in staging, monitoring response, surveillance and assessing cancer recurrence in most malignancies. MDCT has the advantages of faster scanning time, thinner slice acquisition and exquisite 3D reconstruction. MRI is the imaging modality of choice in brain, head and neck and pelvic cancers. It has a superior tissue contrast than CT which is vital for imaging in the above cancers. MRI also serves as a problem solving tool in liver, adrenal and bone lesions. FDG-PET provides non-invasive functional tumour imaging. It has an established role in staging lung, oesophageal, malignant melanoma and head and neck cancers. Currently PET is an integral part of management in colorectal cancer and lymphoma. PET alone provides limited anatomical information. The combination of PET-CT adds the anatomical information and serves to reduce the false positive rate of PET alone.

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122 Melchior SW, Brawer MK. Role of transrectal ultrasound and prostate biopsy. J Clin Ultrasound 1996; 24:463–71. 123 Oyen RH, Van Poppel HP, Ameye FE. Lymph node staging of localized prostatic carcinoma with CT and CT-guided fineneedle aspiration biopsy: prospective study of 285 patients. Radiology 1994; 190:315–22. 124 Sonnad SS, Langlotz CP, Schwartz JS. Accuracy of MR imaging for staging prostate cancer: a meta-analysis to examine the effect of technologic change. Acad Radiol 2001; 8:149–57. 125 Jager GJ, Barentsz JO, Oosterhof GO, et al. Pelvic adenopathy in prostatic and urinary bladder carcinoma: MR imaging with a three-dimensional TI-weighted magnetization-prepared-rapid gradient-echo sequence. AJR 1996; 167:1503–7. 126 Partin AW, Pearson JD, Landis PK, et al. Evaluation of serum prostate-specific antigen velocity after radical prostatectomy to distinguish local recurrence from distant metastases. Urology 1994; 43:649–59. 127 Kaji Y, Kurhanewicz J, Hricak H, et al. Localizing prostate cancer in the presence of postbiopsy changes on MR images: role of proton MR spectroscopic imaging. Radiology 1998; 206:785–90. 128 Sharir S. Update on clinical and radiological staging and surveillance of bladder cancer. Can J Urol 2006; 13(Suppl. 1):71–6. 129 Bernhardt TM, Rapp-Bernhardt U. Virtual cystoscopy of the bladder based on CT and MRI data. Abdom Imaging 2001; 26:325–32. 130 Kim B, Semelka RC, Ascher SM, et al. Bladder tumor staging: comparison of contrast-enhanced CT, T1- and T2-weighted MR imaging, dynamic gadolinium-enhanced imaging, and late gadolinium-enhanced imaging. Radiology 1994; 193:239–45. 131 Buy JN, Moss AA, Guinet C, et al. MR staging of bladder carcinoma: correlation with pathologic findings. Radiology 1988; 169:695–700. 132 Slaton JW, Swanson DA, Grossman HB, Dinney CP. A stage specific approach to tumor surveillance after radical cystectomy for transitional cell carcinoma of the bladder. J Urol 1999; 162:710–14. 133 Montie JE. Follow-up after cystectomy for carcinoma of the bladder. Urol Clin North Am 1994; 21:639–43. 134 Kinkel K, Hricak H, Lu Y, et al. US characterization of ovarian masses: a meta-analysis. Radiology 2000; 217:803–11. 135 Buy JN, Ghossain MA, Sciot C, et al. Epithelial tumors of the ovary: CT findings and correlation with US. Radiology 1991; 178:811–18. 136 Sohaib SA, Sahdev A, Van Trappen P, et al. Characterization of adnexal mass lesions on MR imaging. AJR 2003; 180:1297–304. 137 Bagley CM Jr, Young RC, Schein PS, et al. Ovarian carcinoma metastatic to the diaphragm – frequently undiagnosed at laparotomy. A preliminary report. Am J Obstet Gynecol 1973; 116:397–400. 138 Clarke-Pearson DL, Soper JT, Berchuck A, Hunter VJ. Ovarian cancer. In: Moosa AR, Schimpff SC, Robson MC (eds),

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170 Spiers AS, Husband JE, MacVicar AD. Treated thymic lymphoma: comparison of MR imaging with CT. Radiology 1997; 203(2):369–76. 171 Giovagnoni A, Giorgi C, Goteri G. Tumours of the spleen. Cancer Imaging 2005; 5(1):73–7. 172 Moog F, Bangerter M, Diederichs CG, et al. Extranodal malignant lymphoma: detection with FDG PET versus CT. Radiology 1998; 206(2):475–81. 173 Raderer M, Vorbeck F, Formanek M, et al. Importance of extensive staging in patients with mucosa-associated lymphoid tissue (MALT)-type lymphoma. Br J Cancer 2000; 83(4):454–7. 174 Reznek RH, Mootoosamy I, Webb JA, Richards MA. CT in renal and perirenal lymphoma: a further look. Clin Radiol 1990; 42(4):233–8. 175 Chamberlain MC, Sandy AD, Press GA. Leptomeningeal metastasis: a comparison of gadolinium-enhanced MR and contrast-enhanced CT of the brain. Neurology 1990; 40(3 Pt 1):435–8. 176 Moog F, Bangerter M, Kotzerke J, et al. 18-Ffluorodeoxyglucose-positron emission tomography as a new approach to detect lymphomatous bone marrow. J Clin Oncol 1998; 16(2):603–9. 177 Yasumoto M, Nonomura Y, Yoshimura R, et al. MR detection of iliac bone marrow involvement by malignant lymphoma with various MR sequences including diffusionweighted echo-planar imaging. Skeletal Radiol 2002; 31(5):263–9. 178 Cheson BD, Horning SJ, Coiffier B, et al. Report of an international workshop to standardize response criteria for non-Hodgkin’s lymphomas. NCI Sponsored International Working Group. J Clin Oncol 1999; 17(4):1244. 179 Raanani P, Shasha Y, Perry C, et al. Is CT scan still necessary for staging in Hodgkin and non-Hodgkin lymphoma patients in the PET/CT era? Ann Oncol 2006; 17(1):117–22. 180 Reinhardt MJ, Herkel C, Altehoefer C, et al. Computed tomography and 18F-FDG positron emission tomography for therapy control of Hodgkin’s and non-Hodgkin’s lymphoma patients: when do we really need FDG-PET? Ann Oncol 2005; 16(9):1524–9. 181 Naumann R, Vaic A, Beuthien-Baumann B, et al. Prognostic value of positron emission tomography in the evaluation of post-treatment residual mass in patients with Hodgkin’s disease and non-Hodgkin’s lymphoma. Br J Haematol 2001; 115(4):793–800. 182 WHO Handbook for Reporting Results of Cancer Treatment. Geneva: World Health Organisation, 1979, 48. 183 Therasse P, Arbuck SG, Eisenhauer EA, et al. New guidelines to evaluate the response to treatment in solid tumours. J Natl Cancer Inst 2000; 92:205–16.

7 Interventional radiology TARUN SABHARWAL, ANNE P. HEMINGWAY AND ANDREAS ADAM

Introduction Biopsy procedures Percutaneous puncture and drainage procedures Venous sampling Percutaneous tumour ablation

146 147 150 150 151

INTRODUCTION Over the past three decades, a variety of invasive diagnostic and therapeutic procedures have been developed by radiologists. The term interventional radiology (IR) most appropriately refers to therapeutic procedures performed under imaging guidance.1 However, diagnostic invasive techniques are usually carried out by interventional radiologists and are included in this chapter. The emergence of IR as a specialty has been made possible by the enormous technological advances in relation to catheter and instrument design and manufacture, imaging systems and radiological expertise. Some of these procedures have largely replaced more invasive and hazardous surgical alternatives; for example, tunnelled central venous catheters are now usually inserted using imaging-guided percutaneous techniques under local anaesthesia, rather than open surgery under general anaesthesia. A summary of the main types of interventional procedures is shown in Table 7.1. The term invasive is relative; most of the procedures described in this chapter are considerably less invasive than their surgical alternative. However, they all carry some risk, which is interdependent on the underlying condition, the nature of the procedure and the experience of the radiologist. Radiological interventions in cancer patients require comprehensive assessment of the patients and careful consideration of the risks and benefits of the procedure. Factors unique to oncology patients must be evaluated, and decisions regarding therapeutic benefit must be made in light of patients’ prognoses and quality of life considerations. Effective communication of information about the nature,

Dilatation techniques Extraction techniques Infusion techniques Vascular embolization Gene therapy References

153 156 158 158 163 165

Table 7.1 Interventional radiological procedures Procedure Biopsy Drainage Dilatation/stenting

Feeding Venous access Extraction Infusion Embolization

Vertebroplasty Tumour ablation

Examples of indications Need for cytology/histology Obstruction of renal and biliary tracts, pleural effusions, ascites, abscesses Limb/organ ischaemia, gastrointestinal, biliary, ureteric and airway obstruction, superior vena cava/inferior vena cava obstruction etc. Percutaneous gastrostomy Dialysis, chemotherapy, total parental nutrition (TPN) Intravascular foreign bodies Regional, selective infusion of chemotherapy Gastrointestinal haemorrhage, posttraumatic haemorrhage, pseudoaneurysms, skeletal metastases etc. Osteoporosis, vertebral metastases Hepatic, renal, bony and soft-tissue tumours

benefits and potential complications is an integral part of the treatment.2 In this chapter, emphasis is placed on the indications, contraindications and results rather than on detailed technical descriptions.

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BIOPSY PROCEDURES The development of fine needles (Chiba needles) and smallgauge cutting instruments (automated biopsy devices such as the Quick-core, Temno and Biopty gun), which can be accurately directed to virtually any site within the body under imaging control and local anaesthesia, has dramatically reduced the number of patients requiring open surgical biopsy to obtain tissue for a histological diagnosis. It is possible to perform most of these procedures on an outpatient basis. Needle placement for obtaining a cytological or histological specimen may be carried out under fluoroscopic, ultrasonic (US), computed tomographic (CT) or magnetic resonance imaging (MRI) guidance.3–5 An efficient and accurate biopsy service is dependent upon the co-operation and expertise of the local departments of cytology and histology. Ideally, a cytologist should be present at the time of biopsy to determine if the specimen is adequate for examination. An initial cytological report should be available within hours; when larger specimens are sent for histological examination (as may be required with lymphoreticular malignancies), processing, sectioning and staining take longer. In certain other cases, such as primary breast cancer, histological evaluation for oestrogen and progesterone receptors and genetic analysis for the HER-2/neu or the BRCA1 or BRCA2 genes may be needed. A more recent advance is the use of coaxial introducers. The introducer stays in the lesion while the sampling needle is removed for recovery of the sample. This technique allows multiple needle passes to be performed through the introducer with only one puncture through the organ of interest. The coaxial introducer is especially useful for deep lesions or lesions that are difficult to access to minimize the risk and effort inherent in obtaining multiple samples. It is possible to perform image-guided biopsy either percutaneously (transthoracic, abdominal, musculoskeletal, lymph nodes etc.) or transluminally.

Percutaneous transthoracic biopsy Percutaneous transthoracic biopsy is a rapid, safe and effective means of establishing a diagnosis in a patient with an opacity visible on a chest radiograph.6,7 The procedure is performed under local anaesthesia using biplane fluoroscopy, US or CT for guidance (Fig. 7.1). Ultrasound guidance is useful for pleural biopsy, rib lesions, subcutaneous deposits and peripheral lung lesions reaching a pleural surface. For other more central or difficult-access lesions, either fluoroscopy or CT guidance is recommended.8 In general, it is easier, quicker and less expensive to carry out a biopsy under fluoroscopic guidance than to use CT scanning for the procedure. However, CT has several advantages over fluoroscopy. ●

It is easier to visualize small lesions on CT, especially when they are located in such a position as to be

●

●

●

projected over the mediastinum or the spine on lateral fluoroscopy. Biopsies from partially necrotic lesions should be taken from the viable parts of the wall of the mass rather than from the necrotic areas. It is easier to ensure that this is done under CT guidance. When multiple lesions are present, it is difficult to be certain that one is looking at the same lesion in both the anteroposterior and lateral projections on fluoroscopy, but much easier on CT. When a mass is close to a large vascular structure, it is better to use CT for the biopsy, as the vessel is easier to avoid because of the greater precision of the procedure.

Computed tomography guidance is also particularly useful in the performance of mediastinal biopsies. It is easier to distinguish abnormal masses from vascular structures by CT than by fluoroscopy. In addition, it is possible to avoid puncturing the lung, especially when a posterior approach is used, thus minimizing the risk of pneumothorax.9 The major drawback with CT is the lack of real-time imaging and slow image display time. To overcome this limitation, CT fluoroscopy (continuous imaging CT or real-time reconstruction CT) is now being used (Fig. 7.2).10,11 The success rate of imaging-guided biopsy is approximately 80–90 per cent. The most serious complications are pneumothorax and bleeding. On most occasions these can be managed in the interventional suite, e.g. lung aspiration or chest-drain insertion for pneumothorax, and embolization for haemoptysis. Although a small pneumothorax is seen on CT images in the majority of patients after lung biopsy, it is present on plain radiograph in only 15–20 per cent of patients; less than 2 per cent require insertion of a chest drain (cf. open lung biopsy, when all patients require a drain). Needle lung biopsy is contraindicated in patients with a bleeding diathesis, emphysema, contralateral pneumonectomy, hydatid disease or suspected arteriovenous malformation, i.e. any patients who could not withstand a pneumothorax or who might bleed uncontrollably. The procedure is of value not only in pulmonary parenchymal lesions but also in the investigation of pleural and mediastinal abnormalities. If the lesion to be biopsied shows evidence of cavitation, it is useful to obtain material from both its centre and periphery; this may require multiple passes of the biopsy needle, increasing the risk of pneumothorax. It is important to realize that with percutaneous lung biopsy, as with any other form of biopsy, a single negative result cannot be taken as proof that malignancy is not present.

Percutaneous abdominal biopsy In most cases, a percutaneous abdominal biopsy is performed under US or CT guidance. Both of these methods allow the radiologist to visualize not only the lesion to be targeted for biopsy but also the intervening organs, thus

(a)

(b)

(c)

(a)

Figure 7.1 (a) Percutaneous lung biopsy. An opacity is noted in the left upper zone (a) posteriorly (b) (The triangular metallic opacities are nipple markers). The biopsy needle has been inserted under biplane fluoroscopic control (c) Reproduced with permission from Allison (1987).

(b)

Figure 7.2 Percutaneous CT fluoroscopy-guided biopsy of retroperitoneal mass: (a) CT scan, showing soft-tissue mass surrounding the aorta and inferior vena cava; (b) with the patient in the prone position, biopsy needle positioned from left approach (photon starvation artefact confirming position of needle tip). Reproduced with permission from Dr M. Roddie.

Biopsy procedures 149

(a)

(b)

Figure 7.3 A musculoskeletal biopsy. A fine-gauge needle has been inserted into a lytic lesion at the level of C5 using biplane fluoroscopic control: (a) 5AP; (b) 5 lateral. The biopsy was performed under local anaesthesia and a diagnosis of osteoclastoma was made. Reproduced with permission from Allison (1987).

increasing the accuracy and safety of the procedure. The choice between the two techniques depends on the experience and preference of the radiologist and on the precise location of the lesion to be biopsied. For example, retroperitoneal masses are usually easier to visualize on CT scans, whereas lesions in the superior part of the right lobe of the liver immediately below the diaphragm are best biopsied under US guidance because this modality allows an oblique approach that avoids the lung. Ultrasound is usually quicker to perform, does not involve ionizing radiation and is available as a portable technique. In patients with a bleeding diathesis or massive ascites, percutaneous liver biopsy carries an increased risk of major, uncontrollable intraperitoneal haemorrhage. In such patients it is possible to obtain a liver biopsy via a transvascular route.12,13* Specially designed biopsy instruments can be passed via the right internal jugular vein into the hepatic veins. Bleeding arising from a biopsy taken from this position passes directly back into the patient’s circulation and is not therefore of haemodynamic significance. Although successful, this technique is technically demanding and not applicable to focal lesions. An alternative method of percutaneous liver biopsy, which can be used in patients with abnormal blood coagulation, is plugged liver biopsy. The needle is introduced into the liver within a guiding sheath. The biopsy is performed

and the needle is withdrawn, leaving the sheath in place. The biopsy track is then embolized with Sterispon or steel coils as the sheath is withdrawn.14,15

Musculoskeletal biopsy The presence of an abnormality within bone on an isotopic bone scan and/or plain radiography in a patient with known malignancy does not necessarily herald dissemination of the tumour, and it may prove necessary to obtain material for cytology.16,17 Solitary bony abnormalities discovered incidentally in a patient who is otherwise well also pose a difficult diagnostic problem. Lytic lesions are relatively straightforward to biopsy (Fig. 7.3), whereas sclerotic lesions give rise to more difficulties and the procedure may need to be performed under very heavy sedation or general anaesthesia. Computed tomography is extremely useful during the performance of musculoskeletal biopsy because it allows the needle to be guided precisely to the abnormal area. Quite frequently, a soft-tissue mass may be associated with lytic bone lesions, and CT allows this to be visualized and biopsied. In addition, CT demonstrates areas where the cortex is thinnest and thus easiest to penetrate with a biopsy needle. Another advantage of CT, especially when biopsying lesions in thoracic vertebrae, is that the needle

150 Interventional radiology

can be guided extrapleurally, thus avoiding the danger of pneumothorax. In a few cases, US guidance is sufficient. The great benefits of percutaneous biopsy are that the recorded incidence of complications is exceptionally low, the overall success rate is high (70–80 per cent) and the procedure is readily repeatable if the initial result is inconclusive.

Miscellaneous biopsy techniques When a mass extends into the superior or inferior vena cava, the transvascular route provides a safe and convenient way of obtaining a biopsy. The femoral vein is punctured at the groin, and a long sheath is introduced into the inferior vena cava and advanced to lie adjacent to the mass to be biopsied. A modified cardiac bioptome is then inserted via the sheath and the biopsy taken.18 Developments in endoluminal US have allowed lesions deep in the pelvis to be biopsied transrectally (prostate biopsies) or transvaginally (ovarian cysts). The advent of endoscopic and intra-operative US probes has further extended the versatility of this imaging modality (pancreatic, tracheal, oesophageal, colonic).19,20 In the management of breast cancer, non-palpable lesions are biopsied or localized using sterotactic mammography, US or MRI for guidance. In some instances with no apparent safe percutaneous approach, sufficient displacement of vital structures can be achieved by adjacent saline installation to allow safe biospy needle placement. This technique has been applied in the anterior mediastinum to displace internal mammary vessels and in the posterior mediastinum to displace lung. It has also been safely applied elsewhere in the abdomen and pelvis as needed.21

requires the percutaneous transhepatic cannulation of the portal veins. The reader is referred to more specialized texts for detailed descriptions of these techniques.

PERCUTANEOUS PUNCTURE AND DRAINAGE PROCEDURES With the use of fluoroscopy, US, CT or MRI, it is possible to image and drain obstructed renal and biliary systems, cysts, abscesses and effusions.

Renal tract Antegrade pyelography and percutaneous nephrostomy are useful in the management of benign and malignant obstruction of the urinary tract.23 The technique is also of value in a variety of other situations, e.g. in patients with malignancy undergoing chemotherapy resulting in haemorrhagic cystitis, in whom it is desirable to divert the urine to ‘rest’ the bladder. In patients with pelvic malignancy, either the disease or the treatment may result in the development of fistulas between the bladder and rectum or vagina, leading to incontinence. Diversion of urinary flow may assist in healing of the fistulas, ease nursing problems and allow patients to become ‘dry’. The procedure, usually performed under local anaesthetic and US guidance, involves an initial puncture of the pelvicalyceal system with a fine needle, followed by the instillation of radiographic contrast medium to demonstrate the anatomy and determine the level of obstruction. Urine can be aspirated for microbiological and cytological examination.

VENOUS SAMPLING The diagnosis of a hormone-secreting neoplasm is made on the basis of the clinical history and characteristic biochemical abnormalities. The localization of these tumours may, however, be quite difficult. Ultrasound and CT scanning of the common sites for tumours (e.g. adrenal glands for phaeochromocytomas, pancreas for insulinomas etc.) will reveal the majority of tumours. However, a few are either too small to be detected by these means or are found in ectopic sites. In these instances, venous sampling techniques can prove invaluable.22* Both systemic and portal blood specimens are obtained from various sites in the venous system and the areas sampled recorded on a map (Fig. 7.4). The specimens are numbered accordingly and taken immediately for appropriate analysis. Areas of high hormone concentration can then be charted on the map and searched by US, CT, angiography, MRI or surgery. Whereas systemic venous sampling is relatively safe and has a high success rate, localization of pancreatic or gastrointestinal hormoneproducing tumours is a more hazardous technique, as it

Figure 7.4 Systemic venous sampling map. A diagram of a systemic venous system indicates the main venous tributaries. Each of these vessels can be selectively catheterized and a sample of blood obtained for hormone analysis.

Percutaneous tumour ablation 151

Percutaneous nephrostomy entails the insertion of a pigtail catheter with multiple large side ports into the collecting system (Fig. 7.5). The catheter is introduced employing a needle, guide-wire and catheter exchange technique.

Biliary tract Likewise, in patients with infected obstruction to their biliary tree, external pigtail catheters or, preferably, internal–external biliary pigtail catheters can be inserted for temporary drainage.

Abscess drainage Percutaneous puncture of an abscess cavity and aspiration of contents for bacteriological analysis can be followed by insertion of a drainage catheter.24 It is possible to instill antibiotics into the cavity, and percutaneous drainage may be effective either as the definitive treatment or as a temporary measure until the appropriate surgery can be contemplated. Ultrasound, CT or MRI guidance may be used for abscess drainage. Computed tomography is particularly useful for retroperitoneal or mediastinal abscesses, for which visualization by US scanning may be inadequate. Transvaginal or transrectal drainage under US guidance is very useful for certain abscesses in the pelvis.

PERCUTANEOUS TUMOUR ABLATION

Figure 7.5 Percutaneous renal drainage. A patient with obstruction of the renal tract secondary to prostatic malignancy (note the sclerotic vertebral body due to metastatic infiltration). A pigtail catheter has been introduced under local anaesthetic into the dilated pelvicalyceal system and ureter. Urine is able to drain via the side ports in the catheter into a drainage bag on the skin surface. Reproduced with permission from Allison (1987).

(a)

In recent years, local ablative techniques have been employed successfully to treat a variety of tumours. Lesional heating techniques such as radiofrequency (RF) ablation and interstitial laser photocoagulation (ILP) achieve tumour necrosis by hyperthermia. The RF electrodes or laser fibres are inserted into the tumour under US, CT or MRI guidance (Fig. 7.6). Intralesional hyperthermia causes almost immediate coagulation necrosis. Radiofrequency waves induce ionic agitation, which results in frictional heat production within the tissue. Serious

(b)

Figure 7.6 Percutaneous liver tumour ablation: (a) axial CT scan showing radiofrequency electrode positioned within metastasis in liver before treatment; (b) after treatment, an area of necrosis is seen, indicating successful ablation.

152 Interventional radiology

complications are rare and consist mainly of intraperitoneal haemorrhage and liver abscess formation. Interstitial laser photocoagulation produces thermal coagulation by the conversion of absorbed light energy into heat. Hepatic resection is the mainstay in the curative management of primary and secondary hepatic malignancies. Surgical resection significantly improves survival, but only a minority of patients are surgical candidates because of the size or location of the lesions, extrahepatic disease or, in the case of hepatoma, limited hepatic functional reserve secondary to associated cirrhosis. Percutaneous techniques of local tumour ablation may be categorized into three major groups: injectables (ethanol, acetic acid, hot saline), heating (RF, electrocautery, interstitial laser therapy, microwave coagulation therapy and high-intensity focus US) and freezing (cryotherapy). Of these, the most widely used is RF ablation both for hepatocellular carcinoma and for hepatic metastases. Percutaneous ethanol injection therapy (PEIT) was first described in 198325 and since that time has been used extensively for the treatment of unresectable hepatocellular carcinoma.26 Surgery is the treatment of choice for most primary renal tumours. However, patients who are not good surgical candidates, have multiple recurrent tumours (as with von Hippel Lindau syndrome), borderline renal function or a solitary kidney can benefit from treatment with thermal ablation, which has a technical success rate exceeding 90 per cent in several series. Peripheral, small tumours are the easiest to treat (Fig. 7.7). Treating larger, central neoplasms is less successful and more likely to be associated with complications such as ureteric strictures. Techniques such as cooling of the ureter during treatment can help reduce the likelihood of injuring adjacent organs. Radiofrequency treatment is also being used to treat unresectable pulmonary neoplasms and for palliation of bone tumours. The follow-up of patients after all forms of percutaneous tumour ablation includes a combination of imaging, tumour marker assay and selected use of fine-needle aspiration biopsy when the serum levels of these markers are elevated prior to the initiation of therapy. The immediate goal of imaging is to assess whether complete necrosis has been achieved. Ultrasound does not usually provide useful information, as the echogenicity of fibrosis and neoplastic tissue overlaps. Contrast-enhanced MRI and contrastenhanced CT are capable of demonstrating remaining viable tumour requiring treatment. However, in difficult cases, PET scanning may provide additional information. Better methods of imaging guidance and more sophisticated equipment are likely to increase the importance of percutaneous tumour ablation in the future.

Gastrointestinal tract In the management of patients with malignant disease, nutritional support is essential, particularly in those who

(a)

(b) Figure 7.7 Patient with left renal cancer considered as unsuitable surgical candidate treated with percutaneous radiofrequency ablation.(a) contrast enhanced CT showing peripheral left renal cancer, incidental right simple renal cyst. (b) triple needle RFA probe in situ within tumour lesion.

are severely debilitated or unable to swallow. Parenteral nutrition can be provided using central venous catheters, but this is associated with significant morbidity and considerable expense. Enteric feeding is more desirable and can be provided by the insertion of gastrostomy tubes. Gastrojejunostomy tubes are preferable when there is gastric outlet obstruction or in cases of gastro-oesophageal reflux. Several different techniques have been described for percutaneous gastrostomy insertions27,28 with and without gastropexy under fluoroscopic guidance (Fig. 7.8).

Dilatation techniques 153

Figure 7.8 Fluoroscopic insertion of gastrostomy feeding tube. Gastrostomy catheter is locked with pigtail in fundus of stomach. Nasogastric tube and the two ‘stay’ sutures used for the safe insertion of gastrostomy tube are then removed.

Gastrostomy may also be useful in relieving symptoms in patients with gastric outlet obstruction due to retroperitoneal or mesenteric malignancy when insertion of a stent in the pylorus fails to relieve the obstruction. Percutaneous puncture for decompression of the caecum (in cases of distal obstruction) and for afferent loop obstruction have been described.29,30

DILATATION TECHNIQUES Dilatation procedures are most widely employed for nonmalignant conditions in the vascular tree. These techniques can also be applied to stenoses and occlusions in other systems, such as the gastrointestinal tract, renal, biliary and respiratory systems. Fluoroscopically guided oesophageal dilatation has proved to be a particularly useful technique.31* A guide-wire is manipulated through the narrowed area and a balloon catheter of suitable dimensions is then passed over the wire. Intravenous analgesia should be given immediately prior to balloon inflation, as this can cause moderate discomfort. Dilatation alone is unlikely to be effective in malignant oesophageal strictures and should be followed by some form of stenting.32 Rigid plastic tubes inserted endoscopically or under fluoroscopic guidance have been used for several years. However, recently, self-expandable metallic endoprostheses have become available.33,34* With recent advances35

and increased experience in the use of metallic stents, more than 95 per cent of patients with inoperable oesophageal strictures can be palliated successfully with these devices (Fig. 7.9). Strictures at other sites in the gastrointestinal tract can also be treated successfully by radiological dilatation techniques. The relief of obstruction at anastomotic strictures (gastroenterostomies, antral–pyloric strictures, enteroenterostomies and colorectal strictures) is particularly useful.36 In cases of acute malignant obstruction of the large bowel, the insertion of self-expanding stents can provide immediate relief (Fig. 7.10). This may be a temporizing measure, allowing stabilization of the patient prior to definitive surgery, or, alternatively, in patients who are not surgical candidates, the stent may provide adequate palliation.37 Malignant airways obstruction can cause considerable distress to patients. When surgical resection is not possible, self-expanding metallic stents can provide good palliation (Fig. 7.11).38 Plastic-covered stents are very effective in managing tracheo-oesophageal fistulas unsuitable for treatment with covered oesophageal stents.39 The stents are inserted under general anaesthesia or sedation with local anaesthetic using combined fluoroscopic and bronchoscopic guidance, following balloon dilatation of the strictures.40 Within the urinary tract, in the presence of obstruction, if drainage is to be of short duration, it is satisfactory to allow the urine to drain externally into a bag. When long-term drainage is required, a J-J stent is inserted with the proximal pigtail coiled in the renal pelvis and the distal end in the bladder,41 thus allowing the patient to be free of ‘bags’. Patients with obstructive jaundice due to unresectable malignant biliary strictures can be palliated by the insertion of endoprostheses. For surgical candidates, preoperative biliary drainage may be performed to correct metabolic disturbances and stabilize the patient. Most patients with malignant obstructive jaundice undergo endoscopic retrograde cholangiopancreaticography (ERCP) as part of the diagnostic work-up. If ERCP confirms a malignant stricture, an endoprosthesis can be inserted immediately after cholangiography. Endoscopic drainage is less invasive than percutaneous biliary drainage (PBD), is associated with fewer complications and avoids the discomfort of a percutaneous biliary catheter. The majority of strictures of the mid and lower common bile ducts, which are mainly due to carcinoma of the head of the pancreas, can be drained effectively by the endoscopic approach, the percutaneous approach being reserved for patients in whom endoscopic drainage attempts have failed. Patients with obstructive jaundice due to malignant tumours at the hilum of the liver are best palliated by percutaneous drainage methods, as the endoscopic approach in such patients often fails and is associated with a high rate of complications. In most cases, unilateral drainage is sufficient for relieving jaundice and pruritus. The procedure is usually carried out under fluoroscopic and US guidance. First a percutaneous transhepatic cholangiogram (PTC) is performed, using a 22-gauge needle. It is important to visualize the entire biliary system prior to selecting the most suitable duct for the insertion of a

154 Interventional radiology

(a)

(b)

Figure 7.9 Oesophageal stenting: (a) contrast swallow showing lower oesophageal carcinoma stricture; (b) Flamingo Wallstent (selfexpanding metallic endoprosthesis) has been placed fluoroscopically across the stricture. Contrast is now flowing freely into the stomach.

drainage catheter. Self-expandable metallic stents are now widely available and generally preferable to the conventional plastic endoprostheses. Such stents can be inserted using a relatively small introducing catheter and yet achieve a large internal diameter when released across the lesion (Fig. 7.12). The large calibre of these devices ensures that the rate of occlusion is lower than that of plastic endoprostheses. In our experience, the rate of haemorrhage and cholangitis is approximately three times lower with metallic endoprostheses than with plastic stents. Most importantly, the rate of re-intervention for the purpose of replacement of occluded stents has also been found to be three times lower with metallic stents.42 A randomized comparison of endoscopically inserted self-expanding metal stents and plastic stents has confirmed the longer patency of metallic endoprostheses and has shown that although these stents are more expensive than the conventional plastic devices, the cost per patient is lower because of the lower rate of re-intervention.43***

Venous dilatation and stenting The superior vena caval syndrome is most commonly related to mediastinal neoplasia, particularly primary and secondary lung tumours and lymphoma. The obstruction, which can be partial or complete, may be caused by caval compression or invasion by the tumour, and is sometimes complicated by venous thrombosis. Cavography delineates the site and extent of the obstruction. Percutaneous transfemoral dilatation of the narrowed cava, combined with thrombolysis where necessary, followed by the insertion of self-expandable metallic endoprostheses, restores flow and provides excellent palliation of symptoms (Fig. 7.13).44 Malignant involvement of the inferior vena cava can be managed in a similar fashion. Percutaneous insertion of an inferior vena cava filter is indicated in patients with recurrent pulmonary embolism refractory to, or unsuitable for, treatment with medical therapy. In patients with iliac or

Dilatation techniques 155

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(c)

Figure 7.10 Colonic stenting. (a) Contrast study of the sigmoid colon; lateral view of the pelvis, showing carcinoma stricture of the sigmoid colon. A guide-wire and catheter have been placed across the stricture. (b) A self-expanding metallic endoprosthesis has been deployed across the stricture. (c) CT scan, showing the expanded stent within the sigmoid tumour. The patient’s obstructive symptoms were successfully palliated.

(a)

(b)

Figure 7.11 Tracheal stenting. (a) Axial CT scan of a section through the chest, showing tumour and nodal mass encasing and compressing both main bronchi. (b) Chest X-ray after deployment of two self-expanding metal endoprostheses situated in the trachea and extending into both main bronchi.

156 Interventional radiology

(b)

(a)

(c)

Figure 7.12 (a) Percutaneous transhepatic cholangiogram in a patient with hilar cholangiocarcinoma involving the left and right hepatic ducts and the upper common hepatic duct. (b) Self-expandable metallic endoprostheses have been inserted into both hepatic ducts using separate punctures. Drainage of contrast medium is taking place into the duodenum. (c) The stents are shown in position following complete drainage of the contrast medium.

iliofemoral venous thrombosis due to pelvic malignancy, a temporary filter inserted prior to surgical resection of the tumour may protect from pulmonary embolism.

EXTRACTION TECHNIQUES Developments in intravenous feeding therapy and monitoring techniques have led to a vast increase in the number of indwelling venous cannulas and catheters. Unfortunately, these occasionally break or become disconnected, resulting in loss of part or all of the catheter within the venous system.45 It is important to retrieve these intravascular foreign bodies as they can perforate vascular structures and cause

dysrhythmias, and can be a source of infection, particularly in immunosuppressed patients. Surgical retrieval of catheter fragments necessitates a thoracotomy and carries significant risk. It is almost invariably possible to retrieve these catheter fragments percutaneously under fluoroscopic guidance (Fig. 7.14).46 They usually lodge within the right side of the heart or the pulmonary arteries. A wide variety of instruments have been found to be useful in ‘catching’ these foreign bodies, including wire-loop snares, grasping forceps, steering catheters and Dormia baskets. It is usually possible to retrieve the foreign body under local anaesthesia via a percutaneous femoral venous puncture. Detailed descriptions of all the techniques available are beyond the scope of this chapter, but any interventional

Extraction techniques 157

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(c)

Figure 7.13 Superior vena caval stenting. (a) Superior vena cavogram reveals severe narrowing of the superior vena cava (SVC) by tumour in the mediastinum. (b) Metal stents have been placed across the compressed area, which was initially dilated with a balloon. (c) A repeat venogram confirms patency of the SVC. The patient’s symptoms improved immediately and had resolved completely within 24 hours.

158 Interventional radiology

(b)

(a)

radiologist offering a comprehensive vascular service is well advised to acquaint himself or herself with the various methods and have the necessary equipment available.47 The ability to snare or ‘catch’ the end of a catheter can also be of value in patients receiving intravenous cytotoxic chemotherapy in whom the tip of an indwelling central venous catheter has become displaced and lodged in the jugular vein instead of the superior vena cava. It is usually possible to ‘pull’ such a catheter back to the appropriate position using a percutaneous vascular approach under local anaesthesia.

INFUSION TECHNIQUES The ability of the radiologist to site a catheter accurately into virtually any blood vessel within the body has brought into play the concepts of regional infusion of chemotherapeutic agents, monoclonal antibodies and isotopes. The principle underlying these techniques is that a high dose of the therapeutic agent is delivered to the tumour(s) with minimal systemic side effects. Recent advances include the addition of embolic materials (see ‘Vascular embolization’ section below) and the microencapsulation of cytotoxic agents to achieve gradual and sustained release. Lipiodol is now also used in combination with cytotoxic drugs for the treatment of certain hepatic tumours; it is retained in tumour vessels and also acts as a contrast agent, thus allowing monitoring of tumour response to treatment using CT guidance. These techniques have been used with varying degrees of success to treat primary and metastatic liver tumours,48 bone neoplasms, cerebral neoplasms, sarcomas, melanomas and pelvic neoplasms. It is possible to insert fine catheters that can be left in place for weeks at a time.49 A variety of long-term venous access lines (tunnelled central venous catheters, peripherally inserted central catheters (PICC) and Portacaths) have been developed for insertion under fluoroscopic and US guidance.50 Radiological techniques are best suited for their insertion.51 Tunnelled

Figure 7.14 (a) A chest radiograph in a young girl undergoing cytotoxic therapy in whom part of a central venous catheter became detached and migrated into a right lower lobe pulmonary artery (arrows). (b) The catheter fragment after extraction via the femoral vein, grasped in the catheter used for retrieval.

external catheters are most frequently used. The preferred access sites are the internal jugular and subclavian veins, but other veins can be used in cases of difficulty, including the common femoral, translumbar, inferior vena cava and hepatic veins. The PICC lines are more usually inserted for shorter duration of therapy, with the basilic vein being the preferred site of puncture.

VASCULAR EMBOLIZATION This technique involves the deliberate occlusion of arteries and/or veins by the injection of embolic agents through selectively placed catheters. It is one of the major applications of IR in patients with neoplastic disease and has been employed in the management of a wide variety of tumours. Embolization, usually performed by a percutaneous approach under local anaesthesia, offers an attractive alternative to surgery and in some situations it is the only therapeutic option available. A wide variety of embolic agents is available52 and a detailed description is beyond the scope of this chapter. The broad categories of substances used include particulate emboli (sterile sponge [Spongostan], polyvinyl alcohol [Ivalon]), mechanical emboli (balloons, steel coils) and liquids (50 per cent dextrose, absolute alcohol, lipiodol). The appropriate agent or combination of agents depends on the lesion to be treated and its site, with particular attention paid to adjacent vulnerable vascular structures. There are three ways in which embolization can assist in the management of neoplasms: definitive, preoperative or palliative. Definitive treatment can only be offered for benign lesions.

Preoperative embolization This has been widely employed in the management of renal carcinomas, although not all urologists find the technique useful. The tumour is embolized and surgery

Vascular embolization 159

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(d)

(e)

Figure 7.15 Preoperative embolization of a bone neoplasm (osteoclastoma) in a 17-year-old girl which had proved resistant to radiotherapy. A plain radiograph (a) reveals a large soft-tissue mass with extensive bone destruction. Axillary arteriography shows the lesion to be highly vascular. (b) The feeding vessels selectively catheterized and embolized. The postembolization angiogram (c) shows the lesion to be completely devascularized. A plain radiograph 3 months later (d) shows considerable reduction in the size of the mass and bone regrowth. This improvement allowed reconstructive surgery to be performed. A humeral replacement (e) was successfully carried out. Reproduced with permission from Allison (1987).

undertaken within 24–48 hours, while there is maximum devascularization and minimal oedema. Preoperative embolization reduces blood loss, and may minimize dissemination of malignant cells during tumour mobilization.

Preoperative tumour embolization has proven to be of value in other situations, including nasopharyngeal tumours, paragangliomas, meningiomas and bone tumours (Fig. 7.15). In the last-mentioned example, the inclusion of

160 Interventional radiology

a cytotoxic agent within the embolization ‘cocktail’ may further reduce the risk of tumour dissemination during surgery.

Palliative embolization This technique is employed to control pain, haemorrhage and hormone production, as well as to reduce tumour bulk.

It may be used as the primary mode of treatment in inoperable malignancy. Embolization of metastatic deposits has, in some situations, been shown to extend survival times in advanced disease.53 Tumours in many organs have been treated in this fashion: liver, kidney (Fig. 7.16), bone, lung, soft tissues, nervous system and gastrointestinal tract. Hormone-secreting neoplasms, e.g. metastatic carcinoid and APUD cell tumours (Fig. 7.17), show the greatest therapeutic response to arterial embolization. Appropriate

(a)

(b)

(c)

Figure 7.16 Selective right renal arteriography, (a) arterial and (b) and (c) venous phases, reveals a highly vascular renal tumour in the lower pole of the kidney. The vessels supplying the tumour were selectively catheterized and embolized with particulate material, depriving it of its blood supply and relieving the patient of pain and haematuria. Reproduced with permission from Allison (1987).

Vascular embolization 161

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Figure 7.17 Hepatic embolization for metastatic carcinoid tumour. (a) The early arterial phase shows hepatic enlargement. (b) The parenchymal phase reveals multiple tumour deposits. (c) Post-embolization arteriogram shows that the arterial supply has been obliterated. The patient’s symptoms (flushing and diarrhoea) were dramatically alleviated by this procedure. Reproduced with permission from Allison (1987).

162 Interventional radiology

pharmacological blockade is necessary during the embolization to avoid the effects of a massive outpouring of hormone as the tumour is deprived of its blood supply. The beneficial effects of embolization may become apparent within a matter of hours. In embolization procedures it is important that adequate premedication is given prior to the procedure, including broad-spectrum antibiotics. In many situations, e.g. liver and bone, it is advisable to continue antibiotics for 10 days after the procedure to prevent sepsis developing in the devascularized tissue. After embolization, patients commonly experience some discomfort and pain. They may have a pyrexia for a few days, accompanied by a feeling of malaise and an elevated white cell count. This combination of signs and symptoms is known as the post-embolization syndrome (PES), an indicator of the presence of necrotic tissue. Any sustained pyrexia should alert the clinician to the possibility of abscess formation, and blood cultures and regional US should be performed. Serum C-reactive protein (CRP) estimations can also provide a useful indication that infection may be present. Following embolization, CRP reaches a peak at about 4 days, falling off thereafter to reach normal levels at 10 days. A continued CRP rise, or failure to fall, indicates infection.54 In patients with pelvic malignancy and fistulas to the perineum, percutaneous nephrostomy is often insufficient to achieve complete diversion of the urine. It is often necessary to combine nephrostomy with ureteric embolization using steel coils and fragments of gelatin sponge, in order to ensure that no urine reaches the skin of the perineum.55

Chemoembolization Embolic agents in combination with chemotherapeutic drugs are being used in the treatment of certain malignancies.

(a)

In this technique, known as chemoembolization,56 the emboli cause ischaemia of the tumour cells and, by increasing the transit time through the tumour vascular bed, the contact time between the cytotoxic agent and the neoplastic cells is prolonged, resulting in a greater therapeutic effect.

NEUROLYSIS

Alcohol injection is useful in the palliation of the intractable pain that occasionally accompanies retroperitoneal malignancy. For example, certain patients with carcinoma of the pancreas experience severe pain due to infiltration of the coeliac ganglion by the tumour. In these patients the ganglion may be ablated by injecting alcohol in its immediate vicinity under CT guidance (Fig. 7.18).

Percutaneous vertebroplasty Metastases to the vertebrae are common. Radiation therapy is not always effective in relieving the pain. Percutaneous vertebroplasty provides immediate and sustained pain relief, and contributes to spinal stabilization.57 The procedure consists of percutaneous injection of acrylic surgical cement into a vertebra under radiological guidance (fluoroscopy and/or CT) (Fig. 7.19). This technique can also be used for treated bone metastases at other sites. Up to 80 per cent of patients with pain unresponsive to conventional treatment experience a significant degree of pain relief, and few serious side effects have been reported. Kyphoplasty is a modified technique that involves the additional step of high-pressure balloon dilatation prior to cement injection.

(b)

Figure 7.18 Coeliac axis block for intractable pain in a patient with pancreatic carcinoma. (a) Axial CT scan with a 22-gauge needle positioned with its tip at level of the coeliac ganglion. (b) Bilateral spill seen following injection of alcohol.

Gene therapy 163

AORTIC STENTING

The effectiveness of aortic abdominal aneurysm stent grafts has been recognized.58** The experience with endovascular repair in the management of descending thoracic aortic diseases such as thoracic aneurysm, perforated ulcer, intramural haematoma and type B dissection is also very encouraging.59

Amongst the advantages of endovascular techniques over open surgery are the fact that they can be performed in lessfit patients,60 a lower rate of complications, lower mortality rates and reduced hospital stay. CAROTID STENTING

Carotid artery stenting is useful in symptomatic patients, especially those unfit for surgery and particularly those who have had previous head and neck surgery or radiation (Fig. 7.20). The principal reason for intervening in the first place is for the prevention of stroke. Advantages include shorter hospital stay, avoidance of a wound and its associated complications (pain, infection, numbness, haematoma and patch infection), avoidance of cranial nerve injury, and reduced cardiovascular complications (i.e. myocardial infarction).61

GENE THERAPY

(a)

(b) Figure 7.19 Vertebroplasty for relief of pain and provision of bony stability. (a) Fluoroscopy image of needle within diseased vertebral body (b) Completion image after 3ml of cement injection.

The most rapidly evolving area in medicine is gene therapy. The underlying principle is to identify and clone a gene, and then to insert it into a vector capable of directing expression in mammalian tissues.62 The main aim at present is to treat genetic deficiencies and malignant diseases that are refractory to conventional therapies. The delivery systems involved include retroviral vectors (RNA viruses), adenoviral vectors (DNA viruses) and cationic liposomes, along with strategies that involve US-directed gene transfer, CT-guided gene transfer and transcatheter gene delivery, in particular via the hepatic artery. Examples of genes being evaluated in trials include oncogenes, tumour suppressor genes, suicide genes and anti-angiogenesis factors. The liver is an ideal therapeutic target for gene therapy. Hepatic malignancies being considered for treatment include metastatic colorectal carcinoma, hepatoma, cholangiocarcinoma, lymphoma, metastatic melanoma and haemangioma. Gene therapy strategies for managing occluded biliary stents (resulting from tumour ingrowth) and vascular transjugular intrahepatic portosystemic stents (resulting from neo-endothelialization) are also under consideration. In gene delivery, angiographic guidance will be of use in localizing tumour blood supply and directing the targeted intra-arterial delivery of genes of interest, so that vector–DNA complexes can be delivered with accuracy and specificity. Embolization techniques may also be of benefit, by prolonging vector contact with the target cells, thus delaying washout and further enhancing target-cell uptake. Radiological monitoring will be of considerable importance during gene delivery, e.g. the process of liposomal vector delivery can be monitored accurately with US because lipid vesicles are echogenic. Guided biopsy of transduced tissues for histopathologic analysis after gene delivery should also improve confidence in the evaluation of gene expression.

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Figure 7.20 Carotid artery stent in a symptomatic patient with previous laryngeal cancer resection and radiotherapy. (a) angiogram of carotid vessels; arrow pointing to radiation stricture right common carotid artery. Note absent left carotid artery (previously occluded) (b) Selective angiogram of right carotid artery (c) Post stent angiogram demonstrating good flow within carotid artery.

References 165

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An interventional procedure should only be contemplated if it is likely to benefit the patient’s quality of life. Some interventional procedures are replacing surgical alternatives; others are totally new forms of treatment. Diagnostic invasive procedures, e.g. biopsy, are significantly less traumatic than their surgical alternatives. All interventional procedures require a team approach to ensure the best possible outcome for the patient. Advances in imaging technology and instrumentation are constantly occurring, leading to the emergence of new interventional techniques. Many interventional procedures, e.g. tunnelled central venous catheter insertion, SVC stenting and percutaneous drainage, are carried out in conjunction with, and enable the more effective use of, conventional forms of cancer therapy. Interventional radiology is likely to play a critical role in the exciting new field of gene therapy.

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REFERENCES 1 Adam A. (1998) The definition of interventional radiology (or, ‘When is a barium enema an interventional procedure?’). Eur Radiol 1998; 8:1014–15. 2 Bogda K. Radiological Interventions: Special considerations in cancer patients. In: Ray CE, Hicks ME, Patel NH (eds) SIR syllabus-Interventions in Oncology, North Fairfax, Virginia: Society of Interventional Radiology, 2003, 1–7. 3 Haubeck A, Gammelgaard G, Gronvall S, Holm HH. Ultrasonically guided percutaneous puncture and biopsy technique. In: Wilkins RA, Viamonte MJR (eds) Interventional Radiology. Oxford: Blackwell Scientific Publications, 1982, 373–408. 4 Husband JE, Golding SJ. Recent developments in whole body computed tomography. In: Steiner RE (ed.) Recent Advances in Radiology, Vol. 7. Edinburgh: Churchill Livingstone, 1983, 88–106. ◆5 Mueller PR, Stark DD, Simeone JF, et al. MR-guided aspiration biopsy: needle design and clinical trials. Radiology 1986; 161:605–9. ●6 Allison DJ, Hemingway AP. Percutaneous needle biopsy of the lung. Br Med J 1981; 282:875–8. 7 Greene RE. Transthoracic needle aspiration biopsy. In: Athanasoulis CA, Pfister RC, Greene RE, Robertson GH (eds) Interventional Radiology. Philadelphia: WB Saunders, 1981, 587–637.

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van Sonnenberg E, Casola G, Ho M, et al. Difficult thoracic lesions: CT-guided biopsy experience in 150 cases. Radiology 1988; 167:457–61. Adam A, McSweeney JE, Whyte MKB, et al. CT-guided extra-pleural drainage of bronchogenic cyst. J Comput Assist Tomogr 1989; 13:1065–8. Katada K, Kato R, Anno H, et al. Guidance with real-time CT fluoroscopy: early clinical experience. Radiology 1996; 200:851–6. Meyer CA, White C, Wu J, et al. Real-time CT fluoroscopy: usefulness in thoracic drainage. AJR 1998; 171:1097–101. Gilmore IT, Bradley RD, Thompson RPH. Improved method of transvenous liver biopsy. Br Med J 1978; ii:249. Gamble PM, Colapinto RF, Stronell RG, et al. Transjugular liver biopsy: a review of 461 biopsies. Radiology 1985; 157:589–93. Allison DJ, Adam A. Percutaneous liver biopsy followed by embolization of the track with steel coils. Radiology 1988; 169:261–3. Dawson P, Adam A, Edwards R. Technique for steel coilembolization of liver biopsy track for use with the ‘Biopty’ needle. Br J Radiol 1992; 65:538–40. Armstrong P, Calmers AH. Needle aspiration of the spine in suspected disc space infection. Br J Radiol 1978; 51:333–7. Laredo JD, Bellaiche L, Hamze B, et al. Current status of musculoskeletal interventional radiology. Radiol Clin North Am 1994; 32:377–98. Jackson J, Adam A. Percutaneous transcaval tumour biopsy using a ‘road map’ technique. Clin Radiol 1991; 44:195–6. Machi J, Sigel B, Kurohisi T, et al. Operative ultrasound guidance for various surgical procedures. Ultrasound Med Biol 1990; 16:37–42. Ziegler K, Sanft C, Zimmer T, et al. Comparison of computed tomography, endosonography and intraoperative assessment in TN staging of gastric carcinoma. Gut 1993; 34:604–10. Karampekios S, Hatjidakis AA, Drositis J, Gourtsoyiannis N. Artificial paravertebral widening for percutaneous CT-guided adrenal biopsy. J Comput Assist Tomogr 1998; 22(2):308–10. Allison DJ. Therapeutic embolization and venous sampling. In: Taylor S (ed.) Recent Advances in Surgery, Vol. 10. Edinburgh: Churchill Livingstone, 1980, 27–64. Papanicolaou N. Uroradiological intervention. In: Watkinson A, Adam A (eds) Interventional Radiology, a Practical Guide. Oxford: Radcliffe Medical Press, 1996, 88–118. Gerzof SG, Spira R, Robins AH. Percutaneous abscess drainage. Semin Roentgenol 1981; 16:62–71. Sugiura N, Takara K, Ohto M, et al. Percutaneous intratumoral injection of ethanol under ultrasound imaging for treatment of small hepatocellular carcinoma. Acta Hepatol Jpn 1983; 24:920–3. Livraghi T, Solbiati L. Percutaneous ethanol injection in liver cancer: methods and results. Semin Intervent Radiol 1993; 10(2):69–77. van Sonnenberg E, Wittich GR, Cabrera OA, et al. Percutaneous gastrostomy and gastroenterostomy: 2. Clinical experience. AJR 1986; 146:581–6.

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28 Saini SJ, Mueller PR, Gaa J, et al. Percutaneous gastrostomy with gastropexy: experience in 125 patients. AJR 1990; 154:1003–6. ●29 Casola J, Withers C, van Sonnenberg E, et al. Percutaneous cecostomy for decompression of the massively distended cecum. Radiology 1986; 158:793–4. ●30 Lee LI, Teplick SK, Haskin PN, et al. Refactory afferent loop problems: percutaneous transhepatic management of two cases. Radiology 1987; 165:49–50. ◆31 Sabharwal T, Cowling M, Dussek M, Owen W, Adam A. Balloon dilatation myotomy in oesophageal achalasia; a safe and effective technique. Radiology 2002; 224:719–24. ◆32 Sabharwal T, Morales JP, Salter R, Adam A. Esophageal cancer: self-expanding metallic stents. Abdom Imaging 2004; 29:1–9. 33 Neuhaus H. Metal oesophageal stents. Semin Intervent Radiol 1991; 8:305–10. 34 Song H-Y, Do YS, Han YM, et al. Covered, expandable oesophageal metallic stent tubes: experiences in 119 patients. Radiology 1994; 193:689–95. 35 Sabharwal T, Morales JP, Irani FG, Adam A. Quality assurance guidelines for placement of oesophageal stents. Cardiovasc Intervent Radiol 2005; 28:284–8. 36 Grundy A. The radiological management of gastrointestinal strictures and other obstructive lesions. In: Adam A, Allison DJ (eds) Clinical Gastroenterology. Interventional Radiology of the Abdomen, Vol. 6, No. 2. London: Bailliere Tindall, 1992, 319–40. ●37 De Gregorio MA, Mainar A, Tejero E, et al. Acute colorectal obstruction: stent placement for palliative treatment – results of a multicenter study. Radiology 1998; 209:117–20. ●38 Tan BS, Watkinson AF, Dussek JE, Adam A. Metallic endoprosthesis for malignant tracheo-bronchial obstruction: initial experience. Cardiovasc Intervent Radiol 1996; 19:91–6. 39 Morgan R, Ellul J, Denton E, et al. Malignant esophageal fistulas and perforations: management with plastic-covered metallic endoprostheses. Radiology 1997; 204:527–32. ◆40 Hatrick AG, Sabharwal T, Adam A. Tracheobronchial stents: a review. Semin Intervent Radiol 2001; 18(3):243–50. 41 Lu DSK, Papanicolaou N, Girard M, et al. Percutaneous internal ureteral stent placement: review of technical issues and solutions in 50 consecutive cases. Clin Radiol 1994; 49:256–61. ●42 Adam A, Chetty N, Roddie M, et al. Self-expandable stainless steel endoprostheses for treatment of malignant bile duct obstruction. AJR 1991; 156:321–5. 43 Davids PHP, Groen AK, Rauws EAJ, et al. Randomized trial of self-expanding metal stents versus polyethylene stents for distal malignant biliary obstruction. Lancet 1992; 340:1488–92.

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Irving JD, Dondelinger RF, Reidy JF, et al. Gianturco selfexpanding stents: clinical experience in the vena cava and large veins. Cardiovasc Intervent Radiol 1992; 15:351–5. Gibson RN, Hennessy OF, Collier N, Hemingway AP. Major complications of central venous catheterization. A report of five cases and brief review of the literature. Clin Radiol 1985; 36:204–8. Rossi P. Percutaneous removal of intravascular foreign bodies. In: Wilkins RA, Viamonte M (eds) Interventional Radiology. Oxford: Blackwell Scientific Publications, 1982, 359–69. Belli AM, Hemingway AP. Retrieval of intravascular foreign bodies. In: Belli AM (ed.) Interventional Radiology in the Peripheral Vascular System. London: Edward Arnold, 1994, 81–92. Balch CM, Levin B. Regional and systemic chemotherapy for colorectal metastases to the liver. World J Surg 1987; 11:521–6. Chuang VP, Wallace S. Arterial infusion and occlusion in cancer patients. Semin Roentgenol 1987; 16:13–25. Robertson LJ, Mauro MA, Jacques PF. Radiologic placement of Hickman catheters. Radiology 1989; 170:1007–9. Adam A. Insertion of long-term central venous catheter: time for a new look. Br Med J 1995; 311:341–2. Hemingway AP. Materials for embolization. Radiol Now 1986; 3:63–4. Chuang VP, Wallace S. Hepatic artery embolization in the treatment of hepatic neoplasms. Radiology 1987; 140:51–8. Hemingway AP, Allison DJ. Complications of embolization: analysis of 410 procedures. Radiology 1988; 166:669–72. Dick R, Adam A, Allison DJ. Interventional techniques in the hepatobiliary system. In: Grainger R, Allison DJ (eds) Diagnostic Radiology: an Anglo-American Textbook of Organ Imaging, 3rd edn. Edinburgh: Churchill-Livingstone, 1997, 1235–58. Kato L, Nemeto R, Mori H, et al. Arterial chemoembolization with microencapsulated anticancer drug. J Am Med Assoc 1981; 245:1123–7. Sabharwal T, Gangi A. Percutaneous vertebroplasty. CME Radiol 2004; 4(2):71–5. Prinssen M, Buskens E, Blankensteijn JD. Quality of life after open and endovascular AAA repair: results of a randomised trial. Eur J Vasc Endovasc Surg 2004; 27:121–7. Bell RE, Taylor PR, Aukett M, Sabharwal T, Reidy JF. Midterm results for second-generation thoracic stent grafts. Br J Surg 2003; 90:811–17. Morales JP, Irani FG, Jones KG, Taylor PR, Dourado R, Sabharwal T. Endovascular repair of a ruptured abdominal aortic aneurysm under local anaesthesia. BJR 2005; 78:1–3. Veith FJ, Amor M, Ohki T, et al. Current status of carotid bifurcation angioplasty and stenting based on a consensus of opinion leaders. J Vasc Surg 2001; 33:S111–16. Voss SD, Kruskal JB. Gene therapy: a primer for radiologists. Radiographics 1998; 18:1343–72.

