Efficacy of pamidronate in reducing skeletal complications in patients with breast cancer and lytic bone metastases. Protocol 19 Aredia Breast Cancer Study Group.

Background: Bisphosphonates such as pamidronate disodium inhibit osteoclast-induced bone resorption associated with cancer that has metastasized to bone.

Methods: Women with stage IV breast cancer who were receiving cytotoxic chemotherapy and had at least one lytic bone lesion were given either placebo or pamidronate (90 mg) as a two-hour intravenous infusion monthly for 12 cycles. Skeletal complications, including pathologic fractures, the need for radiation to bone or bone surgery, spinal cord compression, and hypercalcemia (a serum calcium concentration above 12 mg per deciliter [3.0 mmol per liter] or elevated to any degree and requiring treatment), were assessed monthly. Bone pain, use of analgesic drugs, performance status, and quality of life were assessed throughout the trial.

Results: The efficacy of treatment was evaluated in 380 of 382 randomized patients, 185 receiving pamidronate and 195 receiving placebo. The median time to the occurrence of the first skeletal complication was greater in the pamidronate group than in the placebo group (13.1 vs. 7.0 months, P=0.005), and the proportion of patients in whom any skeletal complication occurred was lower (43 percent vs. 56 percent, P = 0.008). There was significantly less increase in bone pain (P=0.046) and deterioration of performance status (P=0.027) in the pamidronate group than in the placebo group. Pamidronate was well tolerated.

Conclusions: Monthly infusions of pamidronate as a supplement to chemotherapy can protect against skeletal complications in women with stage IV breast cancer who have osteolytic bone metastases.