Background: Vitamin D status is not evaluated routinely in cancer patients with bone metastasis who are treated with bisphosphonates.

Objectives: To assess the effect of vitamin D status on risk of hypocalcemia and quality of life in these patients.

Methods: We performed laboratory tests for routine serum biochemistry, 25(OH)D, plasma parathyroid hormone (PTH) and bone turnover markers (CTX, P1NP) in 54 patients aged 57.5 ± 13 years treated with intravenous bisphosphonates.

Results: Most of the patients (n=44, 77.8%) did not receive calcium and vitamin D supplementation. Their mean serum 25(OH)D levels (12.83 ± 6.86 ng/ml) correlated with vitamin D daily intake (P = 0.002). In 53 patients (98.1%) 25(OH)D levels were suboptimal (< 30 ng/ml). Albumin-corrected calcium levels correlated with plasma PTH (P = 0.001). No correlation was observed between daily calcium intake and serum calcium (P = 0.45). Hypocalcemia was observed in one patient. Mean plasma PTH was 88.5 ± 65 ng/L. Plasma PTH correlated negatively with 25(OH)D serum levels (P = 0.003) and positively with P1NP (P = 0.004). Albumin-corrected calcium correlated negatively with P1NP (mean 126.9 ± 191 ng/ml) but not with CTX levels (mean 0.265 ± 0.1 ng/ml) (P < 0.001). There was no correlation among quality of life parameters, yearly sun exposure and 25(OH)D levels (P = 0.99).

Conclusions: Vitamin D deficiency is frequent in oncology patients with bone metastasis treated with bisphosphonates and might increase bone damage. Our results indicate a minor risk for the development of severe hypocalcemia in vitamin D-deficient patients receiving bisphosphonate therapy. Although vitamin D deficiency might have some effect on the quality of life in these patients, it was not proven significant.