Relationship between radiotherapy and tumor immunity in hosts

: There are several opinions which denied therapeutic effects of preoperative irradiation, however, we have obtained favorable results by preoperative irradiation for the advanced breast and stomach cancers. Because we treated them by less-fractionated irradiation method with a large dose instead of conventional fractionated one. We adopted this kind of radiation method for the purpose of enhancing the antigenicity of the cancer cells (that means to inhibit the suppression of immune reaction in hosts). Cases of advanced breast cancer were irradiated with 30 Gy at once or 10 Gy at three times a week (total 30 Gy) by betatron electron and we treated advanced stomach cancer with twice a week method (5 Gy or 3 Gy each time, total 40 Gy) by 6 MV X-ray. Cellular infiltration into the stroma of malignant tumor is able to be considered as cellular immunity of the tumor. The same reaction could be observed in radiotherapy for cancer by using above method. After preoperative irradiation, we examined the resected specimen histopathologically. Remarkable cellular infiltrations into the tumor nests, such as neutrophils, lymphocytes, macrophages and plasma cells were observed and these cellular infiltrations after the preoperative irradiation were more remarkable than the cases without radiotherapy or with conventional fractionated radiotherapy. The abscopal effects could be seen in several cases. Peripheral lymphocytes, T cells, B cells and blastoid formation rate induced by PHA in vitro were all increased after less-fractionated irradiation. The reaction to 4 kinds of immunological skin tests was also enhanced.