Research on the variation in radiosensitivity by hypofractionated irradiation of heavy ions

The TCP model based on the LQ model by Webb is used to analyze tumor control probability of heavy particle radiotherapy for non-small cell cancer. Clinical result was found consistent with TCP model among 18 to 4 fractions; however, the model tend to underestimate optimum dose to be required on one-day irradiation. As a reason that causes the discrepancy, we assume that the early recovery plays a certain role. In this present study, we investigate the short-time repair of tumor cells in terms of the survival rate measured by colony forming assay for X ray and carbon beam irradiation. In addition, the survival rate of benign cells is also investigated by colony forming assay in order to clarify the difference in response between fractionated and non-fractionated irradiation. (author)