Dose-Dependent Carcinogenic Effect of Radiostrontium

Four groups of mature CBA male mice were treated intraperitoneally with 90Sr(NO3)2 at dose levels of 1.6, 0.8, 0.4 and 0.2 μCi 90Sr/g body weight. Five mice from each group were killed at intervals of 7, 14, 21 and 30 days after injection of 90Sr, and then at monthly intervals. Blood samples were taken and roentgenologic examination was made before the mice were killed. The heads and selected bones were fixed for histologic examination and the tumours were recorded. Tumours of the bones were found in all dose groups, the largest number being in the 0.8-μCi level. In the highest dose group osteoblastic osteosarcomas predominated, but with decreasing dose the frequency of fibroblastic osteosarcomas increased. However, the highest incidence of carcinomas was found in the 1.6-μCi group. Most tumours of the head were located in the hard palate. The highest incidence of leukaemia appeared in the 0.4-μCi group and the lowest in the 1.6 group. The latency time for carcinomas and osteosarcomas seems to be a function of dose, but this relationship does not seem to be true for 90Sr-induced leukaemias. (author)