Denosumab as Second-Line Treatment in Patients With Metastatic Breast Cancer: A Retrospective Descriptive Pilot Study From a Single Institution

Introduction Bone metastasis in breast cancer patients can lead to poor quality of life and cause significant morbidity. First-line treatments for bone metastases include bone modifying agents that inhibit osteoclast activity to reduce bone resorption. The most commonly used bone modifying agents include zoledronic acid and denosumab. It is currently unknown whether a therapy change from zoledronic acid to denosumab would result in greater symptom control or improved disease outcomes in breast cancer patients. In this single institution retrospective cohort study, we aimed to identify the reasons why patients transitioned from zoledronic acid to denosumab and to determine whether denosumab, as a second-line therapy, led to reduced narcotic use for metastatic bone pain. Materials and Methods Breast cancer patients with bone metastases treated at The Ohio State University Comprehensive Cancer center from 2011-2018 with a bone modifying agent were examined. Nineteen patients who received second-line denosumab following previous exposure to zoledronic acid were identified and included in this study. Results The two most common reasons patients switched from zoledronic acid to denosumab were related to side effect burden (28%) and bone metastasis progression (28%). No reduction in narcotic use due to bone pain was observed six months after starting denosumab. None of the patients developed new skeletal related events after switching to Denosumab. Conclusion Overall, denosumab as a second-line therapy appeared to be well-tolerated in our cohort, as we did not observe any treatment-related toxicity. Patients who switched to denosumab did not experience improved pain control.