8 Vaccination strategies for malignant diseases DEEPAK P. ASSUDANI, STEPHANIE MCARDLE, MURRIUM AHMAD, GENG LI, ROBERT C. REES AND SELMAN A. ALI

Introduction Tumour antigens Tolerance Tumour vaccines

167 168 171 171

INTRODUCTION Unlike conventional vaccines to infectious diseases, which stimulate the immune system to respond specifically to nonself, dangerous, ‘foreign’ microbial antigens, the challenge of developing effective cancer vaccines lies in the ability of the immune system to recognize and respond to self or ‘altered self’, essentially non-dangerous antigens. Apart from virally induced tumours, most tumours express antigens that fit more with a self/altered-self paradigm than with the non-self paradigm antigens of pathogens.1 To answer the most frequently asked question about whether immunity to cancer exists at all, one needs to analyse the occurrence of spontaneous regression in certain cancers and the existence of correlation between tumour prognosis and patient survival with intra-tumoral inflammatory cell infiltrations. The immunosurveillance theory, as postulated by Burnet,2 is based on the ability of the immune system effector cells, recently identified as T cells, actively to assist the body to identify and eradicate incipient tumour cells. The development of inbred strains of mice was the cornerstone in proving this theory, since it was possible for the first time to test experimentally the idea that tumours were immunologically distinguishable from normal cells. Inbred mice could be immunized and caused to reject chemically or virally induced syngeneic tumours, and this could not have happened without the existence of tumour-specific antigens. Boon and Kellermann3 demonstrated for the first time that tumour cells with new mutations induced by in-vivo treatment with a mutagen were unable to produce progressive tumours in syngeneic mice, not because of intrinsic growth defects but

Tumour escape Conclusion Acknowledgements References

178 179 180 180

changes in their antigenicity and ability to trigger an immune rejection response. The cancer immunosurveillance theory was not flawless and has clearly generated more controversial debate than any other immunological concept due to a number of factors, including the failure of immunodeficient mice (nude mice) to develop significantly more cancers than their control counterparts. It has also been postulated that under certain circumstances the immune system can aid cancer progression by selecting tumour cells with lower immunogenicity.4 However, further evidence supporting cancer immunosurveillance has recently emerged, demonstrating an increased cancer incidence in mice lacking specific cellular populations such as T cells, natural killer (NK) cells and immunostimulant molecules such as interferon-gamma (IFNγ) and interleukin-2 (IL-2) This contradiction has finally been resolved by the postulation of a broader immune process termed cancer immunoediting, in which cancer immunosurveillance represents only one of three dimensions of a complex process of interaction between the immune system and cancer, namely (a) immunosurveillance or elimination, (b) equilibrium, and (c) escape.4,5 Although the presence of immunosurveillance, as a tumour suppressor and protective mechanism against neoplasia in immunocompetent patients, is now unquestionable, failure of this process will inevitably lead to an equilibrium phase in which the immune system is unable completely to destroy all tumour cells and finally to the third phase in which tumours escape growth restraint imposed by the immune system. Cancer immunotherapy represents a promising and relatively safe approach compared to chemotherapy and

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radiotherapy, which may be associated with severe toxicity and lack of specificity and in some cases leads to shortduration remission. Treatment involving surgery, chemotherapy and/or radiotherapy together with immunotherapy represents a more rational approach to patient management. The active immunotherapy hypothesis is based on stimulation of the immune system to recognize and destroy tumour cells. This approach to treatment can be divided into two broad areas: non-specific and antigenspecific therapies. The non-specific therapies refer to stimulation or enhancement of the immunity by substances that non-specifically activate the immune system without having pre-defined antigen specificity. This type of therapy was pioneered by a New York physician, William Coley, who more than 100 years ago used a mixture of killed bacteria, ‘Coley’s toxin’, to treat cancer patients. Coley based his novel approach on observations that tumour regression coincided with the development of streptococcal infection within ulcerated tumours. Spontaneous regression of human tumours that coincides with various types of infection is a recognized phenomenon that has been reported in the literature for the past few hundred years ago.6 Nowadays, the majority of non-specific immunostimulants, such as cytokines and other biological modifier molecules, are recognized for their supporting roles in the enhancement of interaction and communication of immune cells. These findings have now been supported by extensive research into the application of viral and bacterial vectors to deliver tumour antigens and adjuvants such as cytokines. There is compelling evidence to suggest that microbial antigens bind to ‘toll-like’ receptors expressed on dendritic cells, leading to the activation and production of T helper 1 (Th1) cytokines, including IFNγ and IL-2.7 Recruitment and local activation of dendritic and NK cells have also been associated with early phases of viral infection; both cells are capable of exchanging bidirectional activating signals that are important for the development of antigen-specific memory.8,9 In contrast, antigen-specific therapies can be accomplished by either adoptive transfer or vaccination. It is now well established that CD8 cytotoxic T lymphocytes (CTLs) can recognize and kill tumour cells displaying peptides from tumour-associated antigens presented by major histocompatibility complex (MHC) class I molecules, and optimally require participation of antigen-specific CD4 helper T cells (Fig. 8.1). The isolation, expansion and re-infusion of tumour-specific T cells derived from tumour biopsies and expanded in vitro have been shown to be feasible, and clinical responses have been demonstrated.10 To induce specific immune responses, vaccination using crude, unidentified specific tumour antigens has been attempted using a number of approaches, including the use of wholecell vaccines, cancer-cell lysates, culture-cell supernatants and delivery systems for tumour antigens, peptides and genetic sequences encoding the antigen specificities.11,12 The success in identifying a wide range of tumour antigens by a variety of techniques, including molecular cloning

Figure 8.1 Cancer and immune responses. Tumour antigens released by dying tumour cells (or administered as vaccines) are taken up by tissue-resident dendritic cells (DCs), which then migrate to the lymph nodes and present these processed antigens to CD4 T cells. Depending on the activation signals, this can lead these CD4 T cells to differentiate into Th1 (Helper T cells 1) or Th2 response. Cross-talk between dendritic cells and CD4 T cells conditions the dendritic cells to present the antigens to CD8; T cells (cytotoxic T lymphocytes, CTLs) and activate them. The CTLs migrate to the tumour cells and mediate their killing. The Th1 cells provide help for the maintenance of CTL and memory response. The Th2 cells help in the generation of the humoral (antibody) response, and these antibodies can also mediate tumour killing via antibody-dependent cellular cytotoxicity. (IFN-γ, interferon-γ, TNF-β, tumour necrosis factor-β, IL-4/5, interleukin-4/5.)

of CTL-defined tumour antigens, has led to the current clinical trials of cancer vaccines. Some of these vaccines have resulted in partial or complete tumour regression in a proportion of treated patients, and have increased the disease-free survival rate in others (see below). These outcomes are more evident in patients suffering from certain cancers, such as melanoma and renal cancer. This chapter attempts to cover aspects of recent advances in the field of tumour immunology, with emphasis on tumour antigens, various types of cancer vaccines in use in the clinic and their limitations due to immune escape of cancer cells.

TUMOUR ANTIGENS Tumour cells differ from their surrounding tissue by the expression of proteins that are either unique to them or over-expressed by them. The identification of tumour antigens capable of inducing antigen-specific anti-tumour immunity represents a challenging task confronting tumour immunologists. Since the cloning of MAGE-1,13 the first gene reported to encode a tumour antigen recognized by T cells, molecular identification and characterization of novel tumour antigens have rapidly evolved.

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The identification of tumour antigens that elicit an immune response in the tumour-bearing host is a prerequisite for the development of immunotherapeutic approaches in cancer. Knowledge of their molecular nature provides us not only with potential targets for immunotherapeutic interventions against tumour cells, but also with new disease markers and new insights into the molecular mechanisms of malignant transformation. Various techniques have been developed over the past 15 years for the identification of these tumour antigens and these have been recently reviewed.14,15 According to their expression pattern, antigens expressed by human tumours can be loosely classified as: ●

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onco-foetal antigens (typically only expressed in foetal tissues and in cancerous somatic cells), onco-viral antigens (encoded by tumorigenic transforming viruses), over-expressed/accumulated antigens (expressed by both normal and neoplastic tissue, with the level of expression highly elevated in neoplasia), cancer–testis antigens (expressed only by cancer cells and adult reproductive tissues such as testis and placenta),

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tissue-specific differentiation antigens (expressed largely by a single cancer histotype), tumour-specific unique antigens (only expressed by cancer as a result of genetic mutation or alteration in transcription), post-translationally altered antigens (tumour-associated alterations in glycosylation etc.), idiotypic antigens (highly polymorphic genes , a specific ‘clonotype’, of which is expressed by a tumour cell i.e. as in B-cell, T-cell lymphoma/leukaemia resulting from clonal aberrancies).

Examples of tumour-associated antigens that fall into each of these categories are provided in Table 8.1. However, these categories are not mutually exclusive, and tumour antigens may fall into more than one. For example, the p53 tumour-suppressor gene is frequently mutated in cancer cells, resulting in the accumulation of p53 protein in these cells and reduced cell-cycle regulatory control by the tumour cells. Based on these parameters, p53 would be classified as both an over-expressed/accumulated tumour antigen and a mutated tumour antigen. In a similar manner, tyrosinase represents a normal melanocytic protein that can be both over-expressed and altered in its

Table 8.1 Classification of tumour antigens Group

Tumour antigens

Cancer expressing the antigen

Cancer–testis

MAGE 1–3 and 12, BAGE, GAGE, HAGE, NY-ESO-1 Head/neck, bladder, gastric and lung

Melanoma, breast

Differentiation antigens

Tyrosinase, gp-100, TRP-1, TRP-2, MART-1

Melanoma

Over-expressed/mutated antigens

HER-2/neu MUC-1 p53 (mutated) p53 (non-mutated) Ras (mutated) WT-1 Proteinase-3 PAP, PSA, PSMA

Breast, ovary, lung Breast, adenocarcinoma Colorectal, lung, bladder, head/neck Breast, colon, other cancers Pancreatic, colon, lung CML, ALL, AML CML Prostate

Viral antigens

EBV HCV HPV

Burkitt’s lymphoma Hepatocellular carcinoma Cervical and penile cancer

Onco–fetal antigens

CEA Alpha-fetoprotein 5T4 Onco-trophoblast glycoprotein

Colon, breast, pancreatic cancer Liver cancer Many carcinomas Many carcinomas

Tumour-specific antigens

Ig idiotype CDK4 Caspase-8 beta-catenin BCR/ABL

B-cell NHL, MM Melanoma Head/neck Melanoma CML

NHL, non-Hodgkin’s lymphoma; MM, multiple myeloma; CML, chronic myeloid leukaemia; ALL, acute lymphoblastic leukaemia; AML, acute myeloid leukaemia; CEA, carcinoembryonic antigen; HPV, human papillomavirus; EBV, Epstein–Barr virus; HCV, hepatitis C virus.

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post-translational modification, leading to differential recognition of melanoma cells versus normal melanocytes by specific T lymphocytes.

Onco-foetal antigens The onco-foetal antigens are ‘self’ proteins normally expressed during foetal development and then undetectable or at low levels in normal healthy adult tissues. On the other hand, these antigens have been detected in the sera of patients with gynaecological cancer. Carcinoembryonic antigen (CEA) was one of the first-known tumour markers; many more have now been described, but CEA remains, alone or in combination with others, the one most used. It is not organ specific, and abnormal values may be found in a wide range of carcinomas.16 One of the most useful applications of this marker is as a post-surgical prognostic indicator in the treatment of neoplasms. Any elevation of CEA after the conventional treatment of neoplasms has been correlated with a recurrence of cancer.17

Onco-viral antigens Some human malignancies are associated with viral infections, e.g. Burkitt’s lymphoma and Epstein–Barr virus (EBV), hepatocellular carcinoma and hepatitis B and C virus (HBV and HCV), cervical and anal carcinoma and human papillomavirus (HPV), T-cell leukaemia and human T-lymphotropic virus (HTLV). Virally encoded tumourassociated molecules in the malignant cells offer exogenous cancer vaccine targets for which there is unlikely to be immunological tolerance at the immune repertoire level. T cells can recognize the strong antigens expressed by virally infected cells and it is appropriate to consider viral vaccines for prophylactic and therapeutic immunization against virus-associated human cancers, as in the case of HPV and cervical cancer and HBV-associated liver cancer.18

Over-expressed antigens/mutated antigens Many genetic alterations accumulate in a normal cell before it becomes fully malignant, thereby increasing its genetic instability, which will render the cell susceptible to more genetic changes. These alterations include point mutations, gene amplification, translocation and viral insertion. As a result, many genes or gene products end up being over-expressed due to an increase copy number of the gene, an increase in the stability of its protein, or a defect in the degradation pathway of its product. These antigens are therefore also expressed in many normal tissues, but at much lower levels. The epitopes processed and potentially presented by normal tissues are below the threshold level of T-cell recognition, whereas their over-expression in tumour cells may trigger an anti-tumour immune response by breaking previously established tolerance.

Cancer–testis antigens These antigens are only expressed by normal tissue in the adult testis and placenta and are termed cancer–testis antigens (CTAs). However, during carcinogenesis, these antigens are re-expressed due to a process called demethylation. The functions of most of the cancer–testis antigens are still unknown. They represent attractive targets for immunotherapy due to their widespread expression in cancer cells but localized expression in immune privileged sites such as testis and placenta. Indeed, cancer–testis antigens have been some of the most extensively investigated antigens in animal models and in clinical trials. MAGE was the first antigen to be discovered in this group, following which a large number of others such as HAGE and GAGE as well as NY–ESO 1 antigen which have been defined using SEREX.19 These antigens are frequently found in a wide range of tumour types such as melanoma, lung carcinoma, head and neck tumour, and bladder carcinoma. Recently, we have applied SEREX to identify novel CTAs from a cDNA expression library constructed from normal human testes that was screened with pooled prostate cancer patients’ sera leading to identification of several known and unknown antigens. cDNA were obtained from human testes and used to express proteins in bacteria with each clone expressing one protein. These are then screened using the antibodies obtained from cancer patients to identify novel antigens to which these patients have generated immune response, since normally testis is an immunopriviledged site and proteins expressed in them do not generate an immune response.

Differentiation antigens These antigens are generally shared between cancer cells and their normal counterparts, and are specific for a particular lineage of cells or a point of differentiation. They are also known as melanoma-associated antigens, as they are mostly found in melanomas and normal melanocytes. Some of these antigens are involved in the biosynthesis of the pigment melanin. The most well known antigens from this group are tyrosinase, TRP-1, gp100 and MART-1. Since these are expressed at low levels in normal tissues, targeting them involves the risk of autoimmune reactions such as vitiligo.

Tumour-specific unique antigens These represent the most attractive immunotherapeutic targets, as they are unique to each individual tumour or shared between specific histological tumour types. Bcr/abl is the most well known antigen in this group, which is formed due to translocation between chromosomes 9 and 22, leading to chronic myeloid leukaemia (CML). Other unique antigens are generated due to point mutations or gene fusions in some of the essential oncogenes or tumour-suppressor

Tumour vaccines 171

genes such as k-ras, β-catenin, CDK4 and p53. Some groups consider these to be the best option for therapy, as they represent the most immunogenic epitopes; however, their identification in each individual patient raises questions regarding their practical application in the wider population. Tailor-made individualized therapies are being considered seriously as an option by certain immunologists, and this group of antigens would be their priority target.

Post-translationally altered antigens Altered glycosylation appears to be a constant phenomenon associated with oncogenic transformation in all types of naturally occurring human cancers. Most of the biochemical or, more recently, immunological methods used to identify tumour-associated antigens have resulted in the isolation of glycolipids or glycoproteins (mucins) with altered glycosylation patterns. Mucins are large (200 kDa) glycoproteins with a high carbohydrate content. They are expressed by a variety of normal and malignant epithelial cells.

Idiotypic antigens B-cell lymphoma arises as a clonal event. Specific immunoglobulins are generated by a unique combination of gene segments during B-cell differentiation, and these are expressed throughout the development of the tumour. The immunoglobulin idiotypic determinants come from unique heavy (VH) and light (VL) chains and provide a unique tumour-associated antigen to target for immunotherapy against lymphoma.

T cells reach the thymus and are presented with the ‘self’ antigens by the residing antigen-presenting cell (APC), leading to either negative or positive selection. T cells having strong affinity to ‘self’ antigens are deleted, as these are potential autoimmune T cells (negative selection). On the other hand, T cells binding to MHC–peptide complex with medium affinity are positively selected to survive and form the peripheral T-cell repertoire. However, the central tolerance mechanisms are not perfect, and sometimes potentially autoreactive T cells are released into the periphery.27 These T cells are kept in check by the peripheral tolerance mechanisms, mainly under the control of regulatory T cells (Tregs). Tregs are perhaps the most important suppressive cells, and control the activation of potentially autoreactive T cells. This suggests that an effective T-cell response against cancerous cells over-expressing normal antigens will require deletion of these Tregs along with antigen-specific vaccination.

TUMOUR VACCINES Research in the field of vaccination for cancer has generated enormous interest since the identification of tumour antigens. Most of the tumour antigens are ‘self’ antigens, hence it is essential to break tolerance against them while avoiding autoimmunity. Moreover, most cancer patients are immunocompromised at later stages of the disease, which makes it difficult to mount an effective immune response against tumour antigens. Successful immunotherapy of cancer will also have to overcome the multiple tumour escape mechanisms employed by the cancer during its evolution. Attempts to overcome these challenges are illustrated by the large number of vaccine strategies that have thus far been developed and tested (Fig. 8.2).

TOLERANCE The development of cancer/malignant disease is often seen as a result of a failure in immune surveillance. Moreover, recent evidence suggests that mechanisms of tolerance that usually exist to prevent autoimmune diseases may also prevent the development of an anti-tumour response against antigens such that even tumours have the ability to preclude a response against their antigens. Immunological tolerance is the failure to mount an immune response to an antigen. This can be either natural/ ‘self’ tolerance or induced tolerance. It is now becoming apparent that there are several ‘bottlenecks’ in the immune response to cancer cells; these include: (a) the lack of highavidity tumour-specific T cells,20–22 (b) the inefficient priming of tumour-specific T cells,22–24 (c) the physical and functional deletion of primed tumour-specific T cells,24 and (d) tumour evasion and counterattack.25,26 T-cell tolerance can be either central or peripheral. Central tolerance occurs in the developing thymus. Developing

Figure 8.2 Types of cancer vaccines. Cancer vaccines can be patient-non-specific, such as allogeneic whole-cell, peptide, DNA/RNA and viral/bacterial vaccines. Personalized vaccines include autologous tumour cell or tumour-derived heat-shock-protein vaccine and dendritic cell vaccine. T cells isolated from peripheral blood mononuclear cells (PBMCs) or tumour-infiltrating lymphocytes can be expanded in vivo and injected as a form of therapy.

172 Vaccination strategies for malignant diseases

Whole-cell vaccines Whole-cell vaccines consist of irradiated autologous or allogeneic tumour cells, with or without any in-vitro modifications, and many clinical trials have explored this method of cancer vaccination. Earlier clinical trials using autologous or allogeneic tumour cells without any modification met with limited success. Galligioni et al.28** immunized 120 renal carcinoma patients with autologous irradiated tumour cells along with bacillus Calmette–Guérin (BCG) as an adjuvant. Although the vaccination was able to generate a tumour-cell-specific immune response as measured by delayed-type cutaneous hypersensitivity (DTCH), it had little effect on patient survival. Subsequently, various approaches have been used in which the tumour cells have been modified in vitro either to express co-stimulatory molecules or to secrete cytokines to enhance their immunogenicity.11,29* Granulocyte–macrophage colony-stimulating factor (GM-CSF) coding gene is the most widely used for the transfection of tumour cells leading to the recruitment and generation of dendritic cells to the site of vaccination. In a phase I clinical trial of prostate cancer patients vaccinated with irradiated autologous prostate tumour cells engineered to secrete GM-CSF, most patients generated prostate-antigen-specific T-cell and B-cell responses.29* Similarly, in a recent clinical trial of patients diagnosed with metastatic non-small-cell lung carcinoma, the patients were vaccinated with irradiated autologous tumour cells engineered to secrete GM-CSF. Immune responses were detected in most of the patients receiving the vaccine, but few clinical responses were recorded.30* In metastatic melanoma patients immunized with autologous melanoma cells modified to secrete IL-12 cytokine, thus favouring the generation of a Th1 response and activation of the innate and adaptive immune system,31*,32 two of the seven patients developed DTH reaction to the autologous tumour cells, whereas one patient had a minor clinical response and generated tumour-specific CD4 and CD8 T-cell infiltrates into the metastases.31* Targeting individual tumour antigens by vaccination limits the number of T-cell clones activated and does not take into account the variable expression pattern in different tumours. This problem could potentially be overcome by using whole tumour cells or their lysates for vaccination: they potentially contain multiple antigens, many of which may be individually specific to the tumour. Thus, although autologous tumour-cell vaccination has generated a tumour-specific immune response in most cases, clinical success has been extremely limited. This approach is restricted by the inability to generate large numbers of autologous tumour cells and is clinically impractical for larger clinical trials. Most of the recent clinical trials have been conducted using modified allogeneic tumour cell lines, as they can be genetically modified and cultured to large numbers prior to injection. Moreover, cross-presentation of antigen to T cells by the APCs does not require the tumour cells to be

MHC matched with the recipient. One concern regarding cultured cell lines in the long term relates to changes of their antigenic profile, immunogenicity and gene expression; thus quality control and consistency of the vaccine are central issues.

Heat-shock-protein-based vaccines Heat-shock proteins (HSPs) are a large family of ubiquitous and inducible proteins involved in the transport of intracellular peptides and which assist in the folding and unfolding of proteins, along with a host of other functions.33 Their role in cancer vaccination was discovered when it was observed that HSP from tumour cells but not from normal cells could be used to immunize animals against autologous tumours, although HSPs prepared from both normal and tumour cells are identical. It was later realized that this immunogenicity of the HSPs was due to bound peptides derived from tumour-associated/ tumour-specific antigens. The ability of tumour-derived HSP to generate anti-tumour responses has been demonstrated for gp96, hsp70, hsp90, hsp110, grp170 and calreticulin.34 Intracellular proteins are processed via the proteosomes in the cell; the peptides thus generated are transported to the endoplasmic reticulum by HSPs, where they bind to newly synthesized MHC molecules. Thus, immunizing with purified HSPs from autologous tumour cells can potentially generate an immune response against non-covalently bound antigenic peptides, and essentially bypasses the need to identify individual peptide epitopes presented by the cancer cells. Moreover, HSPs seem to have an intrinsic adjuvant property and can bind to the receptors on APC, resulting in their maturation and internalization followed by internal processing and presentation of HSP-associated peptides on MHC class I and II molecules.35 This property of HSPs could be extremely important, as not only are they the first and only ‘natural’ adjuvants of mammalian origin, but also they fail to elicit an immune response on their own. Moreover, a very low level of bound peptide is needed to generate a response compared to conventional peptide immunization.36 Immunizing with HSP can generate CD8 T-cell and antibody responses as well as the expansion of the NK cells,37 and they have been nicknamed the ‘Swiss Army knives’ of the immune system due to their ability to elicit diverse responses.38 In cancer patients, antigen-specific tolerance is maintained in the periphery, as T cells are not provided with co-stimulatory or cytokine signals (‘signal 2’) along with antigen presentation. Hence, it has been hypothesized that HSPs might be able to overcome tolerance to tumour cells by virtue of their ability to activate APC and generate ‘signal 2’.39 Several non-randomized clinical trials have been carried out in the last few years with the HSP–peptide complexes. In most of these trials, following surgical excision of

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the primary tumour, HSP–peptide complexes were purified from the tumour and the autologous complexes were injected back into the patient. The clinical response is based on the regression of metastasis and/or stabilization of tumour progression. In one such trial, out of 16 renalcell carcinoma patients immunized with 25 μg of autologous tumour-derived hsp gp96, one of the several heat shock proteins involved in intracellular protein transport, three patients demonstrated complete tumour regression, three had partial responses and three showed prolonged stabilization of the disease.40 Other clinical trials involving cancer patients have also generated some encouraging results, although large randomized controlled trials are needed to establish fully their potential.34 In a recently concluded phase III clinical trial of 300 stage IV melanoma patients immunized with autologous tumour-derived hsp (gp96)–peptide complex vaccines, increased survival period was observed in vaccinated patients compared to control patients. Although only a minority of the patients had M1a AJCC staging system for melanoma category tumour: skin and lymph-node disease only, and normal serum lactate dehydrogenase level, the medial survival period was 626 days, as compared to 383 days in the control group. Moreover, patients receiving ten or more immunizations survived for significantly longer period than those in the control arm of the trial.41

Peptide vaccines As explained previously, CD4 and CD8 T cells are considered to be the main effector cells against cancer, and functional activity by both these cells requires binding of their T-cell receptor (TCR) to the peptides presented to them by the MHC class II and class I molecules respectively. Thus, any peptide presented by the MHC molecule on the surface of tumour cells is a potential target for cancer immunotherapy. In 1992, the first study to identify a nonamer peptide recognized by cytotoxic T lymphocytes in cancer patient was published.42 Since then, several studies have identified immunogenic peptides presented by the tumour cells in vivo and recognized by the cytotoxic T lymphocytes in cancer patients.43 CD8 T cells recognizing peptides derived from tumour antigens have been shown to exist in most cancer patients, and can be activated by vaccination.44 The advantage of the peptide vaccines is that they are easily produced. Moreover, there may be differences in the processing of proteins by the tumour cells and antigenpresenting cells, which may result in the generation of different epitopes. In such instances, immunization with peptides known to be naturally processed by the tumour cells is the desired option. Several studies in animal models have shown the efficacy of peptide-specific CD8 T cells in providing protection against tumour challenge or completely eradicating established tumours.45 A number of clinical trials have

been conducted using peptide vaccines. Initial trials involved immunizing patients with MHC class I restricted peptides alone, and in some instances peptide-specific CTLs were generated, but this immunological response failed to deliver any objective clinical response.46 However, most of the other clinical trials have not produced encouraging results. In two recent independent clinical trials of stage IV melanoma and CML patients, immunizing with peptide vaccines containing epitopes from melanoma antigens (gp100, MART-1, tyrosinase and MAGE-3) and bcr-abl protein respectively produced no objective clinical response in terms of tumour regression or remission induction. However, in both these trials, some of the patients had stable disease that correlated with the generation of vaccine-induced cytotoxic response.47*,48* It has been suggested that low disease burden or combination with other therapy modalities could be more effective. Supporting this, another clinical trial showed that peptide vaccination can reduce the number of recurrences in patients who have a history of at least three resected metastases. Of 44 patients with resected cutaneous melanoma, 9 patients with more than three resected metastases were immunized with melanoma-specific peptide vaccines. Of these 9 patients, 4 had cessation of recurrences and all 4 made an immunologic response to the vaccine.49* Another school of researchers seems to favour targeting mutated antigens that might be specific to individual tumours. In one such clinical trial, patients were screened for specific mutations in p53 and K-ras antigens and then immunized with peptides containing those mutations. Although only a fraction of patients experienced a period of stable disease, median survival time for immunological responders was significantly longer than that for nonresponders.50* These results suggest that although peptide vaccines have had very little clinical benefit in terms of tumour regression, in most cases clinical outcome correlates with immunological response. Experience from animal models showed that for an effective and long-lasting response leading to tumour regression, it was essential to activate CD4 T-helper cells. Not only is T-cell help required for optimal effector and memory CTL response,11 but in certain animal models CD4 T cells have been shown to mediate tumour regression via an IFNγ-mediated mechanism.51 This has led to the intensification of efforts to identify MHC class II restricted peptides.52,53 Recent trials have used a combination of MHC class I and II peptides, but the available evidence is limited and further investigations are required. There are several possible reasons for the limited clinical efficacy of peptide vaccines. The source of the helper peptides for CD4 T-cell stimulation is an important consideration. Several groups include MHC class II epitopes from irrelevant antigens such as tetanus toxoid and hepatitis B together with CTL epitopes in peptide vaccines. The CD4 T-cell repertoire is not likely to be tolerised against these foreign antigens.54 However, there is evidence to

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suggest that immunizing with MHC class II epitopes from antigens expressed by the tumour cells together with MHC class I epitopes is more likely to induce the regression of established tumours. Also, the adjuvant used to administer the peptide vaccines is extremely important and more likely to recruit APCs to the site of the peptide depot and thus be more effective in generating peptidespecific T cells. Currently, the adjuvants permitted for human administration are aluminium-based salts (Alum) and a squalene-oil-water emulsion (MF59).55 There is a need to identify novel and potent adjuvants, especially for peptide vaccines. Peptide vaccines delivered through liposomes or nanobeads or in combination with CpGoligonucleotides have all shown an ability to generate high-avidity CTLs.56,57 Another important factor influencing the effectiveness of vaccines is the ‘quality and quantity’ of the T-cell response. Animal models predict that not only is the number of T cells important, but also their functional status. GM-CSF and IL-2 promote the differentiation of APCs and proliferation of T cells respectively, and are instrumental in generating effector T cells.58* One of the obstacles to the success of cancer immunotherapy is the development of tolerance to ‘self’ antigens. It has been shown that during development, most of the T cells having high affinity for ‘self’ antigens have been deleted in the thymus and only T cells with low to medium binding affinity survive; their activation represents a significant challenge. However, it has been shown, both in human studies and in animal models, that altering certain amino-acid residues of the peptide may increase its binding affinity to MHC molecules and/or to the TCR. This can significantly improve the ‘quality and quantity’ of the T cells, which are able to bind to both the altered and naïve peptide and lyse tumour cells.59,60 Confirming the studies in animal models, Rosenberg et al. showed that immunizing advanced (metastatic) melanoma patients with a modified peptide vaccine and IL-2 resulted in the generation of immunologic responses in 91 per cent of patients, with 42 per cent demonstrating an objective clinical response.59* It was observed that 13 out of 31 patients immunized with modified peptide emulsified in IFA (Incomplete Freund’s Adjuvant) and concomitant IL-2 had objective clinical regressions of the metastases in brain, lung, liver, lymph nodes, skin and subcutaneous tissues. Moreover, in spite of generating an immune response against a differential antigen that is normally expressed in normal skin cells, no autoimmune response were observed in any of the patients.59* Finally, immunizing with epitopes derived from a single tumour antigen usually results in down-regulation of antigen or MHC molecule expression.61 This could be overcome by immunization against multiple epitopes.62 However, the phenomenon of epitope dominance, i.e. immune response being diverted towards one peptide, represents a possible limitation in using multi-epitope vaccines.63

Dendritic-cell vaccines Dendritic cells were first identified some 25 years ago as cells with intertwining dendritic processes that seem to be involved in antigen capture in primary lymphoid follicles.64,65 Their role in generating an immune response then became apparent,66 but it is thanks to methods developed by Steinman67 enabling the isolation and identification of dendritic cells that their extraordinary and unique ability to activate and maintain the survival of T lymphocytes was established. Nowadays it is well recognized that dendritic cells represent the most powerful antigenpresenting cell type, capable of stimulating strong immune responses after trafficking from the periphery, where they take up antigens, to lymph nodes, where they cross-present antigens to T cells through their high number of human leukocyte antigen (HLA) and co-stimulatory molecules, as well as producing important immunomodulatory molecules such as cytokines and chemokines. The origin of the cells, their maturation status and their combination with antigen in the form of peptides, protein, lysate or RNA/DNA, as well as the dose and site of injection are important considerations for optimizing vaccine protocols. Indeed, successful vaccine will have to generate an effective, long-lasting antitumour response. The choice of the antigen will direct the specificity of the immune response, and the choice of the adjuvant will affect the quality and magnitude of the anti-tumour response. Dendritic cells can be generated from various precursor cells after expansion of their progenitors or be directly isolated from various body locations. Their phenotype and function may be altered, depending on the precursor chosen, factors and agents used to mobilize, differentiate and mature them, as well as on the anatomic location from which the dendritic cells were taken. CD34 cells represent the main precursor cells and the main sources of dendritic cells, and can be isolated from blood, bone marrow, umbilical cord, lymph node, tonsil, spleen, skin or even tumours. Patients undergoing chemotherapy may receive cytokine such as granulocyte-colony-stimulating factor (G-CSF) prior to treatment in order to mobilize peripheral blood CD34 cells, which can then be positively selected and used to generate dendritic cells in vivo. More dendritic cells can be generated by this method than from other materials, and many clinical trials have adopted these cells as a source of dendritic cells.68*,69*,70* However, monocyte-derived dendritic cells remain the most widely used type in clinical trials.71 The majority of human chronic and acute myelogenous leukaemia cells can be induced to differentiate into dendritic cells under the influence of a combination of cytokines such as GM-CSF, IL-4, and/or IL-6 and tumour necrosis factor-alpha (TNFα), as estimated by the level of expression of dendritic-cell-specific markers and function.72,73 This offers two major advantages: that the cells can be grown and manipulated in vitro to achieve a maximum number but also that they act as a source of tumour antigens.

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Co-culture of T cells with autologous dendritic cells generated from acute myeloid leukaemia (AML) or CML patients can generate effector cells capable of lysing autologous CML targets with greater efficacy than T cells expanded with IL-2 alone.72,73 Alternatively, exosomes, which are small membrane vesicles containing both major histocompatibility complex (MHC) class-I and MHC class-II molecules secreted by dendritic cells, can be used as potent anti-tumour molecules. However, these have been shown to be efficacious only when co-injected with dendritic cells,74,75 which, following antigen up-take, migrate to the T-cell-enriched areas located in lymphoid organs.76 In order to elicit immunity in cancer patients, dendritic cells have to present the relevant tumour antigens, many of which are newly expressed, uniquely expressed or overexpressed by cancer cells (see Table 8.1). The best tumour antigen would ideally induce a broad repertoire of antigenspecific T-helper and cytotoxic T lymphocytes. The most commonly used sources of antigen in clinical trials are tumour lysates, necrotic or apoptotic tumour cells, peptides and tumour-derived DNA or RNA. Tumour lysates present two main advantages: HLA typing of the cells is not required and the antigen specificity does not need to be defined. Nestle et al. pioneered this work and immunized 16 melanoma patients with advanced disease with immature monocyte-derived dendritic cells pulsed with tumour lysate or a cocktail of peptides known to be recognized by CTLs (such as MART-1, tyrosinase, gp100 or MAGE-1 or -3), depending on the patient’s HLA haplotype. Objective responses were evident in 5 out of the 16 evaluated patients (two complete responses, three partial responses), with regression of metastases in various organs (skin, soft tissue, lung, pancreas) and one additional minor response.77* However, tumour cells will also carry ‘self’ antigen that may induce unwanted immune responses, which would divert the immune response away from cancer-associated antigens. Sufficient tumour material is also required for the preparation of the lysate, and monitoring of cancer-specific responses to undefined antigens is problematic. Some groups have fused dendritic cells directly with tumour cells; the resultant cells thus express both known and unknown tumour antigens as well as co-stimulatory and adhesion molecules necessary for the activation of T cells.78 Patients with metastatic renalcell carcinoma have been vaccinated with a hybrid cell vaccine consisting of autologous tumour cells fused to dendritic cells and, despite the poor prognosis for these patients, objective clinical responses, including four complete remissions, were seen in 7 of 17 (41 per cent) patients.79* Dendritic cells transfected with tumour-derived mRNA offer the advantage of safety over DNA, as the RNA is highly unlikely to integrate into the patient’s genome. Moreover, multiple antigens can be immunized against using this approach without any MHC restriction of the patient.

A phase I clinical trial in metastatic prostate cancer patients demonstrated the feasibility and safety of this technique.80* In this study all 13 patients receiving autologous monocyte-derived dendritic cells transfected with autologous tumour-derived mRNA demonstrated prostatespecific antigen (PSA)-specific T-cell responses without toxicity associated with significant decrease of the serum PSA in six of seven patients. No autoimmune toxicity was observed in these patients and they generated PSA specific immune response as tested in vitro. Also, serum PSA decreased in some patients. Some of these patients also showed a rapid but transient clearance of circulating tumour cells from peripheral blood. Malignancies of B-cell origin express monoclonal immunoglobulins that carry unique tumour-specific antigenic determinants in the variable region, idiotypes. These idiotypes have been isolated from B-cell malignancies and subsequently loaded onto autologous dendritic cells and used for the immunization of low-grade follicular nonHodgkin’s lymphoma (NHL). Durable tumour regression in patients with measurable disease was observed, as well as the induction of anti-idiotype T-cell and antibody response which could specifically recognize tumour cells and mediate objective clinical response.81* Combinations of selected peptides with carefully prepared dendritic cells have been successfully used to eradicate tumour in mice, and with some success against human tumours,77* the major limiting factors being that these peptides are specific for the HLA type of the patient. However, a phenomenon known as ‘peptide spreading’ can occur. This occurs after a strong immune response is generated against a particular peptide, resulting in the killing of tumour cells and leading to new antigens being released as a result of the cell destruction, which can then be taken up and processed by dendritic cells. Thus these dendritic cells present to T cells different tumourspecific peptides that were not included in the initial vaccine.82 Peptide-pulsed dendritic cells also allow the careful monitoring of the immune response in vivo. Microspheres may also be used to load dendritic cells with selected peptides and to prolong their presentation of peptides to the immune system.83 Alternatively, transfection of dendritic cells with tumour RNA or DNA using viruses such as vaccinia viruses and lentiviruses allows a broader range of peptide specificities to be expressed.84,85 Animal studies have shown that the route of immunization with dendritic cells is of prime importance, and that delivery to lymphoid organs is preferable to immunization via non-lymphoid organs such as the blood or skin. Indeed, the route of administration has been shown to determine memory cell distribution and the ability to control tumour outgrowths located at different body sites.86 The preparation of dendritic cells ex vivo to clinical grade standard is labour intensive and remains a major

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challenge. Moreover, ex-vivo-derived dendritic cells may not offer advantages over peptide immunization.87 Although dendritic cells can be injected directly into the tumour or lymph nodes,88 techniques developed to attract and mature dendritic cells at the site of immunization or specifically target dendritic cells in vivo may be more effective in generating a strong CTL response.89

DNA vaccines DNA vaccines consist of an antigen-encoding gene on a bacterial plasmid backbone. The expression of the gene encoded by this plasmid is controlled by a strong viral promoter such as cytomegalovirus (CMV) immediate–early promoter/enhancer. They are cheap and simple to produce, and the chances of DNA integrating into the human genome are extremely low. Compared to peptide vaccines, which would be restricted to specific MHC haplotypes, DNA vaccines are unrestricted and can generate CTLs against multiple epitopes, being able to generate B-cell as well as T-cell immune responses.90* Unlike viral vaccines, DNA vaccines are not influenced by the neutralizing antibodies against the viral vector.91 DNA vaccines can be administered in a number of ways, such as intramuscularly, intranasally and intramucosally, or can be coated onto gold particles and administered into the dermis using a gene gun.92 These plasmids persist in the cell nuclei as circular, non-replicating episomes, resulting in long-term expression of the gene. Apart from when administered by gene gun immunization, the injected plasmids are taken up by somatic cells such as myocytes; these will then express the antigen encoded by the injected gene, process it and present the resulting peptides onto their surface in association with MHC class I molecules.93 The APCs play an important role in the initiation of the immune response by DNA vaccination. Interestingly, the administration of apoptosis-inducing agents along with the DNA vaccination enhances antigen acquisition and T-cell activation by the APCs. In contrast, during gene gun immunization, the plasmid DNA is directly taken up by the resident Langerhans cells in the dermis.94 In both cases, these APCs then travel to the lymph nodes and present the antigens to the T and B cells. The route of immunization with DNA vaccines seems to be important, as several studies in animal models have shown that intramuscular immunization preferentially generates a Th1 response, whereas immunizing with the gene gun generates a Th2 response, although this method requires 100 times less antigen.95 Also, DNA vaccination can be used in conjunction with other vaccination methods, i.e. transfection of dendritic cells with plasmids encoding for tumour antigen or co-stimulatory/cytokine genes prior to injecting them. An important consideration in vaccinating with tumourassociated antigen is the activation of APCs, which is intrinsic to DNA-based vaccines as they contain unmethylated CpG

(cytosine linked to guanine with a phosphate) motifs.96 The motifs are 20-fold more frequent in microbial genes and therefore the mammalian immune system (mainly the APCs) is able to recognize them through their patternrecognition receptors. As additional adjuvants, plasmids encoding cytokine genes, co-stimulatory molecules or chemokines have been shown to increase the efficacy of the vaccination.97 Recently, it has been shown that along with tumour-antigen-encoding plasmids, co-administration of plasmids encoding for dendritic cell chemotactic and growth factors enhances the antigen-specific response in mouse models. DNA vaccines encoding multiple class I and class II peptide epitopes have also been designed for human immunodeficiency virus (HIV) and malaria, targeting either the MHC class I or class II processing pathway by the addition of specific signalling sequences.98 Several clinical trials have been conducted in recent years with plasmid vaccines, and unfortunately none of the human trials has been able to match the remarkable success in the animal models. None of the 22 patients immunized with a plasmid vaccine encoding gp100 antigen was able to mount any immunological and clinical response.99 In another clinical trial, patients with stage IV melanomas were injected intranodally with the plasmid DNA vaccine; 11 out of 26 patients were able to generate immune response. Although none of the patients had any clinical regression, it was observed that more than 50 per cent had unexpectedly long survival at a median follow-up of 12 months.100* Several other phase I trials have been conducted in melanoma and prostate cancer patients, but none has reported any significant objective clinical responses, despite some patients being able to generate humoral and cellular responses.101–103 DNA vaccines by themselves are considered weakly antigenic; however, when used in combination with viral vectors in a ‘prime-boost’ strategy, they appear to be highly effective in generating antigen-specific responses. Priming with plasmid vaccine followed by boosting with recombinant virus was shown to be highly effective compared to either of them alone.104 Recently, xenogeneic immunization, i.e. immunizing with a plasmid encoding homologous antigen from another species, has emerged as a powerful method to break tolerance to several ‘self’ antigens.105 However, the efficacy of these approaches remains to be tested in randomized human clinical trials.

Recombinant viral and bacterial vaccines The requirement for potent immunogenic vectors for the delivery of tumour antigens has led researchers to investigate naturally-occurring microbes as appropriate vehicles. Retrovirus, poxvirus, alphavirus, adenovirus and herpes simplex viruses have been investigated in several animal models and shown to be effective in promoting anti-tumour immunity. Viral vectors can be injected systemically or

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intra-tumorally and used to modify tumour cells ex vivo prior to injection. Many viral vectors are disabled and safe to administer and ideally should infect dividing as well as non-dividing cells and have the capacity to accept large inserts of genetic information. Retroviruses have been used for direct gene delivery to tumour cells as well as for the modification of tumour cells ex vivo prior to use. Out of nine patients injected with a retrovirus encoding for the p53 antigen, three exhibited regression of their lesions and three had disease stabilization. However, the virus could integrate into the host genome and hence pose a biosafety hazard,106 and most viruses currently in use have been attenuated through genetic approaches to make them safe for clinical application. Modified vaccinia Ankara strain is one of the most promising vectors being investigated, as it has proven to be highly effective for gene delivery and safe during smallpox eradication.107 In a phase I/II clinical trial of women with cervical intraepithelial neoplasia, 34 of 36 women injected with modified vaccinia virus showed complete elimination of pre-cancerous lesions and responses correlated with generation of specific cytotoxic response.108** Thus viral vaccination might be more advantageous compared to conventional cryosurgery, as vaccination in addition to treating pre-existing lesions would also generate an immune response against future infections by human papillomavirus. Other viruses belonging to the poxvirus family, such as canarypox and fowlpox viruses, have proven their efficacy in animal models. In a recent clinical trial, vaccination of patients with canarypox virus encoding for melanoma antigen gp100 was found to be superior to peptide vaccination, as 44 per cent of patients generated antigen-specific CTL response compared to none of the peptide-immunized patients.109** In another clinical trial in advanced melanoma cases, 30 patients were immunized with recombinant canarypox virus encoding for MAGE peptides. Only one patient demonstrated partial response and two had stable disease; the response in all patients correlated significantly with antigen-specific CTL generation.110 Adenoviruses have also been shown to be extremely potent in the generation of immune response in animals; however, their efficacy in humans would be limited, as about 85 per cent of the world’s population has antibodies against common serotypes. In one of the early clinical trials, recombinant adenovirus expressing melanoma antigen MART-1 was administered to 16 patients with metastatic melanoma, and one patient experienced a complete response; however, the efficacy was possibly limited due to the high levels of neutralizing antibody generated against the virus.91 Recombinant alphaviruses are potentially very safe vectors that could be used, as they need to be co-transfected with a helper plasmid for the generation of infective viral particles. Moreover, they induce apoptosis upon infection, which would facilitate cross-priming of the antigens.

We have extensively investigated the immunotherapeutic potential of disabled infectious single cycle-herpes simplex virus (DISC-HSV) in a murine tumour model.111 Upon intra-tumour inoculation of DISC-HSV encoding for murine GM-CSF, the regression of established tumours was observed in up to 70 per cent of the mice. The induced tumour regression was concomitant with potent CTL activity that was MHC-I restricted and directed against peptides of known tumour antigens. This vector is very safe, as the essential glycoprotein H (gH) gene has been deleted and it is therefore only capable of a single round of infection.112–114 Another recent clinical trial has also demonstrated potency of viral vaccines by inducing lesion regression of high-grade cervical intra-epithelial neoplasia.115* Recombinant bacterial vaccines from strains such as Salmonella, BCG and Listeria monocytogenes are promising novel vectors for cancer immunotherapy as they can potentially be administered orally and are capable of infecting APCs directly. The dual phagolysosomal and cytoplasmic life cycle of Listeria monocytogenes allows efficient processing of both MHC class II and class I antigens respectively.116,117

Novel vaccine delivery systems Several novel vaccination strategies able to deliver tumour antigens to the APCs, which would lead to appropriate antigen processing and would be ethically safe for human administration have been investigated. Liposomes, consisting of lipid membrane and encapsulating various drug formulations, have been used for a number of years to treat Kaposi’s sarcoma, and studies are now being extended to other cancers.118 Liposomes have the ability to deliver ‘drugs’ directly to the cytosol of the cells by fusion with the cell membrane and release of the drug internally. This property has been exploited to deliver antigens to APCs, and liposomes containing tumour antigens have also been shown to generate antigen-specific responses.119 Liposomal vaccination has been shown to be clinically safe and effective in generating long-lasting CD4 and CD8 T-cell responses in animal models and in patients with advanced stage follicular lymphoma. Antigens, either coupled to beads made of iron, silica or latex, or trapped in poly-lactide-co-glycolide (PLG) microspheres, have been shown to generate CTLs and in some cases are able to provide tumour protection in animal models.120 Recently, peptides coupled to nanoparticles have also been shown to generate peptide-specific CTL responses and provide protection against tumour challenge.57 The administration of viruses encoding tumour antigens has always proved controversial, especially when given to patients with late-stage cancer who are usually immunocompromised. To overcome this concern without losing the therapeutic effect of the viruses, virus-like particles

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(VLPs) have been designed that consist of self-assembled proteins derived from the viruses. These VLPs have been shown to prime antigen-specific responses without the need for adjuvant; however, their efficacy in humans has yet to be shown. Exosomes have recently emerged as an alternative novel method of immunization. Exosomes are small membrane vesicles that are released from various cell types during the fusion of multi-vesicular bodies with the plasma membrane121 and that carry both MHC class I and class II antigens along with co-stimulatory molecules. These exosomes can be purified from various tumour cells and loaded with peptide ex vivo before injecting them into the patients. Exosome immunization has been shown to generate immune response leading to tumour protection and rejection in animal models121 and current clinical studies will establish their utility in cancer therapy.

Cellular adoptive therapy Most cancer vaccination strategies, although proven to be highly successful in animal models, have only generated sporadic responses in clinical trials. It has been suggested that the major limiting factor in these trials is the inability to generate sufficient numbers of efficient tumour-specific T cells. This limitation has been overcome by recent clinical trials conducted using autologous T cells generated from the patients and expanded in vivo prior to infusion. Most of the tumours contain infiltrating lymphocytes that are reactive against mutated or non-mutated antigens expressed by the tumour, which can be isolated from the surgically removed tumours, expanded and activated in vitro and injected back into patients.122 Initial clinical trials with CD8 T cells isolated from autologous tumourinfiltrating lymphocytes (TILs) have provided disappointing results, possibly due to lack of the helper CD4 T cells and/or suppression by regulatory T cells.123 Regression of the tumours would therefore rely on the elimination of such suppressive T cells and the provision of helper cells for the generation of long-lasting immunity.124 Indeed, Rosenberg et al. have recently shown that 18 of 35 treated patients receiving myeloablative chemotherapy in the form of cyclophosphamide and fludarabine, followed by adoptive T-cell transfer of autologous TILs, generated objective clinical responses (50 per cent tumour reduction).10,125* Regression of metastasis in these patients was observed in sites such as lung, brain, liver, lymph nodes and subcutaneous tissues.125* In the past, adoptive cellular therapy was limited by the inability to generate sufficient numbers of tumour-specific T cells upon in-vivo stimulation. This has led to the construction of ‘artificial’ APCs, which are able to present the antigens to the T cells in vivo along with the co-stimulatory molecules and to promote T-cell expansion. An alternative novel strategy has been to clone tumour-antigen-specific T-cell receptors into autologous T cells prior to injecting

these engineered T cells back into patients. Long-lasting regression and/or remission of the tumours in patients resulting from adoptive cellular therapy would be largely dependent on the generation of memory CTLs, which in turn is dependent on the local production of cytokines such as IL-2. However, injecting IL-2 into cancer patients has been associated with several adverse effects. Hence, TILs engineered to contain the IL-2 gene are being developed, the local secretion of which would promote their own growth.10 This obviates the need for exogenous administration of IL-2 and reduces side effects in the patients.

TUMOUR ESCAPE Tumour escape is one major obstacle that has to be addressed prior to designing and delivering successful immunotherapy. There is evidence to suggest that immunogenic tumours in both pre-clinical murine models and cancer patients can be rejected by the immune system under optimum conditions. However, despite this, a large number of tumours continue to grow and evade the immune system, and the limited success of current immunotherapeutic strategies may be due to a number of reasons:126 ●

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failure of effector cells to compete with the growing tumour burden; the production of humoral factors and immunosuppressive cytokines by tumours that locally block immune attack; antigen/MHC-loss tumour variants; T-cell dysfunction; the production of suppressor T cells.

When considering novel immunotherapeutic approaches for cancer, one has to consider simultaneously the correction of immune activating signals, the eradication of inhibitory factors and the evasion of newly developed immuno-resistant tumour phenotypes.

Activation versus suppression in tumour progression Tumours can grow undetected by the immune system, being seen as ‘normal tissue’ as they do not exhibit the danger signals for immune activation.127,128 It is also believed that even during progressive growth, the tumour has the ability to activate the immune system and that a fine balance between activation and suppression exists, which may determine the fate of the tumour. Tumour vaccines may induce activation and expansion of specific CD8 T cells and destruction of tumour cells in cancer patients; this has been observed in approximately 5–20 per cent of vaccinated melanoma patients. However, this activation can be diminished by the lack of appropriate

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co-stimulation or the presence of immunosuppressive cytokines such as IL-10 and TGF-β. The eventual fate of the tumour is therefore decided by the net effect of immune activation and inhibition. The mechanisms of tumour escape from immune recognition/destruction are likely to be multi-factorial.

epitope.135 These mutations severely diminish T-cell recognition of the tumour antigen by a variety of mechanisms, including modulation of MHC–peptide interaction and TCR binding to MHC–peptide complex.

Immunosuppressive cytokines HLA class I down-regulation/loss Altered MHC class I antigen expression in tumours is a well-known phenomenon. It has been described in a variety of mouse models, including the T-cell leukaemic cell line, methylcholanthrene (MCA)-induced tumours and murine leukaemia-virus-induced tumours. The changes in MHC class I expression allow the tumours to avoid recognition or attack by CD8 T cells – a widespread phenomenon that has been confirmed by immunohistological studies.129 HLA class I molecule down-regulation occurs frequently in many cancers, and this abnormality might adversely affect the clinical course of disease and hence the outcome of T-cell-based immunotherapies. Changes in HLA expression can occur via a number of different mechanisms – genetic mutations, abnormalities in regulation and/or defects in HLA class-Idependent antigen processing. The various types of HLA loss have been classified into the different phenotypes that are recognized.130

Tumour antigen down-regulation, mutation or loss An alteration of tumour-associated antigen (TAA) expression is one mechanism by which tumour cells can escape CTL detection. Changes in TAA expression can range from a simple down-regulation to a complete loss and this can occur independently of the deregulation of HLA class I expression. Tumour-antigen expression is known to be heterogeneous, even within the same tumour,34 and a decrease in the expression of gp100 and MART-1 was associated with disease progression.131 The emergence of stable antigenloss variants has also been shown to be responsible for tumour escape in the murine mastocytoma P815 model.132 Antigenic drift, a mechanism used by viruses to escape immune recognition, has recently been described for tumours. Transgenic mice expressing TCR (T cell receptor) for a single antigenic epitope have been used extensively in establishing antigenic mutation(s) as a mechanism for viral escape of T-cell recognition.133,134 A transgenic mouse line expressing TCR specific for tumour antigen P1A35-43 presented by H2Ld was also developed and used to study tumour escape mechanisms. The recurrence of tumours in mice that have responded favourably to transgenic T-cell adoptive therapy was found to correlate with the presence of tumour variants with mutations within the P1A

Tumour cells produce various cytokines and chemokines that can have a suppressive effect on immune cells. In patients with non-small-cell lung cancer, the mRNA expression of IL-4, IL-10, TGF-α and TGF-β was significantly higher than that of IL-2, IL-12, IL-18 and IFN-γ as determined in pleural effusion and tumour tissue.136 Vascular endothelial growth factor (VEGF) is secreted by a number of tumours137 and is known to be a contributory factor in tumour escape. It is important for tumour vascularization and is also produced by solid tumours to inhibit immune recognition.138,139 It also prevents dendritic-cell differentiation and maturation by suppressing the transcription factor NF-κB (nuclear factor-kappa B) in haemopoietic stem cells.140 Elevated VEGF in blood was correlated with poor prognosis in human neoplasms,137 possibly as a result of its angiogenic properties and/or its ability to suppress dendritic-cell maturation. Interleukin-10 is a cytokine that is often said to be ‘suppressive’ in nature, and high levels of IL-10 have been detected in patients with melanoma141 and pancreatic cancer.25,142 It has the ability to exert its effects in many ways: it inhibits antigen presentation, IL-12 production and the induction of a Th1 response in vivo. With respect to TGF-β, high concentrations of this cytokine are found in cancer patients25,142 and are usually also associated with ‘tumour progression’.

CONCLUSION Using various vaccine-based strategies such as antigen pulsed dendritic cells or targeting dendritic cells along with appropriately delivered tumour antigens, clinical responses have been observed in patients with various types of tumour. However, these results have been rather disappointing and have failed to meet expectations. Although animal models have provided invaluable information regarding the efficacy of vaccines against tumours in preclinical studies, one has to remain cautious because most studies have used rodent tumours, the majority of which are chemically induced and grow much faster than those encountered in humans. Many human tumours evolve slowly, taking sometimes years to develop malignant potential, and undergo a series of genetic and cellular changes leading to tumour progression and avoidance of the host defence mechanisms. Also, murine tumours are usually implanted at a site other than the tissue of origin, thereby not matching the organ-specific physiological characteristics

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of the tumour. Therefore, the immune system of patients is slowly acclimatized to tumours, whereas the immune system of animals transplanted with tumour cell lines is abruptly exposed to the cancer and its antigenic composition. Moreover, animal tumours sometimes acquire endogenous viruses and express viral antigens, rendering the tumour more immunogenic; this situation may not occur in human cancers. Cancer patients often die as a result of metastasis, which is where therapeutic vaccination should primarily focus. However, more appropriate animal models are being developed for studying and optimizing therapeutic cancer vaccines. An additional reason for the lack of progress in immunotherapy and low response rates observed in human clinical trials is that most patients involved in these trials are in stage III–IV of the disease – at a time when the immune system is already compromised. For vaccines to be effective, they will have to be used when minimal residual disease is present in order to achieve a favourable effector-to-target ratio. The mechanisms responsible for immune tolerance versus activation are being dissected, and the results of studies have provided a better understanding of host–tumour interactions. Collaboration between innate and adaptive immune responses in order to mount a strong and long-lasting immune response against tumours is considered important. Moreover, with the emergence of more powerful technologies, such as RNA amplification, proteomic technologies and DNA micro-arrays, events within the tumour microenvironment following vaccination can be studied. The identification of new biomarkers might allow the diagnosis of cancer at earlier stages of progression and at a time when immunotherapy may be of significant benefit to patients. In conclusion, immunotherapy represents an attractive modality for treating cancer but is limited by our understanding of the biological complexity of the disease and the patient. The past decade has witnessed remarkable progression in our understanding of the immune recognition of tumours, escape mechanisms and strategies for vaccination and cellular therapy. It is necessary to consider immunotherapy as an adjunct to conventional treatments and not necessarily as separate. The areas of concern relate to the selection of ‘resistant’ cells during treatment and whether combined approaches can eradicate these variants. In order to overcome tolerance and tumour escape mechanisms without side effects of autoimmunity, it will be necessary to select the most appropriate immunotherapy combined with traditional treatments. Moreover, we are faced with the challenge of understanding complex biological mechanisms, which may be cancer-type specific, and determining their relevance to ‘treatment outcome’. Finally, we do not as yet have a clear understanding of the important ‘self-renewing’ cancer stem cells and their relative susceptibility or resistance to treatments. These cells are difficult to detect and cultivate and very little information is available concerning their ‘immune phenotype’.

KEY LEARNING POINTS ●

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Most human tumours are immunogenic and immunosurveillance plays an important role in the clearance of many possible tumours. The immune system also helps in shaping the phenotype of cancerous cells. Hundreds of tumour antigens that can potentially be targets for the immune system have been identified. Most tumour antigens are ‘self’ antigens, hence tolerance to these antigens limits the efficacy of cancer vaccination. Various forms of vaccination, such as whole-cell, peptide, DNA, viral/bacterial vaccines, have generated limited clinical benefits in clinical trials in spite of clearly evident immunological responses. Recently, adoptive transfer of in-vitro-expanded autologous tumour-infiltrating lymphocytes has generated significant clinical responses in patients, although their widespread application is debatable. Immune escape mechanisms also limit the efficacy of tumour vaccines. Delineating the escape mechanisms and circumventing them are likely to be the key factors for successful immunotherapy. Recent progress in proteomic and genomic technologies will allow us to identify early cancer-specific markers that will enable early treatment to be given to patients and disease progression and recurrence to be monitored, and will aid decision-making concerning treatment.

ACKNOWLEDGEMENTS The authors wish to acknowledge the support of the John and Lucille van Geest Foundation, the European Commission (specifically funding received from ALLOSTEM, ENACT AND OISTER) and the National Eye Research Council for supporting research into cancer vaccines in this laboratory.

