THE POTENTIAL FOR RADIOBIOLOGICAL MODELING IN RADIOTHERAPY TREATMENT DESIGN

The application of the linear-quadratic (LQ) model to various types of fractionated radiotherapy is now well established, and has demonstrated ways in which treatment might be improved. Whilst attitudes to fractionated therapy are undergoing radical review, other aspects of radiotherapy are also moving through a period of significant change. In recent years there has been a growing interest in other, more complex techniques, e.g. the use of permanent implants of iodine-125 seeds, the use of more versatile brachytherapy units which may treat a variety of sites at a range of dose-rates, and the use of biologically targetted radionuclides. The quantitative radiobiological assessment of such treatments poses a number of new problems, a complete understanding of which may take some while to provide. In spite of current limitations the LQ model has, in its more general form, the potential to be applied to a wider variety of clinical circumstances than is sometimes appreciated. Additionally, although the model does not provide a rigorous description of all the underlying radiobiological phenomena which govern the outcome of radiation treatment, it does have the capacity (unlike previous models) to draw clearer distinctions between the various contributing processes, and to focus attention on those parameters which are most likely to govern radiotherapy. © 1990.