Induction of osteosarcomas in mouse lumbar vertebrae by repeated external beta-irradiation.

Besides skin tumors, osteosarcomas were induced at high frequency in the lumbar vertebrae of ICR mice by repeated local external irradiation of the back with 90Sr-90Y beta-rays when irradiation was repeated three times a week until tumors appeared. The optimum dose range for osteosarcoma induction was 250-350 cGy per exposure at the surface of the back, or 125-175 cGy at the depth of the center of the bone. With the same irradiation schedule, the optimal dose of radiation for induction of osteosarcomas was much lower than that for induction of skin tumors.