Dosimetry of Bone-Seeking Radiopharmaceuticals for Palliative Therapy of Bone Metastases: A Simulation Study Using GATE Monte Carlo Code
Purpose: Radiopharmaceutical Therapy (RPT) is one of the effective methods for pain palliation of bone metastases. Bone marrow is a critical organ in bone structure whose absorbed dose should be kept below a certain threshold. The purpose of this study was to calculate and compare absorbed doses of bone-seeking radiopharmaceuticals used in the palliative treatment of bone metastases.
Materials and Methods: In this study, the GATE Monte Carlo code was used to simulate a femur bone, which consists of bone marrow, endosteal layer, bone, and soft tissue phantom model. Absorbed doses of the 153Sm-EDTMP, 89SrCl2, 177Lu-EDTMP, 188Re-HEDP, and 223RaCl2 radiopharmaceuticals were calculated in the femur phantom compartments.
Results: bone absorbed doses per disintegration from alpha particles of 223RaCl2 is approximately 24 times higher than absorbed doses from beta particles of 89SrCl2. Also, absorbed dose per disintegration from beta particles of 89SrCl2 in the bone is approximately 12, 6 and 1.5 times higher than 177Lu-EDTMP, 153Sm-EDTMP, and 188Re-HEDP, respectively. Moreover, the bone and bone marrow absorbed dose from beta particles of 153Sm-EDTMP is 1.9 times higher than 177Lu-EDTMP. Besides, absorbed dose per disintegration from beta particles of 188Re-HEDP in the bone marrow is approximately 40, 30, 7, and 4 times higher than 223RaCl2, 89SrCl2, 177Lu-EDTMP and 153Sm-EDTMP, respectively.
Conclusion: Our results show that 223RaCl2 could be a more efficient radiopharmaceutical for radionuclide therapy of bone metastases. Also, 177Lu-EDTMP, due to low marrow toxicity and comparable bone absorbed dose with 153Sm-EDTMP, can be used for achieving bone pain palliation. Moreover, significantly high bone marrow absorbed dose of 188Re-HEDP should be considered for palliative therapy of metastatic bone patients.
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