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tumour antigen by splenic parenchymal CD4 T cells in mice failing immunotherapy with DISC-mGM-CSF. Int J Cancer 2005; 115:951–9. Rees RC, McArdle S, Mian S, et al. Disabled infectious single cycle-herpes simplex virus (DISC-HSV) as a vector for immunogene therapy of cancer. Curr Opin Mol Ther 2002; 4:49–53. Ali SA, Lynam J, McLean CS, et al. Tumor regression induced by intratumor therapy with a disabled infectious single cycle (DISC) herpes simplex virus (HSV) vector, DISC/HSV/murine granulocyte–macrophage colonystimulating factor, correlates with antigen-specific adaptive immunity. J Immunol 2002; 168:3512–19. Assudani DP, Ahmad M, Li G, et al. Immunotherapeutic potential of DISC-HSV and OX40L in cancer. Cancer Immunol Immunother 2006; 55:104–11. Garcia-Hernandez E, Gonzalez-Sanchez JL, AndradeManzano A, et al. Regression of papilloma high-grade lesions (CIN 2 and CIN 3) is stimulated by therapeutic vaccination with MVA E2 recombinant vaccine. Cancer Gene Ther 2006; 13:592–7. Gentschev I, Fensterle J, Schmidt A, et al. Use of a recombinant Salmonella enterica serovar Typhimurium strain expressing C-Raf for protection against C-Raf induced lung adenoma in mice. BMC Cancer 2005; 5:15. Weiskirch LM, Pan ZK, Paterson Y. The tumor recall response of antitumor immunity primed by a live, recombinant Listeria monocytogenes vaccine comprises multiple effector mechanisms. Clin Immunol 2001; 98:346–57. Ferrari M. Cancer nanotechnology: opportunities and challenges. Nat Rev Cancer 2005; 5:161–71. Mandal M, Lee KD. Listeriolysin O-liposome-mediated cytosolic delivery of macromolecule antigen in vivo: enhancement of antigen-specific cytotoxic T lymphocyte frequency, activity, and tumor protection. Biochim Biophys Acta 2002; 1563:7–17. Tartour E, Ciree A, Haicheur N, et al. Development of nonlive vectors and procedures (liposomes, pseudo-viral particles, toxin, beads, adjuvantsellipsis) as tools for cancer vaccines. Immunol Lett 2000; 74:45–50. Cho JA, Yeo DJ, Son HY, et al. Exosomes: a new delivery system for tumor antigens in cancer immunotherapy. Int J Cancer 2005; 114:613–22. Zhou J, Dudley ME, Rosenberg SA, Robbins PF. Persistence of multiple tumor-specific T-cell clones is associated with complete tumor regression in a melanoma patient receiving adoptive cell transfer therapy. J Immunother 2005; 28:53–62. Dudley ME, Wunderlich JR, Yang JC, et al. A phase I study of nonmyeloablative chemotherapy and adoptive transfer of autologous tumor antigen-specific T lymphocytes in patients with metastatic melanoma. J Immunother 2002; 25:243–51. Antony PA, Piccirillo CA, Akpinarli A, et al. CD8 T cell immunity against a tumor/self-antigen is augmented by CD4 T helper cells and hindered by naturally occurring T regulatory cells. J Immunol 2005; 174:2591–601.

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Dudley ME, Wunderlich JR, Yang JC, et al. Adoptive cell transfer therapy following non-myeloablative but lymphodepleting chemotherapy for the treatment of patients with refractory metastatic melanoma. J Clin Oncol 2005; 23:2346–57. Ahmad M, Rees RC, Ali SA. Escape from immunotherapy: possible mechanisms that influence tumor regression/progression. Cancer Immunol Immunother 2004; 53:844–54. Cabrera CM, Jimenez P, Cabrera T, et al.Total loss of MHC Class I in colorectal tumors can be explained by two molecular pathways: beta 2-microglobulin inactivation and MSI-positive tumors and LMP7/TAP2 downregulation in MS negative tumors. Tissue Antigens 2003; 61:211–19. Cabrera T, Pedrajas G, Cozar JM, et al. HLA class I expression in bladder carcinomas. Tissue Antigens 2003; 62:324–7. Jager E, Jager D, Knuth A. CTL-defined cancer vaccines in melanoma and other epithelial cancer. In: Stern PL, Beverely PCL, Carroll MW (eds) Cancer Vaccines and Immunotherapy. Cambridge: Cambridge University Press, 2000, 207–217. Boursnell MEG, Entwistle C, Ali SA, et al. Disabled Infectious Single Cycle (DISC) Herpes Simplex Virus as a vector for immunotherapy of cancer. Adv Exp Med Biol 1998; 451:379–84. Dunn GP, Bruce AT, Ikeda H, et al. Cancer immunoediting: from immunosurveillance to tumor escape. Nat Immunol 2002; 3:991–8. Melcher A, Todryk S, Hardwick N, et al. Tumor immunogenicity is determined by the mechanism of cell death via induction of heat shock protein expression. Nat Med 1998; 4:581–7. Melero I, Singhal MC, McGowan P, et al. Immunological ignorance of an E7-encoded cytolytic T-lymphocyte

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epitope in transgenic mice expressing the E7 and E6 oncogenes of human papillomavirus type 16. J Virol 1997; 71:3998–4004. Mellor AL, Munn DH. Tryptophan catabolism and T-cell tolerance: immunosuppression by starvation? Immunol Today 1999; 20:469–73. Mukherjee P, Ginardi AR, Madsen CS, et al. MUC1-specific CTLs are non-functional within a pancreatic tumor microenvironment. Glycoconj J 2001; 18:931–42. Plescia OJ, Grinwich K, Plescia AM. Subversive activity of syngeneic tumor cells as an escape mechanism from immune surveillance and the role of prostaglandins. Ann N Y Acad Sci 1976; 276:455–65. Ragnarsson GB, Mikaelsdottir EK, Vidarsson H, et al. Intracellular Fas ligand in normal and malignant breast epithelium does not induce apoptosis in Fas-sensitive cells. Br J Cancer 2000; 83:1715–21. Ramal LM, Feenstra M, van der Zwan AW, et al. Criteria to define HLA haplotype loss in human solid tumors. Tissue Antigens 2000; 55:443–8. Ramal LM, Maleno I, Cabrera T, et al. Molecular strategies to define HLA haplotype loss in microdissected tumor cells. Hum Immunol 2000; 61:1001–12. Gabrilovich DI, Velders MP, Sotomayor EM, Kast WM. Mechanism of immune dysfunction in cancer mediated by immature Gr-1 myeloid cells. J Immunol 2001; 166:5398–406. Restifo NP. The new vaccines: building viruses that elicit antitumor immunity. Curr Opin Immunol 1996; 8:658–63. Rohrlich PS, Cardinaud S, Firat H, et al. HLA-B*0702 transgenic, H-2KbDb double-knockout mice: phenotypical and functional characterization in response to influenza virus. Int Immunol 2003; 15:765–72.

9 Biological therapies: cytokines and adoptive cell therapy FIONA C. THISTLETHWAITE, PETER L. STERN AND ROBERT E. HAWKINS

Introduction Cytokines in cancer therapy

186 188

INTRODUCTION This chapter covers bio-immunotherapies for cancer that directly or indirectly exploit the anti-tumour activities of particular cytokines or immune effector cells. The impetus for these approaches has been reinvigorated as a result of the renaissance of the concept of immunosurveillance1 and the significant advances that have been made in our understanding of the molecular and cellular mechanisms underpinning tumour immunity.2 Faith in the concept that the immune system could control tumour development had fallen away in the 1970s when experiments of tumour induction with chemical carcinogens showed no increased frequency in animals with a severe deficiency in T-lymphocyte-mediated (T-cell-mediated) immune function – athymic nude mice. Indeed, a recent major review identifying the supposed hallmarks of cancer failed to acknowledge any significant role for the immune system in cancer.3 In part, the problem with the nude mouse experiments was the underestimation of the role of small numbers of residual T cells, as well as of natural killer (NK) cells, and the importance of cytokine effector molecules. However, there is now convincing evidence that the cellular immune system and associated cytokine networks are key players acting to control tumour emergence. This is most dramatically demonstrated by the increased susceptibility to tumour induction by methyl cholanthrene in various knock-out mouse models with defects in T-cell, B-cell and NK-cell function or in their interferon (IFN) pathways. These include mice deficient in RAG2 TCRαβ, TCRγδ, perforin, STAT1 and IFN-γ as well as the SCID model. Interestingly combinations of these defects such as RAG2 x

Adoptive cell therapy References

194 198

STAT1 or perforin x IFN-γ mice show evidence of increased spontaneous tumours and subtle difference in the prevalence of types.1 There is abundant evidence that tumours are immunogenic during cancer pathogenesis with both antibody and T-cell-recognized antigens.4,5 These tumour-associated antigens (TAAs) include the products of mutated oncogenes, other altered gene products, cancer–testis antigens, differentiation and virally encoded antigens. The tumour microenvironment, consisting of neoplastic cells, immune cells, stromal cells and extracellular matrix, is the principal combat zone. It is the result of complex interactions between all these components that ultimately determines whether tumour surveillance is successful and the tumour eradicated, or it fails and the tumour becomes established. It is likely that in the early phases of tumorigenesis a lack of danger signals is an important factor in any failure to activate the innate arm of the immune response.6 The innate response plays an important role in co-ordinating inflammatory reactions and provides the first line of defence against infection. It includes soluble factors such as complement proteins in addition to cells such as granulocytes, macrophages, NK cells and mast cells. The process of establishing an innate response critically influences the activation of antigen-presenting cells (APCs) such as dendritic cells, the sentinels that awake the adaptive response.7 Endogenous danger signals are important triggers in the initiation of the innate response. Released by damaged, stressed or abnormally dying cells these danger signals include heat shock proteins, nucleotides, reactive oxygen intermediates and cytokines. However, it is clear primary tumours often do not provide adequate danger

Introduction 187

signals, and thus avoid any early activation of innate immunity. Adaptive immunity supplies the potential for specific recognition of TAAs and subsequent expansion and differentiation of anti-tumour cytotoxic T lymphocytes (CTLs) as well as providing for memory populations. Importantly, the signals provided by the local innate immunity influence the antigen-presenting activated dendritic cells and can influence the subsequent adaptive immune response. Thus specific T-cell responses can be biased to either a T helper 1 (Th1) or T helper 2 (Th2) type, which preferentially promote the development of CTLs or B-cell antibody production and class switching respectively.8 The important role that the adaptive immune system plays is reflected in the observation that for many solid tumours, significant lymphocyte infiltration can be correlated with reduced frequency of metastasis and improved patient survival.9 The nature of tumour development per se, however, involves genomic instability and this provides the engine for generating variant tumour clones.3 Evidence exists for the selection of tumour variants that can avoid both antigen-specific T-cell and NK anti-tumour activities as a result of the immune pressure exerted over the natural history of the malignancy.10 Multiple mechanisms have been described that can account for such tumour evolution. Both T-cell and NK-cell populations are controlled by the presence or absence of the major histocompatability complex (MHC) class molecules respectively, and loss of these is a very common event during tumour evolution.1,11 The natural history of tumour development in humans is long, so sufficient time is available to allow for the emergence of tumour variants lacking the appropriate human leukocyte antigen (HLA) restricting element for TAA-specific CTL sensitivity, whereas such allele-specific loss does not lead to increased NK sensitivity.12 Chronic sub-optimal stimulation of anti-tumour T cells can lead to depletion of key populations of effector T cells. It is increasingly clear that in cancer patients there are significant increases of T regulatory (Treg) cells, which can act both specifically and non-specifically to limit anti-tumour immunity.13–15 Thus, in the presenting tumour microenvironment, there are probably strong negative regulatory influences on positive anti-tumour responses. Tumours also have endogenous mechanisms that provide for immune suppression, such as the production of immunosuppressive cytokines (TGF-β),16 the ability to induce apoptosis in infiltrating lymphocytes through Fas–Fas ligand interactions,17 and the activation of T cells without appropriate co-stimulatory molecules leading to anergy of TAA-specific T cells.18 Figure 9.1 summarizes some of the key factors that can influence the regression or progression of a tumour in the face of its recognition by cellular immunity during the natural history of a cancer. As discussed in Chapter 8, one approach to immunotherapy is to try to immunize patients using various means either to produce de-novo anti-tumour immunity (trying to engage a new anti-tumour repertoire) or to stimulate existing cellular immunity so as to overcome the various negative

Elimination

Regression

TUMOUR Escape Natural Selection / Heterogeneity

Progression

1. Poor inflammation • No Danger Signals 2. Poor immunogenicity 3. Immune suppression • Tumour (TGF β) • T regulatory cells

1. Innate immunity 2. APC processing 3. Th1 cell response 4. CTL generation 5. Long term memory

(a) TUMOUR Elimination

Regression

Escape Natural Selection / Heterogeneity

1. Innate immunity 2. APC processing 3. Th1 response 4. CTL generation 5. Long term memory

Progression

1. Blunt innate response 2. Interfere APCs 3. Skew Th1 v Th2 4. Anergize T response 5. No long term memory

(b) TUMOUR Elimination

Regression

Escape Natural Selection / Heterogeneity

1. Innate immunity 2. APC processing 3. Th1 cell response 4. CTL generation 5. Long term memory

Progression

1. Multiple tumour variants 2. MHC/Ag loss on tumour • NK and T resistance 3. T repertoire depletion 4. T regulatory cells 5. Other very bad stuff

(c)

Figure 9.1 Key factors that influence the regression or progression of a tumour. Early in the natural history, if the tumour is immunogenic, danger signals may activate an immune response resulting in cancer regression and elimination (a). With time, however, the tumour may develop escape mechanisms that lead to an equilibrium (b), or ultimately tolerance and establishment of the cancer (c).

influences discussed above. The challenge becomes increasingly daunting with more advanced cancers, especially where there is widespread metastasis of heterogeneous tumour cells. In order to treat such patients effectively, a very rapid response of the tumour target to treatment will obviously be advantageous. The basic rationale of treatments that use cytokines or adoptive cell transfer is that, as with monoclonal antibody therapy, they may exert a bolus anti-tumour activity that can override many immune modulatory mechanisms of the tumour targets. They can thus produce a shift in the equilibrium, allowing the action of other pre-existing

188 Biological therapies: cytokines and adoptive cell therapy

anti-tumour activity, thereby delivering a favorable clinical outcome with longer-term control.

CYTOKINES IN CANCER THERAPY Cytokines are secreted or membrane-bound proteins that regulate the growth, differentiation and activation of immune cells in a coordinated fashion.19 They are released in response to a wide variety of cellular stresses, including infection, inflammation and carcinogen-induced injury, and function to stimulate and coordinate a host response. A variety of cells within the tumour microenvironment produce cytokines, including host stromal cells, infiltrating immune cells and the malignant cells themselves. The biological effect of an individual cytokine can be highly pleiotrophic and determined by many factors, including the array of expressed cytokines, their relative concentrations and cytokine receptor expression patterns. In the context of immunosurveillance, the net influence of a cytokine network may be to tilt the balance towards the activation of immune effector mechanisms that limit the growth of the tumour. Alternatively, it may be tipped towards tumour growth, invasion and metastasis. Figure 9.2 highlights some of the network of important cytokine and lymphocyte interactions that occur within the tumour microenvironment.

DC

The manipulation of this cytokine balance has proved to be an attractive target for cancer therapies. Cytokines can be divided into five major families. 1. 2. 3. 4. 5.

Type I cytokines – interleukins (ILs). Type II cytokines – interferons (IFNs). Tumour necrosis factors (TNFs). Immunoglobulin supergene family. Chemokines.

The list of individual members of these families and their receptors extends to more than 100 molecules. It is clearly beyond the scope of this chapter to detail all of them individually, their biological actions and their clinical potential. However, Table 9.1 lists some of the cytokines that have had a significant impact on our understanding of the area, and highlights their principal biological and therapeutic effects. Many are currently being explored in trials and may become part of accepted clinical practice in years to come. The following is a more detailed evaluation of the cytokines used in clinical practice today.

Interferons Interferons are widely expressed cytokines with important anti-viral, anti-proliferative and immunomodulatory functions. The IFN family includes two main classes, referred to

NK IFN-α  IFN-β IL-12 

Tumour Kill 

CD8 

IL-10

IL-2 IFN-Y TNF-β



Tumour

TGF-β IL-10



T-reg

Th1



IL-10  CD4

Th2

IL-4 IL-5  IL-6 IL-10 IL-13

B-Cell

Figure 9.2 Complexity of the cytokine and lymphocyte interactions within the tumour microenvironment. CD4 cells are influenced by cytokines such as IL-12, IL-18 and IFN-α to differentiate down the Th1 pathway. Upon activation Th1 cells produce an array of cytokines including IL-2, IFNγ and TNF-β. CD8 cells are activated by these following specific recognition of peptides presented from MHC class I molecules on APCs (primary DCs) via their TCR, and co-stimulation from molecules such as CD28. Further positive signals come from IFNα, IFN-β and IL-12 which induce CD8 CTLs and NK cells to destroy target cells, by apoptosis, via multiple pathways. These pathways include secretion of granules of perforin and granzyme, or by triggering receptors for TNF-like receptors on target cells by soluble molecules such as Fas Ligand, TRAIL.

Table 9.1 Cytokines, their principal biological effects and current or potential clinical uses Cytokine

Biological effects

Therapeutic potential

IL-1α

Pro-inflammatory: increased expression of genes such as COX-2 and promotion of infiltration of leukocytes

Trials have shown some evidence of prevention of thrombocytopenia, but at the expense of significant toxicity limiting further development19

IL-1β

Role in angiogenesis: activation of vascular endothelial cells Increased invasiveness of malignant cells

Blockade of IL-1 can be helpful in inflammatory conditions, but was not found to be effective at preventing graft-versus-host disease20 in allogeneic transplantation

IL-2 (see text)

T-cell proliferation Enhanced cytotoxicity of T cells and NK cells Increased vascular permeability Co-factor in activating macrophages and B cells

Used primarily in melanoma and renal cell carcinoma Toxicity can be severe, including ‘capillary-leak’ syndrome, fever, hypotension, diarrhoea, renal and hepatic impairment

IL-3

Stimulation of proliferation and differentiation of haematopoietic stem cells Enhanced tumour-antigen presentation

Clinical trials have investigated a role in increasing haematopoiesis, for example in myelodysplastic syndrome21 Used to sustain haematopoietic stem cells ex vivo

IL-4

B-cell activation and differentiation, mediation of Ig class switching Pluripotent effects on cells, including monocytes, macrophages, mast cells, myeloid and erythroid precursors, endothelial cells and fibroblasts Directs activated T cells to Th2 pathway

Co-stimulatory immunoadjuvant Early-phase trials as direct anti-tumour drug have determined maximum tolerated dose, but not yet demonstrated efficacy22 Therapeutic target in inflammatory diseases

IL-6

Inflammatory mediator Central role in acute-phase response and fever Enhanced T-cell and B-cell function

Prognostic marker in several tumour types, including lymphoma and multiple myeloma Anti-tumour effects in clinical trials of IL-6 have been limited Promising results with anti-IL-6 antibodies in B-lymphoproliferative disorders,23 Castleman’s disease and rheumatoid arthritis Anti-IL-6 antibodies may also have a role in treating cancer-related cachexia

IL-7

Enhanced T-cell function Growth and differentiation factor for precursor B cells

Not yet tested clinically

IL-10

Inhibition of Th1 response Inhibition of macrophage-antigen presentation Inhibition of macrophage production of pro-inflammatory cytokines such as IL-1, IL-6 and TNF

Clinical trials using IL-10 in inflammatory conditions have as yet failed to define a clear role Anti-IL-10 antibodies are under investigation in systemic lupus erythematosus24

IL-11

Stimulation of haematopoiesis, particularly induction of production of megakaryocytes Spectrum of effects similar to IL-6

Administration of IL-11 has been shown to reduce the platelet transfusion requirement in breast cancer patients at high risk of thrombocytopenia25

IL-12

Stimulation of proliferation, cytokine production (especially IFN) and lytic activity of cytotoxic T cells and NK cells Promotion of maturation and activation of Th1 cells

Clinical trials have investigated subcutaneous or intra-tumoral administration as single agent or in combination, for example with IFN-α26 or monoclonal antibodies27 Clinical responses with IL-12 have been observed in lymphoid malignancies28 (non-Hodgkin’s lymphoma and cutaneous T-cell lymphoma)

IL-15

Enhanced T-cell and NK-cell proliferation and cytotoxicity

No published clinical data May have therapeutic potential similar to IL-2 May have a role in ex-vivo expansion of cells for adoptive therapy29

IL-18

Synergism with IL-12 to induce production of IFN-γ from NK and T cells Promotion of development of Th1 responses

Anti-tumour effects in vivo have been demonstrated in mouse models and clinical trials are awaited30

190 Biological therapies: cytokines and adoptive cell therapy

Table 9.1 (Continued) Cytokine

Biological effects

Therapeutic potential

IL-21

B-cell differentiation and antibody production NK-cell and T-cell differentiation, proliferation and cytotoxicity

Early-phase clinical trials currently underway

M-CSF

Proliferation and differentiation of monocyte/macrophage lineage

Lack of clinical evidence of direct anti-tumour effect in human trials Some indication that the incidence of chemotherapyrelated febrile neutropenia may be reduced when administered following chemotherapy31 Animal models show it induces thrombocytopenia, which may limit clinical applications

GM-CSF

Proliferation and activation of granulocyte and macrophage cell lineages

Phase II trials have explored its use in a number of tumour types either as a single agent or in combination, for example with chemotherapy32,33 Clinical responses noted when administered as aerosol to patients with pulmonary metastases34 Immunogenic effect noted when combined with chemotherapy and IL-2 in patients with metastatic colon cancer35 Phase III data awaited GM-CSF-based vaccines have shown promising early results36

IFN-α and IFN-β (see text)

Stimulation of proliferation and cytotoxicity of T cells and NK cells Promotion of increased Th1 responses Increased IgG secretion from B cells Regulatory and immunomodulatory effects on other cytokine and chemokine secretion Increased MHC expression and antigen presentation

The use of both has been explored, either as single agents or in combination with other molecules such as IL-2 IFN-α is widely used in many haematological and solid malignancies, particularly renal-cell carcinoma and melanoma To date, no conclusive therapeutic benefit has been demonstrated for IFN-β in malignancy (although it is extensively used to modify the course of multiple sclerosis)

IFN-γ (see text)

Augmentation of NK-cell and cytotoxic T-cell activity Induction expression of MHC molecules

Used in combination with TNF-α and melphalan for the treatment, by IPL, of in-transit metastases from melanoma and sarcoma, but activity as a single agent not proven

TNF-α (see text)

Pro-inflammatory Proliferation and activation of NK cells, T cells, B cells, macrophages and dendritic cells Induction of tumour-cell apoptosis

Dose-limiting toxicity at sub-therapeutic doses has limited systemic therapy, but, as described in the text, IPL has been shown to be clinically useful in melanoma and sarcoma Anti-TNF-α antibodies have therapeutic benefit in inflammatory conditions such as rheumatoid arthritis

FLT3 ligand

Expansion and mobilization of stem cells and progenitors Dendritic-cell and NK-cell differentiation from haematopoietic progenitor cells

Early-phase trials are examining the use of FLT3 ligand as a strategy to increase the number of dendritic cells, for example post-haematopoietic-cell transplant.ation37

Lymphotactin

Chemokine that enhances T-cell recruitment

Transgenic expression of lymphotactin (and IL-2) from an allogeneic neuroblastoma-cell vaccine has produced promising results in a phase I trial38

IL, interleukin; M-CSF, macrophage colony-stimulating factor; GM-CSF, granulocyte–macrophage colony-stimulating factor; IFN, interferon; TNF, tumour necrosis factor FLT3, fms–like tyrosine kinase 3; Th1/Th2, T helper 1 cell/T helper 2 cell; NK, natural killer; Ig, immunoglobulin; IPL, isolated limb perfusion.

Cytokines in cancer therapy 191

as type I and type II IFNs. Type I IFNs are a gene family consisting of about 20 members, including IFN-α, IFN-β, IFN-δ, IFN-ε, IFN-κ, IFN-τ and IFN-ω. IFN-α can be further subdivided into 13 functional genes in humans. The genes for the type I IFNs are located on the short arm of chromosome 9, and their proteins share significant aminoacid sequence homology. By contrast, there is only one type II IFN, IFN-γ. The gene that encodes it is located on chromosome 12 and does not share significant structural homology with the type I IFN genes. Interferon-α is the only IFN that is widely used in oncology at present, and is discussed in the paragraphs below. Therapeutic roles for IFN-β and IFN-γ have also been explored, either as single agents or in combination with other cytokines such as IFN-α or IL-2. Consistent additional therapeutic benefit has not been demonstrated for either of these agents when administered systemically.20,21 Interferon-γ, in combination with TNF-α and melphalan, has, however, been used in isolated limb perfusion (ILP) for metastatic disease for melanoma,22 which is discussed further in a later section. INTERFERON-α

Biology Interferon-α is produced primarily by leukocytes, classically when stimulated by viral infection, but other stimuli clearly exist, including bacterial endotoxins, unmethylated DNA (CpG DNA) and double-stranded RNA.23 Once induced, IFN-α must bind to its receptor to exert its biologic effect. All type I IFNs share a common receptor, which is composed of two subunits, a 100-kDa ligand-binding subunit (IFN-α R1) and a 125-kDa subunit (IFN-α R2), involved in both ligand binding and signal transduction. Binding of IFN-α to this receptor results in a cascade of events,24 including the activation of Janus tyrosine kinases JAK1 and TYK2. This enables the phosphorylation and subsequent dimerization of the signal transducers and activators of transcription 1 and 2 (STAT1 and STAT2) to form one of two distinct transcriptional activator complexes, namely IFN-α-activated factor (AAF) and IFN-stimulated gene factor 3 (ISGF3). These complexes disassociate from the IFN receptor and translocate to the nucleus, where they bind to the IFN-stimulated response element of the α-response genes, causing the induction of hundreds of target genes. The subsequent biologic effects of IFN-α on the immune system are extensive, involving both the innate and the adaptive immune branches. For example, in the innate response, NK-cell activity, trafficking, secretion of IFN-γ and cytotoxicity are increased.25 In the adaptive response, IFN-α influences CD8 T-cell and B-cell responses by up-regulating MHC class I and class II expression, increasing antigen presentation and increasing CD8 T-cell-mediated killing of tumour cells.26 Clinical roles Interferon-α is available in recombinant formulations and is licensed for the treatment of a number of malignancies

as well as chronic hepatitis B and C (usually in combination with ribavirin). Two types of recombinant IFN-α are widely used in oncology, IFN-α-2a and IFN-α-2b. They differ only slightly in their carbohydrate components, but no comparative data regarding toxicity or efficacy exist with regards to them, or to any of the other formulations available. Toxicities of IFN-α include flu-like symptoms, such as fever, chills, myalgia and fatigue, as well as weight loss, altered taste, depression, anaemia, leucopenia and elevated liver function test results. For many patients, the administration of IFN-α at bedtime can limit the impact of symptoms, and some adverse effects, especially the flu-like symptoms, diminish during long-term therapy. Interferon-α has been shown to induce responses in several haematological conditions,24 including hairy-cell leukaemia, multiple myeloma and chronic myeloid leukaemia (CML), but it is in its use in solid malignancies that there are significant areas of contention. Melanoma The use of IFN-α as adjuvant therapy in patients with resected melanoma at high risk of relapse has been a longrunning point of contention. An early report suggested that for patients randomized to receive low-dose IFN-α, administered for 18 months, there was evidence of significantly increased relapse-free survival (p  0.038) and a trend towards an overall survival benefit (p  0.059).27 Interferon-α was subsequently licensed for the adjuvant treatment of high-risk malignant melanoma in Europe. More recently, a systematic review of this trial plus four other published randomized trials comparing low-dose IFN-α with observation has failed to detect a statistically significant improvement in overall survival.28 For example, in the AIM HIGH study from the United Kingdom Coordinating Committee on Cancer Research, 674 patients with completely resected stage IIB and stage III cutaneous malignant melanoma were randomized to receive either low-dose IFN-α (3 MU three times per week for 2 years) or observation.29 At median follow-up of 3.1 years, no significant differences in overall survival (p  0.6) or relapse-free survival (p  0.3) were detected and it was concluded that low-dose IFN-α as adjuvant therapy could not be recommended in these circumstances. It is, however, the use of high-dose INF-α that has generated the greatest controversy. Whilst many of the published trials have produced improvements in diseasefree survival, this is at the expense of significant toxicity, and inconsistent results for overall survival benefits, particularly in three Eastern Cooperative Oncology Group (ECOG) studies, have generated extensive debate. In the first ECOG trial, 1684, 20 MU/m2 intravenous IFN-α was administered five times a week for 4 weeks, followed by maintenance with 10 MU/m2 three times a week for a further 11 months, and compared to an observation arm.30 A significant survival benefit was initially observed in the high-dose IFN-α arm, but this advantage was lost with longer follow-up. A confirmatory study, ECOG 1690, also failed to demonstrate

192 Biological therapies: cytokines and adoptive cell therapy

an improvement in overall survival.31 It was suggested that this might be a result of a significantly greater proportion of patients in the observation arm being salvaged by an IFN-containing regimen (31 per cent of recurrences versus 15 per cent in the IFN-α arm; p  0.003) or biochemotherapy (17 per cent of recurrences in the observation arm versus 6 per cent of recurrences in the IFN-α arm; p  0.013). An imbalance in the randomization arms of ECOG 1684, due to lack of stratification according to positive lymph-node number, was also cited as a possible contributory factor. A third ECOG trial, 1694, compared high-dose IFN-α with a vaccine, GM-2KLH (GM ganglioside-keyhole limpet hemocyanin).32 At a median follow-up of 2.1 years, highdose IFN-α demonstrated superiority to the GM2-KLH vaccine in terms of both overall survival (hazard ratio 1.33; p  0.04) and relapse-free survival (hazard ratio 1.33; p  0.006). This result has been interpreted as favoring high-dose IFN-α, but a commonly expressed concern is that without a no-treatment control arm the possibility of a detrimental effect of the vaccine cannot be ruled out. Several meta-analyses have been published looking at trials of IFN-α in the adjuvant setting.28,33 From their study, Wheatley and colleagues concluded that relapsefree survival was improved with IFN-α (hazard ratio for recurrence 0.83; 95% confidence interval (CI) 0.77–0.90; p  0.000003), corresponding to a 17 per cent reduction in the odds of recurrence. However, there was no clear benefit for survival (hazard ratio for mortality 0.93; 95% CI 0.85–1.02; p  0.1). Subgroup analysis indicated a significant trend for an increasing benefit of IFN with increasing dose in terms of relapse-free survival. In a recent publication, however, Verma and colleagues pooled the results from the three ECOG studies described. A meta-analysis of 2-year death rates yielded a risk ratio of 0.85 (95% CI 0.73–0.99; p  0.03). In light of this and the improvement in disease-free survival, they suggested that high-dose IFNα should be considered for patients at high risk of relapse following resection of their primary melanoma. The high cost, significant toxicity and small benefit do, however, still make the widespread adoption of high-dose IFN-α for these patients a contentious issue. Renal-cell carcinoma Interferon-α has undergone extensive clinical evaluation during the past two decades in metastatic renal-cell carcinoma. Most studies have shown modest anti-tumour activity, with objective response rates tending to be in the order of 10–15 per cent. Four randomized studies have been published in which IFN-α was compared to a non-IFN-α arm in the context of advanced renal-cell carcinoma.34–37 In the study from the Medical Research Council (MRC), 10 MU IFN-α administered subcutaneously three times a week for 12 weeks was compared to medroxyprogesterone acetate and was found to confer a survival benefit.34 Indeed, a recent Cochrane Collaboration Review has found that the response rate overall in these studies comparing IFN-α to a non-IFN-α arm was generally greater than for the control

arm and, overall, IFN-α was associated with a reduced 1-year mortality (OR (odds ratio) for death by 1 year 0.56; 95% CI 0.40–0.77).38 The weighted average median survival showed a modest improvement of 3.8 months. The relationship between improved survival and IFN-α dose or duration of therapy has not been established, but increased doses are certainly associated with more severe toxicity and are thus difficult to justify. Several studies have looked at the addition of various agents to IFN-α in an attempt to improve efficacy. These include chemotherapy (for example vinblastine), hormones, cytokines such as IL-2 or IFN-α, and other miscellaneous agents, including aspirin and cimetidine.38 Overall, there has been little evidence of a significant effect or survival benefit, although the combination of IFN-α and subcutaneous IL-2 with intravenous 5-fluorouracil (5FU) has been advanced in Europe as an active regimen in renal-cell carcinoma.39 It is currently being tested in metastatic disease in the MRC trial RE04. Whether or not there is any benefit of nephrectomy in patients with renal-cell cancer found to have metastatic disease at diagnosis has been the source of much debate over the years. Anecdotal reports have suggested that responses from immunotherapy are rare in patients who still have the primary tumour in situ. Two studies have addressed this question.40,41 In both trials, good performance status (ECOG performance status 0–1) patients were randomized to undergo nephrectomy or not prior to receiving IFN-α administered subcutaneously at a dose of 5 MU/m2 three times a week. Although response rates were low (6 per cent of patients in both studies combined), there was a significant survival benefit in the combined analysis (12.6 months versus 7.8 months with or without nephrectomy respectively), and this benefit was even more pronounced for the fittest patients. Other solid malignancies Some efficacy for IFN-α has been observed in carcinoid tumours, but evidence from randomized trials is often affected by the small sample size dictated by this rare tumour. This is illustrated by one study, which examined its use in patients with midgut carcinoid tumours with liver metastases who had undergone prior primary surgery and hepatic arterial embolization. Sixty-eight patients were randomized to receive octreotide alone or in addition to IFN-α. The results suggested a significantly reduced risk of tumour progression during follow-up for the patients who received the combination therapy (p  0.008), but failed to show a significant difference in survival.42 In another recent randomized trial, no difference was observed in the numbers of patients with disease progression at 1 year between the three treatment arms (lanreotide 1 mg three times a day versus IFN-α 5 MU three times a week versus a combination of both).43 Side effects leading to an interruption of therapy were, however, more frequent in the combination arm. There is some suggestion from small randomized studies that IFN-α in combination with induction chemotherapy

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may confer a survival advantage for limited-stage small-cell lung cancer,44 but larger studies are required to confirm this finding. In human immunodeficiency (HIV)-related Kaposi’s sarcoma, response rates to IFN-α of around 40 per cent have been demonstrated,45 but this disease is becoming rarer in the Western world, and other agents, such as liposomal doxorubicin, are now available with reduced toxicity and improved efficacy. A further indication is the use of intra-vesical IFN-α for the treatment of superficial transitional carcinoma-in-situ of the bladder. Complete response rates of 30–60 per cent with less toxicity than with the conventional intra-vesical treatment with Bacillus Calmette–Guerin (BCG) have been reported, but in a direct comparison, total number of recurrences and disease-free interval were in favour of BCG.46 Thus, whilst BCG remains the standard of care, there may be a role for intravesical IFN-α in patients who develop resistance or intolerance to BCG.

Interleukins INTERLEUKIN-2

The existence of Interleukin-2 (IL-2) was first proposed 30 years ago when it was discovered that the presence of a growth factor could induce the in-vitro proliferation of human T cells.47 The molecule, initially termed T-cell growth factor, was later isolated, cloned and subsequently designated interleukin-2.48 The biological effects of IL-2 are a result of binding to specific surface receptors. The high-affinity IL-2 receptor consists of three sub-units: α, β and γ chains. Binding of IL-2 to this receptor induces numerous downstream events, including the recruitment of kinases such as the src family member p56lck (49) and the JAK family of tyrosine kinases including JAK1, JAK2 and JAK3. In turn this leads to activation of various members of the STAT family, including STAT1, STAT3 and STAT5, in T cells.50 There are numerous consequences of this cascade of events, including proliferation, production of secondary cytokines such as IL1, IL-6 and TNF, and enhanced cytolytic activity of T cells and NK cells. Potent anti-tumour activity in vitro led to the exploration of IL-2 as an anti-cancer agent in patients with, primarily, renal-cell carcinoma and melanoma. Renal-cell carcinoma High-dose IL-2 has been used in the treatment of patients with metastatic renal-cell carcinoma for a number of years. Its approval by the Food and Drug Administration in the USA in 1992 was based on data presented on 255 patients entered into seven phase II clinical trials.51 The patients received between 600 000 and 720 000 IU/kg of recombinant human IL-2 by 15-minute infusion every 8 hours during two 5-day courses, with courses separated by 5–9 days. Treatment courses were repeated at 8–12-week intervals in responding patients. Objective responses were seen in 37 (15 per cent) of patients, with 20 partial responses (8 per cent)

and 17 complete responses (7 per cent). Whilst underwhelming in themselves, these figures belie the remarkable durability of some of the responses, particularly for those who achieved a complete response. Follow-up data published in 200252 show that although there have been some late relapses, the majority of complete responders remain in remission, and in addition four patients who achieved partial responses and subsequently underwent surgical resection of all of their residual disease remain alive and disease free. Since the response duration curve appears to have levelled off after the 30-month time point, it can be argued that these patients are unlikely to regress and may actually be cured of their metastatic disease. The widespread adoption of high-dose IL-2 as a standard therapy has been limited, not just because of the low response rates described, but also due to the significant associated toxicity. Although the side effects are limited to a few hours, due to the short half-life of IL-2, they can be severe and not infrequently require admission to an intensive care unit. They commonly include fever, chills, lethargy, diarrhoea, nausea, anaemia, thrombocytopenia, diffuse erythroderma, hepatic and renal dysfunction, and confusion. IL-2 can also cause a ‘capillary leak syndrome’, leading to fluid retention, hypotension, respiratory distress syndrome and cardiac failure. Administration of high-dose IL-2 has therefore been restricted to highly selected patients with good performance status and organ function in centres with extensive experience of this approach. In view of the significant toxicity associated with highdose IL-2, regimens using lower doses of IL-2 either alone or in combination with IFN-α have been explored. Unfortunately, these have generally produced lower response rates and reduced quality of life compared to high-dose IL-2. For example, in one study, 192 patients were randomized to receive either low-dose IL-2 (5 MU/m2 subcutaneously every 8 hours for three doses on day 1, then daily 5 days per week for 4 weeks) plus IFN-α (5 MU/m2 subcutaneously three times a week for 4 weeks) every 6 weeks or high-dose inpatient IL-2 (600 000 IU/kg per dose intravenously every 8 hours, days 1–5 and 15–19, to a maximum of 28 doses) every 12 weeks. The response rate for high-dose IL-2 was significantly higher than that for low-dose IL-2 plus IFN-α (23 per cent versus 9 per cent), and although there was no significant difference in median overall survival (17 months versus 13 months respectively; p  0.12), there appeared to be a trend towards progression-free survival at 3 years (9 patients versus 2 patients; p  0.06). Melanoma Treatment of metastatic melanoma with high-dose IL-2 can also result in durable responses. For example, in one report, a database of 270 patients treated with high-dose IL-2 between 1985 and 1993 was analysed.53 The overall objective response rate was found to be 16 per cent, with 17 patients achieving complete response (CR) (6 per cent) and 26 patients with partial response (PR) (10 per cent). Ten of the patients with CR remained disease free, and disease

194 Biological therapies: cytokines and adoptive cell therapy

did not progress in any patient responding for more than 30 months. However, unsurprisingly, severe toxicity was reported and 6 patients died (2 per cent) as a result of sepsis. This, combined with the lack of randomized controlled trials, means that, as with renal-cell carcinoma, the use of highdose IL-2 is restricted to selected centres.54

Tumour necrosis factor For many years it has been observed that patients with serious pyogenic infections could undergo spontaneous regressions of their tumours. This observation led to the hypothesis that, as a consequence of these infections, a substance might be released that has the ability to provoke tumour cell death. During the 1970s it was indeed shown that a circulating factor induced by bacterial infection had anti-tumour activity in animal experiments.55 This molecule, now known as TNF-α, was isolated and cloned in 198456 and was found to be a member of a family of molecules, known as the TNF superfamily. Unfortunately, clinical trials with systemic administration of recombinant human TNF-α failed to demonstrate significant clinical benefit due to the development of dose-limiting toxicity at levels well below those required for therapeutic effect.57 Isolated limb perfusion has, however, been successfully applied to the local administration of TNF-α and is discussed in more detail below.

rates and palliation from IPL are impressive, information regarding any survival benefit is limited, and many questions remain with regard to dosing and optimal combinations of agents.60 DIRECT TUMOUR INJECTION OF CYTOKINES

Intra-lesional therapy is another approach aimed at delivering cytokines to the local tumour environment. Various cytokines have been investigated, including IFN-α, IFN-β, granulocyte–macrophage colony-stimulating factor (GMCSF) and IL-2. IL-2 in particular has met with some success. For example, in a phase II trial of 24 patients with American Joint Committee on Cancer (AJCC) stage III or IV melanoma, Radny and colleagues injected a total of 245 metastases with IL-2 and achieved CR in 209 (85 per cent) lesions and PR in 21 (9 per cent) lesions.61 The treatment was well tolerated, and biopsies from metastases showed a dense intra-tumoral and peri-tumoral lymphocyte infiltrate surrounding and infiltrating areas of necrotic tumour cells. One potential drawback of injection with cytokines is their short half-life, and approaches that have been explored to address this include the injection of pegylated IL-262 and the intra-tumoral injection of recombinant viral vectors coding for cytokines such as IFN-γ.63

Cytokines in vaccine strategies Local administration of cytokines A number of therapeutic strategies have been developed in an attempt to reduce the systemic toxicity commonly seen with cytokine administration. ISOLATED LIMB PERFUSION

This technique allows elevated concentration of the drugs to the isolated extremity without general systemic exposure and its associated toxicities. The therapeutic mechanism of TNF-α in ILP appears to involve destruction of endothelial cells and vasculature of tumours rather than direct killing of tumour cells.58 Subsequent augmented tissue penetration of chemotherapeutic agents such as melphalan explains the synergism observed when used in combination with TNF-α. Multiple clinical trials have shown that ILP, with or without other agents, including melphalan and TNF-γ, can achieve response rates of more than 70 per cent in patients suffering from stages IIIAB and IIIB (in-transit metastases) malignant melanoma.22 In a multi-centre European study of 186 patients with soft-tissue sarcomas that would have normally required limb amputation, there was a 29 per cent (54 patients) CR rate with ILP, and 82 per cent of patients (152) underwent limb salvage surgery.59 Whilst the response

Vaccines are discussed in more detail in Chapter 8, but it is noteworthy that vaccines that incorporate the expression of cytokines are showing particular promise.64–66 For example, in one study, 21 patients with relapsed or refractory neuroblastoma received up to eight subcutaneous injections of a vaccine combining lymphotactin-secreting and IL-2-secreting allogeneic neuroblastoma cells.65 Immunological responses included significant increases of circulating CD4 T cells, NK cells, IL-5 and immunoglobulin G (IgG) antibodies that bound to the immunizing cell line. Clinical responses were also observed, including two complete responses. Systemic cytokines have also been administered in conjunction with vaccination, with some evidence of success. For example, IL-2 has been reported to increase the tumour response rate to melanoma vaccines,67 and IL-12 has also been tested in pre-clinical and clinical studies on cancer vaccination, with encouraging preliminary results.68

ADOPTIVE CELL THERAPY Adoptive cell therapy involves isolation, sensitization or activation of autologous or allogeneic cells in vitro followed by re-infusion into the patient. Host immunity is stimulated in an attempt to overcome the natural tolerance to

Adoptive cell therapy 195

the established tumour. The basic principle was developed by Borberg and co-workers in 1972, who showed that the intravenous injection of lymph-node cells from mice and sheep immunized with a chemically induced tumour induced regression or inhibition of established grafts of the same tumour in syngeneic mice.69 The power of adoptive cell therapy in the allogeneic setting has been clearly demonstrated in patients with relapsed leukaemia following bone-marrow transplantation through the use of donor lymphocyte infusions (DLIs). Lymphocytes isolated from the allogeneic donor and infused into the patient are thought to respond to tumour through MHC mismatches (either major or minor MHC mismatches) and consequently to eliminate tumour through a graft-versusleukaemic (GVL) effect. However, by the same process, they can also be destructive to healthy host tissue. This unwanted side effect, graft-versus-host disease (GVHD), is associated with high rates of morbidity and mortality. T cells are the critical component, as their depletion from the DLIs abrogates both GVL and GVHD effects. In the autologous setting, a number of effector cells have been investigated for use in adoptive cell therapy. Early strategies, for example the use of lymphokine-activated killer (LAK) cells, concentrated on non-antigen-specific cytotoxicity. In recent years, however, the resurgence in interest in adoptive cell therapy has been focused on targeting specific tumour antigens. Various strategies are under development, but common to all of them are a number of obstacles that must be overcome if adoptive cell therapy is to be accepted as part of mainstream clinical practice. These approaches, as well as some the most promising innovations in the field, are discussed below.

Lymphokine-activated killer cells Animal models have shown that if lymphocytes are expanded and activated in vitro with IL-2 and then returned to the host with intravenous IL-2, they can kill tumour cells. The cells responsible for this MHC-unrestricted killing in response to IL-2 have been termed lymphokine-activated killer cells. They display a wide spectrum of cytotoxicity and have been used clinically by adoptive transfer in conjunction with high-dose infusional IL-2. However, a randomized trial of IL-2 plus LAK infusion versus IL-2 alone failed to demonstrate either a significantly higher response rate (27 per cent versus 18 per cent; two-sided p value [p2]  0.16) or significant survival benefit (36-month actuarial survival 31 per cent versus 17 per cent; p2  0.089).70 Any trend towards response rate or survival was at the expense of unacceptably severe systemic toxicity that was attributed to the IL-2 therapy, and the treatment is also expensive in terms of infrastructure and man-hours. A number of further studies failed to capitalize, and the emphasis in this field has since shifted to targeting specific tumour antigens and defining effector-cell populations more accurately.

T cells for Epstein–Barr virus-induced malignancies Epstein–Barr virus (EBV) infection can result in malignant transformation of infected B cells leading to EBV-related lymphoproliferation and is also associated with other malignancies such as Hodgkin’s lymphoma and nasopharyngeal cancer. The EBV is highly immunogenic, and specific T cells, which can recognize EBV-infected cells but do not crossreact with normal cells, can be generated with relative ease. These features make EBV-related malignancies a suitable test for adoptive immunotherapy. Encouragingly, the EBV specific T cells can have remarkable effects against EBVrelated malignancies in the post-allogeneic transplant setting71 and can persist for some time, producing long-lasting immune control.72 Such cells can also be used in the nontransplant setting and have been shown to have beneficial effects on patients with Hodgkin’s lymphoma73 and nasopharyngeal cancer.74 The encouraging successes of EBV-specific T cells in the therapy of malignant disease have promoted the application of T-cell therapy in other diseases (see below) and have also stimulated the exploration of ways to simplify this approach. One such means of simplifying therapy is to have a ‘bank’ of specific cells that can be HLA matched and used as ‘off the shelf’ therapy for appropriate individuals. Initial evaluation of this approach is promising, and further testing is on-going.75

Tumour-infiltrating lymphocytes Tumour-infiltrating lymphocytes (TILs) are cells that infiltrate into the stroma of tumours. They provided evidence of the existence of tumour antigen-specific T cells when MHC-restricted TILs were isolated from melanoma biopsy samples.76 In an early trial using adoptively transferred TILs, cloned melanoma-reactive T cells were given to patients with metastatic melanoma.77 Despite the transferred cells being highly reactive against melanoma antigens, no objective responses were seen. In murine models, prior host immunosuppression has been shown to improve the antitumour effects of adoptively transferred cells.78 Further benefits can be gained by the systemic administration of cytokines such as IL-2. Thus, in a second trial carried out by the same group, patients were pre-treated with escalating doses of non-myeloablative, lympho-depleting chemotherapy prior to receiving cloned TILs and IL-2.79 The final cohort of patients received cyclophosphamide (60 mg/kg for 2 days) and fludarabine (25 mg/m2 for 5 days) and IL-2 (720 000 U/kg every 8 hours up to 15 doses) in conjunction with cell transfer. Disappointingly, no objective responses were found and in-vivo persistence of the TILs was so poor that transferred clones could not be detected in the peripheral blood 2 weeks after administration. It was hypothesized that the absence of CD4 helper cells within the transferred CD8 cloned populations may have limited their in-vivo activation and persistence. Thus

196 Biological therapies: cytokines and adoptive cell therapy

the protocol was modified to administer populations of TILs including both CD8 and CD4 cells that were selected for being highly reactive against melanoma antigens, but were not cloned. This also had the advantage of reducing the intensity of the ex-vivo stimulation and expansion process, with the aim of adoptively transferring cells with an improved activity and proliferation potential. The results of a study involving 35 patients with metastatic melanoma who received TILs expanded in this way in conjunction with the previously described lympho-depleting chemotherapy and IL-2 was recently published.80 The patients had bulky metastatic melanoma affecting multiple organs that was refractory to standard treatments, including chemotherapy, radiation and cytokine therapies. Eighteen out of these 35 patients (51%) had an objective response, including 4 complete responses (11%). Of note was the fact that response strongly correlated with persistence of administered anti-tumour T cells, and in some cases this translated to 70–80 per cent of peripheral blood lymphocytes for longer than 4 months. Clinical responses were also associated in some cases with the development of autoimmune phenomena such as vitiligo and uveitis. This probably reflects the shared expression by normal tissues of the relevant TAA. The autoimmunity observed in this trial was of relatively minor clinical significance, but it may be a major limitation in other trials in which other TAAs are targeted if autoimmunity is more widespread or difficult to control. This trial clearly represents a significant advance in adoptive cell therapy, although it remains to be seen whether the excellent response rate demonstrated can be maintained when this therapy is transferred to other centres around the world. Furthermore, TIL therapy has a number of limitations: TILs are only present in significant numbers in a few tumour types, primarily melanoma and renal-cell carcinoma; selection relies on reactivity to, and hence the knowledge of, specific tumour antigens; and to obtain sufficient numbers of cells there must be tumour that is amenable to surgical removal to isolate the TILs. Despite these limitations, the dramatic results from these trials clearly warrant further evaluation through multi-centre clinical trials.

Genetically engineered T cells In view of the difficulties in developing TIL therapy for a broad range of tumour types, researchers are actively investigating more generally applicable adoptive cell therapy strategies. The advent of effective methods for gene transfer into T cells provides a means for creating T cells that are specific for a defined tumour antigen.81 Retroviral vectors are the most commonly used systems for gene transfer, but other approaches, including adenoviral, lentiviral and nonviral systems, are also under development. Broadly speaking, these genetically engineered T cells can be divided into two groups: T cells expressing physiological T-cell receptors (TCRs) and T cells expressing chimeric immune receptors (CIRs).

T CELLS EXPRESSING PHYSIOLOGICAL T-CELL RECEPTORS

T-cell specificity is mediated through the TCR, a heterodimer made up of an α-chain and a β-chain. The TCR chains specific for a chosen target antigen can be molecularly cloned using polymerase chain reaction (PCR)-based methods and introduced into T cells by gene transfer. A number of tumour antigens are under investigation for targeting in this way, including the melanoma tumour antigens MART1 and MAGE-A1, p53 and MDM2.81 This approach, however, has a number of potential limitations, not least the fact that the ability of the TCR to recognize a tumour cell is HLA restricted. Thus a different TCR must be used to recognize an antigen in each HLA background. In addition, tumours can escape T-cell recognition by down-regulating expression of the HLA class I molecules on their cell surface. A further concern is the risk that TCR transduction could lead to the formation of hybrid TCRs between the transduced and endogenous αchains and β-chains, leading to novel specificity with the potential for autoimmunity. Recent work has investigated engineering the transferred TCR in such a way that it is not possible for it to pair with the endogenous chains.82 T CELLS EXPRESSING CHIMERIC IMMUNE RECEPTORS

In 1989 it was demonstrated that T cells can respond to antigen independently of the TCR–MHC interaction when transduced with a CIR.83 Many different varieties of CIRs have been developed and described,84 but the basic configuration consists of an extracellular antigen-binding motif (most commonly an scFv antibody fragment) fused to a signalling moiety (most commonly the CD3ζ chain of the TCR) by means of a transmembrane domain. Antigen recognition is thus directed to native cell-surface structures and is not MHC restricted, unlike the physiological TCR.

Future development of adoptive cell therapy Currently, adoptive cell therapy is attractive and appears clinically promising. Trials are underway involving both CIR-transduced and TCR-transduced T cells in various tumour types. Figure 9.3 summarizes the principal steps involved in adoptive cell therapy, but there are numerous aspects in the process that require optimization. CELL GROWTH

The optimal dose of cells for adoptive therapy is likely to vary according to clinical target and cell type being used. However, in many instances the numbers of cells required will necessitate a period of ex-vivo expansion. This process can be expensive, labour intensive and require specialist facilities that comply with ‘Good Manufacturing Practice’ (GMP). Where peripheral blood T cells are being used for adoptive transfer, it may also be complicated by the fact

Adoptive cell therapy 197

a

e

b

f

g

c

d

Figure 9.3 Adoptive cell therapy strategy. Suitable patient with malignancy is identified (a). Lymphocytes are isolated for example by leukapheresis or from a biopsy sample (b). The cells are modified for example by transduction with a retroviral vector that encodes a TAA specific TCR (c). The transduced cells are expanded ex vivo (d). Meanwhile remaining in vivo lymphocytes (including regulatory T cells) are eliminated from the patient for example by using non-myeloablative conditioning chemotherapy (e). The modified lymphocytes are infused back into the patient (f) and cytokine IL-2 ‘support’ therapy is given to support the further in vivo expansion of the adopted modified lymphocytes (g).

that patients with advanced malignancy are likely to have depleted T-cell pools as a result of heavy pre-treatment, making isolation and expansion more difficult. Current clinical protocols for T-cell expansion involve the initial stimulation of the cells with antibodies, often followed by transduction, then subsequent IL-2-driven expansion. While relatively simple and effective in terms of the number of cells generated, these conditions may not be optimal, for example CD4:CD8 T-cell subset ratios can be altered, with greater numbers of CD8 T cells being generated, and T-cell functionality may be adversely affected by prolonged ex-vivo expansion. Certainly it appears important not to ‘exhaust’, the proliferative cell’s potential during the expansion process, as telomere length appears to correlate with invivo persistence.85 The use of artificial APCs86 and limiting time in culture may be ways to achieve this. Other areas of active interest include optimization of the cytokine growth media, and there are already encouraging data for the use of IL-15.87–89 It is also possible to introduce cytokine genes into T cells to facilitate growth.90,91 CELL SELECTION

Greater understanding of the immune system also reveals the potential for cell selection prior to expansion or gene modification. Certainly the importance of Treg cells in cancer is being increasingly recognized,92 and using methods

to deplete these cells before use in adoptive transfer may be beneficial.93 ENGRAFTMENT AND CELL SURVIVAL

Several factors limit the survival of adoptively transferred cells in vivo, including host regulatory immune forces. Importantly, there is increasing evidence to support the use of lympho-depleting chemotherapy prior to adoptive cell therapy in enabling engraftment and rapid homeostatic expansion of adoptively transferred cells. Notable success with regard to this has been achieved by Rosenberg and colleagues in the treatment of patients with metastatic melanoma using TIL therapy as described above.79,80,94 Invivo expansion and persistence may also be aided by more stringent myelosuppression than that currently used – certainly this is the case in animal models.95 ENGINEERING CELLS FOR OPTIMAL FUNCTION

Current trials of gene-modified cells use ‘first-generation’ receptors as described above. A ‘second generation’ of receptors is now being developed which incorporate important co-stimulatory molecules. The rationale behind this is that, in addition to antigen-specific signals resulting from interaction TCR with peptide – MHC complexes (signal 1), T cells receive additional signals from cell surface molecules

198 Biological therapies: cytokines and adoptive cell therapy

known as co-stimulatory molecules (signal 2). These act to enhance and fine-tune the effector functions of the T cell as well as influencing the survival of the activated T cell. Of the pathways studied to date, the CD28-B7 pathway is the best characterized. Similar to engineering the ‘signal 1’ pathway, the CD28 pathway can also be engineered.96 A further enhancement is to include two signals (both CD3ζ and CD28) in one molecule, and certainly such receptors are more active in animal models.97 Other approaches include the manipulation of the apoptotic pathways to avoid premature apoptosis of transferred cells by introducing antiapoptotic genes such as Bcl-XL or Bcl-2.98,99 The clinical application of these possible advances remains to be established, as associated with a greater signalling power is the potential for deleterious effects such as non-specific activation and increased risk of malignancy, as was seen in gene therapy trials for SCID.100 Reassuringly, to date, gene therapy using gene transfer into differentiated T cells appears to have a better safety profile than transfer into stem cells. Several gene-marking studies have been published using retroviral vectors to transduce either TILs or mature peripheral T cells. Longterm follow-up of these patients has not shown any evidence of oncogenesis.101 However, monitoring of patients for any indication of clonal expansion is clearly appropriate for all current trials of adoptive cell therapy. In addition, researchers are actively pursuing ways to enhance the safety of vectors by engineering in ‘suicide’ genes into them. The expression of these ‘suicide’ genes can be induced if required and result either in the death of genetically modified cells,102 or control of the expression of the vector.103

as macrophages or NK cells. Certainly the Fc receptors on macrophages can be engineered in similar ways,104 and it is also possible to engineer stem cells and thus multiple effector arms.105 Overall, the possibilities for developing such cellular therapies are enormous, but they remain complex and will require careful clinical testing in expert centres if the potential is to be realized.

REFERENCES ◆1

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ENGINEERING OTHER CELLS IN THE IMMUNE SYSTEM

To date, the major focus has been on T-cell adoptive transfer. However, the same processes can, in principle, be applied to other effector cells in the immune system such

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Immunotherapies in the form of cytokines or adoptive cell therapy can overcome tolerance to tumours. Interferon-α is used particularly in melanoma and renal-cell carcinoma, but controversy still surrounds the use of high-dose IFN-α in resected melanoma at high risk of relapse. Although high-dose IL-2 is toxic, it is associated with rare, but durable, complete remissions, even in patients with metastatic disease. Many other cytokines are showing promise in their development for clinical applications. Adoptive cell therapy is a complex approach, but recent successes make it an attractive target for further development.

