The effects of denosumab on calcium profiles in advanced cancer patients with bone metastases.

OBJECTIVE: To retrospectively examine the incidence and management of hypocalcemia for patients with bone metastases treated with denosumab. METHODS: Patients who had a record of filling a prescription of denosumab for treatment of bone metastases at the outpatient pharmacy at the Odette Cancer Centre from May 2011 to February 2013 were included in the analysis. Demographic information, previous bisphosphonate usage, calcium and albumin values, and adverse events were obtained using the Sunnybrook Electronic Patient Record system (EPR) and the Oncology Symptom Control and Information Resource (OSCIR). Hypocalcemia was defined as a calcium value below 2.0 mmol/L within a 28-day±7-day window after the last injection of denosumab based on the Common Terminology Criteria for Adverse Events (CTCAE) grade 2 hypocalcemia. RESULTS: A total of 55 patients had record of a prescription for denosumab filled with an average age of 62 years (range 40 to 93 years), 18 (32.7%) were males and 37 (67.3%) were females. Twenty-nine (52.7%) patients had primary breast cancer, 12 (21.8%) prostate, 10 (18.2%) lung, and 4 (7.3%) with other types. Using CTCAE grading of hypocalcemia, 17 (32.7%) patients experienced grade 1, 4 (7.7%) patients grade 2, 4 (7.7%) patients grade 3, and 1 (1.9%) patient grade 4. The number of injections before the incident of hypocalcemia was a median of one injection (range 1 to 14). Time from the first hypocalcemia lab value to normocalcemia was a median of 33 days. CONCLUSIONS: This study found that 9 of 52 (17.3%) patients had at least one incidence of hypocalcemia of grade 2 or higher after receiving denosumab. Cautionary measures should be taken to avoid hypocalcemia in patients receiving denosumab.