Incidence and Risk Factors of Hypomagnesemia in Patients With Bone Metastasis From Solid Malignancies Treated With Denosumab: A Retrospective Chart Review

Background:Hypomagnesemia is associated with poor clinical outcomes in cancer patients. Patients with bone metastasis from solid malignancies receiving denosumab (Dmab) to prevent skeletal-related events often receive concurrent antineoplastic agents for cancer treatment. The incidence and risk factors of hypomagnesemia in patients receiving Dmab and the optimal frequency of monitoring serum magnesium (Mg) levels have not been studied in these patient populations.Objective:The objective is to investigate the incidence and potential risk factors of hypomagnesemia and the optimal frequency of monitoring serum Mg levels.Methods:A retrospective chart review identified patients with solid malignancies with bone metastases treated with Dmab at the Loma Linda University Cancer Center between January 2013 and February 2024. The incidence of hypomagnesemia was determined using the number of patients with hypomagnesemia and the total number of patients in the study. Univariate and multivariate logistic regression analyses identified risk factors for hypomagnesemia.Results:Hypomagnesemia was observed in 19% (29/153) of patients, the majority of whom were on concurrent antineoplastic agents with ≥15% hypomagnesemia incidence (high-hypomagnesemic antineoplastics) or nonantineoplastic drugs with documented cases or incidence of hypomagnesemia (hypomagnesemic nonantineoplastics) in addition to high-hypomagnesemic antineoplastics. Multivariate analysis showed increased odds of developing hypomagnesemia with high-hypomagnesemic antineoplastics (odds ratio [OR]: 174.93, 95% confidence interval [CI]: 12.82 to 387.43, P < 0.001); hypomagnesemic nonantineoplastics plus high-hypomagnesemic antineoplastics (OR: 210.09, 95% CI: 11.80 to 3740.12, P < 0.001); and Mg level ≤ 0.85 prior to Dmab administration (OR: 16.79, 95% CI: 2.30 to 122.41, P = 0.005).Conclusion and relevance:This study describes the incidence and potential risk factors for hypomagnesemia in patients with solid malignancies and metastatic bone disease treated with Dmab. This study’s findings provide additional clinical insight into potential risk factors for hypomagnesemia and the need for more frequent serum Mg level monitoring of at-risk patients. Future prospective studies are needed to determine the exact frequencies most appropriate in monitoring serum Mg levels in this group of patients.