DTPA Therapy for Chelation of 239Pu in Bone

Data are presented illustrating the role of local bone resorption in the removal of 239Pu deposited in the bones of immature rats following intravenous injection. Chelation of plutonium bound in the bone matrix can occur effectively only if the plutonium is first liberated into soft tissue by osteoclast action in the process of bone resorption. When therapy is commenced after skeletal uptake is complete, the proportion of the total bone surface area undergoing resorption dictates the efficacy of delayed therapy in reducing the skeletal burden. The effectiveness of promptly administered DTPA is largely due to the chelation of plutonium in the blood, thus preventing skeletal deposition. Measurements have been made of the activity of 239Pu deposits on bone surfaces and the dose to the osteogenic cells under various conditions of remodelling activity and DTPA treatment. Delayed DTPA therapy is unlikely to reduce the risk of bone cancer induction from 239Pu already deposited in human bone, although the same treatment could be important in reducing the risk of other types of tumour.