Applied Radiobiology and Bioeffect Planning

Author:  David Wigg
ISBN:  9781930524057      ISBN10:  1930524056
Published:  2001 | 486 | Hardcover



The Radiographer  |  December 2004

"Many Australian radiation therapists know the author of this textbook, David Wigg, as an expert in radiobiology. The foreword by the internationally renowned radiobiologist Jack Fowler indicates that this book provides 'the most solid ground in radiobiological modelling for clinical radiation oncology that is available.' The importance and significance of this textbook to the practice of radiation therapy cannot be underestimated.

"Chapter one 'Early Models of Clinical Importance - wrong but useful' describes radiobiological models that have been used in the past and the limitations of these models are highlighted. As the author points out it is necessary to have an understanding of these models as they are often referred to in the literature. It is further emphasised that all radiobiological models should be used with extreme caution.

"In the following five chapters models are derived for bioeffect planning taking into account factors that affect the response of late reacting normal tissue and tumour. These factors are volume effect, fractionated and continuous irradiation, hyperfractionation and incomplete repair, chemotherapy, time and repopulation. Although I found the mathematical theory beyond my level of knowledge the descriptive sections regarding clinical applications of these models were easier to understand and the relevance and importance to clinical practice was well demonstrated.

"Chapter seven provides a biological basis for the treatment of arteriovenous malformations (AVM), which has largely been ignored in the past. It is demonstrated in this chapter that fractionated radiotherapy should be considered in the treatment of AVM given the sensitivity of brain tissue.

"In chapter eight tumour radiosensitivity, proliferation and tumour clonogen numbers are reviewed and defined in terms of their mean values and variability. The proliferation of human tumours was well described and provided me with a much better understanding of the difference between the doubling time of different tumours. This chapter provides excellent reference material for all.

"It is in chapter nine that the clinical relevance of the preceding chapters becomes clear. In this chapter three models named the EFFECT, OPTIMUM and CONFRACT are derived. The EFFECT model can be used to determine late effect probabilities and tumour control probabilities. The OPTIMUM model enables the optimum daily dose or multi-fractions per day to be calculated for a given tissue or tumour types. The CONFRACT model determines the biological effect for continuous irradiation or continuous combined with fractionated treatment. The validity of these models was tested against actual clinical outcomes and found to closely predict the actual effect.

"Chapter ten gives clinical applications of bioeffect planning. This chapter will provide the radiation therapist with an understanding of how bioeffect planning is used and the need for the expansion of its use in radiation therapy. It is clear from these examples that isodose plans do not give a true indication of the biological effects of treatment. The examples used are all sites that we deal with routinely such as brain, lung, breast and pelvis. Plans are produced using conventional isodoses in dose per fraction and compared to the equivalent bioeffet plan. From the comparison of the two plans it can be seen that effect of a hot spot or inhomogeneity in dose has a much greater influence on normal tissue and tumour control probability than would be expected looking just at the isodose plan. Advantages of reducing volumes and the need for compensation are well demonstrated. The limitations of isodose planning and the need to consider biological effects in radiation therapy treatment are clearly identified.

"In the preface to this textbook David Wigg states, 'The main purpose of this book is to encourage the development of bioeffect planning as an experimental tool by which means bioeffect plans may be compared with standard isodose plans.' After reading this textbook I agree that there is a definite need for further development of bioeffect planning.

"I believe this book is essential reading for all radiation therapists as we move into an era of changing fractionations, techniques and dose escalation. Every practitioner should have an understanding of radiobiology and the parameters that can affect outcome. This textbook clearly shows the need for biological effects to be incorporated into planning systems but we must be cautious that any model used will only be predictive and some models are more useful than others."

Marianne Hercus