[Several factors for improving results of radiation therapy]

Various methods have been employed for improving the efficacy of radiation therapy including combined use of radio-sensitizer, chemotherapy, hyperthermia, combination with surgery, intraoperative electron beam therapy, heavy particle therapy, etc. We have evaluated if further improvements in treatment results could be obtained by improving irradiation techniques which are routinely employed in the daily radiation therapy. The results of our evaluation has indicated that therapeutic gains could be raised by: (a) vastly improved radiographic techniques for better visualization of tumor and normal structures, that is, more reliable determination of target volume; (b) improvement of reproducibility of field alignments; (c) improvement of dose distribution by multiportal irradiations.