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Dunn GP, Bruce AT, Ikeda H, et al. Cancer immunoediting: from immunosurveillance to tumor escape. Nat Immunol 2002; 3(11):991–8. Stern PL, Beverley PLC, Carroll MW. Cancer Vaccines and Immunotherapy. Cambridge: Cambridge University Press, 2000. Hanahan D, Weinberg RA. The hallmarks of cancer. Cell 2000; 100(1):57–70. Preuss KD, Zwick C, Bormann C, et al. Analysis of the B-cell repertoire against antigens expressed by human neoplasms. Immunol Rev 2002; 188:43–50. Dermime S, Armstrong A, Hawkins RE, Stern PL. Cancer vaccines and immunotherapy. Br Med Bull 2002; 62:149–62. Matzinger P. The danger model: a renewed sense of self. Science 2002; 296(5566):301–5. Kelsall BL, Biron CA, Sharma O, Kaye PM. Dendritic cells at the host–pathogen interface. Nat Immunol 2002; 3(8):699–702. Kalinski P, Hilkens CM, Wierenga EA, Kapsenberg ML. T-cell priming by type-1 and type-2 polarized dendritic cells: the concept of a third signal. Immunol Today 1999; 20(12):561–7. Zhang L, Conejo-Garcia JR, Katsaros D, et al. Intratumoral T cells, recurrence, and survival in epithelial ovarian cancer. N Engl J Med 2003; 348(3):203–13. Khong HT, Restifo NP. Natural selection of tumor variants in the generation of ‘tumor escape’ phenotypes. Nat Immunol 2002; 3(11):999–1005. Cabrera T, Lopez-Nevot MA, Gaforio JJ, et al. Analysis of HLA expression in human tumor tissues. Cancer Immunol Immunother 2003; 52(1):1–9. Orange JS, Fassett MS, Koopman LA, et al. Viral evasion of natural killer cells. Nat Immunol 2002; 3(11):1006–12. Von Boehmer H. Mechanisms of suppression by suppressor T cells. Nat Immunol 2005; 6(4):338–44. Curiel TJ, Coukos G, Zou L, et al. Specific recruitment of regulatory T cells in ovarian carcinoma fosters immune privilege and predicts reduced survival. Nat Med 2004; 10(9):942–9. Ichihara F, Kono K, Takahashi A, et al. Increased populations of regulatory T cells in peripheral blood and tumor-infiltrating lymphocytes in patients with gastric and esophageal cancers. Clin Cancer Res 2003; 9(12): 4404–8.

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gastroenteropancreatic tumors – the International Lanreotide and Interferon Alfa Study Group. J Clin Oncol 2003; 21(14):2689–96. Prior C, Oroszy S, Oberaigner W, et al. Adjunctive interferon-alpha-2c in stage IIIB/IV small-cell lung cancer: a phase III trial. Eur Respir J 1997; 10(2):392–6. Real FX, Oettgen HF, Krown SE. Kaposi’s sarcoma and the acquired immunodeficiency syndrome: treatment with high and low doses of recombinant leukocyte A interferon. J Clin Oncol 1986; 4(4):544–51. Jimenez-Cruz JF, Vera-Donoso CD, Leiva O, et al. Intravesical immunoprophylaxis in recurrent superficial bladder cancer (Stage T1): multicenter trial comparing bacille Calmette–Guerin and interferon-alpha. Urology 1997; 50(4):529–35. Morgan DA, Ruscetti FW, Gallo R. Selective in vitro growth of T lymphocytes from normal human bone marrows. Science 1976; 193(4257):1007–8. Taniguchi T, Matsui H, Fujita T, et al. Structure and expression of a cloned cDNA for human interleukin-2. Nature 1983; 302(5906):305–10. Hatakeyama M, Kono T, Kobayashi N, et al. Interaction of the IL-2 receptor with the src-family kinase p56lck: identification of novel intermolecular association. Science 1991; 252(5012):1523–8. Leonard WJ, O’Shea JJ. Jaks and STATs: biological implications. Annu Rev Immunol. 1998; 16:293–322. Fyfe G, Fisher RI, Rosenberg SA, et al. Results of treatment of 255 patients with metastatic renal cell carcinoma who received high-dose recombinant interleukin-2 therapy. J Clin Oncol 1995; 13(3):688–96. McDermott DF, Atkins MB. Application of IL-2 and other cytokines in renal cancer. Expert Opin Biol Ther 2004; 4(4):455–68. Atkins MB, Lotze MT, Dutcher JP, et al. High-dose recombinant interleukin 2 therapy for patients with metastatic melanoma: analysis of 270 patients treated between 1985 and 1993. J Clin Oncol 1999; 17(7):2105–16. Tsao H, Atkins MB, Sober AJ. Management of cutaneous melanoma. N Engl J Med 2004; 351(10):998–1012. Carswell EA, Old LJ, Kassel RL, et al. An endotoxin-induced serum factor that causes necrosis of tumors. Proc Natl Acad Sci U S A 1975; 72(9):3666–70. Pennica D, Nedwin GE, Hayflick JS, et al. Human tumour necrosis factor: precursor structure, expression and homology to lymphotoxin. Nature 1984; 312(5996):724–9. Jones AL, Selby P. Tumour necrosis factor: clinical relevance. Cancer Surv 1989; 8(4):817–36. Renard N, Lienard D, Lespagnard L, et al. Early endothelium activation and polymorphonuclear cell invasion precede specific necrosis of human melanoma and sarcoma treated by intravascular high-dose tumour necrosis factor alpha (rTNF alpha). Int J Cancer 1994; 57(5):656–63. Eggermont AM, Schraffordt Koops H, Klausner JM, et al. Isolated limb perfusion with tumor necrosis factor and melphalan for limb salvage in 186 patients with locally

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advanced soft tissue extremity sarcomas. The cumulative multicenter European experience. Ann Surg 1996; 224(6):756–64; Discussion 764–5. Bonvalot S, Laplanche A, Lejeune F et al. Limb salvage with isolated perfusion for soft tissue sarcoma: could less TNF-alpha be better? Ann Oncol 2005; 16(7):1061–8. Radny P, Caroli UM, Bauer J, et al. Phase II trial of intralesional therapy with interleukin-2 in soft-tissue melanoma metastases. Br J Cancer 2003; 89(9):1620–6. Kaplan B, Moy RL. Effect of perilesional injections of PEG-interleukin-2 on basal cell carcinoma. Dermatol Surg 2000; 26(11):1037–40. Dummer R, Hassel JC, Fellenberg F, et al. Adenovirusmediated intralesional interferon-gamma gene transfer induces tumor regressions in cutaneous lymphomas. Blood 2004; 104(6):1631–8. Osanto S, Schiphorst PP, Weijl NI, et al. Vaccination of melanoma patients with an allogeneic, genetically modified interleukin 2-producing melanoma cell line. Hum Gene Ther 2000; 11(5):739–50. Rousseau RF, Haight AE, Hirschmann-Jax C, et al. Local and systemic effects of an allogeneic tumor cell vaccine combining transgenic human lymphotactin with interleukin-2 in patients with advanced or refractory neuroblastoma. Blood 2003; 101(5):1718–26. Nemunaitis J, Sterman D, Jablons D, et al. Granulocyte–macrophage colony-stimulating factor genemodified autologous tumor vaccines in non-small-cell lung cancer. J Natl Cancer Inst 2004; 96(4):326–31. Lotem M, Shiloni E, Pappo I, et al. Interleukin-2 improves tumour response to DNP-modified autologous vaccine for the treatment of metastatic malignant melanoma. Br J Cancer 2004; 90(4):773–80. Portielje JE, Kruit WH, Eerenberg AJ, et al. Subcutaneous injection of interleukin 12 induces systemic inflammatory responses in humans: implications for the use of IL-12 as vaccine adjuvant. Cancer Immunol Immunother 2005; 54(1):37–43. Borberg H, Oettgen HF, Choudry K, Beattie EJ Jr. Inhibition of established transplants of chemically induced sarcomas in syngeneic mice by lymphocytes from immunized donors. Int J Cancer 1972; 10(3):539–47. Rosenberg SA, Lotze MT, Yang JC, et al. Prospective randomized trial of high-dose interleukin-2 alone or in conjunction with lymphokine-activated killer cells for the treatment of patients with advanced cancer. J Natl Cancer Inst 1993; 85(8):622–32. Heslop HE, Brenner MK, Rooney CM. Donor T cells to treat EBV-associated lymphoma. N Engl J Med 1994; 331(10):679–80. Heslop HE, Ng CY, Li C, et al. Long-term restoration of immunity against Epstein–Barr virus infection by adoptive transfer of gene-modified virus-specific T lymphocytes. Nat Med 1996; 2(5):551–5. Bollard CM, Aguilar L, Straathof KC, et al. Cytotoxic T lymphocyte therapy for Epstein–Barr virus  Hodgkin’s disease. J Exp Med 2004; 200(12):1623–33.

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74 Straathof KC, Bollard CM, Popat U, et al. Treatment of nasopharyngeal carcinoma with Epstein–Barr virus-specific T lymphocytes. Blood 2005; 105(5):1898–904. 75 Haque T, Wilkie GM, Taylor C, et al. Treatment of Epstein–Barr-virus-positive post-transplantation lymphoproliferative disease with partly HLA-matched allogeneic cytotoxic T cells. Lancet 2002; 360(9331):436–42. 76 Hom SS, Topalian SL, Simonis T, et al. Common expression of melanoma tumor-associated antigens recognized by human tumor infiltrating lymphocytes: analysis by human lymphocyte antigen restriction. J Immunother 1991; 10(3):153–64. 77 Dudley ME, Wunderlich J, Nishimura MI, et al. Adoptive transfer of cloned melanoma-reactive T lymphocytes for the treatment of patients with metastatic melanoma. J Immunother 2001; 24(4):363–73. 78 North RJ. Cyclophosphamide-facilitated adoptive immunotherapy of an established tumor depends on elimination of tumor-induced suppressor T cells. J Exp Med 1982; 155(4):1063–74. 79 Dudley ME, Wunderlich JR, Yang JC, et al. A phase I study of nonmyeloablative chemotherapy and adoptive transfer of autologous tumor antigen-specific T lymphocytes in patients with metastatic melanoma. J Immunother 2002; 25(3):243–51. ●80 Rosenberg SA, Dudley ME. Cancer regression in patients with metastatic melanoma after the transfer of autologous antitumor lymphocytes. Proc Natl Acad Sci U S A 2004; 101(Suppl. 2):14639–45. ◆81 Sadelain M, Riviere I, Brentjens R. Targeting tumours with genetically enhanced T lymphocytes. Nat Rev Cancer 2003; 3(1):35–45. 82 Willemsen RA, Weijtens ME, Ronteltap C, et al. Grafting primary human T lymphocytes with cancer-specific chimeric single chain and two chain TCR. Gene Ther 2000; 7(16):1369–77. ●83 Gross G, Waks T, Eshhar Z. Expression of immunoglobulin–T-cell receptor chimeric molecules as functional receptors with antibody-type specificity. Proc Natl Acad Sci U S A 1989; 86(24):10024–8. 84 Thistlethwaite F, Mansoor W, Gilham DE, Hawkins RE. Engineering T-cells with antibody-based chimeric receptors for effective cancer therapy. Curr Opin Mol Ther 2005; 7(1):48–55. 85 Zhou J, Shen X, Huang J, et al. Telomere length of transferred lymphocytes correlates with in vivo persistence and tumor regression in melanoma patients receiving cell transfer therapy. J Immunol 2005; 175(10):7046–52. 86 Kim JV, Latouche JB, Riviere I, Sadelain M. The ABCs of artificial antigen presentation. Nat Biotechnol 2004; 22(4):403–10. 87 Brentjens RJ, Latouche JB, Santos E, et al. Eradication of systemic B-cell tumors by genetically targeted human T lymphocytes co-stimulated by CD80 and interleukin-15. Nat Med 2003; 9(3):279–86.

88 Klebanoff CA, Finkelstein SE, Surman DR, et al. IL-15 enhances the in vivo antitumor activity of tumor-reactive CD8 T cells. Proc Natl Acad Sci U S A 2004; 101(7):1969–74. 89 Teague RM, Sather BD, Sacks JA, et al. Interleukin-15 rescues tolerant CD8() T cells for use in adoptive immunotherapy of established tumors Nat Med 2006; 12(3):335–41. 90 Hsu C, Hughes MS, Zheng Z, et al. Primary human T lymphocytes engineered with a codon-optimized IL-15 gene resist cytokine withdrawal-induced apoptosis and persist long-term in the absence of exogenous cytokine. J Immunol 2005; 175,(11):7226–34. 91 Liu K, Rosenberg SA. Transduction of an IL-2 gene into human melanoma-reactive lymphocytes results in their continued growth in the absence of exogenous IL-2 and maintenance of specific antitumor activity. J Immunol 2001; 167(11):6356–65. ◆92 Zou W. Regulatory T cells, tumour immunity and immunotherapy. Nat Rev Immunol 2006; 6(4):295–307. 93 Powell DJ Jr, Parker LL, Rosenberg SA. Large-scale depletion of CD25 regulatory T cells from patient leukapheresis samples. J Immunother 2005; 28(4):403–11. ●94 Dudley ME, Wunderlich JR, Robbins PF, et al. Cancer regression and autoimmunity in patients after clonal repopulation with antitumor lymphocytes. Science 2002; 298(5594):850–4. 95 Gattinoni L, Finkelstein SE, Klebanoff CA, et al. Removal of homeostatic cytokine sinks by lymphodepletion enhances the efficacy of adoptively transferred tumorspecific CD8 T cells. J Exp Med 2005; 202(7):907–12. 96 Alvarez-Vallina L, Hawkins RE. Antigen-specific targeting of CD28-mediated T cell co-stimulation using chimeric single-chain antibody variable fragment-CD28 receptors. Eur J Immunol 1996; 26(10):2304–9. 97 Haynes NM, Trapani JA, Teng MW, et al. Single-chain antigen recognition receptors that costimulate potent rejection of established experimental tumors. Blood 2002; 100(9):3155–63. 98 Eaton D, Gilham DE, O’Neill A, Hawkins RE. Retroviral transduction of human peripheral blood lymphocytes with Bcl-X(L) promotes in vitro lymphocyte survival in proapoptotic conditions. Gene Ther 2002; 9(8):527–35. 99 Charo J, Finkelstein SE, Grewal N, et al. Bcl-2 overexpression enhances tumor-specific T-cell survival. Cancer Res 2005; 65(5):2001–8. 100 Hacein-Bey-Abina S, von Kalle C, Schmidt M, et al. A serious adverse event after successful gene therapy for X-linked severe combined immunodeficiency. N Engl J Med 2003; 348(3):255–6. 101 Recchia A, Bonini C, Magnani Z, et al. Retroviral vector integration deregulates gene expression but has no consequence on the biology and function of transplanted T cells. Proc Natl Acad Sci U S A 2006; 103(5):1457–62. 102 Straathof KC, Pule MA, Yotnda P, et al. An inducible caspase 9 safety switch for T-cell therapy. Blood 2005; 105(11):4247–54.

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103 Alvarez-Vallina L, Agha-Mohammadi S, Hawkins RE, Russell SJ. Pharmacological control of antigen responsiveness in genetically modified T lymphocytes. J Immunol 1997; 159(12):5889–95. 104 Biglari A, Southgate TD, Fairbairn LJ, Gilham DE. Human monocytes expressing a CEA-specific chimeric CD64

receptor specifically target CEA-expressing tumour cells in vitro and in vivo. Gene Ther 2006; 13(7):602–10. 105 Hege KM, Cooke KS, Finer MH, et al. Systemic T cellindependent tumor immunity after transplantation of universal receptor-modified bone marrow into SCID mice. J Exp Med 1996; 184(6):2261–9.

10 Radioimmunotherapy TIM ILLIDGE AND MIKE BAYNE

The principles of radioimmunotherapy Radioimmunotherapy for lymphoma Radioimmunotherapy in leukaemias

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THE PRINCIPLES OF RADIOIMMUNOTHERAPY Introduction The use of monoclonal antibody (mAb) in routine clinical practice is now well established and has led to significant improvements in outcome for patients with haematological malignancies as well as in a wide range of other malignancies, including breast and bowel cancer.1,2 Although the single-agent activity of most mAb has been modest, when used in combination with other anti-tumour therapies, an additive or synergistic effect has been seen.3 The combination of mAb and multi-agent chemotherapy in a number of different histologies of non-Hodgkin’s lymphoma (NHL) has led not only to highly impressive increases in response rates, but also to improved relapsefree survival and even overall survival.3,4 Radioimmunotherapy (RIT) is the administration of therapeutic radioisotopes targeted to tumour through chemical conjugation to mAb or mAb-derived constructs. Monoclonal antibodies were initially regarded simply as direct carriers for the radioisotope that delivers systemically targeted cytotoxic radiation to areas of disease with relative sparing of normal tissue. It is, however, becoming clear that during RIT for lymphoma, the mAb effector mechanisms may also play an important additional role in killing tumour cells. The nature of RIT determines that its efficacy depends on a number of factors, including the properties of the targeted antigen (specificity, density, availability, shedding and heterogeneity of expression), the tumour (volume, degree of vascularization, blood flow and permeability), the mAb (specificity, immunoreactivity, stability and affinity) and the

Radioimmunotherapy for solid tumours Clinical perspectives for the next five years References

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properties of the chosen radioisotope (emission characteristics, half-life and availability).5 A wide variety of different mAbs, delivery schedules, radioisotopes and doses of radioactivity have been used in RIT, and the most impressive results have been achieved in the treatment of NHL.6 Two drugs, namely yttrium-90ibritumomab tiuxetan and iodine-131-tositumomab, have been approved by the US Food and Drug Administration (FDA). Yttrium-90-ibritumomab tiuxetan is also approved for use within the European Union (EU). The use of RIT in leukaemias and solid tumours is less well developed, but the emerging data look highly encouraging, suggesting that RIT may also play a useful role in these malignancies. This chapter focuses on the current clinical indications for radioimmunoconjugates in NHL and provides an overview of the current clinical data related to the use RIT in other malignancies.

Antigen targeting The use of radiation therapy in the treatment of malignancy is well established and often highly effective for localized disease. The disseminated nature of many malignancies frequently prevents effective delivery of external-beam radiotherapy. The systemic delivery of radiation through RIT enables irradiation of tumour cells throughout the body whilst minimizing the dose to normal tissues and is a logical strategy that is showing great promise for the treatment of the exquisitely radiosensitive lymphomas and leukaemias. The effective delivery of RIT requires the selection of a suitable tumour-antigen target.

204 Radioimmunotherapy

Tumour-specific antigens (Box 10.1) would be the ideal targets for RIT, but such a degree of specificity is unusual. In practice, tumour-associated antigens, expressed abundantly on tumour cells as well as on some normal tissues, represent the majority of potential targets. As most NHLs are of B-cell origin, the pan-B-cell antigens such as human leucocyte antigen DR (HLA-DR), CD19, CD20, CD22, CD37, CD52 and MHC II have been extensively evaluated as targets for RIT.1,2,7–10 Box 10.1 shows the antigen characteristics that are considered ideal for RIT. Optimum antigen characteristics will vary depending on the radioisotope employed. For 131I, internalization can be problematic, as it results in rapid dehalogenation and loss of the 131I from the target cell. For 90Y, internalization is less of a concern, as radiometals usually remain trapped in the target cell despite internalization. When alpha-emitters and radioisotopes employing Bremsstrahlung for cytotoxicity are used, internalization is an advantage, as the very short path length of these emissions requires that the isotope comes into close contact with the nuclear material of the targeted cell in order to be effective.

Box 10.1 The characteristics considered ideal in an antigen target for radioimmunotherapy Tumour-cell specific Highly expressed on tumour cells No tendency to mutation Not secreted or shed Not rapidly modulated on antibody binding Critical for target-cell survival Not expressed on critical or non-renewable host cells.

From initial investigations, the CD20 antigen emerged as having many of the characteristics thought to be important for a good tumour target, and therefore targeting this antigen has dominated the clinical RIT of lymphoma.11 The CD20 antigen is a transmembrane phosphoprotein that is expressed on mature B lymphocytes but not on pre-B lymphocytes. The CD20 complex does not internalize or shed from the cell surface, and when bound by mAb may initiate signal transduction that triggers apoptosis through a caspase-dependent pathway.12 CD20 is highly expressed on more than 90 per cent of B-cell lymphomas but is not expressed on stem cells or plasma cells, and consequently following radiolabelled anti-CD20 mAb RIT, the depleted B-cell pool may be replenished and the transient lymphopenia has no significant clinical impact. Although most clinical RIT work has been targeted against the CD20 antigen, other B-cell antigens, such as CD22, are still being actively investigated.13 In leukaemia, CD33, CD45 and CD66 have been the most extensively investigated antigen targets for RIT. CD45 is found on nearly all leucocytes, including lymphoid and myeloid precursors. More than 90 per cent of acute myeloid

leukaemia (AML) biopsy samples and most acute lymphoblastic leukaemia (ALL) biopsy samples show CD45 antigen expression, where cell-surface antigen expression averages 200 000 copies per cell.14 Importantly in the context of RIT, the antigen does not internalize after mAb binding. The antigens targeted in RIT for solid tumours include CEA and HER/2-neu and are discussed in the solid tumour section below.

Radioisotopes used in radioimmunotherapy The physical characteristics considered important for a radioisotope in RIT include half-life, type of radioactive emissions (α, β or γ) and ionization path length. Particle energy and mean path length in tissue are important determinants of therapeutic efficacy. The emission profile of the radioisotope determines not only its suitability for therapy, but also the toxicological profile of the radiopharmaceutical. The majority of clinical trials to date have used either 131 I or 90Y because of their favourable emission characteristics, availability and radiochemistry, permitting reliable and stable attachment to mAbs. Iodine-131 has the advantages of a long history of successful use in the management of thyroid cancer and a well-documented safety profile. It is readily available, inexpensive, easily conjugated and emits both β-particles with a path length of 0.8 mm and penetrating γ-emissions. The γ-photons enable uncomplicated imaging using a gamma camera for dosimetry purposes, but also result in a significant non-targeted normal-tissue radiation dose, as well as radiation protection issues for visitors and medical/nursing staff. Yttrium-90 offers a number of theoretical advantages over 131I, although the radioisotopes have not been directly compared in clinical trials. Yttrium-90 is a pure β-emitter that produces higher-energy radiation (2.3 MeV versus 0.6 MeV) at a longer path length than 131I (5.3 mm versus 0.8 mm). Due to the path length of the β-emissions, cellular damage occurs in both the targeted lymphoma cells and neighbouring cells, as illustrated in Table 10.1 (see p. 9). The greater path length of 90Y would be expected to enhance this ‘cross-fire’ effect and could therefore be potentially advantageous in treating bulky, poorly vascularized tumours with heterogeneous antigen expression.5 It is likely, however, to increase the normal-tissue dose when targeting microscopic disease, for which the shorter β-particle path length of 131I may be preferable. The physical half-life of 90Y is 64 hours and approximates to the biological half-life of murine mAbs. The absence of penetrating γ-emissions enables delivery in the outpatient setting.15 Additionally, if a cell internalizes 90Y, it is likely to be retained within the cell.13 In contrast, once 131I-conjugates are internalized by a cell, there is rapid dehalogenation of the free iodide and subsequent excretion of the iodinated products from the cell, reducing desired tumour-absorbed radiation dose and increasing normal-tissue radiation exposure.16 The major disadvantages of 90Y relate to its

Radioimmunotherapy for lymphoma 205

data related to the treatment of leukaemia appear extremely promising.18,19 In practice, the choice of the optimal radioisotope for RIT remains controversial, with proponents advocating the relative merits of 131I, 90Y, 186Rh, 67Cu, and α-emitters such as 211 At.15 Comparative studies are difficult to conduct and scientifically robust randomized human trials have not been performed. The ideal properties of a radioisotope for RIT remain unclear and it is likely that the optimal radioisotope for a particular situation will depend upon the bulk and type of tumour being targeted. An important area of potential future research will be to define the optimal radioisotope, or cocktail of isotopes, required for different tumour sizes.

RADIOIMMUNOTHERAPY FOR LYMPHOMA Clinical experience

Figure 10.1 The cross-fire effect. Mab conjugated to a radioisotope binds to tumour-associated antigen and delivers ionizing radiation not only to the cell to which it binds but also to cells within a radius defined by the path length of the radioactive emission. For 131I this equates to 30–50 cell diameters and for 90Y this equates to 200–300 cell diameters.

greater expense, relatively limited availability and requirement for chelation radiochemistry making radiolabelling a more complex procedure. Yttrium-90 does not emit γphotons and there is therefore a need to use indium-111 as a surrogate to obtain images for biodistribution and dosimetry studies. Rhenium-186 and copper-67 are both β-emitters with physical and chemical properties that make them attractive alternatives to either 131I or 90Y. Nevertheless, their current limited availability means that these radioisotopes have had limited clinical use.17 Alpha-emitters produce a helium nucleus particle of very high energy but with a very short path length. The high linear energy transfer (LET) radiation of α-emitters may be lethal to cells with a single collision; however, the very short path length means that the isotope must be adjacent to, or internalized by, the cell to be effective and is likely to have little or no ‘cross-fire’ effect. The suitability of α-emitters therefore appears limited to readily accessible tumours such as leukaemia cells confined to the blood or bone marrow. The short half-life of α-emitters (e.g. 211At 7 hours and 213Bi, 45 minutes) complicates the radiopharmaceutical preparation, meaning that such radioisotopes are likely to require generation on the same site as delivery in the clinic. Despite this logistical hurdle, early clinical

Clinical RIT trials in NHL differ in terms of eligibility criteria, mAb and radioisotope used, dose, number of treatments, doses of unlabelled mAb pre-infused or co-infused, and the biodistribution or dosimetry estimations required for administration of a therapeutic dose of radiolabelled mAb. Nevertheless, virtually all clinical studies performed to date have shown high response rates of NHL to RIT and have been well reviewed.5,20–24 DeNardo et al. initially pioneered RIT for NHL with 131Ianti-HLA-DR mAb (Lym-1).8 Escalating fractionated doses of 131I-Lym-1 ranging from 1480 mBq/m2 to 3700 mBq/m2 (40–100 mCi/m2) resulted in an overall response rate (ORR) of 52 per cent in 21 treatment courses administered to 20 patients, with seven patients (33 per cent) achieving complete response (CR) and four patients (19 per cent) achieving partial response (PR).8 Goldenberg et al. used an 131I-LL2 (anti-CD22) mAb to treat a variety of B-cell lymphomas. In one of their trials, four out of 17 patients achieved objective remission, including one CR.25 In another trial, 90Y-LL2 was administered to seven patients with B-cell lymphomas, two of whom achieved PR.25 By far the greatest depth of experience in RIT involves the use of 90Y-ibritumomab tiuxetan and 131I-tositumomab in relapsed B-cell lymphomas, where impressive responses have been observed in all of the clinical trials reported to date. Ibritumomab and tositumomab bind to different epitopes of the same CD20 antigen.26 The radioisotopes 131I and 90 Y also have important differences in their emission characteristics. Table 10.1 compares the main characteristics of 131 I-tositumomab and 90Y-ibritumomab tiuxetan. YTTRIUM-90-IBRITUMOMAB TIUXETAN

Yttrium-90-ibritumomab tiuxetan consists of a monoclonal IgG1 kappa anti-CD20 mAb, the murine parent immunoglobulin of rituximab, covalently attached to a metal chelator molecule (tiuxetan; an isothiocyanatobenzyl derivative of

206 Radioimmunotherapy

the polyaminocarboxylic acid DTPA), which stabilizes the mAb–isotope complex for delivery to the lymphoma site.27 The biological half-life elimination of 90Y-ibritumomab tiuxetan is 30 hours. More than 90 per cent of the β-radiation is absorbed within a 5 mm proximity (corresponding to a diameter of 100–200 cells) of the radiation source. This facilitates highly targeted delivery of radiation without the need for patient isolation or shielding.15 The tiuxetan chelator molecule provides a stable link between the mAb and the radioisotope, and therefore free isotope clearance rates are minimal and predictable, with 7.3 3.2 per cent of the radiolabelled activity being excreted in the urine over 7 days.28 Consequently, 90Y-ibritumomab tiuxetan may be administered on an outpatient basis. Figure 10.2 outlines the 90 Y-ibritumomab tiuxetan therapeutic regimen. Four clinical trials, including three phase I/II and one randomized study, formed the basis of the FDA submission for 90Y-ibritumomab tiuxetan. The initial phase I/II study demonstrated that myelotoxicity was dose limiting.28 The maximum tolerated dose (MTD) was identified as 14.8 MBq/kg (0.4 mCi/kg), to a maximum of 1184 MBq (32 mCi) for patients with a baseline platelet count of 150 109/L and 11.1 MBq/kg (0.3 mCi/kg) for patients with baseline platelet counts 150 109/L but 100 109/L. In this study, a high ORR for the intent-totreat population (n  51) was seen at 67 per cent (CR 26 per cent; PR 41per cent); for low-grade disease (n  34) 82 per cent (CR 26 per cent; PR 56 per cent); for intermediategrade disease (n  14) 43 per cent. A phase II study of patients with mild thrombocytopenia (baseline platelet count 100–150 109/L) was conducted using the reduced dose of 11.1 MBq/kg (0.3 mCi/Kg). The ORR was 83 per cent (CR 37 per cent, CRu [unconfirmed] 6.7 per cent, PR 40 per cent). Kaplan–Meier estimated median time to progression (TTP) was 9.4 months (range 1.7–24.6 months). In responders, Kaplan–Meier estimated median TTP was 12.6 months (range 4.9–24.6 months). Toxicity was primarily haematologic, transient and reversible. The incidences of grade 4 neutropenia, thrombocytopenia, and anaemia were 33 per cent, 13 per cent and 3 per cent respectively. The conclusions from this study were that reduced-dose ibritumomab tiuxetan is safe and welltolerated and has significant clinical activity in patients with mild thrombocytopenia.29 A further single-arm phase II study of 90Y-ibritumomab tiuxetan was undertaken to examine its efficacy in a group with rituximab refractory disease.30 Fifty-four heavily

pre-treated patients with follicular lymphoma were recruited who were refractory to or progressed after rituximab. The trial showed an ORR of 74 per cent and a CR rate of 15 per cent, despite a median of four prior therapies and 73 per cent of patients having bulky disease (5 cm diameter). Kaplan–Meier-estimated DR (duration of remission) was 6.4 months, with a TTP of 6.8 months in all patients and 8.7 months in responders. The randomized phase III trial included 143 patients with relapsed or refractory low-grade follicular or transformed NHL and compared efficacy of a single dose of 14.8 MBq/kg (0.4 mCi/kg) 90Y-ibritumomab tiuxetan with rituximab (375 mg/m2 once weekly for 4 weeks).31 Response rates were significantly higher in the 90Y-ibritumomab tiuxetan arm, with an ORR of 80 per cent versus 56 per cent (p  0.002) and a CR rate of 30 per cent versus 16 per cent (p  0.004). Subgroup analysis revealed a superior benefit for patients with follicular histology, with an ORR of 86 per cent versus 55 per cent (p  0.001) and a significant (p  0.04) improvement in TTP for this subgroup. However, there was no difference in the overall TTP in the two treatment groups, but patients treated with 90 Y-ibritumomab tiuxetan showed a trend towards longer median DR (14.2 months versus 12.1 months) and more often achieved responses lasting longer than 6 months (64 per cent versus 47 per cent). A recent retrospective analysis suggests that treatment with 90Y-ibritumomab tiuxetan is associated with higher response rates and longer DR when used earlier in the therapy schedule.32 An integrated analysis of 211 patients treated in clinical trials compared the efficacy and safety of 90Y-ibritumomab tiuxetan in patients with one prior therapy (n  63) and in patients who had received two or more prior therapies (n  148). Patients receiving 90 Y-ibritumomab tiuxetan as second-line therapy had greater ORR (86 per cent versus 72 per cent; p  0.051) and CR/CRu rates (49 per cent versus 28 per cent; p  0.004) and a significantly longer median TTP (12.6 months versus 7.9 months; p  0.038). Amongst the CR/CRu patients, the median TTP (23.9 months versus 15.6 months; p  0.0442) and median DR (22.8 months versus 14.6 months; p  0.0429) were both significantly increased in those with only one prior therapy (n  53). A large European intergroup study of 90Y-ibritumomab tiuxetan therapy of previously untreated follicular lymphoma has now completed accrual, with more than 400 patients recruited. Patients were treated initially with Day 7

Day 0 Dosimetric dose (250 mg rituximab (1 hr), 185 MBq (5 mCi) 90Y-ibritumomab tiuxetan (1.6 mg) (10 min)

Imaging step (Required in USA) X3

Dosimetric dose used to determine individual pharmacokinetics

Figure 10.2 Treatment regimen for 90Y-ibritumomab tiuxetan.

Dosimetric dose (250 mg rituximab (1 hr), 14.8 MBq/Kg (11.1 MBq/Kg platelet counts N1 Wide-field XRT as for NPC

Not found

RND

Appropriate Rx

ECE

Younger No ECE

Older

Tamoxifen or capecitabine (females)

Capecitabine (males)

BEP-type chemotherapy

Bilateral neck irradiation Clinical follow-up

Figure 16.3 A suggested scheme for the management of a patient who presents with a node in the neck in the absence of an easily identifiable primary tumour.

THE ROLE OF PROPHYLACTIC TREATMENT TO THE NECK IN PATIENTS WITH CLINICAL NEGATIVE NECK AND PRIMARY TUMOURS OF THE HEAD AND NECK

This issue has generated controversy for many years, and no randomized surgical trial has addressed the problem. In some clinical circumstances the argument is, in any event, superfluous. A tonsil ‘commando’ operation is often combined with radical neck dissection because a pectoralis major flap can more easily repair the deficit if a block dissection has been performed. The advantages and disadvantages of elective block dissection are summarized in Box 16.11. The moves towards a more conservative approach to the management of the primary tumour (see the section on chemotherapy and organ conservation) provoke a re-consideration of the role of elective neck dissection. A reasonable approach is to treat the primary and first echelon nodes with radiotherapy (or chemo-radiation). The neck nodes in patients considered to be at high risk of occult nodal disease can be treated by elective neck dissection after completion of treatment to the primary. Prophylactic radiation of the entire neck requires large radiation fields, and total doses of no more than 47.5–50 Gy can be given if treatment is given in 20 fractions over 4 weeks. These doses may be too low to control the primary tumour in patients treated solely by radiotherapy, and boost doses to the primary may be required. Radiotherapists divide into two main schools: those who believe in high-dose, small-volume treatments and

Box 16.11 A summary of the advantages and disadvantages of radical neck dissection in patients with head and neck cancer Advantages of elective neck dissection for N0 neck ● Provides definitive treatment ● Provides prognostic information: ● whether or not nodes are involved ● if so, how many ● presence or absence of extracapsular spread Disadvantages of elective neck dissection ● Prolongs operating time with attendant anaesthetic risks ● Immediate surgical complications: ● haematoma ● lymphocoele ● wound dehiscence ● necrosis of flaps ● wound infection ● carotid rupture ● chylous fistula ● salivary fistula ● Later complications: ● facial oedema ● shoulder pain ● deafferentation pain ● XIth nerve damage

Assessment of patients 375

who therefore do not irradiate the neck prophylactically, and those who believe in using larger volumes, often encompassing all the potentially involved lymph nodes, but lower doses. The main side effect of elective wide-field radiation to the upper cervical nodes is xerostomia, because much of the parotid gland is inevitably included within the fields. A randomized trial of prophylactic neck irradiation in patients with carcinomas of the oral cavity was performed at the Christie Hospital in the 1970s. This trial was briefly reported in an earlier edition of this textbook: no statistically significant benefit could be demonstrated, in terms of survival, for prophylactic radiotherapy to the ipsilateral neck when a dose of 50 Gy was given in 15 fractions over 21 days. Prophylactic radiotherapy to the neck did, however, significantly reduce the rate of recurrence in the neck: 79 per cent of 100 irradiated patients remained free of neck disease compared with 64 per cent of 105 patients who received radiotherapy only to the primary tumour (p by λ2  0.025). If isolated nodal relapse is to occur in patients not treated prophylactically, it usually does so within 2 years of first treatment. Careful follow-up, with patients being seen every 2–3 months, is obviously essential, so that if relapse does occur it can be diagnosed and treated promptly. Patients who are unlikely to co-operate with strict follow-up should have their necks treated prophylactically. THE MANAGEMENT OF POTENTIALLY OPERABLE CERVICAL LYMPHADENOPATHY

Traditionally, operable nodal disease was managed by block dissection in conjunction with removal of the primary tumour. Radiotherapy as primary treatment to operable neck nodes was used only in patients with inoperable primary tumours. Increasing unease with the morbidity associated with radical neck dissection, and an increased awareness of the effectiveness of radiotherapy in controlling both the primary tumour and nodal disease, have led to a reappraisal of the traditional position. Bataini, at the Institute Curie, has clearly shown that even bulky nodal disease can be controlled by radiotherapy provided the dose is sufficiently high.132 Factors that indicate that nodes are unlikely to be controlled by radiotherapy alone include nodes 3 cm, fixed nodes, primary T4 or T3, and prolonged overall treatment time. It is reasonable to recommend radiotherapy, with surgery held in reserve for failure, for patients with N1 disease (3 cm). Patients with more advanced but operable neck disease and operable primary tumours should be considered for radical surgery. Patients with inoperable primary tumours and N2 or N3 disease require high doses of radiation, preferably using concomitant boost techniques, if their neck disease is to be controlled adequately. Radiotherapy need not be given routinely after adequate radical neck dissection. If, however, there is extensive evidence of extra-capsular spread, or resection margins are positive, postoperative radiotherapy can reduce the incidence of failure.

TREATMENT OF INOPERABLE NODAL DISEASE AFTER PREVIOUS RADIOTHERAPY

Large, painful, fungating nodes in the neck are extremely distressing to patients. This problem can occur with the primary tumour controlled in a patient who is otherwise generally well and is, therefore, condemned to a miserable existence with no immediate prospect of release. A combination of surgery and interstitial implantation can be used in an attempt to deal with this difficult problem. The bulk of the disease is removed surgically, in the full knowledge that disease is left behind at the base of the dissection. Afterloading tubes, for later 192Ir interstitial implantation, are placed directly across the tumour bed at the time of the open operation. The tissue deficit is then closed using a myocutaneous flap. The radioactive sources are loaded several days later. This gives a high dose of radiation to the area, at depth, of residual disease. The skin and superficial tissues, having been brought in from elsewhere, have excellent tolerance to radiation. The surgical procedure deals directly with disease bulk and fungation and the radiation delays the re-growth of the tumour, thereby providing a significant period of relief from symptoms.

Carcinoma of the lip Nearly all carcinomas of the lip are squamous carcinomas. Basal-cell carcinomas can involve the lip, but actually originate from the surrounding skin and cannot, by UICC criteria, be regarded as true tumours of the lip. Three sites are recognized: upper lip, lower lip and commissures. More than 90 per cent of squamous carcinomas of the lip arise on the lower lip, presumably because the lower lip is more exposed to the most important aetiological factors – tobacco use, particularly pipe smoking, and sun exposure. Tumours of the upper lip are uncommon and tend to be less well differentiated than tumours of the lower lip. Tumours of the upper lip and commissures, particularly those that are poorly differentiated, are more likely to spread to regional nodes than tumours of the lower lip. The classical description of lymph-node spread is from the upper lip to the deep jugular chain, the centre of the lower lip to the submental nodes, and the more lateral parts of the lower lip to the submandibular nodes. In practice, spread is variable. Overall, less than 10 per cent of welldifferentiated tumours spread to nodes, whereas 30–40 per cent of poorly differentiated tumours are associated with nodal disease. Clinically, carcinomas of the lip present as an indolent ulcer. A history of temporary regression followed by re-growth is characteristic. The ulcer often has a rolled margin, and induration may be palpable well beyond the margins of the visible lesion. There may be evidence of associated leucoplakia. The differential diagnosis can be extensive; syphilis, chronic candidiasis and other infective causes must be excluded. Biopsy is essential.

376 Head and neck cancer

The choice of treatment lies between surgery and radiotherapy, and the final decision often rests on the local availability of specialist skills and techniques. RADIOTHERAPY

Radiotherapy can be administered either as external-beam treatment (electrons or orthovoltage) or as an interstitial implant. Electron-beam treatment has the advantage that the depth of penetration in tissue can be governed by the particular beam energy that is selected. The gums and teeth can easily be shielded using 3 mm or so of lead (backed with wax) as a gum shield. The technical set-up is easy; the field size should be generous, as electron isodoses constrict at depth. Afterloaded iridium wire implants are straightforward and can easily be performed under local or general anaesthesia (17.6 old numbering). Two to three wires are placed in parallel 0.5–1.0 cm apart. SURGERY

The main indication for surgery for the treatment of carcinoma of the lip is the presence of leucoplakia adjacent to the invasive tumour. The tumour and the abnormal surrounding epithelium can be excised together. A W or V incision with primary closure is usually adequate when the extent of the excision is less than one-third of the lower lip. For superficial lesions, lip shave and vermilion advancement will produce an excellent cosmetic result. Larger lesions require excision and reconstruction using a flap. There is no indication for routine treatment to the nodes in patients with carcinoma of the lip. However, patients with larger undifferentiated tumours or who are unlikely to attend for regular follow-up should be offered prophylactic treatment to the nodes, either block dissection or radiotherapy. Patients with clinically involved nodes should be managed along the lines described previously (see the section on nodes). PROGNOSIS

The overall prognosis for carcinoma of the lip is excellent: radiotherapy will control 90 per cent of cases. The status of the neck nodes is important: less than 10 per cent of N0 patients fail, but radiotherapy fails to control disease in nearly 50 per cent of patients with clinically positive neck nodes.

Tumours of the oral cavity Although relatively uncommon in Western societies, oralcavity tumours have a high incidence in the developing world – particularly in India, where the incidence is 21/100 000 a year. This problem reflects social habits – the chewing of tobacco and betel nut. Snuff dipping (taking snuff orally – ‘saffa’ in the Sudan, ‘nasswar’ in Pakistan)

and other forms of use of smokeless tobacco are causally associated with oral-cavity carcinomas. This is scarcely surprising, since commercial snuff products contain extremely high levels of carcinogenic nitrosamines – more than 2000 parts per billion. A worrying development is the increased use of smokeless tobacco products by socially disadvantaged young people in the developed world, including native people of Alaska and the North West territories of Canada, and Blacks in the rural south of the USA. Other important aetiological factors in oral-cavity cancer are cigarette smoking, alcohol and chronic sepsis and, mainly of historical interest nowadays, syphilis. The T staging of tumours of the oral cavity is shown in Box 16.12. PRE-MALIGNANT CONDITIONS OF THE ORAL CAVITY

Leucoplakia Leucoplakia appears as a white patch on the mucous membrane. It cannot be removed by scraping and has a characteristic histological appearance – cellular atypia with acanthosis, hyperkeratosis and parakeratosis. The presence of leucoplakia indicates a high risk of developing carcinoma of the oral cavity – approximately 50–100 times compared to normal. The overall cumulative risk of developing invasive cancer for patients with leucoplakia is about 5 per cent at 20 years. Oral hairy leucoplakia Oral hairy leucoplakia is increasingly recognized as one of the complications of infection with the human immunodeficiency virus (HIV). Epstein–Barr virus is probably the direct cause. Characteristically there is an exuberant

Box 16.12 UICC (2002) T staging for carcinomas of the lip and oral cavity226 TX: T0: Tis: T1: T2:

Primary tumour cannot be assessed No evidence of primary tumour Carcinoma in situ Tumour 2 cm or less in greatest dimension Tumour more than 2 cm but not more than 4 cm in greatest dimension T3: Tumour more than 4 cm in greatest dimension T4: (lip) Tumour invades adjacent structures (e.g., through cortical bone, inferior alveolar nerve, floor of mouth, skin of face) T4a: (oral cavity) Tumour invades adjacent structures (e.g., through cortical bone, into deep (extrinsic) muscles of tongue, maxillary sinus, skin) T4b: Tumour invades masticator space, pterygoid plates or skull base or encases carotid artery (Superficial erosion alone of bone/tooth socket by gingival primary is not sufficient to classify as T4)

Assessment of patients 377

leucoplakia affecting the dorsum of the tongue. In a minority of patients with oral hairy leucoplakia and HIV infection, there can be rapid progression to invasive cancer. Lesions in patients with positive tests for hepatitis B or syphilis are particularly likely to progress. Erythroplasia Erythoplasia appears as a velvety red patch on the mucous membrane. It is associated with a high rate of malignant transformation and histologically there is marked cellular atypia. Submucous fibrosis Submucous fibrosis presents as oral discomfort, often exacerbated by spicy foods. The buccal mucosa is predominantly affected; the mucous membrane is thickened and pale. Histologically, the changes are those of chronic inflammation with accumulation of collagen at the dermoepidermo junction. Submucous fibrosis is found predominantly in people from the Indian subcontinent; the incidence may be as high as l per cent in certain areas. There is an eight-fold increase in the incidence of oral cancer in patients with submucous fibrosis.

Carcinoma of the mobile tongue The mobile tongue (synonyms: oral tongue; anterior twothirds of tongue) extends forwards from the circumvallate papillae. About 40 per cent of all oral cancers arise in the mobile tongue, and there has recently been a change in the sex incidence of these tumours: formerly about 75 per cent of patients were male, but the sex incidence is now approximately equal. Most tumours of the mobile tongue arise on the lateral borders, 15 per cent arise on the inferior surface and 10 per cent on the dorsum or the tip of the tongue. The presenting symptom is usually an ulcer, either painless or uncomfortable, which does not heal. More advanced lesions cause disturbances in speech; severe pain, often referred to the ear, is a late symptom. Secondary infections produce foetor. Occasionally, the primary lesion is unnoticed by the patient, who may present with a lump in the neck secondary to involved lymph nodes. The role of the general dental practitioner in early diagnosis is important. The tip of the tongue drains to the submental lymph nodes; the rest of the mobile tongue drains to the submandibular, subdigastric and middle deep cervical nodes. Neck nodes are frequently involved – 30–40 per cent of patients have palpable lymphadenopathy at presentation and a further 30 per cent have occult disease. Contralateral nodal involvement may occur, even with well-lateralized lesions. ASSESSMENT

Adequate biopsy, usually possible under local anaesthesia, and clinical examination of the primary and neck are

routine. Scanning with MRI is superior to CT scanning in the assessment of invasion and local spread. TREATMENT

There is little to choose, in terms of cure rate, between radiotherapy and surgery for early (stage I or II) tumours of the mobile tongue. In North America, surgery is often preferred, whereas European centres have tended to treat with radiotherapy. Overall, the morbidity rate with surgery is less, but when it does occur after surgery, morbidity may be severe. Speech and swallowing are better preserved after radiotherapy, but often at the expense of xerostomia and long-term dental problems. Surgery for larger lesions often has to be extensive, and it may be preferable to compromise surgical margins slightly and treat postoperatively with radiotherapy rather than create a tissue deficit that cannot be adequately reconstructed. Postoperative radiotherapy can be used to prevent local recurrence in patients with positive or ‘close’ (0.5 cm) margin. SURGERY

Cryosurgery has been used successfully for superficial (0.5 cm depth of invasion) tumours of the tongue. Simple wedge excision is equally effective for small superficial lesions. Larger tumours that do not extend across the midline can be treated by hemiglossectomy. Primary closure may be sensible, but excessive suturing should be avoided and granulation repair is rapid and preferable to avoid impaired function. Lesions that extend across the midline require a more aggressive approach. Exposure is best achieved by splitting the mandible anteriorly; the mandible and skin are then opened like the leaves of a book, providing excellent exposure. Sub-total excisions can be repaired using a radial forearm free flap. When the whole of the anterior two-thirds of the tongue has been removed, bulkier flaps, such as the pectoralis major, latissimus dorsi or rectus abdominis flap, are required. The base of the tongue may then act as a piston and the flap is passively pushed forward during swallowing and speaking. RADIOTHERAPY

Small (1 cm) lesions can be treated entirely by interstitial implant. Alternatively, external-beam techniques using an ipsilateral wedged pair of fields or IMRT may be employed. Such a field arrangement minimizes the volume of salivary tissue within the field and thereby may prevent troublesome xerostomia. The results from either surgery or radiotherapy alone for more advanced tumours (T3 and T4) are poor. The common approach is to combine surgery with postoperative radiotherapy, but the functional result may be poor. Treating the primary with radiotherapy and concomitant chemotherapy and then treating the neck nodes surgically is an alternative, and entirely reasonable, strategy.

378 Head and neck cancer

RESULTS OF TREATMENT, PROGNOSTIC FACTORS AND CAUSES OF FAILURE

The following factors adversely affect the prognosis in patients with carcinoma of the mobile tongue: perineural invasion, intra-lymphatic tumour emboli, more advanced T stage, and tumour thickness. Patients with tumours greater than 2–3 mm thick have reduced survival. Tongue carcinomas developing under the age of 40 appear to be biologically more aggressive than those developing in later years. However, patients over the age of 70 have a poorer prognosis compared with patients 10–20 years younger; this may reflect the better prognosis in tumours associated with HPV infection.8 Between 20 per cent and 30 per cent of patients with clinically negative necks, and who do not receive prophylactic radiotherapy to the neck, will relapse in cervical nodes. Five-year survival in such patients is approximately 30 per cent. There is, however, no clear evidence that routinely treating the neck in all patients improves overall survival. Patients with tumours more than 2–3 mm thick or with T2 or T3 tumours are at sufficiently high risk of recurrence in the neck to justify routine treatment, at least to the first echelon nodes. Second malignancies and intercurrent deaths are a major problem in patients whose primary tumours are controlled: only about 20 per cent of patients actually die from tongue cancer.

Floor of mouth The boundaries of the floor of the mouth are the inner surface of the mandibular arch, the undersurface of the anterior part of the tongue and the anterior pillar of the tonsil. Tumours often arise adjacent to, and may spread along, Warthin’s duct. Comparison between series of patients treated for carcinoma of the floor of the mouth is not straightforward. Some authors include tumours of the floor of the mouth; tumours which involve the undersurface of the tongue along with tumours of the mobile tongue. Other authors simply recognize such tumours as a subgroup, with less favourable prognosis, of floor of the mouth tumours. Cancer of the floor of the mouth is commoner in males – 9:1 male:female ratio. These tumours may not be noticed by patients, but eventually difficulties with speech and excessive salivation may lead them to seek medical advice. Pain usually indicates invasion of the mandible; involvement of the inferior dental nerve will cause anaesthesia of the lower lip on the affected side. The management of carcinoma of the floor of the mouth is, in principle, very similar to that of carcinoma of the mobile tongue. For early lesions, radiotherapy and surgery are equally effective. Where function is not compromised, surgery in experienced hands offers a rapid and straightforward approach. Invasion of the mandible is a

relative contraindication to radiotherapy. Larger lesions (T3, T4) may require a combined approach. SURGERY

The tumour and the immediate lymphatic drainage should be removed en bloc. A neck dissection – either a radical or suprahyoid block dissection – should be performed in continuity with the primary procedure. If the tumour is large, or adherent to the mandible, a marginal mandibulectomy is often required. If there is evidence of erosion of the mandible, resection of the affected segment with suitable replacement is required. The radial forearm free flap is probably best for this purpose, although there are alternatives: a groin flap with iliac bone, a pectoralis major flap with rib, and plating the mandible and packing the cavity with bone chips. RADIOTHERAPY

Radiotherapy alone will cure more than 90 per cent of T1N0 tumours. The control rate drops to below 70 per cent for T2N1 tumours. Tumours larger than 3 cm, or those that extend to the gum, are probably best treated surgically. External-beam radiotherapy can be given using either a parallel opposed pair, with or without unequal loading, or an ipsilateral wedged pair of fields. A dose of 52–55 Gy in 20 fractions in 4 weeks or its equivalent is required. The prognostic factors for tumours of the floor of the mouth are the same as those for tumours of the mobile tongue.

Carcinoma of the buccal mucosa The buccal mucosa forms the lining of the cheeks; the lymphatic drainage is to the submandibular and subdigastric nodes. Tumours often arise in relation to pre-malignant conditions such as submucous fibrosis or leucoplakia. The buccal mucosa is a common site of origin for verrucous carcinomas, the management of which is controversial. Radiotherapy allegedly can cause these well-differentiated tumours to become less differentiated and thereby adversely affect prognosis. There is no evidence to support this contention, and yet the view is often held that radiotherapy is contraindicated for verrucous carcinomas. These tumours should not be singled out for special treatment; their management should simply be as for any other squamous carcinoma.133 Small tumours can be successfully treated with either surgery or radiotherapy. Larger tumours require a combined approach, but severe fibrosis may cause trismus and impair the functional and cosmetic results. ASSESSMENT

Assessment should include adequate biopsy, clinical examination and CT scanning of the primary and neck.

Assessment of patients 379

SURGERY

Local excision for small lesions will leave a defect that can easily be closed, either with a locally rotated mucosal flap or by a split-thickness skin graft. More extensive resections require major reconstruction with flaps: pectoralis major; latissimus dorsi; cervico-facial; radial forearm. RADIOTHERAPY

Small tumours can be treated entirely by implant; larger lesions require external-beam treatment. The dose to the local tumour can be boosted with either implant or electron beam. Electron-beam treatment can be administered externally or using an intra-oral cone. Fibrosis and trismus may cause problems after radiotherapy, but can usually be minimized, provided careful attention is paid to technique and dose and jaw-opening exercises are performed regularly after treatment. Five-year survival for carcinoma of the buccal mucosa is poor: only 30–50 per cent. These figures reflect the poor general condition of many of these patients and the high incidence of second primaries.

Tumours of the hard palate The curious habit of reverse smoking, in which the lighted end of the cigarette is placed in the mouth, is an interesting aetiological factor for these rare tumours.134 SURGERY

When bone is involved, surgery is the preferred treatment. Lesions confined to the mucosa can be excised and the wound left to granulate. Attempts to repair the deficit are both unnecessary and futile. Resection of bone is often required, and careful preoperative planning is necessary because some form of obturator will be required to close the defect. Teeth should be preserved if at all possible, as they provide useful anchorage points for a wire-mounted prosthesis. Temporary obturators can be held in place by circumzygomatic wires. RADIOTHERAPY

Small superficial tumours may be managed by radiotherapy. Electron-beam therapy, using an intra-oral cone, or gold-grain implant can be used, either alone or in conjunction with external-beam treatment. The overall 5-year survival for patients with primary tumours of the hard palate is between 30 per cent and 50 per cent.

Tumours of the gum These tumours usually arise in relation to coexistent leucoplakia on the posterior part of the mandible. There is rich lymphatic drainage and 20–30 per cent of patients have positive nodes at presentation. The lingual surface of the mandible drains to subdigastric, upper deep cervical and retropharyngeal nodes. The buccal surface drains to the submandibular, submental and subdigastric nodes. Invasion of bone is common, and surgery is the treatment of choice. Only exuberant tumours with no evidence of bony erosion or involvement should be considered for radiotherapy. Overall 5-year survival is approximately 50 per cent.

Retromolar trigone According to the UICC, tumours of the retromolar trigone are classified with tumours of the buccal mucosa. The retromolar trigone is the area of mucosa that overlies the ascending ramus of the mandible between and behind the lower third molar and the upper third molar. These tumours behave similarly to tumours of the anterior faucial pillar and should be managed similarly. There is a high risk of bone involvement and, as for gingival tumours, management should be primarily surgical in these cases. External-beam radiotherapy, using a wedged pair technique, is adequate for the earlier tumours.

Carcinoma of the oropharynx The oropharynx is roughly cuboidal in shape and extends from the junction of the hard and soft palates to the level of the floor of the vallecula. The sub-sites are: the base of the tongue, including the pharyngoepiglottic folds and the glossoepiglottic folds; the tonsillar region, which includes the fossa and the anterior and posterior pillars; the soft palate, including the uvula; and the posterior and lateral pharyngeal walls. The T staging for oropharyngeal tumours is summarized in Box 16.13. When assessing the literature, it is important to remember that the epidemiology of oropharyngeal tumours varies considerably. For example, the ratio of male to female

Box 16.13 UICC (2002) T staging for carcinomas of the oropharynx T1: T2: T3: T4a:

Tumour less than 2 cm Tumour greater than 2 cm but less than 4 cm Tumour greater than 4 cm Tumour invades larynx, deep/extrinsic muscles of tongue, medical pterygoid muscle, hard palate or mandible T4b: Tumour invades lateral pterygoid muscles, pterygoid plates, lateral nasopharynx, skull base or encases carotid artery

380 Head and neck cancer

patients is typically between 2:1 and 3:1 in series from Denmark, Canada and the USA, whereas in French series, the ratio is between 12:1 and 15:1. This may, in part, reflect social habits. Hot Calvados, as drunk in Normandy, appears to be a potent carcinogen. Most of these tumours are squamous carcinomas, although at this site non-Hodgkin’s lymphoma is more common than elsewhere in the head and neck. Tumours characteristically present late, sometimes as a node in the neck from an occult primary. Difficulty swallowing or pain in the throat or pain radiating to the ear are the usual symptoms from the primary itself. Spread to retropharyngeal nodes, which can occur late in the course of the disease, may cause cranial nerve palsies (IX, X, XI, XII). Infiltrating tonsillar tumours may produce trismus. On examination, there is usually an ulcerating lesion at the primary site. Induration is caused by local infiltrative spread and is often more extensive than the visible lesion. Careful palpation, more kindly performed under general anaesthetic, is an essential part of the assessment of oropharyngeal tumours, together with adequate biopsy. Computed tomography scanning of the primary site and neck is essential.

Tumours of the posterior third of the tongue About 70 per cent of patients with tumours of the posterior third of the tongue have neck nodes at presentation. The majority of patients present with T3 or T4 tumours; fewer than 15 per cent of tumours are T1 or T2 at presentation. T1 and T2N0 tumours of the posterior tongue should be treated with radical radiotherapy or chemo-radiotherapy to both the primary tumour and the neck nodes. The primary tumour and first echelon nodes can be treated by opposed lateral fields. The low neck can be treated by an anterior split cervical field. The dose to the primary should be 52–55 Gy in 20 fractions over 4 weeks (or its equivalent); the neck nodes should receive 50 Gy in 20 fractions in 4 weeks. This approach produces 5-year disease-free survival rates of between 30 per cent and 40 per cent. For the majority of patients – those with a T3 or T4 tumour – the results of treatment are poorer, with 5-year survival rates of less than 30 per cent. Lymph-node spread is common. The surgical options are limited. A total glossectomy and laryngectomy, with all that that implies in terms of loss of function and quality of life, is unacceptable to many patients. Less aggressive surgery, combined with postoperative radiotherapy, can achieve local control in carefully selected patients. The ability to deliver effective brachytherapy to the posterior tongue may further improve results. Iridium-192-afterloaded wires can be placed either percutaneously or at open operation. Using external-beam radiotherapy and percutaneous iridium implants to both primary tumour and any involved cervical nodes, Puthawala et al. have reported local control in 30/40 (75 per cent) of

patients with T3 tumours and 8/12 (67 per cent) of T4 tumours.135 Treatment of the primary tumour with radiotherapy and of lymph nodes with bilateral neck dissection is an acceptable combination, preserving function with reasonable local control. Concomitant chemotherapy with radiotherapy may improve local control rates by about 10 per cent at the expense of increased acute morbidity.

