Specific information related to the risk of radiation induced tumours and other late effects in man is limited. Studies on acute and late effects in nonhuman primates are relevant for man since the radiation effects in both species do not seem to show significant differences. Studies with larger animals are valuable for risk assessment in man and for estimation of the relative biological effectiveness (RBE) for tumour induction by neutron irradiation of human patients. In addition the induction of deterministic effects in various tissues and the RBE of neutrons for these effects are of increasing importance for radiation protection problems.
The study of total body irradiation of rhesus monkeys with fission neutrons (average dose 3.4 Gy) and X-rays (average dose 6.7 Gy) was initiated in the time period 1963-1973. In the irradiated groups 4 of 29 monkeys are still alive whereas 11 of 29 untreated monkeys (the controls) are still alive. The protective effect of autologous bone marrow transplant was initiallydemonstrated but new research has shown an increasing importance of the application of haemopoietic growth factors which have been performed since 1988. It is too early to expect radiation neoplasms in the latter group.
The average latency period for carcinogenesis amounted to 11 years for 7 out of the 9 neutron irradiated monkeys and to 13 years for 10 out of the 20 X-irradiated monkeys. A variety of neoplasms and in many cases multiple tumours were observed in the irradiated monkeys whereas in the control group only 2 out of 21 monkeys developed single malignancies. Descriptions of the malignant and benign neoplasms observed in the irradiated groups are tabulated.
INCIDENCE OF CANCER AND NON-STOCHASTIC DISEASES IN AN IRRADIATED POPULATION OF RHESUS MONKEYS