(152) Predictors of Hypomagnesemia with Denosumab in Patients with Metastatic Bone Disease from Solid Malignancies: A Single-Institution Retrospective Study

Poster Abstract:

Background: Denosumab (Xgeva®) is a monoclonal antibody that binds to Receptor Activator of Nuclear Factor Kappa-B Ligand (RANKL) and inhibits bone resorption. It is indicated for the prevention of skeletal-related events (SREs) in patients with multiple myeloma or bone metastases from solid cancers. It is well-established that denosumab causes hypocalcemia and hypophosphatemia and it is recommended to routinely monitor serum creatinine, calcium, and phosphorus levels prior to and throughout treatment with denosumab. The denosumab package insert, drug information databases including Lexicomp and Micromedex, and Clinical Practice Guidelines from organizations such as American Society of Clinical Oncology (ASCO) and National Comprehensive Cancer Network (NCCN) also recommend the routine monitoring of serum magnesium levels. However, the incidence of hypomagnesemia with denosumab therapy in patients diagnosed with metastatic solid cancers has not been studied and there is no published data or consensus on the clinical significance of denosumab-induced hypomagnesemia.

Objective: The standard practice at Loma Linda University Health (LLUH) Cancer Center is to routinely monitor serum magnesium levels along with calcium and phosphorous in patients receiving denosumab therapy. The primary objective of the study is to determine the incidence of hypomagnesemia with denosumab therapy for the prevention of SREs in patients diagnosed with metastatic solid malignancies. The study also aims to identify potential patient-specific factors that increases the risk of hypomagnesemia. The findings of this study will encourage investigators to pursue prospective studies on denosumab-induced hypomagnesemia, its potential impact, and the clinical implications associated with denosumab use in oncology patients.

Method: This is a single center, retrospective cohort study of adults with metastatic solid malignancies who have received denosumab (Xgeva®) for the prevention of SREs at LLUH Cancer Center from January 2020 to November 2023. Patients included are ≥18 years old and confirmed diagnosis of solid malignancies with bone metastases who are treated with at least one dose of monthly denosumab. Patients excluded are patients with diagnosis of hematologic malignancies including multiple myeloma, patients treated for hypercalcemia of malignancy or with a bisphosphonate within 3 months of initiating denosumab, patients receiving osteoporosis therapy with either a bisphosphonate or a RANKL inhibitor, patients receiving denosumab every 3 months instead of monthly, and patients without baseline magnesium levels. The primary endpoint is the incidence of hypomagnesemia. Secondary endpoints are patient-specific factors that increase risk for developing hypomagnesemia, the incidence of mild, moderate, severe, and life-threatening hypomagnesemia.

Results: pending

Discussion/

Conclusion: pending

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