Tumours of the tonsillar area The tonsillar area can be divided anatomically into the following sites: the tonsillar fossa, the anterior and posterior faucial pillars, and the glosso-tonsillar sulcus. Because the anterior faucial pillar marks the point of embryological fusion between the oral cavity and the oropharynx, tumours arising from it have more in common with oral-cavity tumours than they do with carcinomas of the oropharynx. The tonsil itself is a lymphatic organ and, together with lymphatic tissue in the posterior tongue, around the lower end of the Eustachian tube, in the nasopharynx and in the soft palate, forms Waldeyer’s ring. Extra-nodal nonHodgkin’s lymphomas of the head and neck often arise from Waldeyer’s ring. There is a clear association between nonHodgkin’s lymphoma arising extra-nodally in the head and neck and lymphomatous involvement of the stomach and small bowel. The investigation and treatment of nonHodgkin’s lymphoma are described in detail in Chapter 43. Clinically, is it often possible to distinguish carcinomas of the tonsil from lymphomas. Patients with tonsillar lymphomas rarely complain of pain; obstructive symptoms or the sensation of a foreign body in the throat predominate. The tumour itself is often smooth and purplish, and ulceration of the overlying mucosa is uncommon. Cervical lymphadenopathy is often bilateral and bulky; the nodes have a characteristic elastic texture, in contrast to the hard, unyielding nodes associated with squamous-cell carcinomas. Squamous carcinoma of the tonsil usually causes pain, often referred to the ear, and painful dysphagia. Typically there is an infiltrating, ulcerated mucosal lesion, although occasionally tonsillar carcinoma can have an exophytic appearance with minimal ulceration or infiltration. Exophytic tumours may have a better prognosis than infiltrative tumours; this clinical impression is not, however, supported by evidence from formal multivariate analysis. The lymphatic drainage of the tonsillar area is to the subdigastric and jugulo-digastric nodes initially and then to the middle deep cervical nodes. Between 60 per cent and 75 per cent of patients have palpable cervical nodes at presentation, and the majority (around 70 per cent) have T3 or T4 primaries. Assessment requires examination under local or general anaesthesia, with biopsy and MRI, with or without CT. Surgery alone or radiotherapy alone is probably equally effective for T1 or T2 tumours of the tonsillar area. Of the two, radiotherapy gives the better functional result, and

Assessment of patients 381

therefore better quality of life. For T3 and T4 tumours, a combined approach is usually required; radical surgery with postoperative radiotherapy is commonly used. A policy of radical radiotherapy with surgery reserved for operable failures is also reasonable and may give a better functional result. SURGERY

Radical surgery for tonsillar tumours was not really feasible until the development of the so-called commando operation in the 1940s: a neck dissection is performed initially and then the mandible is split behind or between the molar teeth. The tumour can then be visualized by rotating the posterior part of the mandible laterally and backwards and is approached via the neck incision; the removal of the tumour and nodes can then be carried out en bloc. Closure involves tissue replacement using, for example, a pectoralis major, latissimus dorsi flap, or free fibula or when bone is resected; iliac crest. Overall 5-year survival after surgery for carcinoma of the tonsil is around 50 per cent.

main cause of treatment failure is recurrent or persistent loco-regional disease.

Hypopharynx The hypopharynx extends from the level of the tip of the epiglottis to the lower border of the thyroid cartilage. There are three main sites: the pyriform sinus, the posterior pharyngeal wall and the post cricoid area. This classification of hypopharyngeal tumours can be criticized. Tumours arising on the pharyngeal surface of the aryepiglottic folds might be more appropriately considered with tumours of the supraglottic larynx. Post-cricoid tumours are more closely related to tumours of the upper third of the oesophagus than they are to tumours of the pyriform sinus. The T staging of hypopharyngeal tumours is shown in Box 16.14. The lymphatic drainage of the hypopharynx is to retropharyngeal nodes and to the subdigastric, upper and middle deep cervical nodes. Post-cricoid tumours may spread to nodes in the upper mediastinum.

RADIOTHERAPY

Early tumours of the tonsillar fossa, with no palpable cervical lymphadenopathy, can be treated using lateralized techniques:136 ipsilateral wedged pair or parallel opposed fields with unequal weighting or IMRT. These techniques may also treat the first echelon nodes. Electron beams have appealing depth–dose characteristics but cannot be relied upon: the dose actually delivered to tissues behind the mandible may be less than expected because of the unpredictable absorption of electrons by bone. For larger tumours, parallel opposed field arrangements, with treatment to the low neck using an anterior split cervical field, will be required. The primary tumour requires a dose of 50–55 Gy in 20 fractions in 4 weeks, or its equivalent. A similar dose is required for palpable neck disease. The clinically negative neck can be effectively treated with 50 Gy in 20 fractions over 4 weeks, or its equivalent. Concomitant chemotherapy offers a small but significant increase in local control. The main cause of treatment failure in patients with carcinoma of the tonsil treated with radiotherapy is failure to control loco-regional disease. Failure to control nodal disease is related to N stage: for N0 disease, the failure rate with prophylactic radiotherapy to the neck is less than 5 per cent; for N3 disease, the failure rate is 70 per cent. It is possible to implant the tonsillar fossa with afterloaded 192Ir wires. The results from series of patients who had implants as part of their treatment are excellent. Possibly this has as much to do with the careful selection of patients as it does with the effectiveness of the treatment. Overall treatment time is an important prognostic factor for local control in carcinoma of the tonsil treated by radiotherapy: by allowing time for tumour-cell repopulation, gaps and delays compromise local control.137,138 The

Pyriform fossa The pyriform (pear-shaped) fossae lie on each side of the laryngeal orifice. They are bounded medially by the aryepiglottic fold, and laterally by the thyroid cartilage and thyrohyoid membrane. The apex usually extends inferiorly as far as the lower border of the thyroid cartilage. Between 60 per cent and 70 per cent of all hypopharyngeal tumours arise in the pyriform fossa. More than 75 per cent of patients are men. The primary tumour only rarely produces symptoms; the usual presentation is with a node in the neck. Eventually the primary tumour will produce pain, hoarseness and dysphagia. These tumours are usually advanced at presentation; T1 tumours are rare (around 5 per cent). Even small primary tumours may be associated with advanced neck disease. Between 40 per cent and

Box 16.14 UICC (2002) T staging for carcinomas of the hypopharynx T1: Tumour less than 2 cm and limited to one subsite T2: Tumour greater than 2 cm but less than 4 cm without fixation of hemilarynx or involves more than one subsite T3: Tumour greater than 4 cm or with fixation of hemilarynx T4a: Tumour invades thyroid/cricoid cartilage, hyoid bone, thyroid gland, oesophagus or central compartment soft tissue T4b: Tumour invades prevertebral fascia, encases carotid artery or extends into mediastinum

382 Head and neck cancer

50 per cent of patients with clinically negative necks have occult nodal disease at presentation. Prophylactic treatment of the neck is therefore indicated in all N0 patients accepted for radical treatment. TREATMENT

Combined treatment is required for nearly all tumours of the pyriform fossa. The exception would be a small tumour arising from the hypopharyngeal surface of the aryepiglottic fold; these tumours can often be adequately controlled by primary radiotherapy. Radical surgery for tumours of the pyriform sinus involves removal of the larynx as well as the hypopharynx. Postoperative radiotherapy is required for the majority of patients. An EORTC randomized trial90 showed that induction chemotherapy is a safe option for patients with advanced hypopharyngeal cancer: patients randomized to initial chemotherapy followed by radiotherapy or surgery (according to response) had equivalent survival to patients treated with surgery and postoperative radiotherapy. The laryngectomy-free survival rate at 5 years was 35 per cent in patients treated with induction chemotherapy (and, obviously, zero in patients treated surgically). SURGERY

The ablative surgical procedure required for patients with hypopharyngeal tumours is a pharyngo-laryngectomy and block dissection of the ipsilateral neck. A permanent tracheostomy is inevitable. Several reconstructive methods have been used to restore continuity of the food passage. Up to 40 per cent of patients reconstructed with myocutaneous flaps or colon transpositions may fail to achieve normal swallowing and require long-term tube feeding. The failure rate with gastric transpositions or free jejunal grafts is lower. The longterm survival rates for patients treated with primary surgery for hypopharyngeal tumours are typically between 25 per cent and 35 per cent – 33 per cent 5-year survival in a recent Australian series.139 The discrepancy between diseasespecific survival (52 per cent) and overall survival (33 per cent) bears witness to the importance of intercurrent deaths and new primaries in this group of patients. RADIOTHERAPY

The standard technique for treating these tumours is to use parallel opposed lateral fields to the primary tumour and the upper neck nodes, with an anterior split cervical field to treat the low neck. If there are concerns about the position of the junction between fields, this can be moved halfway through treatment, for example by adding 2 cm to the lower border of the lateral fields and subtracting 2 cm from the upper border of the anterior field. For patients with short necks or where other technical or anatomical factors create problems, more complex techniques, similar to

those described for tumours of the supraglottic larynx, may be required. The results of primary radiotherapy for cancer of the pyriform fossa are poor. Long-term survival is only 5–25 per cent. Inability to control loco-regional disease is the usual cause of failure. Control of bulky nodal disease is particularly difficult. The macroscopic extent of the primary tumour may be misleading: skip lesions, occult cartilage involvement and clinically inapparent circumferential spread may all occur and will lead to underestimation of the extent of the tumour. Coping with this uncertainty by simply increasing field size may prohibitively increase morbidity. This high rate reflects both field size and the local tissue destruction caused by these advanced tumours. The early results of the FNCLCC-GORTEC trial140 suggest that chemotherapy given synchronously with hyperfractionated radiotherapy is better than hyperfractionated radiotherapy alone for advanced head and neck cancer. Forty of the 163 patients in this trial had hypopharyngeal primaries: there was evidence of benefit from chemotherapy in this subgroup but, presumably because of small sample size, the difference was not statistically significant. Given that the results with radiation alone are so poor, there is an argument for using neoadjuvant chemotherapy to assess the responsiveness of the tumour (and to produce some symptomatic relief). Patients who fail to respond should be treated surgically if operable, and palliatively if inoperable. Patients who respond should be treated with chemoradiotherapy, with salvage surgery held in reserve for failure. The palliative management of patients with pyriform fossa tumours is difficult. Chemotherapy with carboplatin and 5-FU may produce rapid relief of symptoms but, because response is usually short, may only tantalize. Splitcourse radiotherapy 14.8 Gy in four fractions over 1 week followed by a 3-week gap, followed by 14.8 Gy in four fractions over 1 week may provide useful palliation without causing undue mucosal toxicity. For patients whose tumours and general condition improve with treatment, a third course of four fractions may be given after a further 3 weeks: total dose 44 Gy in 12 fractions over 12 weeks.

Post-cricoid tumours These tumours are similar in their behaviour to tumours of the upper third of the oesophagus and should be treated as such (see Chapter 21).

Posterior pharyngeal wall These tumours are uncommon and in most series account for 20 per cent or less of tumours of the hypopharynx. Clinically, they present with dysphagia and the sensation of a foreign body at the back of the throat. As with carcinomas of the oesophagus, these tumours commonly spread

Assessment of patients 383

inferiorly and superiorly; posterior spread of the tumour is limited by the prevertebral fascia. Surgical treatment for these tumours is extremely difficult and they are usually managed using radical radiotherapy. They can be treated using wedged lateral fields to a dose of 50–55 Gy in 20 fractions over 4 weeks. The spinal cord should be shielded at tolerance. The results of treatment are poor, and only about 30 per cent of patients survive free of disease at 3 years. The usual cause of treatment failure is failure to control loco-regional disease.

Larynx Approximately one-third of all cancers of the head and neck arise in the larynx. The majority of patients are middleaged males (male:female ratio 8:1). More than 90 per cent of laryngeal tumours are invasive squamous carcinomas; between 2 per cent and 10 per cent are in-situ carcinomas. Other tumours that may arise primarily in the larynx include oat-cell carcinomas, lymphomas, tumours arising in ectopic salivary tissue and carcinoid tumours. There are three anatomical sub-sites of the larynx: supraglottis, glottis and subglottis. The supraglottis is divided into five sub-sites: suprahyoid epiglottis, laryngeal aspect of the ary-epiglottic fold, arytenoids, infrahyoid epiglottis, and false cords (ventricular bands). There are three glottic sub-sites: cords, anterior commissure, and posterior commissure. The T staging is shown in Boxes 16.15–16.17. For supraglottic tumours, the most important distinction is between tumours of the epilarynx (suprahyoid epiglottis, ary-epiglottic fold and arytenoid) and the rest. Tumours of the epilarynx tend to be more advanced than tumours of the lower supraglottis; over half of the tumours are T4. Nodal spread is also common. The common defining feature of T3 laryngeal tumours is cord fixation. However, cord fixation can arise through a variety of mechanisms, which may alter the prognosis: the sheer size of the tumour may physically trap the cord; the rotation of the arytenoid cartilage may be prevented by tumour involving the cricoarytenoid joint; the terminal branches of the recurrent laryngeal nerve may be affected by tumour, with consequent paralysis of the intrinsic muscles; and the intrinsic laryngeal muscles may be directly infiltrated by tumour. Transglottic spread, a distinction not made by the UICC TNM system, is an adverse prognostic factor within the T3 category of glottic tumours. The UICC TMN system also fails to discriminate between types of T2 glottic tumour. In addition to any consideration of anatomical extent, impaired cord mobility may be an independently adverse prognostic factor. The supraglottis has a rich lymphatic plexus draining to the subdigastric and mid-cervical nodes. The subglottis drains to the lower cervical, paratracheal, and mediastinal nodes. The glottis itself is not well supplied with lymph vessels, and tumours confined to the vocal cords rarely spread to nodes.

Box 16.15 UICC (2002) T staging for carcinomas of the supra-glottic larynx T1: T2:

Tumour limited to one subsite, cords normal mobility Tumour involves more than one subsite or extends into adjacent soft tissues; cord mobility normal T3: Limited to larynx, cord fixation and/or invasion of post-cricoid space, pre-epiglottic tissues, paraglottic space or minor erosion of thyroid cartilage T4a: Tumour invades through thyroid cartilage and/or invades tissues beyond the larynx (trachea, soft tissues of neck, tongue, strap muscles, oesophagus, trachea) T4b: Tumour invades pre-vertebral space, encases the carotid artery or extends into mediastinum

Box 16.16 UICC (2002) T staging for carcinomas of the glottic larynx T1:

Tumour limited to vocal cords, normal mobility T1a: one cord T1b: both cords T2: Tumour extends to subglottis or supraglottis and/or cord mobility impaired T3: Limited to larynx, cord fixation and/or invasion of para-glottic space or minor erosion of thyroid cartilage T4a: Tumour invades through thyroid cartilage and/or invades tissues beyond the larynx (trachea, soft tissues of neck, tongue, strap muscles, oesophagus, trachea) T4b: Tumour invades pre-vertebral space, encases the carotid artery or extends into mediastinum

Box 16.17 UICC (2002) T staging for carcinomas of sub-glottic larynx T1: T2:

Tumour limited to subglottis Tumour extends to cords with normal or impaired mobility T3: Limited to larynx with cord fixation T4a: Tumour invades cricoid or thyroid cartilage and/or invades tissues beyond the larynx (trachea, soft tissues of neck, tongue, strap muscles, oesophagus, trachea) T4b: Tumour invades pre-vertebral space, encases the carotid artery or extends into mediastinum

CLINICAL FEATURES

The cardinal symptom of laryngeal tumours is change in the quality of the voice. This can vary from mild hoarseness, often intermittent, to severe hoarseness with the voice reduced to the merest whisper. Hoarseness is a symptom that is usually taken seriously by both patients and their doctors, and this, combined with the ease with which the

384 Head and neck cancer

larynx can be assessed by indirect laryngoscopy, means that patients with glottic tumours usually present with early disease. Hoarseness is a late symptom in patients with tumours of the epilarynx; mild dysphagia may be the only initial symptom from these tumours. This may go unnoticed, and patients with high supraglottic tumours may eventually present with a lump in the neck, from nodal disease. This delay in presentation may in part explain the poorer overall prognosis for tumours of the epilarynx. ASSESSMENT

All patients with laryngeal cancer require direct laryngoscopy and biopsy as part of their initial assessment. This is usually best carried out under general anaesthesia, although fibreoptic nasendoscopy offers a possible alternative for patients in whom anaesthesia would be hazardous. Adequate biopsies are essential. Cord mobility can usually be assessed on indirect laryngoscopy and cannot be adequately assessed in the anaesthetized, paralysed patient. Computed tomograph scanning is now routinely used in staging laryngeal tumours. By demonstrating early cartilage invasion, evidence of local spread beyond the larynx and nodal disease, the main effect of CT will be to classify as T4 tumours that, on clinical grounds alone, might have been staged as T1, T2 or T3. Stage migration should be remembered when comparing series in which CT has been used for staging and those using clinical staging only. The patient who presents with stridor due to a laryngeal tumour usually has advanced disease, but careful assessment should take place if possible. To avoid tracheostomy, endoscopic debulking may be possible to secure the airway. Although the adverse effect of tracheostomy followed by delayed primary treatment is known, emergency laryngectomy is rarely practicable.

Verrucous carcinomas of the larynx The question of the radiosensitivity (or radioresistance) of verrucous carcinomas of the larynx is controversial. There is no evidence that radiotherapy in any way increases the aggressiveness of these tumours. On the other hand, there is some evidence that radiotherapy may be less effective for verrucous carcinomas than it is for other squamous carcinomas of the larynx. If conservative endoscopic surgery is feasible, this is the best option; if not, patients should be treated with radical radiotherapy rather than laryngectomy.

Supraglottic tumours Tumours of the supraglottis account for 25–40 per cent of all laryngeal tumours in most series, although a much

higher rate (60 per cent) was reported from Finland. Approximately half of the tumours arise from the lower supraglottis and half from the epilarynx. Nearly 50 per cent of patients with epilaryngeal tumours have palpable nodes at presentation, compared with only 23 per cent of patients with tumours of the lower supraglottis. Tumours of the epilarynx behave more like pharyngeal tumours; tumours in the lower supraglottis behave more like tumours of the larynx proper. The epiglottis has a pitted surface and is perforated by laryngeal nerves. This may facilitate direct extension of supraglottic tumour into the pre-epiglottic space. The T staging of supraglottic tumours is summarized in Box 16.15. The choice of treatment for early (T1, T2) supraglottic tumours lies between voice-conserving surgery and radiotherapy. Supraglottic laryngectomy will permit retention of the voice but is not always feasible – there may not be sufficient clearance between the lower end of the tumour and the vocal cords. Many patients are not fit for anaesthesia; involvement of both lingual arteries is also a contraindication to supraglottic laryngectomy. About 50 per cent of all patients are anatomically unsuitable for supraglottic laryngectomy. Of the patients who are anatomically suitable, many will have significant co-morbidity and be inoperable on medical grounds. Overall, therefore, only about one-third of all patients are suitable for supraglottic laryngectomy, and surgeons vary in their enthusiasm for the procedure. For T3 tumours, a policy of radical radiotherapy, with salvage laryngectomy reserved for failure, is appropriate for those tumours with favourable features: exophytic, limited local extension. Local control will be obtained with radiotherapy in 60–70 per cent of such patients. Infiltrating tumours or those with extension or local invasion into the pyriform fossa or glottis are best treated by laryngectomy. Postoperative radiotherapy should not be given routinely. Only patients with positive or minimal (5 mm) surgical margins or with nodal disease with extracapsular spread should be selected for postoperative radiotherapy. RADIOTHERAPY TECHNIQUE

For early (T1, T2N0) supraglottic tumours, it is not necessary to treat the whole neck prophylactically, but fields need to take into account the high incidence of occult nodal disease. Parallel opposed fields extended up to cover potential lymph-node spread at the angle of the mandible with wedges to compensate for the contour of the neck can be used. The dose should be 52–55 Gy in 20 fractions over 4 weeks, or its equivalent. The lower dose should be used for field sizes greater than 50 cm2, otherwise late complications can be severe. Patients with more advanced primary tumours, or who have nodal disease at presentation, require treatment to the whole neck. This can pose a challenge, particularly in patients with short necks. A variety of techniques have been used in order to avoid areas of under-dosage within

Assessment of patients 385

what is often an extensive treatment volume. The angleddown wedged pair offers the most elegant solution: the whole volume is treated en bloc and gaps are avoided. The downward angle is achieved by swinging the foot of the couch 10–15° to the left for the right field and by a similar amount to the right for the left field. The change in neck contour can be compensated for by using wedges with the thick end anterior. The remaining problem is what to do about the cranio-caudal changes in separation, as these will produce inhomogeneities and there is a risk of overdosing the spinal cord. The best solution is probably to use a compensator, but if this resource is unavailable, wedging in both directions may achieve a similar effect: three-dimensional conformal planning increases the potential accuracy of such treatments. In terms of dose distribution, IMRT has advantages over more conventional techniques;141 however, to date, clinical experience with IMRT for supraglottic cancers is limited. The results of radiotherapy alone for supraglottic carcinoma depend critically on stage; the local control rates vary from more than 60 per cent for T1 to less than 40 per cent for T4. The main cause of failure of radiotherapy for supraglottic carcinoma is persistence or recurrence of the primary tumour; only about 10 per cent of patients fail solely in the neck nodes.

CARCINOMA-IN-SITU

This condition may be much more common than we suppose. In one autopsy series, 15 per cent of smokers had carcinoma-in-situ of the larynx. This contrasts with the 2–10 per cent incidence of carcinoma-in-situ observed in large series of patients with laryngeal carcinoma. For carcinoma-in-situ of the vocal cords, simply stripping the cord can provide both material for diagnosis and, in the short term at least, effective treatment. Laser excision is also now commonly used for in-situ carcinoma of the larynx. Experience is preliminary, but for selected patients it may provide a reasonably expedient alternative to radiotherapy. For more extensive lesions, the only surgical approach that is feasible may be cordectomy, which will invariably affect the quality of the voice. Radiotherapy is undoubtedly effective in controlling in-situ carcinoma of the larynx, and there is no evidence whatsoever that irradiation of these lesions will cause them to become invasive. The local control for this carcinoma is between 85 per cent and 90 per cent. The voice quality after radiotherapy is usually excellent: more than 75 per cent of patients have a normal voice after treatment. A radical dose is required: 50–52 Gy in 20 fractions over 4 weeks. Fields can be kept small – 4 4 cm or 5 5 cm – but care must be taken to include the whole of the anterior commissure in the high-dose volume.

Glottic carcinoma The majority (60–70 per cent) of laryngeal carcinomas arise from the vocal cords. The T staging is summarized in Box 16.16. The site distribution by T stage is shown in Figure 16.4. Nodal involvement at presentation is rare (less than 5 per cent), reflecting the poor lymphatic supply to the vocal cords.

70% 60% 50% 40% 30% 20% 10% 0% Tis

T1

T2

T3

T4

Figure 16.4 The distribution of glottic cancers according to T-stage: pooled data from the literature.

EARLY (T1, T2) INVASIVE CARCINOMAS OF THE GLOTTIS

The results of radiotherapy for early glottic cancers are so good – local control of more than 90 per cent for T1 tumours and more than 75 per cent for T2 tumours – that it is ethically difficult to introduce alternative treatments. Nevertheless, for highly selected patients, conservative surgical techniques may offer local control rates as good as those obtained by radiotherapy. Over the last decade, laser resection of early (T1, T2) glottic carcinomas has become established as a viable alternative treatment to radiotherapy, with which it provides comparable results.142 However, in the UK, where old habits die hard, it has yet to gain general acceptance. The criteria for suitability for laser excision of glottic cancer include anterior commissure not involved, patient fit for anaesthesia, and videostroboscopy only minimally abnormal. A few European centres also use the technique for some advanced disease, and although they report good results, such treatment will have to survive the rigours of randomized controlled trials before it becomes a standard therapeutic option. Other conservative surgical approaches to early glottic tumours are possible: fronto-lateral partial laryngectomy, laryngofissure with cordectomy, hemilaryngectomy, and anterior commissure resection. The main problem is that voice quality is not as reliable after conservative surgery as it is after radiotherapy. In the Mayo Clinic series of 159 patients treated with open conservative surgery,143 14 per cent had ‘poor’ voice and, disconcertingly, 11 patients died

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from laryngeal cancer. Within North America there are significant differences in treatment philosophy, the USA tending towards a more surgically orientated approach, with the Canadians favouring radiotherapy. There is no evidence that the Canadian approach is associated, on a population-wide basis, with inferior outcomes.144 In the UK, the vast majority of patients with T1 and T2 tumours of the glottis are treated with a policy of radical radiotherapy, with laryngectomy held in reserve for patients whose tumours persist or recur after primary radiotherapy. With this policy, about 90 per cent of patients with T1 tumours and 70–75 per cent of patients with T2 tumours are cured without requiring laryngectomy. Long-term causespecific survival is around 90 per cent for T1 tumours and 80–85 per cent for T2 tumours. Crude survival is much lower, typically around 50–60 per cent at 10 years. This difference reflects the high rate of intercurrent deaths and second malignancies in these patients. Intercurrent deaths can cause difficulties with attribution in the long-term follow-up of patients with tumours of the upper aerodigestive tracts. If treatment produces distortion and fibrosis of the structures around the epiglottis and larynx, this may interfere directly with the protection of the airway during swallowing, and aspiration may occur. If significant aspiration goes unnoticed, and deaths are simply attributed to bronchopneumonia, this will underestimate the number of deaths occurring as a result of treatment-related complications. Any disparity in rates of death from intercurrent causes in comparisons of treatment for head and neck cancer should always be looked at carefully: this may be a clue to a significantly higher rate of complications in one treatment arm. This problem was particularly apparent in the Edinburgh neutron/photon trials in head and neck cancer, in which there were many more intercurrent deaths in patients treated with neutrons.145 T3 TUMOURS OF GLOTTIS

Surgery for laryngeal cancer is evolving. Trans-oral laser excision has been used in carefully selected patients with T3 tumours without compromising local control.146 The operation of supra-cricoid partial laryngectomy can, again in carefully selected patients, preserve voice and swallowing without compromising cure.147 Nevertheless, fewer than 10 per cent of patients with T3 glottic tumours are suitable for conservative surgery and so the initial choice is almost always between total laryngectomy and radiotherapy. The choice is often difficult. Infiltrative ulcerative tumours are best treated surgically, whereas the more exophytic tumours often respond well to radiotherapy. The general condition of the patient is also important, as many of these patients are not medically fit for anaesthesia. The patient should be involved in the discussions and decisionmaking from the start. Patients’ attitudes to possible compromises between survival and voice preservation differ. Some patients value survival at all costs and will pay virtually any price to increase their certainty of cure.

Other patients value their voices highly and would be prepared to compromise their chances of survival in order to retain normal speech.102 A detailed analysis of specialists’ recommendations for the management of laryngeal cancer showed that them to be heavily influenced by specialty (otolaryngologists as opposed to radiotherapists) and by geography (the USA and Australasia as opposed to Canada, the UK and Scandinavia).148 Surgeons tended to recommend surgery; radiotherapists were less likely to do so. Surgery was more likely to be recommended by clinicians in the USA and Australasia. Primary radiotherapy will control around 40 per cent of T3 glottic cancers. Case selection, with more unfavourable tumours being referred for surgery, invalidates any direct comparison of survival data between surgery and radiotherapy for T3 tumours of the vocal cord. No randomized trial has addressed this question. The influential Veterans Administration Study91 on neoadjuvant chemotherapy for laryngeal cancer has shed no real light on the issue. It has convinced many ENT surgeons that laryngectomy is not always necessary but, because there was no randomization to radiation alone, the relative contributions to tumour control of the radiotherapy and chemotherapy in this study cannot be assessed. The RTOG 91-11 trial89 set out to resolve this issue. Patients with advanced laryngeal cancer were randomized to radiotherapy alone or to platinum/5-FU induction chemotherapy followed by radiotherapy, or to synchronous chemo-radiation with platinum and radiotherapy. Local control at 2 years was significantly better in patients randomized to chemo-radiation (78 per cent) compared with those treated with radiation alone (56 per cent) or with induction chemotherapy followed by radiotherapy (61 per cent). The addition of any chemotherapy halved the rate of metastatic disease – from 16 per cent with radiotherapy alone to 8 per cent or 9 per cent. Treatment allocation had no effect on 5-year survival, which was between 54 per cent and 56 per cent in the three arms. T4 TUMOURS OF GLOTTIS

The majority of patients with T4 glottic cancers who have operable disease and are fit for surgery should probably be treated by laryngectomy or pharyngolaryngectomy. This is particularly true for tumours involving the pyriform fossa, for which the results from radiotherapy are particularly poor – less than 20 per cent local control at 5 years. Early cartilage invasion is not, of itself, a contraindication to radical irradiation. Salvage laryngectomy is, however, rarely possible in patients with T4 glottic tumours who fail radiotherapy. This is a reflection of their poor general condition and the extensive local destruction that can be caused by both the primary tumour and post-irradiation perichondritis. Perichondritis of the thyroid cartilage is a potentially fatal complication of these tumours. Careful supervision after radiotherapy and prompt treatment with antibiotics are essential for its prevention. Surgical series on T4 glottic

Assessment of patients 387

tumours report long-term local control rates of between 30 per cent and 55 per cent.

RADIOTHERAPY TREATMENT TECHNIQUES FOR GLOTTIC CARCINOMAS

Most early glottic tumours can be treated using parallel opposed lateral fields with wedges used to compensate for the decreased separation of the neck anteriorly. In patients with short, fat necks, it may be difficult physically to accommodate lateral fields, and oblique anterior fields with appropriate wedges may be used. Relatively small fields can be used for early tumours provided that careful attention is paid to the anterior margin. The anterior commissure may lie as little as 2–3 mm below the skin surface, and the anterior field margin (defined at 50 per cent) should therefore extend beyond the skin surface. In patients with thin necks, bolus may be required to ensure adequate dose to the anterior commissure. All patients should be treated using an immobilization shell and a well-collimated beam from a 4–6 MV linear accelerator. All fields should be treated daily. It is no longer acceptable to use cobalt units for such treatment. The field should extend from the level of the hyoid to the lower border of the cricoid cartilage, and the posterior border should overlie the vertebral bodies. A randomized study from Japan looked at the influence of field size on local control and complications in patients with T1N0M0 glottic carcinoma. There was no difference in relapse-free survival between patients randomised to 6 6 cm fields compared with patients randomised to 5 5 cm fields.149 However, patients treated with the larger fields had a significantly higher incidence of chronic arytenoid oedema. It is important to remember that the physical size of the larynx varies on an individual basis, and field sizes should be individually appropriate rather than standardized. For T1 tumours, a 3-week schedule of treatment is effective: 50–52.5 Gy in 16 fractions in 21 days.40 In patients with more advanced primary tumours, larger fields may be necessary, but this will increase the risk of significant late morbidity. A dose of 52–55 Gy in 20 fractions over 4 weeks, or equivalent, is adequate for most glottic tumours. If field sizes exceed 50 cm2, it may be necessary to limit the dose to 52 Gy in order to avoid unacceptable late complications.

Subglottic tumours These tumours are very uncommon – less than 5 per cent of all laryngeal tumours. The T staging is shown in Box 16.17. Unlike glottic tumours, they often spread to nodes; the nodal drainage is to the low neck, supraclavicular fossa and upper mediastinum. The clinical presentation is usually with wheeze or stridor, occasionally as a lump in the neck. Because tumours regress towards their site of origin,

the distinction between a true subglottic tumour and a glottic tumour with subglottic extension can sometimes only be made by observing the regression of tumour during treatment. For tumours arising at the level of the thyroid ring, surgery offers the best treatment. Tumours arising from the conus elasticus are more likely to respond to radiotherapy. Even advanced (T3, T4) subglottic tumours may be controlled with radiotherapy: overall local control rates for radiotherapy in subglottic tumours range from 30 per cent to 70 per cent. Long-term survival is 30–50 per cent with radiotherapy and 40–50 per cent with surgery. The radiation fields need to include the lymph nodes of the low neck, the upper mediastinum and supraclavicular fossa as well as the primary tumour. Cruciate anterior and posterior opposed fields are usually required, with a posterior cord block to keep the dose to the spinal cord within tolerable limits. The field size is usually such that a dose of 50 Gy in 20 fractions over 4 weeks, or its equivalent, cannot be exceeded.

Laryngectomy after radiotherapy The indications for laryngectomy after radiation therapy provide interesting clues as to an institution’s radiotherapeutic philosophy. Those centres with an aggressive approach will perform relatively more laryngectomies for necrosis and fewer for recurrence. The pattern will be reversed in centres with a less vigorous approach. In a series of 376 patients with laryngeal cancer reported from Edinburgh, 56/376 underwent laryngectomy. Of the 56 larynxes removed, 43 (77 per cent) contained tumour and 13 (23 per cent) showed necrosis only. There was no difference in symptoms (pain, hoarseness, stridor) between patients with residual tumour and those with necrosis.150 The overall rate for laryngeal necrosis in this series was 13/376 (3.4 per cent). The patients who required laryngectomy for necrosis enjoyed excellent survival – 92 per cent at 5 years. This compares with 59 per cent 5year survival in the patients requiring laryngectomy for recurrence. These data emphasize the importance of careful follow-up, a high degree of suspicion for recurrence, and a low threshold for performing microlaryngoscopy under anaesthetic in patients irradiated for laryngeal cancer. Previous radiotherapy undoubtedly increases the complication rate for laryngectomy. In the Edinburgh series of previously irradiated patients, the complication rate was high – 30/56 (54 per cent) serious complications. Fistula was the commonest complication, affecting 15/56 (27 per cent) of patients. Other complications included infection, wound dehiscence and arterial rupture.150 Follow-up should be every 4–8 weeks for the first year after treatment. In patients who are difficult to examine by indirect laryngoscopy, direct laryngoscopies should be performed at 3 and 6 months after treatment. Follow-up during the second year should be every 2 months. Thereafter, the intensity of supervision can be decreased.

388 Head and neck cancer

Although occasional problems arise after 5 years, it is reasonable to discharge patients from routine follow-up at that time. Using historical data, it is possible to indicate outcome in an imaginary cohort of 100 patients with advanced laryngeal cancer treated with radical radiotherapy. Radiotherapy alone will produce long-term local control in between 50 and 56 patients. Salvage surgery will be attempted in 28–34 patients and this will be successful in between 15 and 20 patients. There will be between 10 and 22 patients with persistent or recurrent disease who are, for one reason or another, unsuitable for salvage surgery. Ultimately, between 65 and 76 patients will obtain local control of their disease. The important feature of this analysis is that it confirms the viability of a policy of radical radiotherapy (or chemoradiation), with salvage surgery for failure, in the treatment of laryngeal cancer. Around one-third of patients will die from causes other than laryngeal cancer. Most of these intercurrent deaths are due to smoking-related diseases – 50 per cent of the deaths in the Edinburgh series of patients requiring salvage laryngectomy. Encouraging patients treated for laryngeal cancer to stop smoking should improve their immediate prognosis, but unfortunately can do little to prevent the long-term harmful effects of the cigarettes they have already smoked. Unless smoking habits change or strategies for secondary prevention prove effective, long-term survival rates for patients with laryngeal cancer will always be eroded by a high rate of intercurrent death – despite curing the majority of patients.

The nasopharynx Tumours of the nasopharynx are biologically distinct from other tumours of the head and neck. These tumours are common in the Far East and North Africa. Three main factors are important for the development of classical nasopharyngeal carcinoma: genetic susceptibility, EBV infection and dietary factors. The importance of genetic factors in the origin of these tumours is illustrated by their familial tendency. There is often serological evidence of EBV infection. The main oncogenic protein associated with EBV infection is LMP-1 (latent membrane protein 1). EBVencoded RNAs (EBER) may interfere with apoptosis151 and thus permit expansion of abnormal clones of EBV-infected cells: in other words, EBV infection may cause a failure of tumour suppression. There may also be abnormal expression of c-kit after EBV infection,152 leading to the tantalizing possibility of using imatinib to prevent, or treat, the disease. The dietary factor that is particularly associated with nasopharyngeal carcinoma is the consumption of salted fish.153 Surveys in China have shown that fish from areas with a high incidence of nasopharyngeal carcinoma contained more carcinogenic nitrosamines than samples of fish from areas with a lower incidence of nasopharyngeal

carcinoma. Thus it is not simply the consumption of salt fish in general that is important: the type of salt fish is also relevant. It is difficult, from a Western perspective, to appreciate just how common nasopharyngeal carcinoma is in Southern China, Hong Kong and Taiwan. In some areas of Guangdong Province the incidence is as high as 40 per 100 000 per annum. If applied to the UK, this rate would produce 21 000 patients per year with carcinoma of the nasopharynx. In Taiwan, 60–70 per cent of all patients treated with radiotherapy are treated for nasopharyngeal carcinoma. Analysis of trends over time suggests that, as China has developed economically, dietary and socio-economic changes have led to a fall in the incidence of this disease.154 Nasopharyngeal carcinoma in China and the Far East may be a somewhat different disease from that encountered in Western Europe. In Hong Kong, less than 10 per cent of conventionally staged patients have metastatic disease at presentation. This increases to around 15 per cent when whole-body 18FDG-PET scanning is used.155 This contrasts with the disease in patients of North African origin, in whom bone metastases are more common, at both presentation and follow-up.156,157 The age–incidence peak for nasopharyngeal carcinoma in China is between 40 and 60 years; males outnumber females by 3:1. In Caucasian patients, there is a suggestion of a secondary peak in incidence around the age of 20 years. In the West, there is also a significant incidence of nasopharyngeal carcinoma in childhood. There are several pathological classifications for nasopharyngeal carcinoma. The World Health Organisation (WHO) classification is the most widely used; three categories are recognized. Type 1: keratinizing squamous, found in 25 per cent of Caucasians with nasopharyngeal carcinoma, not related to EBV infections, behaves more like a typical squamous-cell carcinoma of the head and neck, has the worst prognosis. Type 2: non-keratinizing carcinoma. Type 3: undifferentiated tumours (UCNT). ANATOMY

The roof of the nasopharynx is formed by the base of the skull, which slopes downwards and backwards to become continuous with the posterior pharyngeal wall. The anterior boundary is the posterior choanae and the free posterior edge of the nasal septum. Its lower limit is defined as the level of the uvula, opposite the second cervical vertebra. The lateral wall contains the fossa of Rosenmuller and the Eustachian tubes. The floor is the superior surface of the soft palate. The nasopharynx is difficult to assess clinically. Surgery is rarely used in the management of nasopharyngeal carcinoma and so it is only comparatively recently (with the advent of CT scanning and MRI) that it has been possible to obtain accurate anatomical information about its origins

Assessment of patients 389

and local spread. Most tumours originate in the fossa of Rosenmuller, and the earliest radiological sign is blunting of the angle at the Eustachian cushion. Computed tomography scanning has highlighted the importance of spread into the parapharyngeal space. This is defined as abnormal soft tissue lying in the space between the pharyngeal constrictors and the pterygoid plates. Another feature is the ability of the primary tumour to invade directly into the carotid sheath; previously, involvement of the carotid sheath was assumed to be due to nodal spread. Retropharyngeal nodes are involved early in the disease. They cannot be detected by clinical examination, but can readily be demonstrated on imaging. Around 30 per cent of patients with clinically negative necks will have occult nodal involvement on imaging. Imaging is also essential for assessing the involvement of the skull base: in the pre-CT era, between 10 per cent and 15 per cent of patients had skull-base involvement at presentation; nowadays the figure is nearer 35 per cent. This has obvious implications for comparing treatments over different time periods.116 Intracranial extension and extension into other sinuses is also more common than was previously detected. CLINICAL PRESENTATION

The nasopharynx, together with the pyriform sinus and the base of tongue, is a classic site for a silent primary tumour in the head and neck. About 75 per cent of patients have palpable neck nodes at presentation and the neck mass is the presenting symptom in from 40 per cent to 50 per cent of patients. The remaining patients usually present with nasal symptoms (obstruction, epistaxis) or with symptoms from the ear (deafness, tinnitus). Headache, often severe, central and unresponsive to standard analgesics, usually indicates a locally advanced tumour. Between 20 per cent and 25 per cent of patients have cranial nerve palsies at presentation. This indicates either erosion of the base of skull or spread via the various exit foramina of the cranial nerves. Cranial nerves VI and V are the most commonly involved (50–70 per cent of patients with cranial nerve palsies at presentation). A syndrome of syncope has been described in nasopharyngeal carcinoma and similar problems may occur in other patients with head and neck cancer. The mechanisms are complex but predominantly involve pressure on the carotid sinus, causing reflex bradycardia, and stimulation of the IXth nerve, again causing a fall in heart rate as well as hypotension due to direct vasodilatation. A variety of para-neoplastic syndromes has been described in association with nasopharyngeal carcinoma: hypertrophic osteoarthropathy and the syndrome of inappropriate ADH secretion occur rarely. Younger patients, particularly those from North Africa, may present with a syndrome of nasopharyngeal carcinoma, leukaemoid changes in the peripheral blood, and pyrexia of unknown origin.

CLINICAL ASSESSMENT

Examination under anaesthesia, with adequate visualization of the primary tumour and biopsy, is essential both for confirming the diagnosis and for clinical staging. Adequate imaging (CT and/or MRI) is essential and should include the skull base and lower parts of the anterior and middle cranial fossae and should extend down to the level of the suprasternal notch. Contrast enhancement allows discrimination between vascular structures and soft tissue. Magnetic resonance imaging is extremely useful in assessing nasopharyngeal carcinoma and has the potential to detect early evidence of spread beyond the primary tumour, for example infiltration of the tensor veli palatini. Other routine investigations should include chest X-ray, routine haematology, liver function tests (including LDH) and EBV serology. The issue of routine bone scanning and liver ultrasound is contentious: young North African patients are at particular risk of having disseminated disease at presentation and should be routinely imaged; other patients should only be investigated if they have suggestive symptoms or signs. If there is any doubt about the histological diagnosis, expert pathological review, with re-biopsy if necessary, is essential, particularly in non-endemic areas. The differential diagnosis of tumours at this site is extensive and includes lymphoma, rhabdomyosarcoma, extramedullary plasmacytoma, amelanotic melanoma, polymorphic reticulosis, Wegener’s granulomatosis, sarcoidosis and pharyngeal tuberculosis. STAGING

The clinical staging of nasopharyngeal tumours reflects the fact that, other than biopsy, surgery has little role to play in this disease. The staging for nasopharyngeal tumours is therefore distinct from that of other head and neck cancers (Boxes 16.18 and 16.19; Table 16.13). In the Far East, the Ho system, rather than TNM, was used for many years. This makes comparisons between the West and the East difficult. The N staging in the Ho system is entirely dependent on the level of nodal involvement; size, laterality and fixation are not considered. The UICC system uses size and bilaterality as its criteria. The Ho system T stage depends on extent of the primary tumour, bone erosion and cranial nerve involvement. T stage according to the UICC depends mainly on anatomical extent and does not acknowledge the prognostic importance of cranial-nerve involvement. MANAGEMENT

Radiotherapy is the mainstay of treatment. The role of chemotherapy is slowly being clarified. There is good evidence from randomized controlled trials that chemo-radiation is superior to radiation alone158–164 (Table 16.7). The roles of induction chemotherapy and adjuvant therapy are less clear. A recent overview165 suggested that adjuvant

390 Head and neck cancer

chemotherapy was of little benefit, that there was clear evidence of benefit from concomitant chemo-radiation, and that there was slight benefit from neoadjuvant chemotherapy. For stage III and IV disease it appears that platinum/5FU given synchronously with radiotherapy confers a survival advantage. The acute reactions to concomitant chemotherapy and radiotherapy are undoubtedly more severe and prolonged. The potential late complications of the combination are not fully documented, but it is noteworthy that in the NPC-9901 trial161 the benefit from

Box 16.18 UICC (2002) T staging for carcinomas of the nasopharynx T1: Tumour confined to nasopharynx T2: Tumour extends to soft tissues T2a: to oropharynx and/or nasal cavity without parapharyngeal extension T2b: any tumour with parapharyngeal extension T3: Tumour involves bony structures and/or paranasal sinuses T4: Tumour with intracranial extension and/or involvement of cranial nerves, infra-temporal fossa, hypopharynx, orbit or masticator space

Table 16.13 American Joint Committee on Cancer (AJCC) stage grouping (2002) for nasopharygeal cancer Stage group

Box 16.19 UICC (2002) N-staging for carcinomas of the nasopharynx

0 I IIA IIB

NX: Regional nodes cannot be assessed N0: No regional node metastases N1: Unilateral nodal metastasis above the supraclavicular fossa and less than 6 cm in diameter N2: Bilateral nodal metastases above the supraclavicular fossa and less than 6 cm in diameter N3: Metastasis greater than 6 cm and/or to supraclavicular fossa N3a: greater than 6 cm N3b: to supraclavicular fossa

III IVA IVB IVC

T

N

M

Tis 1 2a 1,2,2a 2b 1,2a,2b 3 4 Any Any

0 0 0 1 0,1 2 0,1,2 0,1,2 N3 Any

0 0 0 0 0 0 0 0 0 1

Stage groupings, based on TNM, for cancers of the nasopharynx.225

Al-Sarraf (1998) Lin (2003) Kwong (2004) Chan (2005) Zhang (2005) Lee (2005) Wee (2005)

.25

.5

.75

Chemort better

1

1.25 XRT alone better

Risk ratio

Figure 16.5 Relative risk, with 3-year overall survival as the end point, in randomized trials in which synchronous chemoradiation was compared with radiotherapy alone for carcinoma of the nasopharynx. For references to trials, please see text.

Assessment of patients 391

adding chemotherapy, in terms of local control, was offset by an increase in the number of intercurrent deaths. The net result was that survival at 3 years was no different in the two arms of the study. RADIOTHERAPY TECHNIQUE

A superb account of radiotherapeutic techniques was given by Ho in the previous editions of this textbook. The essential principle of his technique is to use small lateral fields and a supplementary anterior field to treat the nasopharynx. The neck is treated using an anterior field with a midline shield. An alternative technique is to use larger lateral fields to treat the nasopharynx, the nasal cavity and the upper neck, and to treat the low neck using an anterior split cervical field. A two-phase technique is required in order to shield the spinal cord at tolerance and also to change the level of the junction between the anterior and the lateral fields. The dose required to treat carcinoma of the nasopharynx is 66–70 Gy in 33–35 fractions. A significant incidence of late complications is virtually inevitable. In a series from Queen Elizabeth Hospital, Hong Kong, of 4527 patients assessed for late complications, 1395 (31 per cent) had significant problems: 322/4527 (7 per cent) had severe late morbidity and 62/4527 (1.4 per cent) died as a result of treatment. Most of the fatalities were due to CNS damage, temporal lobe necrosis or damage to the brain stem.166 The commonest form of severe late damage is hearing loss. This can arise from several treatment-related causes: serous otitis media, direct damage to the cochlea by radiation, and damage to the auditory pathways in the mid-brain. Adding cis-platinum to radiotherapy significantly increases the risk of sensori-neural hearing loss.167 Soft-tissue fibrosis is the commonest cause of minor morbidity; when the temporo-mandibular joint is involved, trismus results. Dry mouth and dental problems are common. The incidence of hypothalamo-pituitary dysfunction depends on how hard it is looked for: clinical problems were recognized in only 4 per cent of patients in the retrospective review from Queen Elizabeth Hospital, but up to 60 per cent of patients followed prospectively have demonstrable endocrine dysfunction within 5 years of irradiation. The actuarial incidence of hormone deficiencies at 5 years may be much higher, with rates of deficiency of 60 per cent for growth hormone, 30 per cent for gonadotrophins, 25 per cent for adrenocorticotrophic hormone and 15 per cent for thyroid-stimulating hormone. A significant proportion (10–20 per cent) of patients with nasopharyngeal carcinoma have clinically evident residual tumour in the nasopharynx at the completion of radiotherapy. A variety of techniques for boosting the dose to the primary tumour have been proposed: small external-beam fields; 198Au grain implant; intracavitary therapy with 137Cs or 192Ir; 125I seed implant; and boost with IMRT. Conformal boost techniques have been disappointing,168 but techniques using IMRT appear promising.75,169,170

MANAGEMENT OF RECURRENCE

Patients in whom nodal disease is the sole recurrence or failure should be treated surgically; re-irradiation of the neck nodes is of little benefit. Patients in whom local recurrence is the only problem can be treated by re-irradiation. The long natural history of nasopharyngeal carcinoma means that although long-term survival after re-treatment may only be about 15 per cent, local control, and subsequent relief of symptoms, can be achieved in 30–35 per cent of re-irradiated patients. Late morbidity is a problem if re-irradiation is given solely by external beam. The best approach is probably to give 20–30 Gy by external beam and then 40–50 Gy by intra-cavitary treatment or implant.76 Patients with metastatic disease should be considered for chemotherapy. The bleomycin, epirubicin and platinum regimen used at the Institute Gustave Roussy has yielded the best results so far. PROGNOSTIC FACTORS

The main adverse prognostic factors for survival are presence of metastatic disease, higher nodal stage (when the Ho system is used), cranial-nerve paresis and base of skull involvement. Male patients and patients with parapharyngeal disease may also have a worse prognosis. Levels of circulating EBV DNA in the blood may correlate with prognosis: post-treatment levels can predict both overall survival and freedom from relapse.171 In a multivariate analysis including age, gender, performance status, histological type, T-stage, N-stage, AJCC stage and whether or not plasma EBV DNA was detectable after treatment, the only independently significant factor was the post-treatment EBV DNA status. Patients with detectable EBV DNA had a hazard ratio for death of 22.9 (95% CI 3.0–173.5) compared with patients whose EBV DNA levels were undetectable.172 Prognosis has improved steadily over the past 20 years. This reflects general technical improvements in radiotherapy technique and better pre-treatment evaluation rather than any specific contribution from altered fractionation or the addition of chemotherapy. It also illustrates the danger of using historical controls when evaluating treatment for nasopharyngeal carcinoma. It is likely that this trend will continue as treatment planning improves, IMRT becomes more widely available and synchronous chemotherapy is more often used. CAUSES OF TREATMENT FAILURE

The causes of failure in the series from Queen Elizabeth Hospital, Hong Kong,166 are summarized in Table 16.14. Half the patients died from nasopharyngeal carcinoma, 35 per cent survived, 7 per cent died from intercurrent or unknown causes, 1 per cent died from treatment-related complications, 1 per cent died from second malignancies and 7 per cent were lost to follow-up.

392 Head and neck cancer

Table 16.14 Causes of failure in patients treated for carcinoma of the nasopharynx in Hong Kong

Metastatic at presentation Unfit for radical Rx Metastases as first site of failure LR failure then metastases Regional failure alone Failure of initial treatment to achieve LC Local failure after initial LC

N

(%)

292 258 924 521 177 564 891

6 5 19 11 4 12 20

Abstracted from Lee et al. 1992.166 LC, local control; LR, loco-regional.

Tumours of the nose and para-nasal sinuses Tumours of the nose and para-nasal sinuses are characterized by histological and anatomical heterogeneity. The diversity of the population of normal cells found in the lining of the sinuses is paralleled by the diversity of the histological types of tumour that are encountered in this region: squamous carcinoma, salivary-gland tumours, adenocarcinoma, inverting papillomas, melanoma, esthesioneuroblastoma, lymphoma and sarcoma. The nasal vestibule is lined with squamous epithelium but the nasal cavity and sinuses are lined with columnar ciliated epithelium. Goblet or mucous cells are interspersed amongst the columnar cells, and beneath the basement membrane there is a virtually continuous layer of mucous and serous glands. There is diffuse lymphoid tissue throughout the region. In the olfactory region, the lining comprises three types of cell: bipolar olfactory nerve cells, basal cells and sustentacular cells. ANATOMY

The nasal vestibule is defined as that small area of the nasal fossa just proximal to the nares. The nasal cavity begins at the squamo-columnar junction and extends backwards to the posterior choanae. The nasal septum divides it into left and right, and laterally it is bounded by the ala nasi. The nasal septum ends inferiorly as the columella, the structure that separates the two nostrils. Tumours of the columella should be classified with tumours of the nasal vestibule. The olfactory portion of the nasal cavity comprises the roof, the superior concha and the adjacent upper part of the nasal septum. The maxillary sinuses are pyramidal in shape. The lateral wall of the nasal cavity lies medially, the roof is formed by the orbital floor, the alveolar process forms the floor and the apex extends into the zygomatic process of the maxilla. The cheek lies anteriorly; the pterygoid plates and pterygo-palatine fossa lie posteriorly. The maxillary sinus can be divided into a superior portion (the suprastructure) and an inferior portion (infrastructure)

by an imaginary line, Ohngren’s line, drawn between the medial canthus and the angle of the jaw. This division has prognostic significance. Tumours of the suprastructure have a worse prognosis, present later and may invade locally into the orbit and adjacent structures. The ethmoidal sinuses lie within the ethmoid bone between the medial plate of the ethmoid (part of the lateral wall of the nasal cavity) and the lateral plate of the ethmoid (part of the medial wall of the orbital cavity). The top of the ethmoid bone articulates with the frontal and splenoid bones; its floor articulates with the vomer and the septal cartilage of the nose. The frontal sinuses lie within the frontal bone, immediately above the orbits. Tumours of the frontal sinuses can easily spread into the orbits or to the anterior cranial fossa. The sphenoid sinuses lie within the body of the sphenoid bone. This sinus varies considerably in size and may extend into the occipital bone almost as far back as the foramen magnum. Tumours of the sphenoid sinus may extend directly into the middle cranial fossa. The lymphatic drainage of the nasal cavity and paranasal sinuses is poor. Tumours arising in this region rarely spread to lymph nodes. The main lymphatic drainage is to the submandibular, subdigastric and retropharyngeal nodes. Clinically enlarged nodes associated with these tumours should not be assumed to be metastatic: reactive changes, secondary to chronic infection within poorly draining sinuses, are common. The nasal vestibule and columella drain to the submandibular and subdigastric nodes. The posterior parts of the ethmoid sinus and the whole of the sphenoid sinus drain to the retropharynygeal nodes. THE NOSE

The distribution by site of 1676 tumours of the skin of the nose treated with radiotherapy173 is shown in Figure 16.6. The majority were basal-cell carcinomas, but there was a high incidence of squamous carcinomas in the vestibule (75 per cent) and columella (48 per cent). There was no overall difference in control for squamous carcinomas compared with basal-cell carcinomas. However, site was important. The control rate for carcinomas of the columella was 78 per cent (95% CI 60–95 per cent); the rate was 75 per cent (64–86 per cent) for tumours of the vestibule; and 95 per cent (93–96 per cent) for tumours at other sites. Given these differences, tumours of the nasal vestibule and columella should be considered separately from tumours at other sites on the nose. These latter tumours can be managed similarly to other tumours of the skin. The TNM staging system for skin tumours can also be used for staging carcinomas of the nasal vestibule and columella. Tumours of the vestibule will invade bone cartilage or the skin of the upper lip early, hence the high proportion of T4 tumours. This local invasion may occur surreptitiously, for example along the floor of the nasal fossa. This may, in part, explain the poorer prognosis of tumours at this site compared to other tumours of the nose. Surgery has only a limited role to play in the primary management of tumours of the nasal vestibule or columella.

Assessment of patients 393

n-1 fold Tip Bridge Vestibule Ala Columella Upper lateral Root 0%

5%

10%

15%

20%

25%

30%

Figure 16.6 Relative incidence, by site, of carcinomas of the nasal skin in a series of patients reported by Mazeron et al. in 1988.

An operation extensive enough to remove the tumour with adequate margins will be cosmetically unacceptable. A cosmetically acceptable operation will almost certainly leave positive histological margins and the subsequent requirement for radiotherapy. The appropriate radiotherapeutic technique for managing tumours of the nasal vestibule or columella is controversial. The debate concerns the relative roles of interstitial implantation and external-beam therapy. These tumours can be easily implanted using afterloaded 192Ir wires. The procedure can be carried out under local anaesthetic: 60 Gy at 0.5 Gy/h produces excellent tumour control and good cosmetic results. External-beam treatment should either be with electrons or with an anterior wedged pair of fields using megavoltage X-rays. The vexed question of the relationship between cartilage necrosis and low-energy X-rays can be avoided entirely if orthovoltage therapy is not used. The dose for megavoltage therapy should be 50–55 Gy in 20 fractions, or its equivalent. Only 5–15 per cent of patients have involvement of lymph nodes at presentation. Nodal relapse in the untreated neck is an uncommon course of treatment failure that occurs in only about 10 per cent of patients. There is therefore little indication for treating the nodes prophylactically in patients with carcinoma of the nasal vestibule. Surgical salvage is sometimes possible after failure of radiotherapy. Overall actuarial 5-year survival is between 75 per cent and 80 per cent; patients with T1 or T2 tumours have cause-specific survival of nearly 95 per cent at 5 years. NASAL CAVITY AND PARA-NASAL SINUSES

These tumours are uncommon and account for less than 10 per cent of all tumours of the head and neck. A proportion,

particularly the adenocarcinomas, may be related to occupational factors – wood dust, chromium or nickel fumes, leather dust. The distribution of histological types of tumour depends not only on the site of origin of the tumour but also, presumably as a reflection of occupational factors, on the centre reporting the results. Nevertheless, these differences will influence reported results. Doubts about the precise site of origin of the tumour will provide another source of potential confusion. In some series, it is not possible to define a site of origin in nearly 50 per cent of patients. This uncertainty will produce an effect analogous to stage shift on site-specific prognosis. NASAL CAVITY

Tumours of the nasal cavity characteristically present with nasal obstruction, discharge or epistaxis. Clinically, an ulcerating or infiltrating lesion is usually visible on nasoscopy. The T staging is summarized in Box 16.20. Nodal involvement at presentation is uncommon, between 10 per cent and 15 per cent in most series. Radiotherapy is the primary method of treatment. Anterior wedged oblique fields with 6-MV X-rays can be used, or, alternatively, a weighted anterior field plus wedged lateral fields. Iridium-192 implants may be particularly useful for treating tumours of the nasal septum. Overall survival after radiotherapy is between 50 per cent and 75 per cent. Local recurrence is the predominant course of treatment failure. Isolated nodal relapse is uncommon (less than 20 per cent of patients). Local control is a better yardstick than overall survival for assessing therapy, because approximately 50 per cent of deaths are unrelated to the original tumour.

