The influence of whole-body exposure to x-rays or neutrons on the life span distribution of tumors among male rats.

Adult male rats were irradiated with single, whole-body doses of X-rays (430 or 680 rads) or with neutrons (230 or 320 rads) and maintained in a duration-of-life study. An analysis of the extent of tumorigenesis was made according to the type of tumor, the number of animals with tumors, and the distribution of tumors among organs for each dose group. Greater proportions of the irradiated groups developed greater numbers of tumors than did the controls, even though lifespan was reduced by irradiation. Radiation was particularly effective in inducing malignant tumors of epithelial origin although there were significant excesses of animals with malignant nonepithelial tumors and with benign tumors of both epithelial and nonepithelial origin. Among the numerous organs and tissues in which tumors developed, the skin, kidney, lung, and islets of Langerhans appeared especially responsive to irradiation. Consistent relationships between incidences of animals with tumors and dose or quality of radiation were not apparent.