The Challenge and Opportunity of Individual Variation in Response to Radiation Therapy

摘要

Despite the large investment over the past 10-15 years on studies of assays designed to predict the response of human tumours and normal tissues to fractionated radiotherapy, there has been only limited success. Notably, studies using oxygen electrodes have shown that hypoxia is an important parameter affecting both local control rates of head and neck and cervix cancers as well as being a predisposing factor for metastatic spread. However, the extensive amount of data collected on intrinsic radiosensitivity and clonogen proliferation rate has, with one exception with cervix cancer, proven negative. Also, the promise that late fibrosis might be predicted from fibroblast radiosensitivity so as to individualise doses to patients has not been realised. It would therefore seem that predictive assays for both tumour and normal tissue response are unlikely to fulfil their initial promise. However, an extension of predictive assays, surrogate assays, that can assess treatment modification might be more useful. Such assays could allow clinical evaluation of potential radiation sensitisers with fewer patients and in shorter times than is the case with conventional clinical trials.