394 Head and neck cancer

Box 16.20 UICC (2002) T staging for carcinomas of the nasal cavity and ethmoid sinus

Box 16.21 UICC (2002) T staging for carcinomas of the maxillary sinus T1:

T1:

Tumour limited to one subsite with or without erosion of bone T2: Tumour involving two subsites with or without bone invasion T3: Tumour extends to: floor of orbit or medial orbital wall; maxillary sinus; palate; cribriform plate T4a: Tumour invades anterior orbit, skin of nose or cheek, pterygoid plates, anterior cranial fossa, cribriform plate, sphenoid or frontal sinus T4b: Tumour invades any of: orbital apex; dura; brain; middle cranial fossa; cranial nerves (other than maxillary division of V); nasopharynx; clivus

The most important complication after radiotherapy for nasal cavity tumours is blindness. When tumour extends into or close to the orbit, the ipsilateral eye will be within the high-dose volume. The incidence of visual loss in patients treated with radiotherapy for nasal cavity carcinoma is between 5 per cent and 10 per cent and this must be accepted if tumour control is to be achieved. INVERTING PAPILLOMA (RINGERTZ TUMOUR)

This is a rare tumour that arises primarily in the nasal cavity. Although histologically benign, it has a conspicuous tendency to recur after surgical resection. If left untreated, it can also undergo malignant transformation, to either squamous carcinoma or adenocarcinoma. Radiotherapy has an important potential role in its management. Histologically, these tumours are characterized by hyperplasia and metaplasia of the surface epithelium with infolding into the supporting stroma. Papillary projections are often prominent, but unless there has been malignant change, the basement membrane remains intact. Careful histological review suggests that the carcinomas arise directly from the inverting papilloma rather than as coincidental separate neoplasms. Analysis with in-situ hybridization and the polymerase chain reaction suggests an association between HPV and inverting papilloma. The overall rate of malignancy associated with inverting papilloma is between 8 per cent and 10 per cent. Clinically, these tumours present as nasal obstruction and may be mistaken for polyps. The initial treatment is surgical; lateral rhinotomy and medial maxilloectomy or cranio-facial resection may be required. Although the surgical procedures sound drastic, the cosmetic and functional results are often extremely good. For small tumours, complete resection with good long-term control may be possible with per-nasal endoscopic resection. Recurrence after previous radical surgery or the presence of malignant change is an indication for radiotherapy.

Tumour limited to mucosa of maxillary sinus with no erosion or destruction of bone T2: Tumour with bone erosion or destruction extending into hard palate and/or middle nasal meatus, except extension to posterior wall of maxillary sinus and pterygoid plates T3: Tumour invades any of: bone of posterior wall of sinus; subcutaneous tissues; floor of orbit or medial orbital wall; pterygoid fossa; ethmoid sinus T4a: Tumour invades anterior orbit, skin of cheek, pterygoid plates, infra-temporal fossa, cribriform plate, sphenoid or frontal sinus T4b: Tumour invades any of: orbital apex; dura; brain; middle cranial fossa; cranial nerves (other than maxillary division of V); nasopharynx; clivus

A radical dose of radiotherapy is required: 50–55 Gy in 20 fractions, or its equivalent. The ipsilateral eye may have to be included within the treatment volume. A three-field technique with a weighted anterior and two wedged lateral fields produces a reasonable dose distribution. The longterm prognosis is good: 5-year survival is greater than 90 per cent. MAXILLARY SINUS

Early tumours of the maxillary sinus cause few symptoms: epistaxis and nasal obstruction. Tumours of the infrastructure may present as a palatal or upper alveolar swelling and can be mistaken for a primary tumour of the gum or palate. All patients with tumours of the gum or palate should have radiological investigation of the maxillary sinus to exclude the possibility that the tumour has arisen primarily at that site. Tumours that have spread beyond the sinus will cause swelling of the cheek, diplopia, proptosis, numbness and paraesthesia of the cheek or upper lip. Palpable lymphadenopathy at presentation is uncommon. The majority of tumours are squamous carcinomas. The UICC (2002) staging of maxillary sinus carcinoma is summarized in Box 16.21. It is obvious from the criteria for T staging that clinical examination alone is insufficient for staging maxillary sinus carcinomas. Adequate imaging is essential for the assessment of these tumours. The images will indicate the extent of the tumour and aid in the evaluation of operability and the planning of radiotherapy. The majority of tumours are advanced at presentation: 70–90 per cent are T3 or T4. Some early tumours can be successfully treated by surgery alone or by radiotherapy alone. However, combined treatment is required for the majority of patients. The optimal sequence for radiotherapy and

Assessment of patients 395

surgery has, in the past, been controversial. Preoperative radiotherapy may facilitate the subsequent surgery, but important prognostic information from the surgical pathology may be lost and post-surgical complications may be increased. Postoperative radiotherapy is now the preferred sequence in most centres, but extensive surgical procedures may be required for tumours of the maxillary sinus. A radical maxillectomy is usually the minimum procedure. If there has been orbital invasion, more extended surgery, possibly including orbital exenteration, may be required. Reconstruction will usually involve a myocutaneous flap and, when the orbital contents have been removed, a suitable prosthesis. The removal of the hard palate provides good access to the sinus cavity and facilitates drainage during postoperative radiotherapy. In the longer term, an obturator will be required to permit eating and speaking. The management of these patients is complicated and involves many disciplines; rehabilitation is critical to successful functional results. Radiotherapy can be given using an anterior and wedged lateral fields. When the orbit has been invaded, the eye shielding on the anterior field cannot be used and the dose to the eye may well exceed radiation tolerance. When megavoltage beams are used to treat tumours invading the cheek, bolus will be required to eliminate skin sparing and bring the high-dose volume anteriorly. Tumours that extend across midline will require both right and left wedged lateral fields. It is sometimes possible to spare some of the eye by angling these fields posteriorly, but the problem with doing this is that the dose to the spinal cord will be increased. The dose required postoperatively is 50 Gy in 20 fractions, or its equivalent in 30 fractions. When radiotherapy is used alone, the doses need to be a little higher: 55 Gy or 65 Gy. The probability of 5-year survival varies according to T stage: from 60 per cent for early tumours to less than 40 per cent for T4 tumours. Results with radiotherapy alone may be as good as those achieved with combined surgery and radiotherapy. This calls into question the absolute need for surgery in all patients with tumours of the maxillary sinus. Combined treatment is possibly unnecessary for T1 and T2 tumours and is often impossible for T4 tumours. It is probably only in the T3 tumours, therefore, that combined treatment will be required. The main cause of treatment failure is failure of local control – more than 80 per cent of all failures. Only about 5–10 per cent of patients relapse in the regional nodes. About 5 per cent of patients develop distant metastases and less than 5 per cent develop second primaries. The main late complications of radiotherapy are ocular and neurological. The temporal lobes lie closer to the antrum than is often appreciated and may, for advanced tumours, be within the high-dose volume. Temporal lobe necrosis, often manifest as temporal lobe epilepsy, may occur after radiotherapy. The brain stem and cord are also vulnerable and only careful treatment planning will avoid overdosage. If the eye is within the high-dose volume,

eventual blindness – because of severe dry eye, cataract or retinal damage – is virtually inevitable. ETHMOID SINUS

Tumours of the ethmoid sinus present with headache, visual disturbances, nasal obstruction and, in the later stages, lateral displacement of the globe of the eye. Orbital involvement is common and the ipsilateral eye may have to be sacrificed; this applies whether treatment is by surgery or by radiotherapy. These tumours are extremely rare and a variety of histological types may be encountered: squamous carcinoma, adenocarcinoma, adenoid cystic carcinoma, sarcoma, mucoepidermoid carcinoma and esthesio-neuroblastoma. This makes comparison of various approaches to treatment difficult. The 5-year survival rates reported in the literature vary from 35 per cent to 50 per cent. Local recurrence is the main cause of treatment failure; distant relapse is uncommon. Radical surgery for these tumours may involve craniofacial resection and orbital exenteration. Radical radiotherapy requires a dose of 50–55 Gy in 20 fractions, or its equivalent. The optimal field arrangement is to use a heavily weighted anterior field, with bolus to the medial canthus if necessary, and wedged lateral fields. Computed tomography planning is essential to avoid overdosing the contralateral eye, and also to ensure that any intracranial extension is adequately encompassed. SPHENOID SINUS

The main symptom of carcinoma of the sphenoid sinus is headache, which is persistent, severe and central. Cranialnerve palsies occur later. These tumours are usually advanced at presentation. Radical treatment with radiotherapy may be attempted, but the chance of cure is low. Surgery has little to offer, either as primary or as secondary therapy. For the majority of patients, palliative treatment is all that can be offered.

Tumours of the ear The ear can be divided anatomically into the pinna, the external auditory canal, the middle ear and the mastoid antrum. SQUAMOUS CARCINOMA OF THE MIDDLE EAR

These tumours are extremely rare, with an incidence in the UK of less than 1/1 000 000 per annum. There is an undoubted association with chronic suppurative ear disease: 65–70 per cent of patients with tumours of the middle ear have a history of chronic ear infection. The incidence of malignancy in patients with chronic ear disease has been estimated at between 1 in 4000 and 1 in 20 000. A crude calculation would suggest that chronic ear infection of

396 Head and neck cancer

10 years’ duration would be associated with a five-fold to twenty-five-fold risk of developing a carcinoma of the middle ear. Tumours of the middle ear can be classified by site of origin into petromastoid tumours and tympanotubal tumours. The petromastoid tumours present with pain and discharge and VIIth nerve palsy. The tympanotubal tumours can spread along the Eustachian tube and, with consequent multiple palsies of cranial nerves, imitate nasopharyngeal tumours. Nodal spread is uncommon in petromastoid tumours because the otic capsule provides a barrier to tumour spread. Tumours of the middle ear are often diagnosed late; the symptoms of the associated ear infection mask those of the tumour. Only about 20 per cent of patients have T1 tumours at presentation according to the staging system proposed by Stell.174 T1: Tumour limited to the site of origin, with no facial-nerve paralysis and no bone destruction. T2: Tumour extends beyond the site of origin, indicated by facial paralysis or radiological evidence of bone destruction, but no extension beyond the organ of origin. T3: Clinical or radiological evidence of extension to surrounding structures, dura, base of skull, parotid gland, temporo-mandibular joint etc. TX: Patients with insufficient data for classification. About 30 per cent of patients present with disease that is too far advanced to permit radical therapy. Clinically, there is destruction of the middle ear and a visible tumour obscures any proper assessment of the extent of local invasion into the structures of the middle ear and adjacent bone. Both CT and MRI are therefore essential in the assessment of patients before treatment. These tumours are best managed by a combination of conservative surgery and postoperative radiotherapy. The advantages of using surgery first are that it removes the bulk of the tumour, any infection in bone is physically removed, and the resulting cavity can be easily inspected and monitored during treatment. The surgical specimen also provides information which, taken in conjunction with the radiological investigations, enables the postoperative radiotherapy to be planned accurately and rationally. Most tumours of the middle ear can be treated using an ipsilateral wedged pair of fields. Occasionally, for tumours extending deep into the temporal bone, a contralateral field may also be required. Additional fields using electrons may be useful when there is extensive involvement of the skin and subcutaneous tissues. The absorption of electrons by bone is unpredictable and it is unwise to rely on electrons to treat disease that is unquestionably invading bone. The postoperative radiation dose should be 50 Gy in 20 fractions over 4 weeks. Some very early tumours may be satisfactorily treated solely by radiotherapy; the dose should be 52–55 Gy in 20 fractions. The main risk from radiotherapy to the temporal bone is osteoradionecrosis. Provided

overdosage is avoided – and this will require careful attention to any hot spots seen on the treatment plan – and provided that any infection is aggressively treated, this complication is unlikely. The dose to the brain stem should be limited to 40 Gy in 20 fractions, or its equivalent. Surgery and radiotherapy for carcinoma of the middle ear will produce a 5-year survival rate of around 34 per cent. Failure to control local disease is the usual cause of treatment failure; distant metastases or nodal relapse are uncommon. Effective palliative treatment is extremely difficult for tumours of the middle ear. Extensive surgical resections produce morbidity that is often worse than the disease itself, and any relief of symptoms is often brief. Conventional radiotherapy is not very effective in controlling pain. Unconventional palliative schedules, such as 14.8 Gy in four fractions in 2 days repeated two to three times at 3weekly intervals, may provide some measure of control of the tumour with minimal morbidity or upset. Palliative chemotherapy using cisplatin and 5-FU may have a shortterm benefit. TUMOURS OF THE EXTERNAL AUDITORY CANAL

The majority of malignant tumours of the external auditory canal are squamous carcinomas, but other histologies may also be encountered: adenocarcinoma, adenoid cystic carcinoma and basal-cell carcinoma. Pain and discharge are the usual symptoms, although deafness and a mass around the ear may also occur. Mastoid tenderness may be present on physical examination, but the diagnosis is usually made on the presence of obvious tumour, often polypoidal, in the canal. Facial palsy is unusual (less than 20 per cent of patients). The external auditory canal can be divided into two portions: the osseous and the cartilaginous. There are no defining differences in presentation between the two sites. Tumours of the bony canal may spread to the middle ear and it is sometimes difficult to decide whether a tumour has arisen primarily within the middle ear or has invaded secondarily from the osseous canal. Computed tomography and MRI are required to stage patients adequately. The staging system proposed by Stell174 can also be applied to tumours of the external auditory canal. Conservative surgical excision and postoperative radiotherapy is the treatment of choice. Radiation dosage and technique are similar to those described for tumours of the middle ear. The prognosis for tumours of the external auditory canal is better than that for tumours of the middle ear: long-term survival is typically in the range of 30–50 per cent. TUMOURS OF THE PINNA

Tumours of the pinna usually arise from the skin. The majority are squamous carcinomas; a minority are basalcell carcinomas. Between 5 per cent and 10 per cent of all skin tumours arise on the pinna, a disproportionately high

Assessment of patients 397

incidence. Most of these tumours can be satisfactorily treated with radiotherapy. There are tumours arising at two sites, however, for which surgery may be the preferred treatment: those arising around the origin of the external auditory canal and those arising at the retroauricular sulcus. Electron-beam therapy produces excellent results for carcinoma of the pinna. The beam energy should be chosen according to the thickness of the tumour; build-up will be required for the lower energies. For tumours on the helix, it is usually possible to shield the skin behind the ear using thin lead backed with wax, to absorb any knock-on photons. It may be necessary to use a wax earplug as a compensator for tumours arising around the concha. A dose of 45 Gy in ten fractions in 2 weeks is adequate for small (2 cm) tumours; for larger tumours, a dose of 50–55 Gy in 20 fractions in 4 weeks may be required. Perichondritis may complicate the treatment of these tumours, particularly when the cartilage has been directly invaded. The pinna becomes swollen, reddened and exquisitely tender. Fever may be present. The condition usually responds to prompt therapy with a broad-spectrum antibiotic. Late necrosis of cartilage is an accepted complication of treatment and usually occurs after trauma, particularly from spectacles; treatment with systemic antibiotics and topical steroids is usually effective. The prognosis for carcinomas of the pinna is excellent. Local control with radiotherapy as sole treatment is more than 90 per cent and survival is close to 100 per cent.

Rare and unusual tumours of the head and neck PARAGANGLIOMAS

The nomenclature and classification of these rare tumours are complex, inconsistent and confusing. They can arise at a variety of sites in the head and neck, and are described by a variety of synonyms: chemodectomas, glomus tumours etc. The literature is a poor guide, different authors applying different criteria for inclusion in ostensibly comprehensive series that often turn out to be fairly restricted. Management is controversial: extreme views are often taken with only slender, and highly selected, evidence to support them. Paragangliomas are benign tumours arising from the APUD cells of the chemoreceptor bodies. Histologically, they are highly vascular with cell nests (zellballen) separated by a dense capillary network. The cells are pale and uniform and on electron microscopy contain neurosecretory granules. Only 5–10 per cent of paragangliomas metastasize. They grow slowly, and respond slowly to non-surgical treatment. There is an association between chronic hypoxaemia (for example living at high altitude) and paragangliomas. Familial forms also occur, and there is some overlap with the MEN syndromes. Germline mutations in succinic dehydrogenase genes are associated with familial

paragangliomas.175 A significant proportion (around 20 per cent) of patients will have multiple tumours. This is particularly true of familial cases. In keeping with their neuroendocrine origin, these tumours may secrete enzymes or amines into the bloodstream: NSE, VMA and 5-HIAA. The simplest classification of paragangliomas is by site: ● ● ● ●

middle ear  tympanicum jugular bulb middle ear  jugulare hypopharynx  vagale carotid bifurcation  carotid body tumour.

The incidence is low (2/100 000 per annum) and females outnumber males by approximately 3 to 1. The symptoms and clinical findings depend on the site of origin. Tumours of the middle ear classically present with pulsatile tinnitus (75 per cent of patients), deafness (52 per cent), fullness in the ear (15 per cent) or dizziness or vertigo (10 per cent). Glomus vagale or carotid-body tumours usually present as a mass in the neck. Indentation of the pharyngeal wall is visible in approximately a third of patients with glomus vagale tumours, and there is usually a corresponding external mass just behind the angle of the mandible. A visible mass is usually present on examination of patients with tumours of the middle ear. About 30 per cent may have a visible polyp in the external auditory canal. Cranial-nerve palsies are frequent: VIII, IX, X for tympanojugulare tumours X and XII for vagale tumours. The investigation of patients with paragangliomas has been revolutionized by CT scanning and MRI. Magnetic resonance imaging angiography is an extremely useful investigation for assessing these tumours.176 Assessment of operability and the planning of surgery or radiotherapy are now far more precise than when angiography was the only reliable investigation. Detection of multiple tumours is also important, and radioisotope imaging, with either 131 I-MIBG or 111In-octreotide, can be extremely useful. The choice of treatment lies between surgical resection and radiotherapy. Surgical techniques have improved considerably over the past 10–20 years and much of the older data on surgically treated patients are now only of historical interest. Microsurgical techniques and advances in anaesthesia, with hypothermia and cardiopulmonary bypass, have improved surgeons’ ability to resect tympanicum and jugulare tumours whilst sparing blood vessels and nerves. Advances in diagnostic imaging mean that these tumours are now being diagnosed at an earlier, more easily resectable, stage. Radiotherapy alone offers more than palliation: local control can be achieved in around 75–90 per cent of carefully selected patients. Where radical surgery is feasible, the results are equally good. For younger, fitter patients with resectable tumours, radical surgery is the treatment of choice. Older patients, or those in whom surgical resection would produce unacceptable morbidity, can be treated with radiotherapy. Despite their neuroendocrine background, these tumours do not respond to treatment with somatostatin analogues.177

398 Head and neck cancer

Computed tomography planning is essential for tumours of the middle ear: an ipsilateral wedged pair of fields will usually produce a satisfactory dose distribution. Tumours extending deeply towards the midline may require a contralateral top-up field. The dose should be 50–55 Gy in 25 fractions over 5 weeks. This produces adequate control of disease without excessive morbidity. Response to treatment will depend upon how local control is defined. Paragangliomas are, by virtue of their natural history, tumours for which stable disease is an acceptable and useful therapeutic end-point. Roughly speaking, about 15 per cent of tumours regress completely after radiotherapy, 60 per cent regress by 50 per cent and 15 per cent remain stable; 10 per cent of tumours will grow in spite of treatment. Long follow-up is needed, because even an apparently well-controlled tumour may eventually re-grow. ESTHESIO-NEUROBLASTOMA (OLFACTORY NEUROBLASTOMA)

Esthesio-neuroblastoma is a small round-celled tumour that arises from the olfactory epithelium in the roof of the nasal cavity and may spread into the ethmoid sinus. The age incidence is bimodal, with peaks in the second and sixth decades. The histological appearance varies and the differential diagnosis from other small round-celled tumours may be difficult. Two features are characteristic of olfactory neuroblastoma: an intracellular fibrillary network and Homer Wright rosettes. These latter structures comprise a ring of cells around a central mass of eosinophilic fibrils. Patients usually present with anosmia, nasal obstruction, nasal discharge or epistaxis. Invasion of the orbit will produce proptosis and diplopia. The Kadish system has been used for clinical staging: A: confined to the nasal cavity B: involvement of the paranasal sinuses C: spread beyond the nasal cavity or paranasal sinuses. Treatment is primarily surgical, with craniofacial resection the standard procedure. These tumours are radiosensitive and postoperative radiotherapy should be given to patients with high-grade tumours, or those in whom excision is incomplete. The dose should be 50 Gy in 20 fractions, or its equivalent. Inoperable tumours, or tumours in patients who are unfit for surgery, can be treated with radical radiotherapy. A dose of 55 Gy in 20 fractions, or its equivalent, is necessary. The radiation treatment technique is similar to that used for ethmoid tumours. Computed tomography planning is essential; MRI may demonstrate tumour extension beyond that which is visible on CT. Late recurrence, beyond 10 years, is typical of this tumour. Distant metastases occur in up to 20 per cent of patients. There is some experience with chemotherapy in these tumours: regimens based upon adriamycin, cyclophosphamide and vincristine have traditionally been used. Platinum and etoposide regimens may also be effective.178

Overall, the 5-year survival rate with multi-modality treatment is nowadays around 70 per cent.179 JUVENILE ANGIOFIBROMA

This tumour, originally described by Hippocrates in the fourth century BC, characteristically occurs in adolescent males. The tumour is histologically benign but may behave in a malignant fashion, with local invasion and a tendency to recur after surgical resection. It is nodular, bluish red, glistening and frequently ulcerated, and obtains its blood supply from the internal maxillary artery. The majority of tumours arise at the junction of the nasal cavity and the nasopharynx. The tumour will grow readily into soft tissues and cavities, and erosion of bone is common. Clinically, these tumours present with unilateral nasal obstruction, facial deformity and/or epistaxis. Careful evaluation is required with CT and MRI and angiography. The last mentioned may usefully be combined with preoperative embolization. However, embolization alone is not adequate treatment. The management of these tumours is not straightforward.180 Primary surgery has become the treatment of choice, although radiotherapy can also achieve local control.181 The hazards of surgery should not be underestimated, but in general the principle of avoiding radiotherapy for benign disease, particularly in the young, should be adhered to. Endoscopic surgery now offers a less risky alternative to open operation – with no apparent compromise of effectiveness.182 In cases that recur after surgery, or where there is residual tumour after surgery, radiotherapy is unquestionably of benefit. Low doses are sufficient: 30 Gy in 22 fractions over 4.5 weeks will achieve local control, with minimal morbidity. There is little to be gained from the use of higher doses. There are anecdotal accounts that these tumours respond to oestrogen therapy. Because of unacceptable side effects in the adolescent male, such an approach would be a therapy of last resort. It is suggested that these tumours may regress spontaneously on maturation, and observation is acceptable in some rare cases. MERKEL-CELL CARCINOMA

This neuroendocrine tumour of the skin was first described in 1972. It has at various times also been called primary endocrine carcinoma of the skin or trabecular skin carcinoma. Cases presenting before 1972 were often classified as dermal adult neuroblastoma. Histologically, and in tissue culture, the tumour cells resemble small-cell carcinoma of the lung. Merkel-cell tumours may express NSE and/or calcitonin. Abnormalities of chromosomes, particularly translocations involving p36, 11 and 13 have been described in up to 50 per cent of cases. More than half the cases of Merkel-cell carcinoma described in the literature have involved the skin of the head and neck. Patients are typically elderly and present with a relatively short history. The lesions arise in the dermis and therefore rarely ulcerate; typically they appear as pinkish or

Assessment of patients 399

greyish blebs. About 16 per cent of patients have nodal disease at presentation; survival is poor for patients with positive nodes. Local surgery alone was initially thought to be sufficient treatment for these tumours, but the recurrence rate with this approach is around 40 per cent. The 5-year survival in patients treated with surgery alone is around 30 per cent. Wide local excision and radical node dissection is now the recommended surgical approach, and this should be combined with postoperative radiotherapy. The radiation dose should be 45–50 Gy in 20 fractions for prophylactic radiotherapy and 50–55 Gy in 20 fractions when microscopic disease is present. Both local control and survival will be improved if radiotherapy is routinely used in the management of Merkel-cell carcinoma. Approximately 25 per cent of patients develop distant metastases. Chemotherapy, using regimens similar to those used for small-cell lung cancer, has some logic, but the value is uncertain and the toxicity for the mostly elderly patients may be excessive.

there is doubt about the adequacy of the surgical margins. For patients whose tumours are inoperable, radiotherapy alone may be effective treatment. The dose required will be 50–55 Gy in 20 fractions, or its equivalent. Unconventional fractionation has also been used for melanomas; the 0,7,21 regimen (24 Gy in three fractions over 4 weeks) is simple and effective. Care must be taken with this regimen to the head and neck to ensure that vulnerable normal structures such as brain, spinal cord and retina are shielded after two fractions, as the full three fractions would exceed the tolerance of these organs. There is, however, no evidence that this is superior to conventional fractionation in head and neck melanomas. Long-term survival for patients with mucosal melanomas is poor, with less than 25 per cent in most series surviving for 5 years. Late relapses are typical, and so, given the limited data, it is unlikely that more than 20 per cent of patients with mucosal melanomas are cured by treatment. AMELOBLASTOMA

BASALOID SQUAMOUS CARCINOMA

This aggressive tumour was first recognized as a distinct pathological entity in 1986. Since then, they have been more frequently reported. Histology characteristically shows a basaloid pattern with squamous differentiation. The tumours are cytokeratin positive and there are no neurosecretory granules on electron microscopy. This suggests that basaloid squamous carcinoma is an aggressive variant of squamous-cell carcinoma rather than of any other cellular origin. On fine-needle aspiration cytology, these tumours can be confused with small-cell undifferentiated carcinoma or adenoid cystic carcinoma. The tumours occur most commonly in the hypopharynx, larynx and floor of mouth, although other sites of involvement, such as the buccal mucosa and oesophagus, have recently been recognized. The majority of patients have involved lymph nodes at presentation; extensive local invasion and distant metastases occur early in the course of the disease. The aggressiveness of the treatment should match that of the tumour. The value of chemotherapy, however, remains to be defined. MUCOSAL MELANOMAS

Only about 0.5–4 per cent of melanomas occurring in the head and neck arise from the mucosa. The nose and para-nasal sinuses are the commonest sites, and lymphatic spread is unusual. Since the structure of mucosa is different from that of skin, Clark’s histological staging system is inappropriate for mucosal melanomas. The management of mucosal melanoma has historically been surgical. However, there is increasing appreciation that these tumours may respond well to radiotherapy. Tumours that are resectable should be treated surgically, and postoperative radiotherapy should be given to those patients in whom the tumours were large or thick or where

This rare tumour arises in the vicinity of the tooth socket. Its precise histogenesis is uncertain. The classical site is in the mandible, close to the molar teeth. Patients are usually aged between 20 and 40 years and give a history of a painless swelling, often of several years’ duration. These tumours grow slowly and rarely metastasize. Plain X-rays show non-specific cystic changes, and bone involvement is often more extensive than would be suspected radiologically. The standard treatment is surgical excision. Islands of tumour may be found within the adjacent, apparently normal, bone and the excision may need to be fairly extensive. Curettage is not adequate therapy for ameloblastoma. PLASMACYTOMA

Plasmacytomas can occur as apparently isolated tumours in the head and neck. The sites most often involved are the maxilla, the maxillary antrum and the mandible. Clinically, the tumour presents as a tender swelling. In the extraosseous form of the disease this is simply a reddish purple mass; in the intra-osseous form there is concomitant destruction of bone, and pain may be severe. The diagnosis of plasmacytoma should not be accepted without a search for evidence of multiple myeloma. All patients should have a skeletal survey, bone marrow aspirate, electrophoresis of serum proteins, and urine tested for Bence Jones protein. The presence of a paraprotein does not necessarily imply that a patient has disseminated myeloma. The abnormal protein may be produced by the plasmacytoma itself and might prove useful in monitoring response to therapy. The primary treatment of plasmacytoma of the head and neck is with radiotherapy. A dose of 40–45 Gy in 20 fractions is adequate. Supplementary chemotherapy may be used in patients with extensive tumours, although the

400 Head and neck cancer

role of adjuvant chemotherapy in this context is unproven. Patients who have been treated for plasmacytoma should be carefully followed up, because many, if not all, may progress to develop systemic (multiple) myeloma.

KEY LEARNING POINTS ●

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The majority of cases of Head and Neck Cancer are entirely preventable. If people smoked and drank less the incidence of Head and Neck Cancer would appreciably decrease. Successful management of Head and Neck Cancer requires a multiprofessional, multidisciplinary approach with the individual patient placed firmly at the centre of the decision-making process. Although the majority of Head and Neck Cancers are squamous carcinomas these tumours are remarkably heterogeneous, both biologically and clinically. There are no universal rules for managing Head and Neck Cancer. Systemic therapies (chemotherapy, biologicallybased therapeutic agents) have a limited but increasingly important role to play in the treatment of Head and Neck Cancer. Some of their apparent benefit may be related to their local radiosensitising effects rather than independent cytotoxicity. Technical developments in surgery and radiotherapy will decrease the toxicity and longterm morbidity associated with the treatment of Head and Neck Cancer.

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155 Liu F-Y, Chang JT, Wang H-M, et al. [18F]Fluorodeoxyglucose positron emission tomography is more sensitive than skeletal scintigraphy for detecting bone metastasis in endemic nasopharyngeal carcinoma at initial staging. J Clin Oncol 2006; 24(4):599–604. 156 Altun M, Fandi A, Dupuis O, Cvitkovic E, Krajina Z, Eschwege F. Undifferentiated nasopharyngeal cancer (UCNT): current diagnostic and therapeutic aspects. Int J Radiat Oncol Biol Phys 1995; 32(3):859–77. 157 Khanfir A, Frikha M, Ghorbel A, Karray H, Drira MM, Daoud J. Les cancers metastatiques du nasopharynx: etude clinique et resultats therapeutiques de 95 cas. Cancer/Radiotherapie 2006; 10:545–9. 158 Al-Sarraf M, LeBlanc M, Giri PG, et al. Chemoradiotherapy versus radiotherapy in patients with advanced nasopharyngeal cancer: phase III randomized Intergroup Study 0099. J Clin Oncol 1998; 16(4):1310–17. 159 Chan ATC, Leung SF, Ngan RKC, et al. Overall survival after concurrent cisplatin-radiotherapy compared with radiotherapy alone in locoregionally advanced nasopharyngeal carcinoma. J Natl Cancer Inst 2005; 97(7):536–9. 160 Kwong DLW, Sham JST, Au GKH, et al. Concurrent and adjuvant chemotherapy for nasopharyngeal carcinoma: a factorial study. J Clin Oncol 2004; 22(13):2643–53. 161 Lee AWM, Lau WH, Tung SY, et al. Preliminary results of a randomized study on therapeutic gain by concurrent chemotherapy for regionally advanced nasopharyngeal carcinoma: NPC-9901 Trial by the Hong Kong Nasopharyngeal Cancer Study Group. J Clin Oncol 2005; 23(28):6966–75. 162 Lin J-C, Jan J-S, Hsu C-Y, Liang W-M, Jiang R-S, Wang W-Y. Phase III study of concurrent chemoradiotherapy versus radiotherapy alone for advanced nasopharyngeal carcinoma: positive effect on overall and progression-free survival. J Clin Oncol 2003; 21(4):631–7. 163 Wee J, Tan EH, Tai BC, et al. Randomized trial of radiotherapy versus concurrent chemoradiotherapy followed by adjuvant chemotherapy in patients with American Joint Committee on Cancer/International Union Against Cancer stage III and IV nasopharyngeal cancer of the endemic variety. J Clin Oncol 2005; 23(27):6730–8. 164 Zhang L, Zhao C, Peng P-J, et al. Phase III Study Comparing Standard Radiotherapy With or Without Weekly Oxaliplatin in Treatment of Locoregionally Advanced Nasopharyngeal Carcinoma: Preliminary Results. J Clin Oncol 2005 November 20, 2005;23(33):8461–8. 165 Langendijk JA, Leemans CR, Buter J, Berkhof J, Slotman BJ. The additional value of chemotherapy to radiotherapy in locally advanced nasopharyngeal carcinoma: a meta-analysis of the published literature. J Clin Oncol 2004; 22(22):4604–12. 166 Lee AW, Law SC, Ng SH, et al. Retrospective analysis of nasopharyngeal carcinoma treated during 1976–1985: late complications following megavoltage irradiation. Br J Radiol 1992; 65(778):918–28. 167 Low WK, Toh ST, Wee J, Fook-Chong SMC, Wang DY. Sensorineural hearing loss after radiotherapy and

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chemoradiotherapy: a single, blinded, randomized study. J Clin Oncol 2006; 24(12):1904–9. Wolden SL, Zelefsky MJ, Hunt MA, et al. Failure of a 3D conformal boost to improve radiotherapy for nasopharyngeal carcinoma. Int J Radiat Oncol Biol Phys 2001; 49(5):1229–34. Lee N, Xia P, Quivey JM, et al. Intensity-modulated radiotherapy in the treatment of nasopharyngeal carcinoma: an update of the UCSF experience. Int J Radiat Oncol Biol Phys 2002; 53(1):12–22. McMillan AS, Pow EH, Kwong DL, et al. Preservation of quality of life after intensity-modulated radiotherapy for early-stage nasopharyngeal carcinoma: results of a prospective longitudinal study. Head Neck 2006; 28:712–22. Le Q-T, Jones CD, Yau T-K, et al. A comparison study of different PCR assays in measuring circulating plasma Epstein–Barr virus DNA levels in patients with nasopharyngeal carcinoma. Clin Cancer Res 2005; 11(16):5700–7. Lin J-C, Wang W-Y, Chen KY, et al. Quantification of plasma Epstein–Barr virus DNA in patients with advanced nasopharyngeal carcinoma. N Engl J Med 2004; 350(24):2461–70. Mazeron JJ, Chassagne D, Crook J, et al. Radiation therapy of carcinomas of the skin of nose and nasal vestibule: a report of 1676 cases by the Groupe Europeen de Curietherapie. Radiother Oncol 1988; 13(3):165–73. Stell PM, McCormick MS. Carcinoma of the external auditory meatus and middle ear. Prognostic factors and a suggested staging system. J Laryngol Otol 1985; 99(9):847–50. Bayley JP, van Minderhout I, Weiss MM, et al. Mutation analysis of SDHB and SDHC: novel germline mutations in sporadic head and neck paraganglioma and familial paraganglioma and/or pheochromocytoma. BMC Med Genet 2006; 7:1. van den Berg R, Schepers A, de Bruine FT, et al. The value of MR angiography techniques in the detection of head and neck paragangliomas. Eur J Radiol 2004; 52(3):240–5. Duet M, Guichard JP, Rizzo N, Boudiaf M, Herman P, Tran Ba Huy P. Are somatostatin analogs therapeutic alternatives in the management of head and neck paragangliomas? Laryngoscope 2005; 115(8):1381–4. Dulguerov P, Allal AS, Calcaterra TC. Esthesioneuroblastoma: a meta-analysis and review. Lancet Oncol 2001; 2(11):683–90. Loy AH, Reibel JF, Read PW, et al. Esthesioneuroblastoma: continued follow-up of a single institution’s experience. Arch Otolaryngol Head Neck Surg 2006; 132(2):134–8. Marshall AH, Bradley PJ. Management dilemmas in the treatment and follow-up of advanced juvenile nasopharyngeal angiofibroma. ORL J Otorhinolaryngol Relat Spec 2006; 68(5):211–16. McAfee WJ, Morris CG, Amdur RJ, Werning JW, Mendenhall WM. Definitive radiotherapy for juvenile nasopharyngeal angiofibroma. Am J Clin Oncol 2006; 29(2):168–70. Pryor SG, Moore EJ, Kasperbauer JL. Endoscopic versus traditional approaches for excision of juvenile nasopharyngeal angiofibroma. Laryngoscope 2005; 115(7):1201–7.

183 Hughes J, Stead L, Lancaster T. Antidepressants for smoking cessation. Cochrane Database Syst Rev 2004(4):CD000031 184 Hughes JR, Stead LF, Lancaster T. Anxiolytics for smoking cessation. Cochrane Database Syst Rev 2000(4):CD002849. 185 Silagy C, Lancaster T, Stead L, Mant D, Fowler G. Nicotine replacement therapy for smoking cessation. Cochrane Database Syst Rev 2004(3):CD000146. 186 Rice VH, Stead LF. Nursing interventions for smoking cessation. Cochrane Database Syst Rev 2004(1):CD001188. 187 Lancaster T, Stead L. Physician advice for smoking cessation. Cochrane Database Syst Rev 2004(4):CD000165. 188 Stead L, Lancaster T. Nicobrevin for smoking cessation. Cochrane Database Syst Rev 2006(2):CD005990. 189 Usher M. Exercise interventions for smoking cessation. Cochrane Database Syst Rev 2005(1):CD002295. 190 Hajek P, Stead LF. Aversive smoking for smoking cessation. Cochrane Database Syst Rev 2004(3):CD000546. 191 Stead LF, Lancaster T. Group behaviour therapy programmes for smoking cessation. Cochrane Database Syst Rev 2005(2):CD001007. 192 Lancaster T, Stead LF. Individual behavioural counselling for smoking cessation. Cochrane Database Syst Rev 2005(2):CD001292. 193 Hey K, Perera R. Competitions and incentives for smoking cessation. Cochrane Database Syst Rev 2005(2):CD004307. 194 Hey K, Perera R. Quit and Win contests for smoking cessation. Cochrane Database Syst Rev 2005(2):CD004986 195 Stead LF, Lancaster T, Perera R. Telephone counselling for smoking cessation. Cochrane Database Syst Rev 2003(1):CD002850. 196 Lancaster T, Stead LF. Self-help interventions for smoking cessation. Cochrane Database Syst Rev 2005(3):CD001118. 197 White AR, Rampes H, Campbell JL. Acupuncture and related interventions for smoking cessation. Cochrane Database Syst Rev 2006(1):CD000009 198 Sanchiz F, Milla A, Torner J, et al. Single fraction per day versus two fractions per day versus radiochemotherapy in the treatment of head and neck cancer. Int J Radiat Oncol Biol Phys 1990; 19(6):1347–50. 199 Fu KK, Pajak TF, Trotti A, et al. A Radiation Therapy Oncology Group (RTOG) phase III randomized study to compare hyperfractionation and two variants of accelerated fractionation to standard fractionation radiotherapy for head and neck squamous cell carcinomas: first report of RTOG 9003. Int J Radiat Oncol Biol Phys 2000; 48(1):7–16. 200 Teo PM, Leung SF, Chan AT, et al. Final report of a randomized trial on altered-fractionated radiotherapy in nasopharyngeal carcinoma prematurely terminated by significant increase in neurologic complications. Int J Radiat Oncol Biol Phys 2000; 48(5):1311–22. 201 Horiot JC, Le Fur R, N'Guyen T, et al. Hyperfractionation versus conventional fractionation in oropharyngeal carcinoma: final analysis of a randomized trial of the EORTC cooperative group of radiotherapy. Radiother Oncol 1992; 25(4):231–41. 202 Cummings BJ. Benefits of accelerated hyperfractionation for head and neck cancer. Acta Oncol 1999; 38(2):131-6.

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203 Datta NR, Choudhry AD, Gupta S, Bose AK. Twice a day versus once a day radiation therapy in head and neck cancer. Int J Radiat Oncol Biol Phys 1989; 17 (suppl 1) Abs 35:132–133. 204 Pinto LH, Canary PC, Araujo CM, Bacelar SC, Souhami L. Prospective randomized trial comparing hyperfractionated versus conventional radiotherapy in stages III and IV oropharyngeal carcinoma. Int J Radiat Oncol Biol Phys 1991; 21(3):557–62. 205 Awwad HK, Khafagy Y, Barsoum M, et al. Accelerated versus conventional fractionation in the postoperative irradiation of locally advanced head and neck cancer: influence of tumour proliferation. Radiother Oncol 1992; 25(4):261–6. 206 Awwad HK, Lotayef M, Shouman T, et al. Accelerated hyperfractionation (AHF) compared to conventional fractionation (CF) in the postoperative radiotherapy of locally advanced head and neck cancer: influence of proliferation. Br J Cancer 2002; 86(4):517-23. 207 Van den Bogaert W, van der Schueren E, Horiot J-C, et al. The EORTC randomized trial on three fractions per day and misonidazole (trial no. 22811) in advanced head and neck cancer: long-term results and side effects. Radiotherapy and Oncology 1995; 35(2):91–99. 208 Dische S, Saunders M, Barrett A, Harvey A, Gibson D, Parmar M. A randomised multicentre trial of CHART versus conventional radiotherapy in head and neck cancer. Radiother Oncol 1997; 44(2):123–36. 209 Horiot JC, Bontemps P, van den Bogaert W, et al. Accelerated fractionation (AF) compared to conventional fractionation (CF) improves loco-regional control in the radiotherapy of advanced head and neck cancers: results of the EORTC 22851 randomized trial. Radiother Oncol 1997; 44(2):111–21. 210 Dobrowsky W, Naude J. Continuous hyperfractionated accelerated radiotherapy with/without mitomycin C in head and neck cancers. Radiother Oncol 2000; 57(2):119–124. 211 Olmi P, Crispino S, Fallai C, et al. Locoregionally advanced carcinoma of the oropharynx: conventional radiotherapy vs. accelerated hyperfractionated radiotherapy vs. concomitant radiotherapy and chemotherapy--a multicenter randomized trial. Int J Radiat Oncol Biol Phys 2003; 55(1):78–92. 212 Maciejewski B, Skladowski K, Pilecki B, et al. Randomized clinical trial on accelerated 7 days per week fractionation in radiotherapy for head and neck cancer. Preliminary report on acute toxicity. Radiother Oncol 1996; 40(2):137-145. 213 Jackson SM, Weir LM, Hay JH, Tsang VH, Durham JS. A randomised trial of accelerated versus conventional radiotherapy in head and neck cancer. Radiother Oncol 1997; 43(1):39-46. 214 Overgaard J, Hansen HS, Specht L, et al. Five compared with six fractions per week of conventional radiotherapy of

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squamous-cell carcinoma of head and neck: DAHANCA 6&7 randomised controlled trial. The Lancet 2003; 362(9388):933–940. Poulsen MG, Denham JW, Peters LJ, et al. A randomised trial of accelerated and conventional radiotherapy for stage III and IV squamous carcinoma of the head and neck: a Trans-Tasman Radiation Oncology Group Study. Radiother Oncol 2001; 60(2):113–22. Suwinski R, Bankowska-Wozniak M, Majewski W, et al. Randomized clinical trial on continuous 7-days-a-week postoperative radiotherapy for high-risk squamous cell head-and-neck cancer: a report on acute normal tissue reactions. Radiother Oncol 2005; 77(1):58–64. Sanguineti G, Richetti A, Bignardi M, et al. Accelerated versus conventional fractionated postoperative radiotherapy for advanced head and neck cancer: results of a multicenter Phase III study. Int J Radiat Oncol Biol Phys 2005; 61(3):762–71 Ezzat M, Shouman T, Zaza K, et al. A randomized study of accelerated fractionation radiotherapy with and without mitomycin C in the treatment of locally advanced head and neck cancer. J Egypt Natl Canc Inst 2005; 17(2):85–92 Hliniak A, Gwiazdowska B, Szutkowski Z, et al. A multicentre randomized/controlled trial of a conventional versus modestly accelerated radiotherapy in the laryngeal cancer: influence of a 1 week shortening overall time. Radiother Oncol 2002; 62(1):1–10. Pignon JP, Baujat B, Bourhis J. Apport des meta-analyses sur donnees individuelles au traitement des cancers ORL. Cancer/Radiotherapie 2005; 9(1):31–36. Bourhis J, Audry H, Overgaard J, et al. Meta-analysis of conventional versus altered fractionated radiotherapy in head and neck squamous cell carcinoma (HNSCC): Final analysis. International Journal of Radiation Oncology Biology Physics 2004; 60(Supplement 1):S190–S191. Budach W, Hehr T, Budach V, Belka C, Dietz K. A metaanalysis of hyperfractionated and accelerated radiotherapy and combined chemotherapy and radiotherapy regimens in unresected locally advanced squamous cell carcinoma of the head and neck. BMC Cancer 2006; 6(1):28. Bourhis J, Pignon JP. Chemo-radiation vs altered fractionation in Head & Neck Cancer patients: how, when, for whom? Radiother Oncol 2006; 78(Suppl 1):s19. DerSimonian R, Laird N. Meta-analysis in clinical trials. Controlled Clin Trials 1986; 7:177–188. American Joint Committee on Cancer. Cancer Staging Manual. New York: Springer, 2002 Sobin LH, Witterkind CH, TNM classification of malignant tumors (6th ed.). John Wiley & Sons, New York: UICC 2002, 19–51.

17 Thyroid MASUD HAQ AND CLIVE HARMER

Introduction Epidemiology Aetiology Pathogenesis Pathology and natural history Diagnostic evaluation Management of differentiated thyroid cancer Follow-up

408 408 408 409 410 412 415 421

INTRODUCTION The thyroid follicular cell can give rise to a wide variety of neoplasms, ranging from incidental papillary microcarcinoma that has no effect on life expectancy despite minimal treatment, to lethal anaplastic cancer, invariably fatal despite aggressive treatment. The majority of cases occur in young adults, but thyroid cancer can affect any age group. Although the estimated incidence has increased by 14.6 per cent over the last four decades, the estimated death rate has fallen by 21 per cent. Mortality from thyroid cancer represents less than 1 per cent of all cancer deaths and only 10 per cent of patients with thyroid cancer will die from it. Because of these low rates, morbidity caused by treatment should not exceed that caused by the disease. The management of thyroid cancer demands multidisciplinary care, including consultation with the pathologist, surgeon, oncologist, endocrinologist and nuclear physician.

EPIDEMIOLOGY Thyroid cancer is the commonest endocrine malignancy but it remains rare, accounting for only 1 per cent of all cancers. Incidence rates vary widely, with the highest in Iceland and Hawaii (12–15 per 100 000) and only 2.2 per 100 000 population in the UK. These geographical differences are

Treatment of metastatic disease Dosimetry of 131I therapy Complications of radioiodine treatment External-beam radiotherapy and chemotherapy Management of anaplastic carcinoma Management of medullary thyroid cancer Management of thyroid lymphoma Future prospects References

421 422 423 424 426 428 430 431 433

probably caused by environmental and dietary factors rather than by race or heredity.1 The incidence has been increasing, partly reflecting the past use of radiotherapy for benign childhood conditions but also due to earlier detection with the wide availability of ultrasonography and fine-needle aspiration cytology (FNAC). In England and Wales, a significant increase in incidence was seen during the period 1962–1984, especially in north and mid Wales, where the highest levels of fallout radiation from nuclear reactors were documented.2 In 2001, there were 1431 new cases diagnosed in the UK, with an estimated 300 deaths. Despite these changes, the 5-year survival in the UK has improved to 77 per cent.3 Most cases occur in patients between 25 and 60 years of age, but thyroid cancer can occur in the very young and the elderly. The median age at diagnosis is earlier in females than in males, for both papillary and follicular tumours.4 For papillary carcinoma, the median age at diagnosis is 40 years for females and 44 years for males, while for follicular cancer the median age at diagnosis is 48 years for females and 53 years for males. The incidence of both is higher in women, with a female:male ratio of 3:1.

AETIOLOGY Radiation exposure is the only risk factor known definitively to increase the incidence of well-differentiated cancer,

Pathogenesis 409

although a large study from the Connecticut Tumor Registry showed only 9 per cent of thyroid cancers could be related to radiation.5* By contrast, in several American studies from the 1950s, between 32 per cent and almost 100 per cent of children with thyroid cancer had received prior irradiation for a variety of conditions, including enlarged thymus, tonsils, adenoids or acne. The recognition of the association between irradiation and thyroid cancer led to the elimination of the widespread use of radiotherapy for benign conditions in infants and children by 1960. Large series of patients who had neck irradiation during childhood show that the latent period is at least 3–5 years, with most cases occurring between 20 and 40 years after exposure; there is no apparent drop-off in the increased risk, even after 40 years, following radiation exposure.6* The age at exposure is inversely related to the risk. Analysis of the pooled individual data from seven studies showed that the probability of developing thyroid cancer is related to the radiation dose absorbed by the thyroid;7*** this is a strong indication that radiation is a cause of thyroid cancer. A radiation effect is seen at doses as small as 10 cGy. Over most of the dose range, the data fit best to an excess relative risk model, although an absolute risk model cannot be excluded. At highest doses, cell killing was thought to overtake tumour formation; with increasing dose, the slope (the excess relative risk) of the dose–response curve does not decline, indicating that the relative risk remains significant.6* Data from the acute radiation exposure among the survivors of the atomic bombs in Hiroshima and Nagasaki are similar, showing an increased risk in the younger age population, and in females in particular. The estimated dose to thyroid from these acute incidents also showed a proportional relationship to risk.8*** Improvements in multi-modality therapy incorporating radiation for neoplastic conditions in infants, children and young adults result in many patients cured of tumour who can then be followed up for long-term effects of the therapeutic radiation they received. A dramatically increased relative risk (between 132 and 310) of developing thyroid cancer among individuals treated for neuroblastoma or Wilms’ tumour indicates the significance of age at exposure.9* Patients treated for Hodgkin’s disease or non-Hodgkin’s lymphoma tend to be older and, although the radiation dose to thyroid is high, they more frequently develop hypothyroidism or thyroid nodules than thyroid cancer; the estimated relative risk of developing cancer is 16–80. In the adult population treated with therapeutic radiation, the risk drops off. A relative risk of 2.3 was estimated among 150 000 women treated with radiotherapy for cervical cancer.10* A second type of radiation exposure to the thyroid is from radioisotopes which concentrate in the gland. Large welldesigned studies have shown no increase in thyroid cancer among individuals who had diagnostic nuclide scans or were treated with radioactive iodine for thyrotoxicosis.11* However, data regarding exposure to nuclear fallout in the Marshall Islands, Nevada, and Chernobyl all show a significant increase in thyroid cancer. The importance of age at

exposure is evident in recent studies. In Belarus, the most affected country post-Chernobyl, the incidence increased to 13.5 per 100 000 children in 2000, compared to the usual incidence of less than 1 per 100 000. The majority of cases occurred in children under the age of 10 years at the time of the accident, with at least two-thirds younger than 5.12*** Thyroid tumours can be produced in animals by iodine deficiency or drugs. A common factor in these experimental conditions is prolonged stimulation by thyroid-stimulating hormone (TSH). A sequence of reversible hyperplasia followed by irreversible hyperplasia and in some cases by the subsequent development of follicular carcinoma has been noted.13 Evidence of primary TSH-related induction of thyroid tumours in humans is not convincing. However, papillary carcinoma is more common in iodine-rich areas such as islands, while a number of case-controlled studies have strongly suggested that low dietary iodine content is responsible for the increased rates of follicular and anaplastic cancer in areas of endemic goitre.14*** In addition, dietary iodine supplementation has been shown to increase the relative proportion of papillary cancer and to decrease the frequency of follicular cancer. Because of the strong female predominance, the influence of sex-hormone status has been investigated. Factors such as parity, early menopause, contraceptive use and late age at first birth have been associated with an increased risk of thyroid cancer, although these associations are weak and inconsistent. A pooled analysis of case-control studies also confirmed a weak association of menstrual and reproductive factors with thyroid cancer risk.15*** The biological basis of these epidemiological observations could be that oestrogen acts as a growth promoter on thyrocytes. Some experimental evidence suggests that thyrocytes express oestrogen receptors, and oestrogens may stimulate thyrocyte growth in cell-culture systems. It has also recently been shown that tamoxifen inhibits the growth of papillary cancer cells both in vitro and in vivo. Genetic factors may play a role in a small group of patients with differentiated thyroid tumours. Familial syndromes associated with thyroid tumours of follicular-cell origin include familial adenomatous polyposis coli, Gardner’s syndrome, Turcot’s syndrome, Cowden’s disease and Carney complex. Familial occurrence of differentiated thyroid cancer has also been recognized, although it appears to be rare, occurring in only 2.5–4 per cent of cases.16

PATHOGENESIS Although thyroid follicular cells can give rise to both benign and malignant tumours, the evidence to support an adenoma to carcinoma multi-step pathogenesis is not universally accepted. Malignant transformation is due to the activation of proto-oncogenes or the inactivation of tumoursuppressor genes in combination with environmental factors. Defects to the tyrosine kinase (trk) receptor genes are commonly found in thyroid cancer. The interaction of

410 Thyroid

these receptors with growth factors leads to the activation of the mitogen-activated protein (MAP) kinase pathway through ras and braf proteins, resulting in uncontrolled cell division. Abnormalities of the trk receptor genes have almost exclusively been associated with papillary carcinoma; these include ret/papillary thyroid cancer (PTC) rearrangements, trk rearrangements and met over-expression. The higher frequency of ret/PTC rearrangements in patients post-Chernobyl suggests that radiation exposure may be one of the mechanisms leading to their activation. Activation of the ras proto-oncogene by a point mutation is common in both papillary and follicular tumours (approximately 40 per cent). Activation of this oncogene is found at all stages from benign through well-differentiated to undifferentiated carcinoma, suggesting that it represents an early event and that this defect is not by itself sufficient for carcinogenesis. A high frequency of braf protein point mutations has also been identified in papillary thyroid cancer. This mutation is associated with tumours of aggressive behaviour and may serve as a novel independent molecular prognostic marker in risk evaluation.17* Translocation between genes encoding transcription factors Pax8 (Paired box 8) and PPARγ (peroxisome proliferator-activated receptor gamma) has been identified in both follicular adenoma and carcinoma, suggesting a role in their pathogenesis. Inactivating point mutations in the p53 tumour suppressor gene have been observed in many undifferentiated (anaplastic) thyroid cancers.

PATHOLOGY AND NATURAL HISTORY Thyroid tumours can originate from the follicular epithelium, from parafollicular or C cells, or from non-epithelial stromal elements.18*** The World Health Organisation (WHO) classifies malignant epithelial thyroid tumours as: papillary carcinoma, follicular carcinoma, medullary carcinoma and undifferentiated (anaplastic) carcinoma.19 The pTNM classification is recommended to assist in management decisions and for uniformity of case-series reporting.

Papillary carcinoma Papillary carcinoma is the most common type, comprising 80 per cent of all thyroid malignancies. These tumours are almost three times as common in women as in men, with a peak incidence in the third and fourth decades. The histological hallmarks are branching papillae arranged on a fibrovascular stalk. Tumour cells are cuboidal with homogeneous cytoplasm and characteristic hypochromatic nuclei with absent nucleoli (Orphan Annie eyes) and may contain laminated calcified psammoma bodies (Fig.17.1a). The term ‘mixed’ papillary and follicular carcinoma is no longer used, because the majority of papillary carcinomas do contain some follicular areas. Features of papillary cancer include an

infiltrating pattern of growth, multi-focality (up to 75 per cent of cases) and spread to the regional lymph nodes. Obvious cervical adenopathy is seen in 50 per cent of patients at presentation, but has been reported in as many as 90 per cent of those who underwent elective node dissection. Haematogenous metastases are uncommon and mainly involve the lungs; lung involvement at diagnosis occurs in 5–10 per cent of cases in adults but may be in up to 25 per cent of children. Certain variants of papillary cancer such as the tall cell, columnar and diffuse sclerosing variant have been shown to be more aggressive. Micropapillary or ‘occult’ carcinoma has the same histological features as papillary cancer but has been defined by the WHO to be a tumour 1 cm or less in maximum dimension. These tumours are a common incidental finding at autopsy, their incidence being dependent on overall age of the population, the ethnic group studied and the diligence with which the pathologist looks for these foci. Incidence ranges from 0.5 per cent to 14 per cent, with a greater incidence in older age groups. The discrepancy between the incidences of occult and clinically detected thyroid cancer indicates that these minimal lesions may have a different biology. Although they can metastasize to regional lymph nodes, they rarely cause significant morbidity or mortality.20***

Follicular carcinoma Follicular carcinoma accounts for 5–20 per cent of thyroid tumours, is also three times more common in females than in males, but tends to present in mid-life. It is a tumour of follicular origin but lacks the diagnostic features of papillary cancer. It may be extremely difficult to diagnose when well differentiated, as the appearance is similar to that of both normal thyroid and benign follicular adenoma. The presence of capsular or vascular invasion is often the only feature to denote malignancy (Fig. 17.1b). Depending on the degree of invasiveness, they may be described as minimally or widely invasive. This distinction defines the less favourable prognosis associated with the latter. Lymphnode metastases are less common than in papillary tumours, but haematogenous spread, mainly to bones and lungs, is present in 14 per cent of patients at diagnosis. Hürthle-cell carcinoma was previously considered a variant of follicular cancer and is composed of cells that exhibit oncocytic changes (Fig. 17.1c). However, it is now recognized as a distinct pathological entity because of its different oncogenic expression. The majority of Hürthle-cell tumours are benign, but malignancy is well documented in the form of local recurrence and distant metastases. Histopathological studies have shown that either capsular or vascular invasion is a reliable criterion of malignancy. Although they are usually well differentiated and produce thyroglobulin, these tumours rarely take up iodine. This is probably a contributory factor to their poorer prognosis than other follicular carcinomas.21,22

Pathology and natural history 411

(a)

(b)

(c)

(d)

(e) Figure 17.1 (a) Papillary cancer, tall cell variant; (b) follicular cancer, showing capsular invasion; (c) Hürthle cell carcinoma; (d) medullary carcinoma with amyloid stroma; (e) non-Hodgkin’s lymphoma of MALT type

Insular carcinoma is a form of poorly differentiated tumour arising from follicular cells with behaviour intermediate between differentiated (papillary/follicular) and undifferentiated (anaplastic) carcinoma. Microscopically, the tumour is characterized by a nested growth pattern and prominent vascularity. It invades both lymphatics and veins, resulting in nodal and distant metastases, and has a poor prognosis.

