PURPOSEOsteolytic metastases often give rise to hypercalcemia, fracture, and bone pain, and occur commonly in patients with recurrent breast cancer. We assessed the bisphosphonate, clodronate, which has proven to be a useful treatment for hypercalcemia and may be a potent inhibitor of tumor-induced osteolysis, for its effect on reducing the osseous complications of metastatic breast cancer.PATIENTS AND METHODSWe studied 173 patients with bone metastases due to breast cancer in a randomized, double-blind, placebo-controlled trial of oral clodronate 1,600 mg/d (85 patients) compared with an identical placebo (88 patients).RESULTSThe patients in each wing were comparable in their clinical, radiologic, and biochemical characteristics at trial entry. In patients who received clodronate, there was a significant reduction compared with placebo in the total number of hypercalcemic episodes (28 v 52; P < .01), in the number of terminal hypercalcemic episodes (seven v 17; P < .05), in the incidence of vertebral fra...