Relative Effects of Whole-Body Sublethal Doses of 60-MeV Protons and 300-kVp X-Rays on Disease Incidence in RF Mice

Over 3100 young-adult female RF/Un mice were given whole-body exposure to 60-MeV protons or 300-kVp x-rays (0-400 rads) and were observed for life-shortening effects and neoplastic and nonneoplastic diseases. Complete pathological examination was done on all animals, and 81% were examined histologically. Similar dose-response curves were seen for most diseases but, with the exception of ovarian tumor induction, x-rays were slightly more effective in inducing a specific disease than were protons. For life-shortening, x-rays were more effective at all doses (0.34-0.80 day's life-shortening per rad) with the greatest difference in effect between x-rays and protons found at the two lowest doses, 50 and 100 rads. X-rays increased the combined incidences of thymic lymphoma and myeloid leukemia, but these leukemias did not account for all life-shortening at higher doses (100-400 rads); the remainder may be related to an increase in ovarian tumors. X-rays were more effective than protons in inducing myeloid leukemias at 50-200 rads and thymic lymphoma at 300-400 rads with no differences at other doses. Maximum incidences were reached with x-rays at 300 and 400 rads for thymic lymphoma and at 200 rads for myeloid leukemia while there was no difference in effect between radiations on reticulum cell sarcoma and nonthymic lymphoma frequency. Combined observed incidences of all leukemias were not different from controls and irradiated groups at 50 rads, nor at 100 rads for protons, but increased at higher doses. Lung tumor incidence showed a negative dose-response due to the failure of animals to survive long enough to develop this usually nonfatal disease. Ovarian tumors were increased by all doses of both radiations and this was the only instance where protons were more effective than x-rays; maximum response was seen at 100 rads for both radiations. Pituitary gland and harderian gland tumors may have been increased by radiation (P