Anaplastic carcinoma Anaplastic thyroid cancer is one of the most aggressive of all malignancies and one of the most lethal. Epidemiological studies indicate that the incidence has decreased to approximately 1–3 per cent of all thyroid tumours23* in the period 1968 to 1992. This decrease has been attributed partially to dietary iodine prophylaxis and an overall decrease

412 Thyroid

Table 17.1 Medullary carcinoma of the thyroid (MTC) syndromes. Phenotype Sporadic MTC MEN IIa

Frequency (%)

Presentation

80 9

MTC MTC, phaeochromocytoma, hyperparathyroidism MTC, phaeochromocytoma, neuromas (see Fig. 17.2), Marfanoid habitus MTC

MEN IIb

3

FMTC

8

MEN, multiple endocrine neoplasia; FMTC, familial medullary thyroid cancer.

in endemic iodine-deficient goitre. It is most common in the elderly, with 75 per cent of patients being over 60 years old. Most series quote a ratio of men to women of 1:3. It may be associated with a long history of goitre, and a significant number of cases are probably causally associated with a pre-existing well-differentiated thyroid tumour.24 These tumours also arise from the follicular cell. However, the natural history, clinical presentation and outcome reflect their undifferentiated biology with rapid growth and invasive characteristics. Histological variants include small cell, giant cell and spindle cell, although their behaviour does not differ significantly. Patients present with a rapidly enlarging collar of tumour and confluent lymphadenopathy often invading the trachea, larynx or oesophagus, resulting in stridor, hoarseness or dysphagia. The majority die within 6 months of the first symptom, from aggressive loco-regional disease. At diagnosis, 25–50 per cent of patients have pulmonary metastases and at death this figure approaches 100 per cent.

intestinal peptide (VIP). It is composed of small round cells within an amyloid stroma. Immunohistochemical staining for calcitonin granules is the most accurate method to establish the diagnosis (Fig. 17.1d). Fewer than 20 per cent of sporadic tumours are bilateral, but in the familial syndromes, medullary cancer is usually bilateral and multi-centric. At presentation, involvement of cervical or mediastinal lymph nodes is seen in 11–75 per cent of patients, and distant metastases (mainly to lung, bone and liver) in 12 per cent.

Lymphoma of the thyroid Lymphoma of the thyroid is a rare disease, representing 2 per cent of thyroid malignancies and 2 per cent of extranodal lymphomas. Chronic autoimmune stimulation, as in Hashimoto’s thyroiditis, is a predisposing factor. There is a strong female predominance, ranging from 3:1 to 8:1, while the median age at diagnosis is in the seventh decade, similar to that of anaplastic cancer, from which it must be distinguished (Fig. 17.1e). Patients present with a rapidly enlarging, painless neck mass, and one-third of patients experience compressive symptoms. Symptoms also include fever, night sweats and weight loss, but these are rare.28* Almost all thyroid lymphomas are non-Hodgkin’s of B-cell origin, intermediate or high grade. Biologically, many thyroid, breast, parotid, lung and gastrointestinal lymphomas are a distinct subset of extranodal lymphomas derived from mucosa-associated lymphoid tissue (MALT). These small-cell lymphomas are characterized by a low grade of malignancy, slow growth rate and a tendency for late relapse or second lymphomas in other MALT sites.29*

Rare tumours Medullary carcinoma Medullary carcinoma of the thyroid (MTC) was first described by Hazard in 1959 as a solid neoplasm without follicular histology. It accounts for 7 per cent of all thyroid tumours but for 14 per cent of all thyroid cancer mortality. The incidence has been increasing in recent years due to screening.25*** Sporadic MTC accounts for 70–80 per cent of cases, with the remainder being familial. Hereditary MTC can occur alone – familial medullary thyroid carcinoma (FMTC)26* – or as the thyroid manifestation of multiple endocrine neoplasia type II syndromes (MEN IIa and MEN IIb), as shown in Table 17.1. These are autosomal dominant disorders caused by germline mutations in the RET protooncogene, located on the long arm of chromosome 10, band q11.2, which codes for a tyrosine kinase receptor.27 Medullary carcinoma of the thyroid arises from the parafollicular or ‘C’ cells, which are of neural crest origin and secrete calcitonin as well as other peptides: carcinoembryonic antigen (CEA), adrenocorticotrophic hormone (ACTH), serotonin, bradykinin, prostaglandin and vasoactive

While the relatively low mortality rate of thyroid cancer in general is due to the preponderance of well-differentiated carcinoma, there exists a subset of rare thyroid tumours that exhibit aggressive behaviour and have a poor prognosis. These require careful consideration and different treatment paradigms to optimize clinical outcome. Extremely rare types of thyroid cancer include thymus-like tumours, mucoepidermoid carcinoma, mixed medullary follicular cancers, teratomas and sarcomas, including angiosarcoma and liposarcoma.30* In contrast, the thyroid is more commonly affected by metastases originating from other primary tumour sites.31*

DIAGNOSTIC EVALUATION Palpable thyroid nodules are present in 4–7 per cent of all adults; age, gender, history of exposure to ionizing radiation and method by which the nodules are detected all significantly influence the findings of different retrospective

Diagnostic evaluation 413

Table 17.2 Diagnostic evaluation for thyroid tumours. Procedure History

Physical examination

Finding

Significance

Radiotherapy to head and neck Family history of MTC Family or personal history of phaeochromocytoma or hyperparathyroidism Diarrhoea, flushing Hashimoto’s thyroiditis Solitary thyroid nodule

Known aetiology of thyroid cancer Inherited in an autosomal dominant pattern Suggestive of MEN IIA or IIB syndrome

Common in MTC Known association with thyroid lymphoma Higher incidence of cancer in solitary nodule (5–15%) Lower incidence of cancer; cancer may present in dominant nodule May indicate cancer

Multiple nodules Thyroid fixation, hoarseness, Horner’s syndrome Enlarged cervical lymph nodes Fine-needle aspiration Ultrasonography X-ray Radionuclide imaging (131I, 99 mTc) 131

I mIBG, 111In octreotide

CT scan, MRI Thyroglobulin

Malignant, suspicious, benign, insufficient sample Differentiates solid from cystic nodules, assists in fine-needle biopsy Psammomatous calcification Cold, warm or hot nodule

Imaging of medullary thyroid cancer Extent of primary tumour, lymph nodes and metastases Preoperative elevated value Postoperative elevated value

Calcitonin

More consistent sign of malignancy

Normal value Preoperative elevated value Postoperative elevated value Postoperative normal value

70–97% accuracy Solid nodules more often malignant Suggests thyroid nodule is malignant 15–25% of cold nodules are malignant; lower incidence of cancer in warm and hot nodules May detect residual, recurrent or metastatic cancer Assist in treatment planning Does not distinguish between benign and malignant tumour Indicates residual, recurrent or metastatic thyroid cancer Supportive evidence of lack of disease Indicates C-cell hyperplasia or MTC Indicates residual/recurrent/metastatic MTC Indicates lack of disease

MEN, multiple endocrine neoplasia; MTC, medullary carcinoma of the thyroid; mIBG, meta-iodobenzylguanidine; CT, computed tomography; MRI, magnetic resonance imaging.

studies. In one pathological study, up to 90 per cent of women over the age of 70 years and 60 per cent of men over the age of 80 years had nodular goitre. In most series, a 5–15 per cent risk of cancer in all thyroid nodules for the total population is reported.32 Therefore, it is neither practical nor necessary to remove every nodule in order to exclude malignancy. Investigations should be directed towards selecting those with an increased risk of malignancy. However, no single clinical feature, physical finding or laboratory test is pathognomonic for the detection of thyroid cancer, except for the serum calcitonin level in medullary carcinoma and FNAC. A diagnostic algorithm is presented in Table 17.2. Information from the history and physical examination may help in assessing the risk of malignancy. Exposure to

ionizing radiation, extremes of age, family history of thyroid cancer or MEN syndromes (Fig. 17.2) and other inherited disorders, such as Gardner’s syndrome and Cowden’s disease, increase the suspicion of cancer. Although not specific for malignancy, a history of rapid growth, pain, hoarseness, or airway obstruction is of concern. On examination of the neck, attention should be paid to the size, consistency, mobility and number of nodules as well as to the presence of enlarged lymph nodes. The risk of malignancy is greater in a solitary nodule (5–15 per cent) than in multiple nodules; a dominant nodule or a nodule that changes size in a multinodular goitre requires further investigation. Cervical adenopathy is probably the most consistent feature of malignancy with a thyroid mass, but lacks specificity.

414 Thyroid

Figure 17.2 Patient with MEN IIb demonstrating neuromas of the tongue. Neuromas may also involve the buccal mucosa, eyelid, conjunctiva and glans penis

High-resolution ultrasonography is a useful adjunct to clinical examination for the assessment of nodule size, the detection of multiple nodules and for assisting in FNAC. A hyperechoic nodule with well-defined margins is more likely to be benign. In contrast, a nodule that appears hypoechoic with irregular margins, microcalcification, and increased blood flow should raise suspicion. Despite these features, ultrasound cannot reliably distinguish benign from malignant lesions; it can, however, establish whether a lesion is solid or cystic. In a review of 16 series, 21 per cent of the solid lesions, 12 per cent of the mixed and 7 per cent of the cystic lesions were cancerous.33* Therefore, a solid mass, although most often benign, has the highest chance of being malignant. The single most important investigation for evaluating thyroid nodules is FNAC. It can often be undertaken in the clinic, without the need for ultrasound guidance. The impact this procedure has had on clinical practice is reflected by a reduction in the number of thyroid operations performed, a greater proportion of malignancies removed at surgery, and an overall reduction in the cost of managing patients with nodules.34*** The diagnostic accuracy of FNAC ranges from 70 per cent to 95 per cent, but is dependent on the skills of the operator and the reporting cytopathologist. The report should be defined as inadequate (C1), benign (C2), follicular (C3), suspicious (C4) or malignant (C5). Results typically comprise benign 70 per cent, malignant 4 per cent, suspicious 9 per cent, or inadequate 17 per cent. Inadequate samples should be followed by repeat FNAC, preferably under ultrasound guidance. The malignant potential of follicular neoplasms cannot be determined cytologically, therefore surgical excision is mandatory. False-negative results are reported in 1–6 per cent and false-positive results in 3–6 per cent. Fine-needle aspiration cytology is adequate to diagnose anaplastic cancer, but Trucut biopsy is required to distinguish reliably the subtypes of primary thyroid lymphoma by immunohistochemistry and ascertain MALT status.

Radionuclide imaging with iodine (131I) or sodium pertechnetate (99 mTc) is of limited value in the initial evaluation of thyroid nodules since the advent of FNAC. Malignant thyroid tissue either does not incorporate iodine or incorporates less iodine than normal thyroid, so that a malignant lesion appears as a cold area on the scan.35*** Scanning cannot differentiate benign from malignant nodules and thus is used to assign only a probability of malignancy. Malignancy has been reported in 10–15 per cent of cold nodules, 5 per cent of warm and less than 2 per cent of hot nodules.36*** These results indicate that cold nodules are more likely to be malignant, but warm and hot nodules can also be malignant. The goals of scintigraphy in patients with established thyroid cancer are to locate metastases or residual neoplasm and to predict the efficacy of therapy with 131I. Following thyroidectomy and radioiodine ablation of normal residual thyroid tissue, diagnostic whole-body 131I scanning is highly specific; foci of uptake correspond to thyroid cancer metastases. While it is clear that higher scanning doses improve the visualization of disease, even low doses of 75 MBq diminish the uptake of subsequent therapeutic 131 I. Proposals to avoid this tumour stunning include the use of smaller diagnostic doses and the use of an alternative tracer such as 123I. Less well-differentiated tumours and some that are well differentiated (especially in older patients) may concentrate so little 131I that the diagnostic scan will prove false negative and the therapeutic dose will not treat effectively. Locating these tumours may be helpful in planning alternative treatment such as surgical resection. Thallium-201 chloride and radiolabelled somatostatin analogues concentrate in more than half of thyroid tumours not visualized by 131I.37*,38* Fluorodeoxyglucose positron emission tomography (18FDG-PET) may also be useful in suspected recurrent well-differentiated tumour, but is of greater value for poorly differentiated carcinoma and MTC. Indium-111 (111In) octreotide and 131I meta-iodobenzylguanidine (mIBG) are concentrated in 25–60 per cent of MTC and may be helpful in locating sites of disease, particularly in patients with an elevated calcitonin but no clinical or radiological evidence of tumour39*** see Table 17.2. Pentavalent dimercapto succinic acid (V-DMSA) whole-body scintigraphy is the best method for locating occult MTC, but has no therapeutic potential. Computed tomography (CT) can define the morphology of the thyroid gland, tumour extension to structures such as trachea or vessels, and nodal involvement in the neck and mediastinum. Imaging of the chest may reveal micronodular disease in the lungs not shown on chest X-ray. In addition, CT is particularly valuable in radiotherapy treatment planning and in assessing the effectiveness of therapy. Magnetic resonance imaging (MRI) is preferred in order to avoid the use of iodinated contrast, which remains in the body for a considerable time, reducing the uptake of subsequent radioiodine therapy. Magnetic resonance imaging is useful in depicting lesion margins, the invasion of adjacent

Management of differentiated thyroid cancer 415

structures and cervical lymphadenopathy. The presence of a cystic node or a nodal diameter of 15 mm suggests metastasis; using these two criteria, a specificity of 100 per cent with an 82 per cent accuracy but a sensitivity of only 60 per cent has been estimated.40* Magnetic resonance spectroscopy has yet to be evaluated.

MANAGEMENT OF DIFFERENTIATED THYROID CANCER Differentiated thyroid cancer is one of the most controversial malignancies as regards treatment. Debate involves almost every stage of management decision: the extent of initial surgery, the need for lymph-node dissection, the role of radioactive iodine ablation, the value of dosimetry in radioiodine therapy, and the role of adjuvant externalbeam radiotherapy (EBRT).41*** The major reasons for these ongoing controversies are that thyroid cancer is rare and that its behaviour is indolent (although there are groups of tumours that behave more aggressively). Due to lack of prospective studies, the potential for relapse may be either underestimated, resulting in patients receiving inadequate treatment, or, due to referral bias, overstated and patients are overtreated. Evidence-based guidelines for the management of thyroid cancer in adults were published in 2002 by the British Thyroid Association in conjunction with the Royal College of Physicians of London.42 Certain factors have been linked to the behaviour of welldifferentiated carcinoma and are used to determine prognosis. Groups such as the Mayo Clinic, the Lahey Clinic and the European Thyroid Association have published data on factors identified through retrospective analyses that correlate with survival. Because all factors are closely interrelated,

only multivariate analysis can identify their individual prognostic significance. In most studies, age is found to be the most important predictor of outcome; a significant increase in mortality is seen over the age of 40 (Fig. 17.3). Males tend to fare worse than females, but gender is of much less prognostic importance. Tumour size, extension and grade are also related to the risks of recurrence and survival (Fig. 17.4). Patients with papillary cancer fare better than those with follicular well-differentiated carcinoma; less well-differentiated follicular tumours show a significantly higher relapse rate and shorter survival. The impact of nodal status is controversial. In some series, it is found to be associated with an increased risk of loco-regional recurrence, although the effect on survival is less clear. The results of multivariate analysis for 1390 patients with differentiated thyroid cancer treated at the Royal Marsden Hospital, London, between 1929 and 1999 are shown in Table 17.3.43 Based on these prognostic factors, several scoring systems have been developed to help in assessing individual patient risk of dying from cancer and planning treatment (AGES, AMES, GAMES, MACIS). None of these systems is perfect, but all succeed in identifying at least high-risk and low-risk patients.44*,45*** The low-risk group includes young patients with small (1 cm) well-differentiated tumours confined to the gland with no evidence of nodal or distant spread. Prognosis in this group is excellent, with cancerspecific mortality less than 1 per cent at 30 years.46* The recurrence and survival rates are strikingly different in the high-risk group, which includes older patients with locally advanced or metastatic disease at presentation47* or less well-differentiated tumours. Risk-group analysis makes a selective approach to treatment possible and can spare many patients the morbidity of unnecessarily aggressive treatment, without compromising outcome.

% Probability of cause-specific survival

100

80

40 40–49

60 50–59 40 60 AGE 40 N  548 AGE 40–49 N  275 AGE 50–59 N  243 AGE 60 N  321 Chi-squared  242.2

20

O  31 O  49 O  67 O  123 df  3

E  127.1 E  58.6 E  41.9 E  42.4 p  0.000

0 0

10

20

30

Time since diagnosis (years)

40

50

Figure 17.3 Differentiated thyroid cancer: Royal Marsden Hospital experience 1929–99 (1390 patients). Cause-specific survival according to age.

416 Thyroid

Both serum Tg monitoring and iodine scanning may be difficult to interpret in the presence of a substantial thyroid remnant. Remnant ablation in this situation is associated with a low success rate, of the order of only 30 per cent, with higher administered activities or repeat doses required to achieve complete ablation. The main argument against radical surgery, i.e. morbidity, is less important now that experienced surgeons are reporting reduced complication rates. Vocal-cord paralysis occurs in only 1–3 per cent and permanent hypocalcaemia in 1–6 per cent in most specialist centres following total or near-total thyroidectomy. The role of elective level VI tracheo-oesophageal groove clearance of nodes down to the level of the thymus awaits clarification. Those in favour argue that this is the commonest site of lymph-node metastases,52* that the potential morbidity associated with re-operating at a later date is much greater, and that there is an increased risk of subsequently finding inoperable disease. However, this procedure does carry a slightly increased risk of hypoparathyroidism and recurrent laryngeal nerve damage. Our policy is to perform an elective tracheo-oesophageal groove clearance on the ipsilateral side only, proceeding to a lateral neck dissection if paratracheal disease is demonstrated clinically, radiologically or during the operation. If extensive superior mediastinal disease is detected, we favour a combined thoraco-cervical approach using a sternal split to extend dissection down to the arch of the aorta.53* The surgical management of lymph-node metastases is also controversial. The presence of metastatic disease in nodes, especially in the lower-risk young patients, is not always seen as an adverse prognostic factor.50* It does correlate with increased loco-regional recurrence in most series, although the effect on survival is not clear. However, the largest single institution series of papillary carcinom a (2192 cases) did confirm a significant adverse effect of

Surgical treatment Surgery remains the initial and potentially curative treatment for differentiated thyroid cancer. However, there is no universal agreement as to the extent of the surgical procedure, partly because many still regard thyroid cancer as a non-fatal disease. There have been no prospective randomized trials and in retrospective analyses there is always patient-selection bias as well as the confounding effect of non-surgical adjuvant therapy. The minimum requirement is complete excision of all macroscopic disease, which usually includes ipsilateral lobectomy and isthmusectomy, avoiding damage to the parathyroid glands and recurrent laryngeal nerves.48 A more radical initial approach is advocated by the majority of surgeons in view of the high incidence of bilateral multi-focality (as high as 87 per cent), especially in papillary carcinoma. Most studies have shown a significant reduction in local recurrence rates following total (or near-total) thyroidectomy, with some also reporting improved overall survival.49*,50* Even in the low-risk patients with tumours smaller than 1 cm diameter, the loco-regional recurrence rate after lobectomy significantly exceeded that seen after total thyroidectomy – 20 per cent and 5 per cent respectively at 20 years – although overall survival was similar.46* Survival was improved with bilateral resection in patients with unfavourable prognostic factors.49* This was also true for locally advanced tumours invading the aerodigestive tract: following complete resection, the 5-year survival was greater than 50 per cent, but without such intervention, 80 per cent of these patients were dead at 5 years.51* Other major advantages in favour of total thyroidectomy are that postoperative follow-up using serum thyroglobulin (Tg) and radioiodine diagnostic scanning are facilitated, as well as subsequent 131I therapy if this becomes necessary.

100

% Probability of survival

80

T1

60

40

T2

T3 T1 N  206 T2 N  684 T3 N  199 T4 N  254

20

Chi-squared  140

0 0

10

O  27 O  183 O  80 O  116

E  65.6 E  238.5 E  55.2 E  46.7

df  1

p  0.0001

20

T4 30

Time since diagnosis (years)

40

50

Figure 17.4 Differentiated thyroid cancer: Royal Marsden Hospital experience 1929–99 (1390 patients). Survival according to tumour stage

Management of differentiated thyroid cancer 417

Table 17.3 Prognostic factors for survival, local recurrence and distant recurrence for 1390 patients with differentiated thyroid cancer treated at RMH between 1929 and 1999 (Cox proportional hazards regression model for multivariate analysis). HR (95% CI) Factor Age (years) 40 40–49 50–59 60 T stage T1 T2 T3 T4 M stage M0 M1 Surgery NT/TT ST/HT/L B/E Iodine ablation No Yes Grade I II III

Survival

Local recurrence

Distant recurrence

1.0 2.5 (2.3–2.7) 6.2 (5.6–6.8) 15.3 (13.9–16.8) P  0.001

1.0 1.4 (1.3–1.6) 2.1 (1.9–2.3) 2.9 (2.7–3.2) P  0.001

1.0 1.8 (1.6–2.1) 3.3 (2.9–3.7) 6.0 (5.3–6.8) P  0.001

1.0 1.9 (1.7–2.1) 3.5 (3.1–3.9) 6.5 (5.8–7.2) P  0.001

1.0 1.7 (1.5–1.9) 2.8 (2.5–3.2) 4.8 (4.2–5.4) P  0.001

1.0 1.8 (1.6–2.1) 3.4 (2.9–3.9) 6.2 (5.4–7.2) P  0.001

1.0 6.9 (5.4–8.7) P  0.001

1.0 0.92 (0.51–1.6) NS

1.0 3.9 (2.6–6.0) P  0.001

1.0 1.89 (1.49–2.4) 4.66 (3.56–6.1) P  0.001

1.0 1.8 (1.38–2.36) 3.48 (2.49–4.85) P  0.001

1.0 1.87 (1.3–2.5) 3.72 (2.5–5.5) P  0.001

1.0 0.67 (0.55–0.82) P  0.001

1.0 0.39 (0.31–0.50) P  0.001

1.0 0.4 (0.3–0.58) P  0.001

1.0 2.6 (2.3–2.9) 6.6 (5.9–7.5) P  0.001

1.0 2.0 (1.7–2.3) 3.8 (3.3–4.5) P  0.001

1.0 2.6 (2.1–3.1) 6.7 (5.6–8.0) P  0.001

RMH, Royal Marsden Hospital; NS, not significant; NT, near total thyroidectomy; TT, total thyroidectomy; ST, sub-total thyroidectomy; HT, hemi-thyroidectomy; L, lobectomy; B, biopsy; E, enucleation; HR, hazards regression.

clinical nodal status on survival.54* Papillary carcinoma can be found in the regional lymph nodes of 35–75 per cent of patients when dissections are performed and carefully examined. However, recurrence is not seen in 75 per cent of patients with clinically uninvolved nodes not undergoing routine neck dissection. This argues against the need for elective lateral deep cervical-node dissection of the clinically uninvolved neck. If clinically apparent nodal disease is present, many surgeons recommend a modified neck dissection preserving the sternomastoid, spinal accessory nerve and internal jugular vein.55*** However, some still perform simple node excision, previously known as ‘berry picking’; although regional recurrence rates are high, a survival disadvantage has not been proven. If nodes are clinically involved,

we favour a selective node dissection of levels II, III, IV and VI; thyroid cancer rarely spreads to submandibular or posterior cervical lymph nodes (levels I and V).

Endocrine treatment Thyroid stimulating hormone is the main regulator of thyroid function, differentiation and proliferation. Binding of TSH to its receptor on thyroid cells primarily activates a cyclic adenosine monophosphate (cAMP) cascade, leading to thyroid hormone synthesis and release, as well as to expression of thyroid-specific genes, including those encoding Tg and thyroperoxidase. Differentiated thyroid

418 Thyroid

100

% Probability of survival

80

60

40 Iodine ablation Iodine ablation N  923 None N  467 Chi-squared  14.61

20

O  192 O  233 df  1

E  231.2 E  193.8 p  0.001

None

0 0

10

20

30

Time since diagnosis (years)

carcinomas retain some degree of thyroid-specific gene expression and function similar to normal thyroid cells; therefore they are responsive to stimulation by TSH. In thyroid cancer cell lines, TSH has been shown to stimulate vascular endothelial growth factor secretion and angiogenesis. Thus TSH may promote growth in some thyroid cancers.56* The beneficial effect of TSH suppression has not been assessed in prospective studies. However, available data suggest that thyroxine reduces the risk of recurrence, tumour progression and death from thyroid cancer.57*** It is generally accepted that a TSH level below 0.1 mU/L is desirable,42 but there is no evidence that undetectable TSH levels offer any advantage over low but detectable levels. Monitoring the free thyroxine (T4) level in the athyroid patient receiving thyroxine often gives a false high value, therefore we favour total TSH suppression (0.1 mU/L), maintaining the free tri-iodothyronine (T3) level in the normal range in order to avoid hyperthyroidism.58* Concern regarding permanently low TSH levels on bone metabolism have failed to show an increased fracture risk despite accelerated bone turnover59*,60* based on biochemical markers of osteoclastic activity. Nevertheless, postmenopausal women who are at risk may benefit from adequate dietary calcium intake, biphosphonates, or hormone-replacement therapy.

Radioactive iodine ablation of residual thyroid tissue The value of postoperative 131I to ablate residual normal thyroid is still debated. Arguments in favour of remnant ablation are that it permits the subsequent identification by a whole-body scan of any residual or metastatic carcinoma and increases the sensitivity of Tg measurement for follow-up.61 Most importantly, several retrospective

40

50

Figure 17.5 Differentiated thyroid cancer: Royal Marsden Hospital experience 1929–99 (1390 patients). Survival in relation to radioiodine

studies have documented that it decreases tumour recurrence and death50*,62*** (Fig. 17.5). However, the beneficial effect of 131I ablation can be seen mainly in patients who are at high risk of recurrence, such as those with larger tumours, extrathyroid extension and involved lymph nodes, as well as those with residual disease.63* In low-risk patient groups, and especially in those with microcarcinoma, prognosis is so favourable after surgery alone that little further improvement is possible with 131I ablation.46* The optimal activity of 131I required to achieve successful ablation remains controversial, with doses ranging between 1.1 GBq and 3.7 GBq. Higher initial iodine doses were thought to be more effective in achieving complete ablation with a single administration. The philosophy of a large dose ablation was based on the possibility that it ablates not only remnants but also possible micrometastatic deposits.64* The same authors also stressed the importance of delivering maximal radiation dose from the first iodine administration; due to mechanisms that are at present poorly understood, the biological half-life of subsequent administrations falls, therefore reducing the radiation dose delivered. In 1976, McCowan et al. were the first to report that iodine doses of 3–3.7 GBq were not more effective than 1.1 GBq,65* findings that were confirmed by several retrospective analyses.66* The long-term tumour recurrence rate was 7 per cent following a low dose of 1.1–1.85 GBq, compared with 9 per cent following a high dose of 1.9–7.4 GBq.67*** The advantages of administering the smallest effective dose of 131I are patient convenience and lower cost, as well as a reduced risk of treatment-related complications from lower whole-body radiation exposure. The only prospective randomized clinical trial to evaluate the optimal 131I ablation dose (involving 149 patients) showed that increasing the administered activity beyond 1.85 GBq resulted in plateauing of the dose–response curve; a radiation absorbed dose to the thyroid remnant

Management of differentiated thyroid cancer 419

New patient referred with Differentiated Thyroid Cancer History and clinical examination Review histology With total thyroidectomy

Without total thyroidectomy Completion thyroidectomy ⴙ Level VI

selective dissection of levels II, III,  IV

At 4 weeks – avoid sea food, added salt, iodine-containing medicines and x-ray contrast FBC, biochemistry, TSH, Tg, CXR Ablation dose 3 GBq 131I 131

I whole body scan at 3 days, start T3 OPD appointment at 6 weeks TSH, T3, Tg

Abnormal scan or adverse feature Book 4 months after ablation 5.5 GBq 131I Stop T3 for 14 days FBC, biochemistry, TSH, Tg

Normal scan, no adverse feature 185 MBq 131I whole-body scan only if Tg-antibodies or clinical suspicion. Stop T3 for 14 days (or give rhTSH) TSH, Tg

Therapy dose 5.5 GBq 131I 131

I whole body scan at 3 days, restart T3

OPD appointment at 6--8 months stimulated-Tg  neck US If tests negative, change to thyroxine  200mcg, target TSH  0.1mU/l

OPD appointment at 6 weeks TSH, T3, Tg

Known tumour Negative scan PBI  0.01%

Reconsider surgery

Positive scan Tg  3ug/L PBI  0.01%

Normal

External beam radiotherapy

Annual follow-up TSH, T3, Tg

Repeat 5.5 GBq 131 I at 6 months

Figure 17.6a New patient referred with differentiated thyroid cancer. T3, tri-iodothyronine; FBC, full blood count; TSH, thyroid-stimulating hormone; CXR, chest radiograph; US, ultrasound; Tg, thyroglobulin; PBI, protein-bound radioactive iodine concentration; rhTSH, recombinant human TSH.

greater than 300 Gy did not result in a higher ablation rate.68** Successful ablation was achieved in 77 per cent of thyroid remnants with the lower dose of 1.85 GBq. Maxon et al. used dosimetry to individualize administered activity so as to deliver a radiation dose of 300 Gy to the thyroid remnants.69* They reported an 81 per cent ablation rate, with no apparent gain from using a dose greater than 300 Gy. However, one meta-analysis found that a single administered activity of 1110 MBq was more likely to be unsuccessful in fully ablating thyroid remnants compared to higher activities of 2775–3700 MBq.70***

Four weeks after total thyroidectomy, by which time the level of TSH should be 30 mU/L,71*** we recommend an ablation dose of 3 GBq 131I to all patients with differentiated thyroid cancer, except children over the age of 10 with small node-negative tumours and patients in whom carcinoma is an incidental microscopic histological finding (Fig. 17.6a). This dose ablates 75 per cent of remnants and delivers a mean radiation dose of 410 Gy.72* Scans of the neck and whole body are obtained on the third day (Fig. 17.7), when the patient is usually discharged from the ward, subject to the total-body radioactivity having fallen below the

420 Thyroid

Follow-up algorithm: differentiated thyroid cancer low risk patients Patients clinically disease free at 6–8 months after surgery and 131I ablation

Clinical examination, US neck, stimulated-Tg* on TSH suppression

Tg < 1ug/L no other abnormality

Tg between 1 and 2ug/L no other abnormality

Tg > 2ug/L or clinical disease

MRI neck, CT chest

surgery or radioiodine therapy

repeat rhTSH-Tg* after 6 months

Tg  1ug/L

Tg stable

Tg rising

post-therapy scan

Positive

Negative

annual follow-up Tg on TSH suppression rhTSH – FDG PET/CT

18

Patients suitable for inclusion:Low risk patients for recurrence or persistent disease Papillary and minimally invasive follicular thyroid cancers Initial total or near-total thyroidectomy followed by 131I ablation No uptake outside the thyroid bed post-ablation Undetectable Tg (1ug/L) on TSH suppression Absence of anti -Tg antibodies

Patients excluded:Distant metastases at presentation Extensive disease pT4 Poorly differentiated tumours Incomplete surgery Anti -Tg antibodies

* Stimulated –Tg, rhTSH on TSH suppression Days 1 and 2 – 0.9 mgs im injections, Day 5 – Tg (72 hrs after last injection) TSH day 3 measurement

Figure 17.6b Follow-up algorithm: differentiated thyroid cancer, low-risk patients. Tg, thyroglobulin; MRI, magnetic resonance imaging; CT, computerized tomography; US, ultrasound; TSH, thyroid-stimulating hormone; 18FDG-PET/CT, 18-fluorodeoxyglucose positron emission tomography/computerized tomography

permitted level. Replacement thyroid hormone is then commenced in the form of T3 20 mcg three times a day. Blood is also taken on day 6 to measure the protein-bound 131 I level (PBI). Historically, ablation success was determined by a diagnostic scan performed with 74–185 MBq of 131 I at 6–12 months,73* and was defined by no visible uptake in the thyroid bed or uptake of less than 0.1 per cent

above background in association with an undetectable Tg. This is no longer universally practised, except in patients with anti-Tg antibodies, when serum Tg becomes invalid. The current recommended criterion for successful ablation is an undetectable serum Tg (1 μg/L) following recombinant TSH (rhTSH) stimulation (in association with a negative neck ultrasound) at 9–12 months.74 Provided these

Treatment of metastatic disease 421

disease, psychiatric disorders, post-partum, hypopituitarism, and those unable to tolerate prolonged hypothyroidism. Its expense currently limits wider use in the UK, although not in Europe or North America.

FOLLOW-UP

Figure 17.7 Whole-body scan following an ablation dose of 3 GBq 131 I, showing intense uptake in the thyroid bed

criteria are met and there are no adverse features, no further treatment is required (Fig. 17.6b). The patient is switched to lifelong T4 at an average daily dose of 200 mcg in order to suppress TSH to an undetectable level. If the results prove abnormal, further imaging and treatment are required. If therapeutic radioiodine is indicated, this should be repeated at 6–12-monthly intervals until uptake disappears and the Tg becomes undetectable. To optimize iodine uptake by both residual normal thyroid and cancer, TSH stimulation is necessary and therefore patients should be hypothyroid at the time of 131I administration. Proper preparation is achieved by a low-iodine diet, avoidance of iodine-rich contrast media, and discontinuation of T3 for 14 days (or 28 days for T4) prior to ablation. As an alternative to thyroid hormone withdrawal, patients may be prepared for ablation with rhTSH while remaining on thyroid hormone. The uncertainty over whether ablation rates differ between patients given rhTSH and those prepared with standard withdrawal has largely been resolved. A retrospective study comparing the ablation rate in 42 patients prepared with withdrawal and 45 patients with rhTSH reported comparable success rates (81 per cent versus 84 per cent).75*** The more recent prospective study following ablation with 3.7 GBq confirmed comparable ablation rates (each of 100 per cent) in patients prepared by either rhTSH or withholding thyroid hormone.76** Previously, rhTSH was available only for diagnostic 131I scans and stimulated Tg measurement. This has now changed, with rhTSH licensed in the UK for ablation with activity of 3.7 GBq, although it remains unlicensed for lowdose ablation or 131I therapy.77 It markedly improves the patients’ quality of life, which is otherwise severely impaired during prolonged periods of hypothyroidism. We recommend its routine use for diagnostic purposes and for ablation or therapy, especially in patients unable to produce TSH and those in whom thyroid-hormone withdrawal is medically contraindicated. This includes patients with cardiac

Annual follow-up comprising clinical examination and estimation of free T3, TSH and Tg is essential to ensure normal thyroid function with TSH suppression and to detect recurrent tumour. Early discovery of recurrence is of paramount prognostic significance, for both cure and survival.78* Local or regional relapse develops in 5–20 per cent of patients with differentiated thyroid cancer. Most relapses occur during the early years of follow-up, but may be detected even after 40 years; follow-up should therefore be lifelong. The risk of loco-regional failure relates partly to tumour aggressiveness, being higher with certain histological subtypes (tall cell, columnar cell and diffuse sclerosing papillary variants), poorly differentiated carcinomas, large tumours and lymph-node involvement at presentation. The risk of recurrence is also closely related to the extent of initial treatment, with limited thyroidectomy resulting in a higher recurrence rate than complete thyroidectomy.57*** Recurrence in the thyroid bed or cervical lymph nodes may be discovered by palpation. Ultrasonography or MRI is useful to delineate disease extent. Serum Tg is usually elevated, although it may be undetectable in 20 per cent of patients on T4 who have isolated lymph-node metastasis.79* Whole-body scanning following the administration of 131I, especially high activities, will reveal uptake in 60–80 per cent of patients with lymph-node disease. Surgery is the treatment for loco-regional recurrence, and complete resection should be attempted in all patients who are fit. Even if disease cannot be completely removed, surgical debulking is beneficial and facilitates the subsequent use of radioiodine. If surgical removal would result in unacceptable morbidity or has to be incomplete, both radioiodine treatment and EBRT should be used to control local disease.80*,81* The outcome for patients with locoregional recurrence is closely related to its site, initial prognostic factors and response to treatment. Mortality after local recurrence has been high in most series; a 10-year survival rate of only 60 per cent has been reported.67***

TREATMENT OF METASTATIC DISEASE Distant metastases develop in 5–23 per cent of patients with differentiated thyroid carcinoma, mainly in lung and bone, less frequently in liver and brain. In any individual patient, the long-term result of treatment is unpredictable; an interplay between patient and tumour characteristics seems to determine outcome. Both univariate and multivariate analyses have highlighted the adverse prognostic effect on survival of older age at the time of discovery of metastases.78*,82* Treatment comprises repeated doses of

422 Thyroid

(a)

(b)

Figure 17.8 (a) Whole-body scan following an ablation dose of 3 GBq 131I demonstrating diffuse lung metastases plus uptake in the right side of the neck. (b) Following repeated 131I therapy, the last post-therapy whole-body scan demonstrates complete eradication of tumour

radioiodine. Activities ranging from 3.7 GBq to 11.1 GBq at 3–9-month intervals have been employed; many centres use a dose of 5.5 GBq at 6-monthly intervals (Fig. 17.8). There is no maximum limit to the cumulative 131I dose that can be given to patients with persistent disease, provided that individual doses do not exceed 2 Gy total-body exposure, progressive improvement can be documented and each pre-treatment blood count confirms the absence of bone-marrow damage. A whole-body scan 3 days after iodine administration (by which time the blood background will be negligible) provides scintigraphic assessment of disease, and serial scanning will document response to treatment. Diagnostic scanning using a tracer dose of iodine is not necessary prior to therapy and may have an adverse effect, because tumour stunning by the diagnostic dose may reduce the uptake of therapeutic 131I.83* The value of 123I as a scanning agent to prevent stunning has been confirmed.84* In addition, a significant proportion of patients with residual tumour, as evidenced by an elevated Tg, demonstrate a negative diagnostic scan but uptake can be documented in the posttherapy scan.85*,86* The real benefit of iodine treatment has been questioned; however, at least one large study clearly demonstrated its

independent prognostic benefit on survival. Younger patients with limited-volume disease, mainly in the lungs, who achieve a complete response to radioiodine treatment have been consistently shown to have the best prognosis, with a 15-year survival of 89 per cent.78* In contrast, older patients and those with large metastases or bone involvement are less likely to respond.87* Although distant metastases, particularly in the lung, may remain stable for years, there is evidence that early treatment may affect outcome. Microscopic foci are more radiosensitive; complete response was reported in 82 per cent of patients with uptake in lung metastases not seen on chest radiography but in only 15 per cent of those with visible micronodules or macronodules.88* The radioresistance of large deposits may be due to poor vascularity, resulting in limited and inhomogeneous iodine distribution, or to the appearance of radioresistant clones. Bone lesions demonstrate a low response rate to radioiodine; surgical excision, when possible, or EBRT should be added.89*,90* Surgical resection with curative intent for patients with a solitary deposit not concentrating iodine and those with bulky disease resistant to iodine has achieved a 5-year post-metastasectomy survival of 46 per cent.91* Sometimes metastases persist despite the administration of substantial 131I therapy doses.92 This may be the consequence of rapid turnover of radioiodine in tumour (short effective half-life) with discharge before adequate energy has been deposited. The effective half-life in metastases responding to therapy has been shown to be more than twice as long as in those not responding: 5.5 days compared with 2.5 days.93* Lithium carbonate can prolong the biological halflife of 131I within thyroid tumours without increasing wholebody radiation exposure.94* However, blood levels need to be monitored closely to avoid toxicity, and the need for psychiatric expertise to be available makes its routine use impracticable. In a retrospective review of 400 patients, FDG-PET positivity was a strong adverse predictor of survival on multivariate analysis (in addition to age), suggesting that these patients should be treated more aggressively.95*

DOSIMETRY OF 131I THERAPY Historically, the use of radioiodine has been empirical. Fixed activities of 1–3.7 GBq for remnant ablation and 3.7–7.5 GBq for therapy are still administered based on experience and likely side effects. However, measurement of the absorbed dose (Gy) has several advantages.96,97 One is that patients are not over-treated and their overall radiation exposure is kept as low as possible. Second, it is the only way to determine whether further 131I therapy will be effective, so that alternative treatment can be considered in unsuccessful cases. But the most important reason for basing iodine therapy on lesion dosimetry is that optimizing the administered dose gives the highest probability that the lesion will be eradicated. Because current information suggests that a stunning effect occurs with incomplete or inadequate therapy and may be permanent, the most effective

Complications of radioiodine treatment 423

Radiation absorbed dose (Gy)

1000

100

10

1 NR

PR Patient clinical response

strategy is to attempt to eradicate a tumour with either a single 131I administration or as few treatments as possible. Over the last decade attempts have been made to calculate the radiation absorbed dose by thyroid remnants and metastatic deposits.69*,72* In order to calculate the radiation dose (D), three parameters must be determined: the initial activity in the target tissue (Ao), the effective half-life of the radioiodine (Te) and the mass of tissue (m). We use single photon emission computerized tomography (SPECT) or PET imaging to measure the volume of metabolically active thyroid tissue or tumour, and following iodine treatment, perform sequential quantitative scans from which time–activity curves can be produced. By fitting the data and extrapolating to the time of administration, the initial activity in the target tissue and the effective half-life of iodine are determined. Calculations are then performed using the Medical Internal Radiation Dosimetry (MIRD) formula: D  0.16AoTe/m. Preliminary analysis of 25 dosimetry studies in patients with metastatic lesions showed a wide variation in radiation absorbed dose (5–621 Gy) from a fixed administered 131 I activity of 5.5 GBq.98 There was evidence of a dose–response relationship clearly explaining the spectrum of clinical response (Fig. 17.9). However, MIRD dosimetry calculations are based on two major assumptions: that radioactivity is uniformly distributed throughout the tumour, and that washout of 131I is governed by a single exponential function. If either of these assumptions is inaccurate, errors will be introduced into the dosimetry estimates. In addition, errors on each parameter (percentage uptake, target activity, half-life and mass) will contribute to a combined error of absorbed dose.99 Given all the problems with dosimetry and the potential for large errors, it could be questioned whether trying to perform dose calculations is worthwhile. With current efforts to produce accurate

CR

Figure 17.9 Dose–response relationship in radioiodine therapy for patients with metastatic thyroid cancer. NR, no response; PR, partial response; CR, complete response

sequential registered three-dimensional SPECT images and dose–volume histograms of therapy distributions, a greater level of accuracy may be achieved eventually, resulting in improved effectiveness of treatment.

COMPLICATIONS OF RADIOIODINE TREATMENT Radioiodine therapy is well tolerated, with a few patients experiencing mild nausea within the first 24 hours postadministration. Radiation thyroiditis may occur in the first week following ablation and is characterized by pain, swelling and localized tenderness in the neck. Symptoms may be severe if there is a large thyroid remnant, but respond to steroid treatment. Acute sialadenitis affecting the parotid or submandibular glands occasionally occurs within 48 hours of administration and may last a few days. A liberal fluid intake and frequent use of lozenges after the first 24 hours should be routine to reduce salivary uptake and limit this reaction. Intravenous administration of amifostine has been reported to result in reduced salivary uptake.100* Sialadenitis may persist into a chronic phase, with episodes recurring over years; about 70 per cent of patients showed a significant decrease in salivary function, which can result in xerostomia and appeared to be dose related.101* Persistent painful masses may require excision. Most patients demonstrate a transient slight reduction in platelet and white cell counts (lymphopenia) after 131I therapy. It is of no clinical importance. These effects reach a nadir at 4–6 weeks after therapy, with recovery in the majority within 6 months. Myelodysplasia leading to aplastic anaemia is rare and likely to occur only in patients with extensive bone metastases who have received a high cumulative dose in excess of 2 Gy per treatment.102* Acute radiation pneumonitis and chronic pulmonary fibrosis have been reported in patients with diffuse functioning lung metastases following single therapeutic activities exceeding 9 GBq.103* A 6–12-month interval between iodine doses may reduce

424 Thyroid

the risk of this complication. If serial lung function tests indicate early damage, future doses can be fractionated. Because differentiated thyroid cancer occurs in women of childbearing age and young men, the possibility that iodine treatment may affect fertility has created concern. A temporary increase in follicular stimulating hormone (FSH) levels has been noted following 131I treatment in both male and female patients, indicating temporary gonadal dysfunction. A positive correlation between FSH levels and the cumulative activity of iodine has been also reported.104* In a small prospective study using thermoluminescent dosimetry, the radiation absorbed dose to the testes was found to be relatively low: 5.4–9.8 cGy and 12–19.2 cGy following the administration of 3 GBq and 5.5 GBq respectively.105* Regarding female patients, no significant difference was observed in fertility rates, birth rates or prematurity among women treated with radioiodine and those not treated.106*,107* Amongst 406 patients under the age of 40 years, temporary amenorrhoea and minor menstrual irregularities were seen in 20 per cent; 427 normal children were born to 276 women, with only one patient unable to conceive.108* The carcinogenic hazard of 131I in the treatment of differentiated thyroid cancer (DTC) has been the subject of several reports.109* An increased risk of acute myeloid leukaemia was seen in the past, especially in patients receiving a cumulative activity in excess of 40 GBq, although patient numbers were small.110*** A recent multi-centre study involving 6841 thyroid cancer patients has quantified the risk of subsequent second primary malignancy.111* Compared to the general population, an increased risk of 27 per cent was seen. It was estimated that a 3.7 GBq dose of 131 I would result in an excess of 53 solid malignant tumours and 3 leukaemias in 10 000 patients during 10 years of follow-up. In addition, a strong correlation existed between the cumulative activity of radioiodine and the risk of bone, soft-tissue, colorectal and salivary-gland cancers. These results highlight the need to restrict radioiodine treatment to those likely to benefit.

EXTERNAL-BEAM RADIOTHERAPY AND CHEMOTHERAPY The role of EBRT in the management of differentiated thyroid cancer remains controversial because published data are conflicting. In many reports, results are presented with no distinction between prophylactic (adjuvant) postoperative EBRT and the treatment of microscopic or macroscopic residual disease. Due to the rarity of the disease and its long natural history, there are no prospective randomized controlled trials. External-beam radiotherapy does not prevent the simultaneous administration of radioiodine, although 131I should be given first whenever possible, as uptake may be diminshed after radiotherapy and if there is good uptake by tumour, EBRT may become unnecessary. However, 20 per cent of tumours fail to concentrate iodine effectively.

Radiotherapy is not indicated in patients with favourable prognostic features, or in young patients with residual disease demonstrating avid iodine uptake.112*** Patients at higher risk of persistent disease or loco-regional recurrence comprise patients at presentation with a large number of lymph-node metastases (greater than 10), nodes demonstrating extracapsular extension (greater than 3), involvement of central lymph nodes, and tumour size greater than 4 cm.113* Indications for EBRT therefore include macroscopic unresectable residual tumour and microscopic disease or involved excision margins. Adjuvant irradiation is required only in older patients with less differentiated cancers that are unlikely to concentrate radioiodine, especially those with extensive extra-thyroidal spread, extracapsular lymph-node extension or recurrent disease. Farahati et al. suggest that adjuvant EBRT should be restricted to patients older than 40 years with locally advanced tumours (pT4) that are non-iodine avid.114* Treatment improved local control in those aged over 40 years with invasive papillary cancer and lymph-node involvement from 22 per cent to 90 per cent at 10 years (p  0.01). A similar group of patients with follicular cancer did not show any significant benefit. In patients without lymph-node disease, loco-regional recurrence is infrequent, such that EBRT is rarely necessary. In 1985, Tubiana et al. reported 97 patients treated with EBRT after incomplete surgery:81* local recurrence at 15 years was 11 per cent in the irradiated group compared to 23 per cent in those treated with surgery alone. More recently, Tsang et al. reported on 207 patients (155 papillary, 52 follicular) with postoperative residual microscopic disease.115* In papillary carcinoma, those irradiated had a 10-year cause-specific survival of 100 per cent and a local relapse-free rate of 93 per cent, compared to the non-irradiated group with a cause-specific survival of 95 per cent (p  0.038) and a local relapse-free rate of 78 per cent (p  0.01). External-beam radiotherapy did not significantly effect cause-specific survival or local relapse-free rate in follicular tumours. The most plausible explanation is that patients with follicular carcinoma have a worse survival due to haematogenous spread, and any benefit of local treatment may be obscured by this biological pattern of behaviour. The presence of gross inoperable macroscopic disease is another indication for EBRT. In our retrospective study, complete regression was achieved in 37.5 per cent and partial regression in 25 per cent.80* Similarly, Chow et al.116* reported the beneficial effects of EBRT in patients with gross macroscopic residual disease, with an improvement in local control from 24 per cent to 56 per cent at 10 years (p  0.001). Irradiation is also effective for advanced and recurrent inoperable Hürthle-cell carcinoma, claiming a relatively more important role because this tumour takes up iodine less frequently.22 Despite the small study size, the 5-year local recurrence rates from Birmingham UK indicate a possible dose response.117* These were 63 per cent following a dose of less than 50 Gy but only 15 per cent and 18 per cent for doses of

External-beam radiotherapy and chemotherapy 425

50–54 Gy and more than 54 Gy. Most patients had either macroscopic or microscopic residual disease. Our policy is to use EBRT infrequently because high dose is required and side effects, especially oesophagitis, are unavoidable. The phase I target volume comprises both sides of the neck (bilateral deep cervical plus supraclavicular nodes), thyroid bed and superior mediastinum from the level of the hyoid down to the carina, with shielding of the subapical portions of the lungs (Fig. 17.10). Anterior and undercouched fields ensure comprehensive coverage,

Figure 17.10 Radiotherapy technique for thyroid cancer: phase I volume covering the thyroid bed, neck and superior mediastinum

with the patient supine and the neck maximally extended. Lead protection of the submandibular salivary glands is required if the treatment volume needs to extend proximally to the mastoid tips. A Perspex shell is avoided initially so as to achieve skin-sparing, but is then fashioned for the phase II volume, which includes sites of microscopic or macroscopic tumour. We recommend three-dimensional planning and conformal beam shaping assisted by a multileaf collimator (Figs 17.11 and 17.12). The aim is to deliver 60 Gy in 30 daily fractions over 6 weeks using 4–6 MV photons. The phase I prescription should be a mid-plane dose of 46 Gy in 2-Gy daily fractions (maximum spinal cord tolerance), with phase II delivering 14 Gy in seven fractions. Known residual tumour in the region of the thyroid bed or neck nodes may be treated with a small phase III volume, adding 6 Gy in three fractions, provided there is no additional dose to the spinal cord. Intensity-modulated radiotherapy can improve the dose distribution by minimizing the dose to the spinal cord and thus permit dose escalation.118* A brisk cutanoeus erythema is invariable, with radiation oesophagitis requiring liquid analgesia, liberal hydration and adequate dietary intake. Symptoms resolve within 2 weeks after the completion of treatment. Acute laryngitis and dysphonia also resolve completely. Late effects include dysphagia, which may occur months or years later, caused by stricture or motility changes as a result of muscle or nerve damage. Reduction in the length of the oesophagus in the phase II volume minimizes such risks. Due to shielding of the subapical portions of the lungs, apical fibrosis may be visible on chest radiograph but is of no clinical significance. Palliative radiotherapy is indicated for fungating nodes, bleeding, stridor, dysphagia and superior vena caval obstruction due to progressive inoperable disease. Bone metastases causing pain, vertebral involvement threatening the spinal cord, long bone involvement if there is a potential

Figure 17.11 Three-dimensional plan (anterior and pair of antero-oblique fields) for phase II volume covering microscopic disease in the thyroid bed (See Plate Section.)

426 Thyroid

for fracture, and brain metastases should also be treated with palliative radiotherapy. Tumour in the lung or mediastinum can be treated if unresectable. Low dose is inadequate; 35 Gy in 15 fractions is required, or 6 Gy once weekly for up to 4 fractions when the central nervous system is not in field. Experience with chemotherapy in differentiated thyroid cancer is limited by the rarity of tumours not controlled by surgery, radioiodine and EBRT. There is, however, a minority of patients who do not respond to conventional therapy and survive for many years with minimal symptoms. Because the presently available drugs are of limited benefit and cause significant morbidity, chemotherapy is reserved for patients with inoperable progressive and symptomatic disease that fails to concentrate radioiodine.119* Of the several agents investigated, doxorubicin has been the most effective, with response rates of 30–40 per cent. Combination with cisplatin has produced similar response rates but with greater toxicity. Responses are usually partial and of short duration, although worthwhile palliation has been reported.120*** Doxorubicin in combination with EBRT appeared to be effective in some patients with large inoperable tumours.121* Chemotherapy may be beneficial in patients with advanced non-iodine-concentrating thyroid cancer by inducing uptake and allowing subsequent radioiodine therapy.122

leaving residual tumour for treatment by radiation and/or chemotherapy.123* Unfortunately, initial surgery is rarely possible. Anaplastic cancer is the least radiosensitive of all thyroid tumours. Doses of less than 50 Gy given in conventional fractionation are associated with a very low probability of local control; the evidence for control with higher doses is scant and subject to selection bias. Experience with 50–60 Gy administered over 5–6 weeks achieved local response in less than 45 per cent of patients, and 75 per cent still died from local progression.124* There is little effect on survival, and the majority of patients spend a significant period of their remaining lives undergoing treatment and recovering from its toxicity. In an attempt to improve local control, alternative approaches were investigated, including accelerated radiotherapy and chemotherapy. Clinical and some laboratory data on the proliferation rate of high-grade thyroid cancer suggest that the potential tumour doubling time is less than 5 days, making accelerated radiotherapy attractive. Several centres have shown an improvement in local tumour response. In our series of 17 patients treated twice daily, 5 days a week, to a dose of 60.8 Gy in 32 fractions over 20–24 days, significant response was achieved in 59 per cent (including three patients with a complete clinical response). Unfortunately, there was a corresponding increase in treatment toxicity that was unacceptable; grade 3–4 oesophagitis occurred in more than 90 per cent of patients and persisted for several weeks following the cessation of radiotherapy.125 Furthermore, despite success in achieving local control, survival remained poor, with almost all patients dying within 6 months of treatment. Better response rates are reported with combined chemotherapy and radiotherapy, particularly if the latter is delivered in a hyperfractionated schedule, although at the

MANAGEMENT OF ANAPLASTIC CARCINOMA Patients with anaplastic carcinoma present with rapidly progressive local and regional nodal disease. The prognosis is dismal, with a median survival of only 6 months from the original symptom. Local growth results in upper airway and oesophageal obstruction. For this reason, it was thought that maximal surgical debulking should be attempted,

(a)

(b)

Figure 17.12 Three-dimensional reconstruction showing field positions in relation to planning target volume and critical organs: (a) spinal cord; (b) lung apices

Management of anaplastic carcinoma 427

New patient referred with Anaplastic Thyroid Cancer History and clinical examination Haematology, biochemistry, CXR, review histology or FNAC CT neck, mediastinum, lungs, liver and bone scan Predominantly Loco-Regional Tumour Surgery Total resection (not usually possible) (Tracheostomy only if unavoidable)

Accelerated Radiotherapy Anterior and undercouched Phase I 1.67 Gy twice daily MPD: 40 Gy 24# 2.5 weeks outpatient or day ward Therapy CT scan for Phase II (excluding cord) 1.67 Gy twice daily TD: 10 Gy 6# 3 days In-patient for 2 weeks

Surgery Total resection (not usually possible)

Chemotherapy Doxorubicin (or equivalent)

Surgery Total resection (not usually possible)

Predominantly Metastatic Disease Progressive, symptomatic

Localised Radiotherapy Simulator planning

Lung

Bone

6 Gy MPD weekly 1– 4 (excluding cord)

Chemotherapy Doxorubicin or experimental agent to maximal response Other – mediastinum, brain, abdomen 35 Gy MPD 15# 3 weeks

Follow-up monthly ⴞ referral to continuing care

Figure 17.13 New patient referred with anaplastic thyroid cancer. CXR, chest radiograph; FNAC, fine-needle aspiration cytology; CT, computerized tomography; MPD, mid-plane dose; TD, total dose

cost of increased morbidity.126* Doxorubicin is the most effective agent and even low doses in combination with radiation appear to have a synergistic effect. There is a very small number of patients who demonstrate prolonged survival having been rendered free of disease by subsequent surgery. In a study from Sweden, 22 patients were treated with hyperfractionated accelerated radiotherapy (46 Gy in 29 fractions, each of 1.6 Gy, twice daily) concurrently with 20 mg doxorubicin weekly 3, followed by debulking surgery. Despite the patients’ advanced ages (over 60 years) and locally extensive disease, such an aggressive treatment modality was feasible. Local control

was achieved in 77 per cent, and in those undergoing surgery, none demonstrated local failure; 9 per cent of patients survived for more than 2 years.127* Control of local disease is important both for palliation and if there is to be any chance of prolonging survival. Improvements in radiotherapy fractionation schedules and conformal beam shaping could maximize the probability of local control whilst limiting toxicity. Finally, since almost all patients who achieve local control still die from metastatic disease, a more effective systemic treatment awaits discovery. No response was observed in distant metastases in either the Swedish study127* or the French

428 Thyroid

study126* employing doxorubicin (60 mg/m2), cisplatin (90 mg/m2) and local radiation. Experimental agents are under study. Our management algorithm is shown in Figure 17.13.

