[Morphological characteristics of rectal adenocarcinoma after radiation therapy using a 25-MeV betatron].

The effect of brehmstrahlung irradiation from a 25 MEV betatron on rectal adenocarcinoma was studied in 34 patients in comparison with control material from 61 patients. It was found that pronounced changes in tumor tissue are caused by such preoperative treatment: tumor is reduced in size, DNA synthesis and mitotic activity are suppressed considerably and pathological mitoses increase. Morphological observations show that rectal adenocarcinoma is markedly susceptible to brehmstrahlung irradiation from a 25 MEV betatron.