Biodistribution and dosimetry of 177Lu-DOTA-IBA for therapy of bone metastases

Abstract

Abstract Background We designed and synthesized a novel bisphosphonate radiopharmaceutical (68Ga- or 177Lu-labeled DOTA-ibandronate [68Ga/177Lu-DOTA-IBA]) for the targeted diagnosis and treatment of bone metastases. In this study, the biodistribution and internal dosimetry of a single therapeutic dose of 177Lu-DOTA-IBA were evaluated using a series of single-photon emission computerized tomography (SPECT) images and blood samples. Five patients with multiple bone metastases were included in this prospective study. After receiving 1110 MBq 177Lu-DOTA-IBA, patients underwent whole-body SPECT/CT imaging and venous blood sampling over 7 days. Dosimetric evaluation was performed for the main organs and tumor lesions. Safety was assessed using blood biomarkers. Results 177Lu-DOTA-IBA showed fast uptake, high retention in bone lesions, and rapid clearance from the bloodstream in all patients. In this cohort, the average absorbed doses in the bone tumor lesions, kidneys, liver, spleen, red marrow, bladder, and osteogenic cells were 5.740, 0.114, 0.095, 0.121, 0.095, and 0.333 Gy/GBq, respectively. Although no patient reached the predetermined dose thresholds, the red marrow will be the dose-limiting organ. There were no adverse reactions recorded after administration of 1110 MBq 177Lu-DOTA-IBA. Conclusion Dosimetric results show that the absorbed doses for critical organs and total body are within the safety limit and with high bone retention. It is a promising radiopharmaceutical alternative for the targeted treatment of bone metastases, controlling its progression, and improving the survival and quality of life of patients with advanced bone metastasis.