MANAGEMENT OF MEDULLARY THYROID CANCER Total thyroidectomy with routine dissection of lymph nodes in the central compartment of the neck and sampling of lateral jugular nodes is the optimal surgical treatment for MTC. Total thyroidectomy is indicated because in more than 90 per cent of familial and about 20 per cent of sporadic cases disease is multi-centric and bilateral. Furthermore, the incidence of local recurrence is lower in patients treated by radical surgery.128 Cervical lymph-node involvement at presentation ranges from 15 per cent to 75 per cent. A modified neck dissection with preservation of the sternomastoid muscle, the spinal accessory nerve and the internal jugular vein is indicated if metastatic nodes are found during sampling.129* Bilateral neck dissection has been recommended130* because adequacy of the initial operation is a prerequisite for cure. Excision of mediastinal lymph nodes, if involved, should be attempted. Aggressive surgery is justified by the initial loco-regional extent of disease in most cases. Ideally, calcitonin will fall to an undetectable level postoperatively. Measurement of calcitonin level should be repeated at annual follow-up, together with clinical evaluation. Lifelong thyroxine is prescribed at physiological dose; there is no advantage in TSH suppression. Unfortunately, elevated calcitonin levels often persist following initial operation and may be detected in up to 70 per cent of patients with node involvement.131* The most common sites of disease are nodes in the neck and mediastinum, and distant metastases may involve the liver, lungs and bones. Non-invasive imaging methods for detecting occult disease include ultrasonography, computed tomography (CT) scan or magnetic resonance imaging (MRI) and radionuclide scanning (99 mTc-pentavalent dimercaptosuccinic acid (DMSA), 123I-metaiodobenzylguanidine (mIBG), 111In-octreotide), although none of the latter is specific. We have previously reported a 30 per cent sensitivity of radionuclide imaging in MTC.132 Other methods of investigating recurrent MTC include selective venous catheterization to assay calcitonin levels133* and radioimmunoscintigraphy with monoclonal antibodies such as 131I-anti-carcinoembryonic antigen (CEA).134* More recently, PET has probably become the investigation of first choice.135* The frequent identification of liver metastases by angiography136* explains the low efficacy of lymph-node dissections to render a high calcitonin level undetectable postoperatively. Residual MTC is usually progressive, as reflected by a rise in calcitonin levels over time; a mean annual increase of 117 per cent of the initial value was calculated in 35 of 40 patients137* This progressive increase can continue from

the first postoperative measurement but may not appear until after a long period of stability. In a series from the Mayo Clinic, only 11 of 31 patients with raised calcitonin but negative imaging developed overt recurrent disease when followed for a mean period of 12 years. Re-operation for clinically documented local recurrence did not result in normalization in calcitonin level. However, overall survival at 5 and 10 years was 90 per cent and 86 per cent, respectively.138* Analysis of calcitonin doubling times in 65 patients with abnormal calcitonin levels after total thyroidectomy and bilateral lymph-node dissection by the French Neuroendocrine Tumour Group revealed that all 41 patients with a doubling time of more than 2 years were alive at the end of the study (3–30 years). On univariate analysis, TNM stage and doubling time were significant predictors of survival, but only the latter was significant on multivariate analysis (p  0.002).139* A more aggressive approach towards the localization of residual disease was adopted by Tisell, who performed meticulous 12-hour neck dissections, often removing 40–60 cervical lymph nodes.140* In a series of 11 patients, the calcitonin normalized in four (36 per cent) and dramatically improved in four. However, follow-up was short (2–4.5 years) and there is no evidence that these biochemical improvements translate into a survival advantage.141* This policy is not without risk, with higher complication rates than conventional surgery. In view of this and the long-term survival seen with patients on observation, many advocate close follow-up, with surgery reserved for when clinical recurrence can be documented.25*** The role of postoperative radiotherapy is controversial due to the lack of prospective studies; retrospective series comparing surgery alone with surgery plus radiotherapy are subject to selection bias. Favourable responses in terms of tumour reduction and local control have been reported.142*,143*** At the Institut Gustave-Roussy, the survival of 68 patients treated with surgery alone was similar to that of 59 who received postoperative radiotherapy. However in patients with involved lymph nodes, 5-year survival improved significantly with postoperative radiotherapy, from 36 per cent to 81 per cent.144 In contrast, an adverse effect of radiotherapy was reported from the M.D. Anderson Cancer Center, Houston, USA; survival was significantly worse for 24 patients given postoperative radiotherapy compared with 39 age-matched and disease-matched patients treated with surgery alone.145* We recommend the use of adjuvant radiotherapy in patients with locally advanced disease at presentation, and multiple involved lymph nodes in particular, who have persistently elevated calcitonin levels postoperatively, indicating microscopic residual disease, as shown in Figure 17.14.146* Radiotherapy should be also considered for patients with bulky inoperable tumours, for whom significant palliation can be achieved with doses of 60 Gy in 6 weeks; occasionally, subsequent surgery becomes possible. Palliative radiotherapy also has a role in inoperable mediastinal masses and painful bone metastases.

Management of medullary thyroid cancer 429

New patient referred with Medullary Thyroid Carcinoma Partial thyroidectomy ⴞ Lymph node biopsy History and clinical examination Review histology Calcitonin and CEA CT neck, superior mediastinum

Exclude hyperparathyroidism serum Ca, AlkP, Phosphate / PTH

Exclude phaeochromocytoma BP Urine  serum catecholamines

Exclude familial MTC Family history Refer to genetics clinic

Completion thyroidectomy ⴞ Modified neck dissection ⴙ Central compartment resection Radiotherapy if extensive disease

Normal post-op calcitonin

Elevated post-op calcitonin

Annual clinical follow-up Calcitonin  CEA

Determine site of tumour CT neck, chest, abdomen Bone scan,18FDG-PET 123I mIBG, 111In-octreotide Inoperable

Excision ⴞ Radiotherapy Normal post-op calcitonin Annual clinical follow-up

Positive mIBG or octreotide

Pre-treatment dosimetry Therapeutic 131I mIBG or 90Y-octreotide

Repeat after 6/12

Negative imaging Progressive ⴙ Symptomatic

Chemotherapy ⴞ Radiotherapy Somatostatin analogues (octreotide) Pain relief, continuing care

Asymptomatic

Follow-up only

Figure 17.14 New patient referred with medullary thyroid carcinoma. CEA, carcinoembryonic antigen; CT, computerized tomography; MTC, medullary thyroid cancer; Ca, serum calcium; AlkP, serum alkaline phosphatase; PTH, parathyroid hormone; 99 mTc-DMSA, 99 mTc pentavalent dimercaptosuccinic acid; 18FDG PET, 18F-fluorodeoxyglucose positron emission tomography; mIBG, meta-iodobenzylguanidine; 111 In, 111-indium; 90Y, 90-yttrium

Many patients with metastatic medullary cancer survive for years with minimal symptoms and, apart from medications to control diarrhoea, may not require any other treatment. Chemotherapy should be reserved for those with unresectable progressive and symptomatic disease. Doxorubicin produces symptomatic response in about 30 per cent of cases, but most are partial and of short duration.119* The same response rate is obtained when doxorubicin is used alone or in combination with other drugs.147* The selective uptake of 131I-mIBG and 111In-octreotide by 30–50 per cent of medullary cancers has generated interest in their potential use for targeted radiotherapy, although treatment is

relatively ineffective.148*** Treatment with unlabelled somatostatin analogues may be helpful to control severe diarrhoea from metastatic disease, although side effects can be troublesome. Finally, the use of recombinant interferon alpha-2a has not demonstrated significant benefit. The clinical course of MTC varies widely. In our series, overall survival was 72 per cent at 5 years, 56 per cent at 10 years, 40 per cent at 15 years, and 30 per cent at 20 years.149* Patients with MEN IIb have the most aggressive tumours, often with early development of metastases and death. On multivariate analysis, older age at diagnosis, lymph-node involvement, metastases at presentation and

430 Thyroid

incompleteness of initial surgical resection were significant adverse prognostic factors.149* In some retrospective series, patients with familial cancer have a significantly longer survival compared to those with sporadic cancer;145* however, when patients were matched for age, gender, extent of disease and treatment, this difference disappeared.

Management of familial medullary thyroid cancer (FMTC, MEN IIa and IIb) The RET proto-oncogene is a 21-exon gene on chromosome 10q 11-2 that encodes for a tyrosine kinase transmembrane receptor. The goal of screening for MEN II is to identify gene carriers early in an attempt to modify the outcome of the disease. The two manifestations that are life threatening are MTC and phaeochromocytoma. There is compelling evidence for both that early intervention will improve outcome.150* Genetic testing is the most cost-effective approach to detect affected individuals.151*** All techniques currently use DNA fragments generated by polymerase chain reaction (PCR) amplification of genomic DNA. Several analytic techniques have been applied to detect specific mutations, including direct DNA sequencing, denaturing gradient gel electrophoresis, restriction analysis of amplified products and allele-specific hybridization. Each of these has proved reliable for the detection of the most common mutations causing MEN II or FMTC. Genetic testing should be performed soon after birth. Family members found not to be gene carriers by RET mutation analysis do not require further genetic or biochemical testing and no tests need to be performed on their descendants. Adults who are gene carriers are at high risk of developing MTC; total thyroidectomy with central lymphnode dissection should be performed after exclusion of phaeochromocytoma. For the management of children found to be gene carriers, annual pentagastrin stimulation of calcitonin is performed.152*** The concern related to pentagastrin testing is failure to identify C-cell abnormalities at the earliest stage, since approximately 50 per cent of children had microscopic MTC rather than C-cell hyperplasia.153* Thus, in MEN IIb, total thyroidectomy should be performed as soon as possible, even under 2 years of age.154 Surgery is well tolerated, and the risks of recurrent laryngeal nerve damage or hypoparathyroidism are no greater than in older children.150* In MEN IIa, total thyroidectomy should be performed at 10 years of age or less if the pentagastrin stimulation test is positive. In FMTC, yearly follow-up should be performed, with a pentagastrin stimulation test, with surgery indicated at the first positive test. Annual measurement of urinary catecholamines and metanephrines on a 24-hour specimen provides a straightforward outpatient screening approach to detect phaeochromocytoma. Elevated epinephrine or an elevated epinephrine:norepinephrine ratio is the most commonly observed pattern. Basal or exercise-stimulated plasma catecholamines provides an alternative method of screening.

Magnetic resonance imaging is used to confirm phaeochromocytoma or an enlarged medulla. In most cases abnormalities involve both adrenals, and bilateral adrenalectomy is recommended.25*** The procedure is well tolerated but must be preceded by alpha-blockade and beta-blockade for 7–10 days. Measurement of serum calcium should be performed annually in MEN IIa gene carriers to screen for hyperparathyroidism. Once hypercalcaemia is documented, serum intact parathyroid hormone (PTH) should be measured to confirm the diagnosis. The majority of patients with hyperparathyroidism have diffuse but unequal multiglandular hyperplasia, with only a small proportion (10–15 per cent) having a single adenoma. There is controversy regarding total parathyroidectomy with immediate autotransplantation versus subtotal parathyroidectomy. The value of genetic screening is beyond doubt. However, it is important that family members be counselled regarding the impact of a positive genetic test. A long-term strategy of education and support is recommended.

MANAGEMENT OF THYROID LYMPHOMA Most patients with primary thyroid lymphoma present with confluent cervical/mediastinal lymphadenopathy (stage IIE), but in about one-third, tumour is confined to the thyroid gland (IE). Haematology, biochemistry, CT scan of the neck, thorax and abdomen, and bone-marrow aspirate plus trephine are required for staging. However, these patients are often elderly and may require urgent therapy to relieve airway obstruction, making full staging impracticable until later. Aggressive surgery to debulk the tumour is neither feasible nor necessary. For localized disease, EBRT has been the standard practice for several decades, resulting in 5-year survival rates of approximately 35 per cent. Local bulky disease and gross mediastinal involvement are significantly associated with failure distant from the irradiated volume.155* Chemotherapy for high-grade lymphomas has demonstrated better local and distant disease control, with overall long-term disease-free survival of about 50 per cent. The combination of radiotherapy preceded by chemotherapy has become the standard practice in most institutions and has resulted in 5-year survival rates of 65–90 per cent.156* Six cycles of rituximab plus cyclophosphamide, doxorubicin, vincristine and prednisolone (R-CHOP) given over 4 months are usually recommended.157 Lymphomas showing MALT characteristics usually present as localized extra-nodal tumours without adverse prognostic factors and follow a more indolent course.158* Radiotherapy as single-modality treatment resulted in a complete response rate of almost 100 per cent, a relapse rate of around 30 per cent, a salvage rate of more than 50 per cent, and an overall cause-specific survival of almost 90 per cent at 5 and 10 years.29* Our policy is to treat stage IEA MALT-positive lymphoma with radiotherapy only, but to use combination treatment for all other tumours, as

Future prospects 431

New patient referred with Primary Lymphoma of the Thyroid History and clinical examination Haematology, biochemistry, CXR, review histology CT neck, thorax, abdomen, pelvis Bone marrow aspirate and trephine

Stage IE or IIE

Stage III or IV

Surgery Open biopsy (if not already done) (Tracheostomy only if unavoidable)

MALT Positive IE

MALT Negative

Chemotherapy R - CHOP q21 6 cycles

Radiotherapy Simulate for anterior and undercouched Phase I to neck and mediastinum 2 Gy daily MPD: 40 Gy 20# 4 weeks

Partial response

Complete response

consider additional chemotherapy

Radiotherapy 35 Gy 20# 4 weeks involved field

no additional response

Follow-up clinic 3 monthly Haematology and CXR

Complete remission

Recurrence

Chemotherapy

Figure 17.15 New patient referred with primary lymphoma of the thyroid. CXR, chest radiograph; MALT, mucosa-associated lymphoid tissue; R-CHOP, rituximab, cyclophosphamide, hydroxydaunomycin (doxorubicin), vincristine (Oncovin), and prednisone; MPD, mid-plane dose. Ann Arbor Classification: Stage IE: disease in single lymph-node region; Stage IIE: disease in two or more lymph regions on same side of diaphragm; Stage III: disease in lymph-node regions on both sides of the diaphragm; Stage IV: widespread disease, including multiple involvement at one or more extra-nodal sites, such as the bone marrow

shown in Figure 17.15. Treatment volume includes the neck and superior mediastinum, irradiated by a pair of anterior and undercouched fields to 35–40 Gy in 20 fractions over 4 weeks. Primary Hodgkin’s disease of the thyroid is very rare and treated in a similar fashion to extra-nodal Hodgkin’s at any other site.

FUTURE PROSPECTS A large randomised, prospective, multi-centre trial (HiLo, Cancer Research UK) began recruiting patients in 2007 to compare the efficacy of low-dose (1.1 GBq) versus high-dose (3.7 GBq) remnant ablation prepared with either rhTSH or

432 Thyroid

thyroid hormone withdrawal. This study will serve to address the controversy remaining concerning the optimal activity to achieve successful ablation, but will also evaluate the roles of rhTSH and thyroid hormone withdrawal. Over the past decade, developments in dosimetry have permitted the calculation of absorbed tumour dose in metastatic disease with greater accuracy. This has enabled the construction of dose–response curves that explain the spectrum of clinical response from fixed activities of radioiodine.98 These developments allow for the tumoricidal dose to be calculated and may enable precise prescription of further 131I therapy so as to maximize tumour kill while minimizing toxicity, staff exposure and unnecessary expense. The fundamental problem for recurrent or metastatic iodine-negative disease is the decreased expression of the sodium iodide symporter. In these patients, the options for treatment are limited. Initial reports with redifferentiation to enhance the efficacy of iodine uptake have not been substantiated.159* However, studies using selective agonists of retinoic X receptors have been demonstrated to enhance sodium iodide symporter gene expression in vitro. An alternative approach is the administration of peptide receptor-targeted therapy with 90Y-lanreotide, based on the premise that non iodine-avid tumours may express somatostatin receptors.160* Initial results have been promising and invite further studies. In patients with advanced progressive disease, chemotherapy with doxorubicin is disappointing, yielding poor overall response rates, with success limited by cardiotoxicity. The challenge therefore remains to find an effective agent with minimal cardiac toxicity. This may be possible with the introduction of polyethylene glycolcoated (pegylated) liposomal doxorubicin (Caelyx). A multicentre prospective study is ongoing in the UK (Newcastle, U. Mallick) with liposomal doxorubicin for any advanced metastatic thyroid cancer. Chemotherapy may also be beneficial in patients with non iodine-avid disease by inducing the uptake of subsequent radioiodine therapy. A recent study has reported significant uptake in previously non iodine-avid lesions following cisplatin and doxorubicin.122 The use of monoclonal antibodies against the epidermal growth factor receptor (EGFR) has demonstrated a reduction in tumour growth in thyroid cancer cell lines.161* Phase II studies are in progress evaluating tyrosine kinase inhibitors for non iodine-avid tumours and metastatic MTC.162*** The use of gene therapy using vectors that lead to the expression of proteins in cancer cells that are directly toxic or aid the sensitivity of cancer treatments has been described as suicide gene therapy. Preliminary work has demonstrated success in follicular, anaplastic and MTC cell lines but requires assessment in patients. A further area of interest is associated with the p53 gene that encodes the p53 protein, a regulator of DNA repair. p53 mutations are more common in anaplastic thyroid cancer. However, malignant cells bearing the wild-type p53 mutation are more susceptible to chemotherapy agents compared to other p53 mutations. Re-expression of wild-type p53 in thyroid cancer cell lines

results in growth arrest, but no human studies are currently being performed. A combination of treatments targeting several steps involved in tumour growth may have a synergistic effect and improve outcome. Medullary thyroid cancer is a particularly attractive target for gene therapy. Potential gene targets include the inhibition of oncogene RET signalling, suicide gene therapy, immunotherapy and combination therapy. In animal models, RET signal transduction can be blocked, resulting in the suppression of tumour growth. Suicide gene therapy using gene transfer of herpes simplex virus thymidine kinase in combination with application of the antiviral drug ganciclovir or nitric oxide synthase has been assessed. Immunotherapy with delivery of interleukin 2 or 12 may help support the normal immune response in MTC, but combination treatment appears to be more effective than treatment with any single agent.163*** The British Society of Paediatric Endocrinology and Diabetes (www.bsped.org.uk) has recently published guidelines for the management of thyroid cancer in children; an updated version of the guidelines for adults is now available. The British Thyroid Foundation Cancer Group has also published a patient information leaflet for patients (www.btf-thyroid.org). A national thyroid dataset (UK) has received conditional approval from the NHS Information Authority Standards Board. This should improve patient records, data retrieval and analysis for the future.

KEY LEARNING POINTS ●

●

●

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The incidence of thyroid cancer has increased significantly over the past decades. However, mortality rates have fallen, possibly reflecting earlier diagnosis and improved treatment. Fine-needle aspiration cytology represents the gold-standard investigation for evaluating thyroid nodules. Age is the single most important independent predictor of recurrence and survival in differentiated thyroid cancer. Tumour size, grade, extension and the presence of metastases also predict outcome. Surgery remains the initial and potentially curative treatment for differentiated thyroid cancer and medullary carcinoma. Remnant 131I ablation post-thyroidectomy reduces the risk of loco-regional recurrence and cause-specific mortality in differentiated thyroid cancer, particularly in patients with adverse prognostic features. Radioiodine therapy is the mainstay of treatment for metastatic differentiated thyroid cancer: a significant proportion of patients can be cured, and durable palliation can be achieved in others.

References 433

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Benua R, Cicale NR, Sonenberg M, Rawson RW. The relation of radioiodine dosimetry to results and complications in the treatment of metastatic thyroid cancer. Am J Roentgenol Radium Ther Nucl Med 1962; 87:171–82. Rall JE, Alpers JB, Lewallen CG, et al. Radiation pneumonitis and fibrosis: a complication of radioiodine treatment of pulmonary metastases from cancer of the thyroid. J Clin Endocrinol Metab 1957; 17(11): 1263–76. Pacini F, Gasperi M, Fugazzola L, et al. Testicular function in patients with differentiated thyroid carcinoma treated with radioiodine. J Nucl Med 1994; 35(9):1418–22. Hyer S, Vini L, O’Connell M, et al. Testicular dose and fertility in men following I(131) therapy for thyroid cancer. Clin Endocrinol 2002; 56(6):755–8. Dottorini ME, Lomuscio G, Mazzucchelli L, et al. Assessment of female fertility and carcinogenesis after iodine-131 therapy for differentiated thyroid carcinoma. J Nucl Med 1995; 36(1):21–7. Schlumberger M, de Vathaire F, Ceccarelli C, et al. Exposure to radioactive iodine-131 for scintigraphy or therapy does not preclude pregnancy in thyroid cancer patients. J Nucl Med 1996; 37(4):606–12. Vini L, Hyer S, Al Saadi A, et al. Prognosis for fertility and ovarian function after treatment with radioiodine for thyroid cancer. Postgrad Med J 2002; 78(916):92–3. Edmonds CJ, Smith T. The long-term hazards of the treatment of thyroid cancer with radioiodine. Br J Radiol 1986; 59(697):45–51. Maxon HR III, Smith HS. Radioiodine-131 in the diagnosis and treatment of metastatic well differentiated thyroid cancer. Endocrinol Metab Clin North Am 1990; 19(3):685–718. Rubino C, de Vathaire F, Dottorini ME, et al. Second primary malignancies in thyroid cancer patients. Br J Cancer 2003; 89(9):1638–44. Harmer C, Bidmead M, Shepherd S, et al. Radiotherapy planning techniques for thyroid cancer. Br J Radiol 1998; 71(850):1069–75. Leboulleux S, Rubino C, Baudin E, et al. Prognostic factors for persistent or recurrent disease of papillary thyroid carcinoma with neck lymph node metastases and/or tumor extension beyond the thyroid capsule at initial diagnosis. J Clin Endocrinol Metab 2005; 90(10):5723–9. Farahati J, Reiners C, Stuschke M, et al. Differentiated thyroid cancer. Impact of adjuvant external radiotherapy in patients with peri-thyroidal tumor infiltration (stage pT4). Cancer 1996; 77(1):172–80. Tsang RW, Brierley JD, Simpson WJ, et al. The effects of surgery, radioiodine, and external radiation therapy on the clinical outcome of patients with differentiated thyroid carcinoma. Cancer 1998; 82(2):375–88. Chow SM, Law SC, Mendenhall WM, et al. Papillary thyroid carcinoma: prognostic factors and the role of radioiodine and external radiotherapy. Int J Radiat Oncol Biol Phys 2002; 52(3):784–95.

117 Ford D, Giridharan S, McConkey C, et al. External beam radiotherapy in the management of differentiated thyroid cancer. Clin Oncol (R Coll Radiol) 2003; 15(6):337–41. ●118 Nutting CM, Convery DJ, Cosgrove VP, et al. Improvements in target coverage and reduced spinal cord irradiation using intensity-modulated radiotherapy (IMRT) in patients with carcinoma of the thyroid gland. Radiother Oncol 2001; 60(2):173–80. 119 Hoskin PJ, Harmer C. Chemotherapy for thyroid cancer. Radiother Oncol 1987; 10(3):187–94. 120 Ahuja S, Ernst H. Chemotherapy of thyroid carcinoma. J Endocrinol Invest 1987; 10(3):303–10. 121 Kim JH, Leeper RD. Treatment of locally advanced thyroid carcinoma with combination doxorubicin and radiation therapy. Cancer 1987; 60(10):2372–5. 122 Morris JC, Kim CK, Padilla ML, Mechanick JI. Conversion of non-iodine-concentrating differentiated thyroid carcinoma metastases into iodine-concentrating foci after anticancer chemotherapy. Thyroid 1997; 7(1):63–6. 123 McIver B, Hay ID, Giuffrida DF, et al. Anaplastic thyroid carcinoma: a 50-year experience at a single institution. Surgery 2001; 130(6):1028–34. 124 Levendag PC, De Porre PM, van Putten WL. Anaplastic carcinoma of the thyroid gland treated by radiation therapy. Int J Radiat Oncol Biol Phys 1993; 26(1): 125–8. 125 Mitchell G, Huddart R, Harmer C. Phase II evaluation of high dose accelerated radiotherapy for anaplastic thyroid carcinoma. Radiother Oncol 1999; 50(1):33–8. 126 Schlumberger M, Parmentier C, Delisle MJ, et al. Combination therapy for anaplastic giant cell thyroid carcinoma. Cancer 1991; 67(3):564–6. ●127 Tennvall J, Lundell G, Wahlberg P, et al. Anaplastic thyroid carcinoma: three protocols combining doxorubicin, hyperfractionated radiotherapy and surgery. Br J Cancer 2002; 86(12):1848–53. 128 Modigliani E, Franc B, Niccoli-sire P. Diagnosis and treatment of medullary thyroid cancer. Baillieres Best Pract Res Clin Endocrinol Metab 2000; 14(4):631–49. ●129 Dralle H, Scheumann GF, Proye C, et al. The value of lymph node dissection in hereditary medullary thyroid carcinoma: a retrospective, European, multicentre study. J Intern Med 1995; 238(4):357–61. 130 Scollo C, Baudin E, Travagli JP, et al. Rationale for central and bilateral lymph node dissection in sporadic and hereditary medullary thyroid cancer. J Clin Endocrinol Metab 2003; 88(5):2070–5. 131 Block MA, Jackson CE, Tashjian AH Jr. Management of occult medullary thyroid carcinoma: evidenced only by serum calcitonin level elevations after apparently adequate neck operations. Arch Surg 1978; 113(4):368–72. 132 Vini L, Al-Saadi A, Pratt B, Harmer C. The role of radionuclide imaging (V-DMSA, 131I-mIBG, 111In-Octreotide) in medullary thyroid cancer. Nucl Med Commun 1998; 19:384. 133 Medina-Franco H, Herrera MF, Lopez G, et al. Persistent hypercalcitoninemia in patients with medullary thyroid cancer: a therapeutic approach based on selective venous

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sampling for calcitonin. Rev Invest Clin 2001; 53(3):212–17. Juweid M, Sharkey RM, Swayne LC, Goldenberg DM. Improved selection of patients for reoperation for medullary thyroid cancer by imaging with radiolabeled anticarcinoembryonic antigen antibodies. Surgery 1997; 122(6):1156–65. Diehl M, Risse JH, Brandt-Mainz K, et al. Fluorine-18 fluorodeoxyglucose positron emission tomography in medullary thyroid cancer: results of a multicentre study. Eur J Nucl Med 2001; 28(11):1671–6. Szavcsur P, Godeny M, Bajzik G, et al. Angiography-proven liver metastases explain low efficacy of lymph node dissections in medullary thyroid cancer patients. Eur J Surg Oncol 2005; 31(2):183–90. Tisell LE, Dilley WG, Wells SA Jr. Progression of postoperative residual medullary thyroid carcinoma as monitored by plasma calcitonin levels. Surgery 1996; 119(1):34–9. van Heerden JA, Grant CS, Gharib H, et al. Long-term course of patients with persistent hypercalcitoninemia after apparent curative primary surgery for medullary thyroid carcinoma. Ann Surg 1990; 212(4):395–400. Barbet J, Campion L, Kraeber-Bodere F, Chatal JF. Prognostic impact of serum calcitonin and carcinoembryonic antigen doubling-times in patients with medullary thyroid carcinoma. J Clin Endocrinol Metab 2005; 90(11):6077–84. Tisell LE, Hansson G, Jansson S, Salander H. Reoperation in the treatment of asymptomatic metastasizing medullary thyroid carcinoma. Surgery 1986; 99(1):60–6. Moley JF, Wells SA, Dilley WG, Tisell LE. Reoperation for recurrent or persistent medullary thyroid cancer. Surgery 1993; 114(6):1090–5. Fife KM, Bower M, Harmer CL. Medullary thyroid cancer: the role of radiotherapy in local control. Eur J Surg Oncol 1996; 22(6):588–91. Simpson WJ. Radioiodine and radiotherapy in the management of thyroid cancers. Otolaryngol Clin North Am 1990; 23(3):509–21. Schlumberger M, Gardet P, de Vathaire F. External radiotherapy and chemotherapy in MTC patients. In: Calmettes C, Guliana J (eds), Medullary Thyroid Carcinoma. Paris: Inserm/John Libbey, 1991, 213–20. Samaan NA, Schultz PN, Hickey RC. Medullary thyroid carcinoma: prognosis of familial versus sporadic disease and the role of radiotherapy. J Clin Endocrinol Metab 1988; 67(4):801–5. Fersht N, Vini L, A’Hern R, Harmer C. The role of radiotherapy in the management of elevated calcitonin after surgery for medullary thyroid cancer. Thyroid 2001; 11(12): 1161–8. Nocera M, Baudin E, Pellegriti G, et al. Treatment of advanced medullary thyroid cancer with an alternating combination of doxorubicin–streptozocin and 5 FU–dacarbazine. Groupe d’Etude des Tumeurs a Calcitonine (GETC). Br J Cancer 2000; 83(6):715–18.

148 Kaltsas G, Rockall A, Papadogias D, et al. Recent advances in radiological and radionuclide imaging and therapy of neuroendocrine tumours. Eur J Endocrinol 2004; 151(1):15–27. ●149 Hyer SL, Vini L, A’Hern R, Harmer C. Medullary thyroid cancer: multivariate analysis of prognostic factors influencing survival. Eur J Surg Oncol 2000; 26(7):686–90. 150 Wells SA Jr, Chi DD, Toshima K, et al. Predictive DNA testing and prophylactic thyroidectomy in patients at risk for multiple endocrine neoplasia type 2A. Ann Surg 1994; 220(3):237–47. 151 Ponder BA. Genetic screening for multiple endocrine neoplasia type 2. Exp Clin Endocrinol 1993; 101(1):53–6. ◆152 Brandi ML, Gagel RF, Angeli, A et al. Guidelines for diagnosis and therapy of MEN type 1 and type 2. J Clin Endocrinol Metab 2001; 86(12):5658–71. 153 Gagel RF, Tashjian AH Jr, Cummings T, et al. The clinical outcome of prospective screening for multiple endocrine neoplasia type 2a. An 18-year experience. N Engl J Med 1988; 318(8):478–84. 154 Pinchera A, Elisei R. Medullary thyroid cancer: diagnosis and management. In: Mazzaferri E, Harmer C, Mallick U, Kendall-Taylor P (eds), Practical Management of Thyroid Cancer – a Multidisciplinary Approach. London: SpringerVerlag, 2006; 255–279. 155 Tupchong L, Hughes F, Harmer CL. Primary lymphoma of the thyroid: clinical features, prognostic factors, and results of treatment. Int J Radiat Oncol Biol Phys 1986; 12(10):1813–21. ●156 Matsuzuka F, Miyauchi A, Katayama S, et al. Clinical aspects of primary thyroid lymphoma: diagnosis and treatment based on our experience of 119 cases. Thyroid 1993; 3(2):93–9. 157 Haq M, Harmer C. Rare thyroid cancers. In: Mazzaferri E, Harmer C, Mallick U, Kendall-Taylor P (eds), Practical Management of Thyroid Cancer. London: Springer-Verlag, 2006 393–402. 158 Thieblemont C, Mayer A, Dumontet C, et al. Primary thyroid lymphoma is a heterogeneous disease. J Clin Endocrinol Metab 2002; 87(1):105–11. 159 Short SC, Suovuori A, Cook G, et al. A phase II study using retinoids as redifferentiation agents to increase iodine uptake in metastatic thyroid cancer. Clin Oncol (R Coll Radiol) 2004; 16(8):569–74. ●160 Christian JA, Cook GJ, Harmer C. Indium-111-labelled octreotide scintigraphy in the diagnosis and management of non-iodine avid metastatic carcinoma of the thyroid. Br J Cancer 2003; 89(2):258–61. 161 Gabler B, Aicher T, Heiss P, Senekowitsch-Schmidtke R. Growth inhibition of human papillary thyroid carcinoma cells and multicellular spheroids by anti-EGF-receptor antibody. Anticancer Res 1997; 17(4B):3157–9. 162 Kodama Y, Asai N, Kawai K, et al. The RET proto-oncogene: a molecular therapeutic target in thyroid cancer. Cancer Sci 2005; 96(3):143–8. 163 Herbst RS. Role of novel targeted therapies in the clinic. Br J Cancer 2005; 92(Suppl. 1):S21–7.

18 Endocrine cancer MARIA GUEORGUIEV, ASHLEY B. GROSSMAN AND P. NICHOLAS PLOWMAN

The APUD concept and APUDomas Pituitary tumours Parathyroid adenoma and carcinoma Medullary thyroid carcinoma Gastro-entero-pancreatic endocrine tumours Carcinoid tumours

438 438 449 450 451 452

THE APUD CONCEPT AND APUDOMAS In 1966 Pearse first described cytochemical and ultrastructural properties which were shared by several apparently disparate cell series in the body – initially adrenomedullary chromaffin cells, enterochromaffin cells, the corticotroph, the melanotroph, the pancreatic islet B cell and the thyroid C cell. Pearse later proposed the generic name APUD for these cells from the initial letters of their common cytochemical characteristics, which include amine precursor uptake and decarboxylase activity within the cells.1 Since that time, the list of APUD cells has expanded enormously. The structural and chemical similarity of APUD cells to neurons suggested a neural crest origin. Indeed, APUD cells of the adrenal medulla, melanocytes, thyroid, gastrointestinal tract and carotid body are of principally neuroectodermal lineage, and the ultrastructural similarity is true for all APUD cells. Pearse considered these cells as ‘neuroendocrine’ programmed cells derived from determined precursors arising in the embryonic epiblast, or in one of its principal early descendants. They are conceived as constituting a diffuse neuroendocrine system (DNES), which may be regarded as a third division of the nervous system, products of which suppress, amplify or modulate the activities of the other two divisions. 2 The DNES is divided into central and peripheral divisions, the first of which contains the cells of the hypothalamo-pituitary axis and the pineal gland, while the cells of the second division are primarily located in the gastrointestinal tract and pancreas, where they comprise the gastro-entero-pancreatic endocrine cells. However, APUD

Phaeochromocytoma Multiple endocrine neoplasia Adrenocortical tumours Key references References

454 456 457 459 459

cells are actually distributed throughout the body, where they are all prone to both hyperplasia and neoplasia, and more recent concepts have tended to decrease the emphasis on a truly discrete and distinct neuroendocrine ‘network’, and also on their presumed embryological commonality. This chapter deals with many neuroendocrine tumours, although pineal tumours and medullary carcinoma of the thyroid are covered in more detail in their respective chapters. The management of pituitary tumours is discussed first, followed by some of the more important neoplastic conditions in other organs. Finally, the topic of adrenocortical tumours is covered.

PITUITARY TUMOURS Tumours of the pituitary gland are not uncommon and represent approximately 10 per cent of all intracranial tumours. However, this figure is usually based on mass lesions of the pituitary, which present with visual-field defects or local destructive changes, and it is now realized that small, hormonally active pituitary tumours are considerably less rare. These smaller tumours present due to the consequent endocrinopathy, most commonly sexual or reproductive dysfunction. The management of such tumours differs considerably from conventional oncological treatment programmes. Nevertheless, tumours of the pituitary form a continuum from the relatively insignificant minor aberration requiring no treatment to the lethal massive tumour resistant to all modalities of therapy.

Pituitary tumours 439

Classification Pituitary tumours were originally classified in terms of their staining characteristics with conventional histological techniques, and have been principally divided into eosinophilic, basophilic and chromophobe adenomas. In such a classification the majority of tumours are either eosinophilic or chromophobe, with 10–15 per cent being basophilic. However, the staining characteristics are principally a reflection of the nature of the secretory product of the cell, and these can now be visualized directly using immunohistochemistry or immunofluorescence in most instances. The hormone product of the cell is also more closely related to the function of the tumour, its clinical presentation and its biological behaviour, and is thus a more logical way to classify histological types. On this basis, pituitary tumours may be classified as either secretory or non-secretory, and the former may be subdivided on the basis of their principal hormone product. The majority of secretory pituitary tumours are undoubtedly prolactin secreting or prolactinomas. Prolactincontaining vesicles are usually seen throughout the cytoplasm, and may be released aberrantly from non-apical surfaces of the adenomatous lactotroph. Occasionally, tumours of the somatotrophs (growth hormone (GH)secreting cells) have lactotrophs (prolactin-secreting cells) scattered throughout their substance, appearing as though such cells had become isolated in the tumour matrix during its growth. However, there are also true mixed tumours consisting of adenomatous elements of both lactotrophs and somatotrophs, and certain tumours appear to secrete both prolactin and GH from the same cytoplasmic granules. It has been speculated that the latter tumours have arisen from a common prolactin–GH cell, the ‘somato-mammotroph’, which may be present in normal pituitary tissue or might represent a progenitor of both lactotrophs and somatotrophs. Basophil tumours contain one of the glycoprotein hormones and most often consist of adenomatous corticotrophs. Adrenocorticotrophin (ACTH) is not itself glycosylated, but originates from a 31-kDa precursor, pro-opiomelanocortin, which has sugar moieties attached at several sites upstream and downstream to ACTH. Approximately 10–15 per cent of all pituitary tumours are classified conventionally as ACTH-secreting basophil adenomas. Tumours of the thyrotroph, secreting thyroid-stimulating hormone (TSH), are rare. However, approximately 30 per cent of all large pituitary tumours are said to be non-secretory or functionless, and are usually chromophobe adenomas. Many of these may be shown by electron microscopy to contain secretory vesicles. It appears increasingly likely that these tumours are related to, or originate from, gonadotrophinsecreting cells. They often secrete alpha-subunit, the common subunit of luteinizing hormone (LH), folliclestimulating hormone (FSH) and TSH, both in vivo and in vitro; in addition, secretion of LH and FSH may frequently be demonstrated in vitro. However, they rarely present

with clinical symptoms and signs of gonadotrophin excess; true gonadotrophinomas are extremely rare. Tumours of the posterior pituitary are occasionally seen, but generally arise from the glial or non-endocrine elements of the gland. Secretory tumours of the neurohypophysis have not been described.

Treatment objectives It is particularly important in the management of pituitary disorders that the objectives of treatment are clarified. In the case of pituitary tumours, the principal problems are due to the local mass effects of the lesion, especially visual impairment, partial or complete hypopituitarism, and the distant (target tissue) effects of any hormonal hypersecretion. Treatment thus needs to be directed towards reversing the neurological impairment and avoiding its recurrence, replacing any endocrine deficits and normalizing the levels of any elevated hormones. The disruption of the patient’s lifestyle should be minimized; this implies careful consideration of the necessity for long-term medication, with its possible side effects, and the frequency of outpatient visits and inpatient reassessments. It is difficult to optimize all these objectives, as it is usually the case that the more radical therapy with the highest probability of tumour sterilization will be most likely to induce long-term endocrine sequelae. Furthermore, individual patients may differ in their requirements for a normalization of their endocrine status and their desire to avoid medication. Not all neuroendocrine changes defined by subtle alterations during complex test procedures necessitate therapeutic intervention. It is, evident, therefore, that a range of treatment options can often be made available, and a therapeutic plan optimized according to the needs and wishes of the individual patient.

Prolactinomas Prolactin-secreting pituitary adenomas (prolactinomas) are the most common functional pituitary tumours. Although these adenomas are classified with regard to their size, they differ also with regard to their biological behaviour and clinical features. Microadenomas or microprolactinomas measure less than 1 cm in maximum diameter and are entirely contained within the pituitary fossa. Macroadenomas or macroprolactinomas are larger than 1 cm and usually expand beyond the pituitary fossa and cause local compression and displacement of adjacent structures. MACROPROLACTINOMAS

Clinical symptoms are the consequence of direct effects of hyperprolactinaemia, or of tumour expansion either due to local compression of anterior pituitary (hormonal deficits) or of adjacent structures. Usually, serum prolactin levels are markedly increased in prolactinomas, and correlate with

440 Endocrine cancer

tumour size, but mild hyperprolactinaemia can be present in patients with hypothalamic or pituitary lesions of other aetiology. Serum prolactin usually exceeds 4000–6000 mIU/L in patients with a macroprolactinoma, but such levels can occasionally be found with non-functioning pituitary adenomas (normal level, 450 mIU/L).3 Indeed, prolactin release is predominantly regulated by the inhibitory action of hypothalamic dopamine, and any disruption of the portal vasculature causing a decrease in dopamine delivery to the lactotrophs would result in an increase of prolactin levels. A skull X-ray will usually show an enlargement of the pituitary fossa. Improvement in radiodiagnostic techniques such as computed tomography (CT) and, particularly, magnetic resonance imaging (MRI) with gadolinium allows the visualization of the pituitary adenoma and its extra-sellar extension, and the exclusion of a possible hypothalamic lesion. The conventional surgical approach for macroprolactinomas was originally transcranial craniotomy with extirpation of the tumour and fossa contents. This technique is highly effective in the rapid restoration of visual deficits and debulking tumoral mass, but is associated with high morbidity and often with hypopituitarism.4 Trans-ethmoidal surgery has been used, but a high rate of orbital cellulitis has led to its abandonment. Originally introduced by Harvey Cushing, and then substantially improved by Guiot and Hardy, trans-sphenoidal resection, (currently with or without endoscopic assistance) with an operating microscope and intra-operative screening and, most recently, with computer-assisted neuronavigation, was then widely used for pituitary adenomas of all types. Rare cases of tumours with significant temporal or anterior cranial extension may still necessitate a trans-cranial approach or a combined trans-sphenoidal and trans-cranial approach. Morbidity is low in experienced hands, with a rate of less than 1–2 per cent for major complications (cerebrospinal fluid (CSF) rhinorrhoea and meningitis, ischaemic stroke or intracranial haemorrhage and visual loss) and of approximately 5 per cent for minor complications; surgically induced diabetes insipidus is usually transient. Transsphenoidal surgery for macroprolactinomas is rarely curative, as small residual tumoral rests remain. In a large series, trans-sphenoidal surgery induced remission in 56 per cent of patients with macroprolactinomas (normalization of postoperative prolactin levels), with a recurrence rate of 13 per cent (including microadenomas and macroadenomas) at 10 years.5*** The addition of postoperative standard external-beam radiotherapy to this regimen decreased the risk of recurrence from 50 per cent to 3 per cent or less at 10 years.6* Following the introduction in 1972 of the ergot alkaloid bromocriptine for the treatment of galactorrhoea and hyperprolactinaemia, it was rapidly introduced into tumour practice, where it was shown to normalize prolactin levels in patients with prolactinomas when used in addition to surgery and radiotherapy. Wass et al.7* reported a reduction in tumour size with bromocriptine in 9 out of 11 hyperprolactinaemic patients with presumed prolactinomas, and

normalization of visual fields in 5 patients. It appears that the majority of patients (75–80 per cent) with large prolactinomas, even with a significant extra-sellar extension, will show tumour reduction. These changes often occur very rapidly, and clinical symptoms may improve within hours of initiation of bromocriptine therapy, although there may still be ongoing shrinkage even after many months. Marked tumour shrinkage of large prolactinomas with large extra-sellar extensions may lead to a partially empty fossa, and occasionally CSF rhinorrhoea. Although significant tumour reduction is expected to occur within 6 weeks,8 our experience showed that these tumours may continue to decrease in size more slowly over many months of treatment. Other dopamine agonists have proven to be as effective: lisuride, pergolide, mesulergine, the longacting cabergoline9–12 and the non-ergot quinagolide.13,14 Re-expansion of tumour after the cessation of therapy may occur relatively rapidly, or more slowly in about 10 per cent cases.15–17 For example, Figure 18.1 demonstrates the serial CT scans of one of our patients treated for 2 years with bromocriptine who demonstrated marked tumour shrinkage; on cessation of therapy (due to patient noncompliance) for 5 weeks, there was marked and rapid re-growth of the tumour to its former size. However, there are also reports of patients in whom withdrawal of dopamine agonist after several years of therapy did not induce tumour re-growth, at least in the short term. Progressively, bromocriptine and, more recently, cabergoline therapy has become the primary therapy for all prolactinomas. Clinical improvement follows tumour shrinkage and includes early resolution of visual defects if their duration has not been too long.18 Evaluation of the therapeutic response to cabergoline and related drugs should be made within 4–6 weeks after the initiation of therapy. A long-term management decision should then be taken, but this may need to be earlier if there is no response or only a very limited one. If the prolactinoma has considerably decreased in size and the optic chiasm is free of tumour, we previously advised that external-beam radiotherapy be given. Tsagarakis et al.19* reported that radiotherapy induced normalization of prolactin levels in substantial numbers of patients 5–10 years postradiotherapy, although there is a long-term risk of hypopituitarism due to hypothalamic damage, most importantly the early loss of GH reserve.20–22 However, most would now simply maintain the dopamine agonist at the lowest effective dose, with the possibility of long-term ‘cure’ on removal of the drug in a significant minority of patients.23** The outcome of trans-sphenoidal surgery may be improved with prior bromocriptine; however, complete cure is unlikely and postoperative radiotherapy or dopamine agonist is usually necessary. It should be noted that in a woman of childbearing age there remains a 25 per cent probability of symptomatic tumour expansion during pregnancy. Bromocriptine withdrawal is also associated with this risk and may be required for life even if dose requirements decrease, although recent studies have suggested

Pituitary tumours 441

(a)

(b)

(c)

(d)

Figure 18.1 CT scans of a patient with a large prolactinoma: (a) at presentation (prolactin 206 000 mU/L) and (b) after 2 years bromocriptine treatment (prolactin 170 mU/L); the patient then stopped bromocriptine treatment for 5 weeks and his tumour enlarged rapidly, as shown in (c), when his prolactin had risen to 50 000 mU/L. He was restarted on bromocriptine, and was re-scanned 3 months later (d), by which time his serum prolactin had fallen to 400 mU/L.

that after long-term treatment re-expansion of the tumour following treatment cessation may be relatively uncommon.23** In the case of patients in whom a tumour with large supra-sellar extension with associated visual impairment persists after 4 weeks bromocriptine or cabergoline treatment, decompressive trans-sphenoidal surgery must be undertaken. Indeed, the decision for medical primary therapy in a patient with visual deficit can be taken only if experienced physicians work closely with neurosurgeons, and also have the facilities serially to monitor visual fields and acuity, as well as tumour volume with MRI scanning. Very rarely, ‘escape’ from therapy may occur,24 or an important supra-sellar extension may remain, which may represent fibrous change within the tumour, making trans-sphenoidal extirpation difficult.25 In the case of very large prolactinomas with invasion to adjacent structures, complete or partial surgical resection may be difficult, and cabergoline treatment may eventually be completed with radiotherapy unless there is evidence for drug-induced tumour necrosis.4 In summary, dopamine agonist therapy has transformed the management of macroprolactinomas, and surgery has been limited to those patients demonstrating residual chiasmal compression after attempted tumour shrinkage. Such

surgery is rarely curative and may occasionally have to be complemented by radiotherapy. There remains uncertainty concerning the optimal long-term therapy; some centres advise tumour control with dopamine agonist therapy alone, whereas others would suggest that definitive treatment with radiotherapy will lead to gradual sterilization of the tumour, with a low medium-term risk of hypopituitarism. However, the high incidence of GH deficiency, and the increasing acceptance of the morbidity associated with this state, has led to a decrease in enthusiasm for radiotherapy in this situation. With either approach, longterm close surveillance is necessary. MICROPROLACTINOMAS

Microprolactinomas have a prevalence of up to 10 per cent in adults, as revealed by some autopsy series, although hyperprolactinaemia is produced by these tumours in only 0.1 per cent of female patients.26 The prevalence in men is much lower (0.005 per cent), presumably due to their different hormonal milieu. There is, however, no evidence that oestrogen-containing oral contraceptives are oncogenic.27 The biochemical diagnosis of microprolactinoma

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may be difficult, as similar serum prolactin levels are found in patients with ‘functional’ or ‘idiopathic’ hyperprolactinaemia (up to 4000–6000 mIU/L).28 High-resolution MRI scans reveal abnormalities of the pituitary fossa in the majority of these patients. In this context, most women with persistent serum prolactin levels above 1000 mIU/L are likely to have microprolactinomas. Most clinical centres would recommend primary therapy with dopamine agonist as treatment for secondary amenorrhoea in such patients; resistance to this drug is rare and there is little cross-intolerance between different agonists.29 Previous estimates of pregnancy-induced tumour expansion were almost certainly exaggerated, and it seems unlikely that such problems will occur in more than 1 per cent of pregnancies, although authorities differ as to the exact incidence. When this does occur, it may be treated rapidly by the re-institution of dopamine agonist therapy. However, treatment may need to be continued for many years, as spontaneous resolution is only infrequently seen. Occasionally after treatment with a dopamine agonist, serum prolactin may return to a level much lower than previously, such that therapy may be discontinued;30 this tends to occur particularly following a pregnancy.31 Very rarely, there is progression from a microadenoma to a macroadenoma, with a gradual increase in tumour size and prolactin level and the onset of local compressive symptoms. In such a case the treatment should be adapted to that appropriate for a macroprolactinoma. We now generally initiate treatment with cabergoline, starting with 0.25 mg once a week and increasing over 2–3 weeks to 0.5 mg once or twice a week. True resistance may occasionally be responsive to an alternative dopamine agonist such as bromocriptine or quinagolide, but this is rarely so in our experience. Most data on safety in inducing conception have been obtained with bromocriptine, with more than 20 years’ evidence of a lack of teratogenicity or problems in pregnancy. To date, cabergoline and quinagolide appear to be equally safe, but the relative long-term experience is much more limited. In a recent Italian study with 2–5 years’ follow-up,23** withdrawal of long-term cabergoline used as primary therapy resulted in recurrent hyperprolactinaemia at rates of 31 per cent and 36 per cent in patients with microprolactinomas or macroprolactinomas respectively (although levels remained lower than those before treatment), but in the absence of tumour re-growth. The estimated rate of recurrence at 5 years was higher if a residual tumour was visible on MRI at the time of cabergoline withdrawal. These results suggest that it is safe to interrupt long-term cabergoline treatment under careful monitoring during follow-up, as there probably exists a persistent anti-tumoral effect of cabergoline that is additive to the natural evolution of some microprolactinomas. In a situation in which there is drug resistance or intolerance, surgical intervention may be considered. In large centres with an experienced neurosurgeon, trans-sphenoidal removal is curative in 70–90 per cent of patients, with an inverse correlation between cure rate and initial serum

prolactin levels.32,33 In recent series,5*** the recurrence rate for prolactinomas following trans-sphenoidal surgery is estimated to be about 13 per cent at 10 years, with remission assessed by normalization of prolactin levels in 87 per cent of patients with microprolactinomas. The risk of hypopituitarism is very low in the case of microprolactinomas. In our opinion, trans-sphenoidal surgery is, on current evidence, an acceptable alternative to dopamine agonist therapy only for those patients unable or unwilling to take long-term medication; 10-year and 15-year followup studies of these patients are awaited with interest. If a patient’s symptoms are minimal, it may be prudent in some cases to avoid treatment altogether. The natural history of the microprolactinoma is generally benign, and many patients only require reassurance. There are, however, three provisos. First, since hyperprolactinaemia may cause subtle changes in sexual function and libido, every patient should at least be offered a trial of a dopamine agonist to assess their clinical response. Second, hyperprolactinaemia is associated with oestrogen deficiency and long-term osteoporosis and therefore should necessarily be treated when it causes either complete amenorrhoea or low circulating oestradiol levels.34–36 (As a general rule, we consider that menses should not be less frequent than every other month.) Finally, all patients should be followed up long term to monitor the possible progression to a macroprolactinoma. An alternative approach is simply to treat the patient with some form of oestrogen replacement therapy, to induce regular withdrawal bleeds and minimize the risk of osteoporosis. Although such treatment has previously been contraindicated owing to the assumed risk of tumour-growth stimulation, several studies have demonstrated that such a risk may be relatively small.37 Pregnancy in a patient with a microprolactinoma has a low but positive risk of oestrogen-induced tumour expansion. It is probably wise, therefore, to monitor such patients during pregnancy for clinical symptoms and visual-field defects. Postpartum, it is unlikely that the tumour will enlarge in size if it has not done so previously, and thus lactation should proceed normally. Microprolactinomas appear to be extremely uncommon in men. It has been suggested that this is because the principal clinical symptom of impotence is not brought early to medical attention38 and the patients are only seen if they progress to a macroprolactinoma some 10 years later. Whatever the case, the treatment of a male microprolactinoma follows the same guidelines as in the female. Finally, a number of patients with apparent hyperprolactinaemia and a relative absence of symptoms may have ‘macroprolactinaemia’, where biochemical assays show a spuriously elevated level due to prolactin’s association with an immunoglobulin. This can be established by various techniques, but it is a vital test in all patients with hyperprolactinaemia in whom the clinical and hormonal correlates are discordant. One additional caveat is that in some prolactin assays the presence of very high prolactin levels will saturate the assay antibody and may show a spuriously low or even normal level of prolactin – the ‘hook effect’. Most

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laboratories are aware of this and will dilute out samples where this may be a confounder, and in an case modern assays are usually robust up to 1 000 000 mIU/L. In summary, microprolactinomas generally have a benign natural history, and therapy must take this into account. The mainstay of treatment is dopamine agonist therapy, supplemented where necessary by trans-sphenoidal surgery. Radiotherapy should only be considered where the tumour gives evidence of high growth characteristics such as local invasiveness or a very high serum prolactin, or there is resistance to dopamine agonist therapy.

Functionless tumours A significant proportion (30–40 per cent) of large pituitary tumours are apparently functionless, as they are unassociated with a hypersecretory syndrome, although a number may be capable of secreting a hormonal product in very low quantities, and about 80 per cent exhibit positive immunostaining for one glycoprotein hormone, mainly gonadotrophins. In 10 per cent of these tumours, proopiomelanocortin-derived products can be detected, and about 2 per cent immunostain for GH. These tumours represent the so-called silent corticotroph adenomas, gonadotrophinomas or somatotropinomas. The rest are chromophobe adenomas, although sparse secretory granules and some endoplasmic reticulum may be evident ultrastructurally. These tumours usually present due to mass effects consequent on their size and with visual defects and headache, but partial or complete hypopituitarism is often present on dynamic testing. The principal treatment for functionless tumours is surgical.39 Surgery is used to decompress the visual pathways, and nowadays this is almost always trans-sphenoidal in all but the most massive tumours.40 As functionless pituitary tumours express dopamine and somatostatin receptors, early work suggested that pre-treatment with dopamine agonists or somatostatin derivatives might cause tumour shrinkage, similar to that seen with prolactinomas. However, prospective studies of patients carefully followed up for prolonged periods have shown that any shrinkage that does occur is relatively minor or even if more important is observed in a small number of patients, and does not obviate the need for surgery.18,29,41,42 It is conceivable that the slight but definite evidence of a decrease in apparent tumour size is due to a diminution in size of the normal lactotrophs or somatotrophs, but that once this has occurred, the inevitable tumour progression is seen. Whatever the mechanism, dopamine agonists or somatostatin analogues only very rarely induce a clinically useful improvement in symptoms or signs in patients with functionless tumours, and we would advise urgent definitive surgical treatment in patients with large pituitary tumours and a normal or minimally elevated serum prolactin (1000 mU/L). Newer somatostatin analogues with selectivity for somatostatin receptor subtypes more characteristic of the non-functioning tumours may alter this approach in the future.

If the surgeon believes that he or she has achieved complete clearance, and if the tumour shows no obvious evidence of invasiveness, many centres would follow this with serial MRI scans (the first at 3–6 months) to assess recurrence. However, a number of surveys in the 1990s demonstrated significant recurrence rates, even in those tumours thought to have been removed completely, of the order of 50 per cent at 10 years.43,44* More recently, Laws et al.5*** reported better results, with 16 per cent recurrence at 10 years (but only 6 per cent requiring re-operation), and 83 per cent of patients alive and without evidence of disease. Postoperative improvement of visual deficits occurred in 87 per cent and normalization of hormone secretion in 27 per cent of patients. It is therefore our own policy to consider external-beam radiotherapy in the majority of patients following surgery, accepting that there will be a gradual increase in hypopituitarism in those patients with postoperative preserved pituitary function. Of course, other factors need to be taken into account, such as the age of the patient and the presence of pre-existing hormone defects, but generally, adhering to this policy, the rate of recurrence has been much less than 5 per cent at 10 years. We have not seen clear evidence of second tumours or neurocognitive defects using our current prescription, although a second-tumour rate, particularly meningioma, of up to 3 per cent at 10 years has been reported. There remains the group of patients whose serum prolactin varies between 1000 mU/L and 6000 mU/L, who may have either a prolactin-secreting tumour or a functionless tumour causing stalk compression hyperprolactinaemia. Both categories respond to dopamine agonists with a normalization of serum prolactin, but only the former are likely to show tumour regression. A short trial of cabergoline may be appropriate to test the response of the tumour, but this must be monitored extremely carefully by serial visual-field testing and MRI scanning, as recourse to surgery is important in non-responders. Silent corticotroph tumours, gonadotrophin-secreting and TSH-secreting tumours should be treated as functionless tumours. Some silent corticotroph tumours may progress to clinical Cushing’s disease and should be treated particularly vigorously. Thyroid-hormone-secreting tumours may be sensitive to dopamine agonists or to the somatostatin analogue octreotide, which may be given a therapeutic trial, while gonadotrophinomas may occasionally respond to gonadotrophin-releasing hormone (GnRH) antagonists (and, infrequently, to GnRH agonists). In summary, the primary approach to the functionless tumour is surgical, trans-sphenoidal in the great majority, followed either by radiotherapy or a policy of regular imaging and close monitoring.

Acromegaly and gigantism Acromegaly is generally considered a rare condition, with an incidence of about three to four new cases per million of population per year.45,46 Its prevalence in the UK is

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approximately 40 per million population. In more than 99 per cent of cases acromegaly is due to a benign pituitary GH- secreting adenoma, the majority being macroadenomas. The large majority of somatotrophinomas are sporadic, although they could be part of a familial syndrome. As part of multiple endocrine neoplasia type I (MEN-I), they represent about 10 per cent of the associated pituitary tumours and occur, as in sporadic cases, during the fourth and fifth decades of life. These tumours can also appear in the context of Carney complex, where they are the exclusive pituitary tumours found in about 21 per cent of patients. Carney complex has been linked to loss of heterozygosity (LOH) at chromosome 17q or 2p, and to germ-line mutations in the protein kinase A (PKA) regulatory subunit 1 (PRKAR1A) gene;47–49 its loss of function results in constitutive activation of PKA and its signalling, and consequently increased somatotroph proliferation. This signalling pathway is also activated by somatic mutations of GSα gene, detected in up to 40 per cent of sporadic somatotrophinomas,50,51 but also by mutations in patients with McCune–Albright syndrome, characterized by frequently present somatotroph hyperplasia and adenoma.52 Isolated familial somatotrophinomas cluster in some families, with earlier onset (in two-thirds of subjects before the age of 30 years) in the absence of other endocrinopathies; they are associated with LOH at chromosome 11q13, and this is suggestive of a tumour suppressor gene not yet identified – no mutations detected have been in the menin gene.53,54 However, as pituitary imaging and biochemical assays for GH have become more widespread, the spectrum of the disease has widened, with increasing numbers of patients having purely intra-sellar tumours or microadenomas. This has, in turn, modified the balance of the principal therapeutic approaches. It is now clearly established that, when untreated, acromegaly is associated with an increased

mortality. In addition, acromegalic patients have an increased risk (3-fold to 14-fold) of developing colorectal carcinoma or tubular adenomas.55 The association of acromegaly with breast and prostate cancer remains uncertain, but, if present, is a very low risk.56,57 Definitive treatment of acromegaly aimed at lowering serum GH and IGF-1 is indicated in almost all cases. Diagnosis is based on an elevated serum IGF-I and a serum GH that fails to suppress to 0.2 μg/L during a standard glucose tolerance test.58–60 Trans-sphenoidal surgery is highly effective in considerably reducing tumour mass and substantially lowering mean GH levels in the majority of patients, although a surgical cure is rare. Previous considerations for ‘cure’ of acromegaly (mean serum GH, basally or after glucose, 5 mU/L, 10 mU/L or even 20 mU/L) have become more strict in the last years, establishing a therapeutic aim for a serum GH below 5 mU/L (2.5 μg/mL, as residual mean GH levels above 5 mU/L were still associated with elevated mortality.61 Most series report a fall in mean serum GH to less than 5 mU/L in approximately 40–60 per cent of all acromegalic patients treated surgically, but this ‘cure’ rate rises to 80–90 per cent for microadenomas. More recent surgical series (using strict criteria for cure: normalization of IGF-1 levels, random GH 2.5 μg/L and 1 μg/L during the glucose tolerance test) report improved results, with a cure rate of 65 per cent for macroadenomas and 88 per cent for microadenomas, and a 10-year overall recurrence rate of 1.3 per cent.5***,62 Hypopituitarism occurs in approximately 25 per cent of such patients. External-beam radiotherapy has also been used extensively in the treatment of acromegaly, and although it induces a fall in mean serum GH, this may take several years to become fully effective (Fig. 18.2). In our own series 250

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