Identification of risk factors and development of detection algorithm for denosumab‐induced hypocalcaemia

WHAT IS KNOWN AND OBJECTIVE: This study used electronic medical records to identify risk factors and establish a detection algorithm for denosumab-induced hypocalcaemia. METHODS: We identified 201 patients with cancer who were initially prescribed denosumab. Hypocalcaemia was defined as an adjusted serum calcium level of ≤2.13 mmol/L. A diagnosis of denosumab-induced hypocalcaemia was confirmed by two physicians after reviewing patient medical records. We evaluated patient characteristics as potential screening factors. Moreover, a retrospective cohort study was conducted to identify risk factors for denosumab-induced hypocalcaemia. Odds ratios (ORs) were estimated using logistic regression analysis. RESULTS: We analysed 164 patients with a low risk of hypocalcaemia. Among these, 29 (17.7%) patients were suspected to have denosumab-induced hypocalcaemia. The times to onset of definitive hypocalcaemia were shorter among these patients than among patients with non-denosumab-induced hypocalcaemia. Based on receiver operating characteristic curve analysis, we used time to onset of hypocalcaemia of ≤90 days as a second screening factor. The positive predictive value of this factor was 87.5%. In the retrospective cohort study, a significant difference was observed among patients with serum alkaline phosphatase (ALP) levels of >5.95 μkat/L before initial prescription (P < 0.01). Patients with higher serum ALP levels had a 6.63 times higher risk of developing hypocalcaemia than those without increased serum ALP levels (OR: 6.63, 95% confidence interval [CI]: 1.79-29.31). The same results were observed in a sensitivity analysis using another database. WHAT IS NEW AND CONCLUSION: We developed a detection algorithm for denosumab-induced hypocalcaemia based on calcium levels and time to onset of hypocalcaemia. We also identified elevated ALP levels as a risk factor for hypocalcaemia. Clinicians should carefully monitor initial serum calcium levels and screen for signs of hypocalcaemia in patients receiving denosumab who demonstrate elevated serum ALP levels.