Phase Ii Study Of Ra-223 Combined With Hormonal Therapy And Denosumab For Treatment Of Hormone Receptor-Positive Breast Cancer With Bone-Dominant Metastasis.

1065Background: Radium-223 dichloride (Ra-223) is a targeted alpha therapy that induces a localized cytotoxic effect on bone metastases. We evaluated the efficacy of combined Ra-223, hormonal therapy, and denosumab in patients with hormone receptor (HR)-positive, bone-dominant metastatic breast cancer. Methods: In this single-center phase II study (NCT02366130), patients received Ra-223 (55 kBq/kg intravenously) on day 1 and then every 4 weeks for 6 cycles. Patients also received a hormonal agent (i.e., tamoxifen, aromatase inhibitor, or fulvestrant) at standard dosage and denosumab (120 mg) every 4 weeks. One non-bone metastatic site was allowed. There was no limit on the number of prior hormonal therapies, and one prior chemotherapy was allowed for metastasis. Response was evaluated by PERCIST on FDG PET-CT at baseline, 6 and 9 months (mo). Primary objective was disease control rate at 9 mo. Secondary objectives were tumor response rate at 6 mo and safety. Results: After patient accrual (n = 36), the fi...