Double-blind, placebo-controlled, dose-response trial of oral clodronate in patients with bone metastases.

Abstract

PURPOSE Despite evidence that clodronate inhibits tumor-induced osteolysis, no studies have directly assessed the optimal dose for long-term treatment. The aim of this double-blind, placebo-controlled study was to determine the safety and efficacy of different doses of clodronate in affected patients. PATIENTS AND METHODS Eighty-four patients with tumor-induced osteolysis were randomized to receive treatment with placebo, or 400 mg, 1,600 mg, or 3,200 mg of clodronate, daily for 4 weeks. Patients were reviewed weekly during treatment. Fasting urinary calcium excretion was the primary variable used to assess response. Visual analog pain scores and adverse events were documented. RESULTS In the clodronate-treated groups, there was a dose-dependent reduction in fasting calcium excretion with a highly significant difference between placebo and 1,600 mg clodronate (P = .0002) and placebo and 3,200 mg clodronate (P = .0001), but no significant difference between 1,600 mg and 3,200 mg clodronate. There was no discernible change in pain scores or analgesic requirements. Bone-derived isoenzyme alkaline phosphatase values increased in all groups, with a significant difference between baseline and final values in the 1,600-mg and 3,200-mg groups (P < .01 and P = .03, respectively). Adverse events were distributed evenly across the four treatment groups. Compliance was greater than 99% in all treatment groups. CONCLUSION Oral clodronate at a dose of 1,600 mg or 3,200 mg will inhibit bone resorption. Since there was no significant difference between these two doses in terms of efficacy at 4 weeks, 1,600 mg/d can be recommended for long-term treatment. This dose is well tolerated and may promote bone repair, as judged by increases in bone alkaline phosphatase levels.