Bisphosphonate treatment does not affect serum levels of osteoprotegerin and RANKL in hypercalcemic cancer patients.

Bisphosphonates are the standard treatment for hypercalcemia of malignancy. We hypothesized that bisphosphonate treatment and the subsequent fall in serum calcium might induce changes in the RANK/RANKL/OPG system, which plays a pivotal role in the regulation of bone resorption. Soluble RANKL and OPG levels were measured in the serum of 15 hypercalcemic patients at baseline and on 5 consecutive days following treatment with the amino-bisphosphonate ibandronate. At day 0, the median soluble OPG level was elevated (p=0.0021) in the hypercalcemic group as compared to normal controls, while the median serum RANKL level was not significantly different. Ibandronate treatment and the resulting decrease (p<0.0001) in serum calcium levels did not affect the serum concentrations of OPG, serum RANKL, or the serum RANKL/OPG ratio. In comparison with day 0, these factors did not change significantly at any time-point analyzed.