[Improvement of treatment results in radiotherapy]

There are three purpose in radiation therapy: (1) the increase of the local control rate, (2) the decrease of the radiation injury in the surrounding normal tissues and (3) the improvement of the QOL (quality of life) of patients in palliative treatment. The increase of local control rate is the most important in these three aims, but clinically it is difficult to obtain the statistically significant gain in local control rate, because of the heterogeneity of tumor cells in radiosensitivity. In contrast, the slope of the dose-response curve of the normal tissues is usually steep and the slight decrease of the dose produces good results. In palliative irradiation it is important to set up the new criteria to evaluate the treatment results in each situation.