Studies on incorporated short-lived beta-emitters with regard to the induction of late effects.

The rare earth radionuclides 177 Lu and 153Sm were administered as single i.p. injections in NMRI mice. Lu was deposited principally (up to 60%) in the skeleton if the quantity of stable carrier was low. Increase of stable carrier enhanced deposition in the reticulo-endothelial system. Sm was preferentially deposited in the liver; the liver deposits were further increased by the addition of stable Sm. Liver doses of between 75 and 150 Gy, resulting from a single injection of 153Sm together with 2 mg/kg stable carrier, led to severe lesions in the liver five months after treatment. Administration of 177Lu resulting in skeletal doses of between 28 and 224 Gy was found to be osteosarcomogenic. Up to 40% osteosarcoma incidence was obtained in animals with 56 and 112 Gy doses in the skeleton. Skeletal doses of this order of magnitude are also known to be osteosarcomogenic when given as 90Sr injections. The analogous situation with alpha-emitters is discussed.