The Dose-Response Relationships of Beta-Ray-Induced Skin Tumors in the Rat

Abstract

Single doses of beta radiation ranging from 230 to 10000 rads were applied to 35-cm² skin areas on the backs of young male rats. The resultant dose-tumor incidence curves were highly nonlinear: the incidence of tumors of all types increased abruptly at about 2000 rads, reached a peak at about 4000 rads, and declined at higher doses. The sharp upturn in tumor formation occurred at doses which prcduced mild to moderate skin damage, while markedly pilocidal doses had a suppressing effect on the formation of adnexal tumors. There was a shifting distribution of tumor types with respect to dose: the hair follicle and sebaceous tumors predominated at the intermediate levels, whereas epidermoid carcinomas were more common at doses which produced very severe skin damage. The appearance time of tumors seemed to have little dose dependence in contrast to the magnitude of tumor incidence. The frequency distribution of tumors on individual rats was found to conform fairly well to a calculated Poisson distribution, suggesting that the presence of some tumors on the irradiated skin dces not markedly affect the formation of others. (auth)