DECREASED INCIDENCE OF THYMIC LYMPHOMA IN AKR MICE AS A RESULT OF CHRONIC, FRACTIONATED LOW-DOSE TOTAL-BODY X-IRRADIATION

We have investigated whether low-dose total-body X irradiation could s uppress the development of lymphoma in AKR mice. Male mice were irradi ated with 5 cGy three times a week or 15 cGy two times a week from 11 weeks of age for 40 weeks. The incidences of lymphoma were 80.5% in sh am-irradiated mice, 67.5% in mice irradiated with 5 cGy three times a week and 48.6% in mice irradiated with 15 cGy twice a week. Incidence of lymphoma was significantly reduced by irradiation with 15 cGy twice a week (P = 0.006). The mean survival time was significantly prolonge d from 283 +/- 3 days in control mice to 316 +/- 10 days in mice irrad iated with 15 cGy twice a week (P = 0.008) and to 309 +/- 14 days in m ice irradiated with 5 cGy three times a week (P = 0.040). Because abou t 80% of male AKR mice die of lymphoma, it is likely that the prolonge d life span observed in the irradiated mice is due to the reduced inci dence of lymphoma. (C) 1996 by Radiation Research Society