Calcium and vitamin D supplementation during bisphosphonate administration may increase osteoclastic activity in...

Bone metastasis are a frequent complication of cancer, occurring in up to 70% of patients with advanced breast or prostate cancer. The consequences of bone metastasis are often devastating. Osteolytic metastasis can cause different kinds of skeletal related events including severe pain, pathologic fractures, life-threatening hypercalcemia, spinal cord compression, and other nerve-compression syndromes. These skeletal-related events are the result of the resorption of mineralized bone by osteoclasts. Bisphosphonates are synthetic analogues of naturally occurring pyrophosphate compounds that inhibit bone resorption. Potent bisphosphonates, pamidronate and, more importantly zoledronic acid may cause hypocalcemia, but mostly asymptomatic, mild, transient in most cases. Sufficient calcium and vitamin D intake needs to be ensured in patients with malignancy who have borderline or low levels of calcium when commencing treatment with bisphosphonates. Vitamin D itself induce the formation of osteoclasts by increasing the expression of RANKL on marrow stromal cells. Local calcium also promotes tumor growth and the production of parathyroid hormone-related peptide which in turn stimulates bone resorption. Vitamin D and calcium supplementation during bisphosphonate administration for the purpose of elimination of the side effects related to hypocalcemia in patients with bone metastasis may increase the bone resorption and decrease the efficacy of bisphosphonates. Therefore, vitamin D and calcium supplementation must not be routinely recommended during bisphosphonate administration.