Maintenance etidronate in the prevention of malignancy-associated hypercalcemia.

Normocalcemic patients with cancer who had been successfully treated for an episode of hypercalcemia were enrolled in a randomized, multisite, double-blind, placebo-controlled trial designed to determine the efficacy of maintenance oral etidronate in preventing the recurrence of moderate to severe hypercalcemia (serum calcium level, greater than 11.5 mg/dL [greater than 2.87 mmol/L]). Ten (40%) of 25 etidronate-treated patients and 17 (46%) of 37 placebo-treated patients had recurrence of hypercalcemia within 150 days. Although patients taking etidronate had a longer time to the development of hypercalcemia (median, 55 days vs 28 days), this was not significantly different from the control group. The high attrition rate in this trial from hypercalcemia and other malignancy-related causes represents a major difficulty in conducting studies with agents that may require prolonged administration before producing a therapeutic effect.