Abstract

Background: Targeted radiopharmaceutical therapy is one of the most common methods for relieving pain in patients with bone metastasis. In this type of treatment, the bone marrow absorbed dose, as a critical organ, needs to be considered as a limiting factor. Until now, beta-emitter radiopharmaceuticals have been considered for this treatment modality, which one of the most commons is samarium-153-ethylene diamine tetramethylene phosphonate (153Sm-EDTMP), but recently the radium-223-dichloride (223Ra-Cl2) alpha emitter radiopharmaceutical has been approved by the US Food and Drug Administration (FDA). The aim of this study was to compare the bone marrow absorbed dose of 153Sm-EDTMP and 223Ra-Cl2 radiopharmaceuticals. Methods: In this study, a lumbar vertebral bone phantom was used for simulation. The radiopharmaceuticals were distributed in the phantom, and the simulation was performed using the GATE Monte Carlo toolkit. After estimating the absorbed dose per decay in different parts of the phantom, the absorbed dose of radiopharmaceuticals in the bone marrow of a patient with 70 kg weight, was calculated using the Medical Internal Radiation Dosimetry (MIRD) method. Findings: For 153Sm-EDTMP, the bone marrow absorbed dose was equal to 9.60 Gy for the administered activity of 2590 MBq. For 223Ra-Cl2, the bone marrow absorbed dose was calculated as 0.83 Gy for administered activity of 3.85 MBq. Conclusion: Due to the lower bone marrow absorbed dose by 223Ra-Cl2 alpha emitter radiopharmaceutical, the use of this radiopharmaceutical as an alternative to 153Sm-EDTMP beta emitter radiopharmaceutical is recommended for palliative therapy of patients with bone metastasis. © 2021 Isfahan University of Medical Sciences(IUMS). All rights reserved.