Radiosensitivity of the Pre-irradiated Yoshida Sarcoma

Abstract

ACQUIRED radioresistance of cancer has been discussed clinically and experimentally by several authors^1–5. The various opinions concerning its mechanism may be summarized as follows: (1) selection of cancer cells; (2) induction of mutation and its adaptation; (3) connective tissue response or tumour bed response. Experimental confirmations are less pronounced than clinical observations. One^1,2 of the recent experiments showed development of radioresistance using repeated frequent X-ray irradiations of intramuscular implantation of Ehrlich carcinoma, whereas others³ noticed no change of radiosensitivity following frequent whole-body γ-ray irradiations of mice bearing Ehrlich ascites carcinoma. The results of the latter may be due to insufficient dose to develop a radioresistance.