Abstract PO1-12-07: Denosumab vs. Pamidronate in the Management of Osteolytic Bone Metastases Secondary to Breast Cancer, a Multi-Institutional Analysis

Abstract

Abstract Breast cancer is one of the most common cancers in women and is associated with poor outcomes due to the metastatic potential of high-grade tumors. One common site of breast cancer metastasis is to the bone, leading to serious adverse effects such as bone pain, bone fracture, and spinal cord compression. Denosumab, a monoclonal antibody against the receptor activator of nuclear factor kappa-b (RANK) ligand (RANKL), and Pamidronate, a bisphosphonate, are two pharmacologic agents offered for the treatment of these adverse complications. The goal of this study was to conduct a retrospective cohort analysis across multiple institutions to compare the efficacy of Denosumab vs. Pamidronate in the management of osteolytic bone metastases secondary to breast cancer by evaluating the risk of adverse events. TriNetX, an online network that provides access to anonymized medical records for more than 108 million patients in 72 large healthcare organizations, was used in this study. Two cohorts, consisting of 847 patients with a diagnosis of bone metastases and breast cancer, were created and subsequently matched for age, race, gender, and ethnicity. One cohort was given Denosumab while the other was given Pamidronate, and each cohort was excluded from receiving the other medication. The occurrence of pathologic fracture in each arm, spinal cord compression, and overall five-year survival rate was measured and analyzed. The results of this study showed that Denosumab had a statistically insignificant risk reduction in both pathological fracture (2.7% vs. 2.8%, p = 0.88) and spinal cord compression (2.6% vs. 2.7%, p = 0.88) and a statistically insignificant difference in the overall five-year survival rate (45.5% vs. 52.4%, p = 0.78) when compared to Pamidronate. As a result, additional factors such as financial cost, route of administration, dosing schedule, and potential adverse side effects should be discussed with each individual who requires pharmacological therapy for bone metastases secondary to breast cancer. Citation Format: Megan Bradley, Mabry Nichols, Brittany Miles. Denosumab vs. Pamidronate in the Management of Osteolytic Bone Metastases Secondary to Breast Cancer, a Multi-Institutional Analysis [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-12-07.