Organ Dosimetry of [90Y]Y-EDTMP in Humans: A High-Potential Radiopharmaceutical for Bone Pain Palliation

Bone-targeting radiopharmaceuticals play a pivotal role in the treatment of skeletal metastases, particularly in patients with widespread bone involvement. Among these agents, [⁹⁰Y]Y-EDTMP emerges as a promising candidate due to the favorable β⁻ emission characteristics of yttrium-90 and the high affinity of its ligand for bone tissue. In this study, the radiopharmaceutical was synthesized by labeling yttrium-90 chloride with EDTMP under optimized conditions. Radiochemical purity was assessed using extraction paper chromatography, confirming a labeling efficiency greater than 98% without the need for further purification. Biodistribution data were obtained from rat models, and absorbed doses to human organs were estimated using the MIRD formalism. Time-integrated activity coefficients were extrapolated using standard mass-scaling methods and combined with organ-specific S-values derived from ICRP reference phantoms. Dosimetric results showed that the highest absorbed dose was delivered to the bone surface (0.91 mGy/MBq), followed by the bone marrow (0.88 mGy/MBq). This property may be beneficial for treating large and invasive skeletal metastases. Additionally, the low absorbed doses to critical organs such as the kidneys, liver, and heart indicate a favorable biodistribution profile and minimal systemic toxicity. These findings support the clinical applicability of [⁹⁰Y]Y-EDTMP in both targeted and palliative treatment of patients with skeletal metastases