Technologist’s Guide

PET/CT Radiotherapy Planning Part 3

October 2012

In 2008 approximately 13 million new cases of cancer were diagnosed worldwide and nearly 8 million deaths were attributed to it. The most common causes of cancer death were lung, stomach and liver cancer [1]. Worldwide, the incidence of cancer is a fifth higher in men than in women. As the population grows, cancer will inevitably increase, too – even if incidence rates remain the same. Over half of all cancers are diagnosed in the developing countries, and this proportion is expected to increase over time. Based on current rates, projections indicate that by 2030 there will be around 21 million new cases diagnosed annually and approximately 13 million deaths from cancer [2].

Whilst cancer rates have increased, the ability to treat cancer effectively has improved substantially owing in major part to better diagnostic procedures that permit more timely detection of cancer. The enhanced prognostic ability of diagnostic tests allows for streaming of patients into more appropriate treatment or palliation (individualised) schemes. And, of course, the methods by which cancer can be treated or managed have improved considerably. Alongside these developments, new approaches to treatment/management continue to be tested and then introduced. Thirty years ago, many patients who developed cancer saw it as a death sentence; today this is no longer the case as many cancers are curable. Improvements in radiotherapy treatment regimens have created the need for more accurate planning. Various factors have brought about this change. For instance, there have been moves towards less radical surgical techniques, sparing healthy tissue but placing demands on the radiotherapy service to ensure that residual cancerous tissue is treated. Radiotherapy itself has evolved, too, with more targeted treatment fields being applied, again so as to spare healthy tissue and thereby help minimise unwanted effects of radiation therapy. In order to meet this goal, it is necessary to ensure that the radiotherapy field is planned as accurately as possible. Until recently, CT has played the major role in radiotherapy planning but now PET/CT has started to evolve to help define radiation treatment fields. In 2008 [3], the IAEA released helpful information which proposed that PET/CT would likely prove valuable in radiotherapy planning. More recently, EANM selected a collection of journal papers that may also prove useful in understanding the value of PET/CT in radiotherapy planning; these can be accessed via the EANM website [4]. The philosophy which underpins the use of PET/CT is related to the fact that the combination of PET and CT data allows structural and functional information to be demonstrated and evaluated together. The combination of anatomical (CT) and functional (PET) information can give the healthcare team better insight into not only cancer distribution and physical tumour size but also metabolic activity levels.

This book, the third and final in the PET/CT series, gives an introduction and overview of PET/CT for radiotherapy planning. Knowing that the readership could include those with limited familiarity with radiotherapy, we have included background information about this. Consequently, the early chapters introduce cell biology, radiobiology, side-effects of radiation therapy and radiation tolerance doses; these are followed by an overview of external beam radiotherapy (conventional, IMRT/Rapid Arc and stereotactic). Treatment planning is then introduced. At this stage, those new to radiotherapy planning will have gained a level of understanding to help contextualise the remaining chapters, which concentrate on PET/CT for radiotherapy planning. Whole-body FDG PET/CT scanning for radiotherapy planning is becoming the “state of the art”, done on a multidisciplinary basis by qualified staff from the Radiotherapy Department and the Nuclear Medicine and PET Department [5]. Therefore we took a strategic decision to invite authors from our collaborators, ESTRO and SNMT, to contribute their expertise in this field for this Tech Guide Book. ESTRO authors, as experts in radiotherapy planning, have contributed with the chapters ”Introduction to Radiotherapy”, “Method and Treatment Planning” and “4D CT and 4D PET”. SNMT, our American counter partner, has written about future prospects for PET/ CT in radiotherapy based on the introduction of novel tracers in the chapter “New tracers”. We would like to thank all chapter authors and peer reviewers who have helped us to create this book, in close collaboration with ESTRO and SNMT, for radiation therapy technologists, radiographers and nuclear medicine technologists and guests in your departments. We hope the reader will enjoy reading and using the book.

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