Preparation and biological evaluation of 186/188Re-HEDP as a new cocktail radiopharmaceutical for palliative treatment of osseous metastases in wild type rat

Introduction: The palliative care in patients with bone metastasis includes variety of techniques such as conventional analgesics, surgery, external beam radiotherapy, hormone therapy, chemotherapy and using bone-seeking radiopharmaceuticals. Even some of the recent works used combined methods like chemotherapy and radionuclide therapy or using radionuclide therapy as adjuvant to external beam therapy or even using tandem 2 separate radiopharmaceuticals. In line with combined methods, due to the improved efficacy of two radioisotopes with complementary properties in treatment, in this study we proposed using compositional radiopharmaceuticals as a new idea. In this study as a new idea the combined radionuclide therapy have been investigated with utilizing 188Re and 186Re complementary features in the 188/186Re-HEDP cocktail to achieve the maximum efficacy. Methods: 186Re and 188Re have been produced simultaneously with identical activities by natural rhenium irradiation. Produced 188/186Re-HEDP with high radiochemical purity was administered intravenously to rats. Biodistribution data were collected at 2, 4, 24, 48 and 72 hours post injection and scintigraphic images were taken at 24 hours after administration of radiopharmaceutical. Results: 188/186Re-HEDP was prepared with radiochemical purity of nearly 99%. Its biodistribution data showed high uptake and durability in the skeletal tissues without significant uptake in other major organs. Conclusion: The study results demonstrate that the combination of 186Re and 188Re in cocktail radiopharmaceutical form is achievable and safe. The complementary features of 188Re and 186Re, due to their different energies, half-lives and penetration ranges can lead to more efficacy in bone metastases treatment.