Objective(s): Bone metastases are a major complication in various tumors such as prostate, breast, kidney, and lung carcinomas, and are associated with progressive bone pain. Bone-seeking beta-emitting radiopharmaceuticals, such as lutetium-177 methylene diphosphonate (177Lu-MDP), are considered promising agents for palliating bone pain.

Methods: In this study, the radiation absorbed dose of 177Lu-MDP radiopharmaceutical was estimated for adult humans based on biodistribution data obtained from male Sprague-Dawley rats. The MIRD dose calculation method, alongside the Sparks and Aydogan methodology, was applied.

Results: The results show that approximately 60% of the radiation absorbed dose is localized in osteogenic cells (2.860 ± 0.375 mGy MBq-1). Additionally, the radiation absorbed doses of 177Lu-MDP for red bone marrow, liver, and lung tissues were estimated to be approximately 0.497 ± 0.065, 1.134 ± 0.149, and 0.125 ± 0.036 mGy MBq-1, respectively. The maximum administered activity was calculated as 57.5 MBq kg-1 (1.55 mCi kg-1) of body weight, resulting in a bone surface absorbed dose of approximately 11.6 Gy for a 70 kg adult man. In addition, the effective dose was estimated to be approximately 0.16 mSv MBq-1. The maximum tolerable dose of bone marrow (2 Gy) was achieved with 4.0 GBq (108.11 mCi) administration of 177Lu-MDP radiopharmaceutical.

Conclusion: Dosimetric studies indicated that 177Lu-MDP can deliver a significant dose to bone malignancies, suggesting its potential usefulness in palliating bone pain.