Hypercalcemia in Patients Treated with Oral Bisphosphonates for Tumor-Induced Osteolysis

Objective: Hypercalcemia as the consequence of an excessive bone resorption is a common complication in patients with cancer. The aim of the study was to analyze the prevalence of hypercalcemia in patients with tumor-induced osteolysis starting therapy with bisphosphonates. Methods: The questionnaire-based survey (data collected during three consecutive examinations within a 3-month period) was conducted among 1,450 patients treated with bisphosphonates for tumor-induced osteolysis. Results: Hypercalcemia was found in 8.7% respondents starting the treatment with bisphosphonates. The most common cause of malignancy-associated hypercalcemia was prostate cancer, multiple myeloma and breast cancer. On the other hand, hypercalcemia was the most prevalent among patients with multiple myeloma, metastatic cancer of an unknown primary origin and bladder cancer. Metastases were reported in 342 patients, while pathological fractures in 37. The normalization of calcium level was obtained in 91.4% of the patients treated with bisphosphonates, mostly clodronate. During the bisphosphonate therapy, pathological fractures occurred in 4.6% of patients and the percentage of the patients reporting bone pain decreased from 79.9% to 30.9%. Conclusion: Multiple myeloma, prostate and breast cancer are the most common causes of hypercalcemia of malignancy in patients with tumor-induced osteolysis starting therapy with bisphosphonates