Pamidronate therapy previously has been shown to reduce skeletal complications effectively for up to 12 months in breast carcinoma patients with bone metastases. The current study data provide further follow‐up results regarding the effects of long term (up to 24 months) pamidronate treatment in women with breast carcinoma and osteolytic metastases.

Follow‐up results from two prospective, multicenter, randomized, double‐blind, placebo‐controlled intervention trials conducted at academic and community oncology centers were combined to provide a large data set with which to evaluate the long term efficacy and safety of pamidronate therapy. Seven hundred fifty‐four women with Stage IV breast carcinoma and osteolytic metastases were randomized to the 2 treatment arms of the trial. Three patients were excluded from the intent‐to‐treat population for the analysis. A total of 751 evaluable patients were randomized to receive either a 90‐mg intravenous pamidronate infusion (367 patients) or a placebo infusion (384 patients) every 3–4 weeks. The primary outcome measures were skeletal morbidity rate (events/year), proportion of patients developing a skeletal complication, and time to first skeletal complication.

Of the 367 women receiving pamidronate, 115 (31.3%) completed the trial and 81 (22.1%) discontinued the study due to adverse events. Of the 384 women who received placebo, 100 (26.0%) completed the study and 76 (19.8%) discontinued the study due to adverse events. The skeletal morbidity rate was 2.4 in the pamidronate group and 3.7 in the placebo group (P < 0.001). In the pamidronate group, 186 of the 367 patients (51%) had skeletal complications compared with 246 of the 384 patients in the placebo group (64%) (P < 0.001). The median time to first skeletal complication was 12.7 months in the pamidronate group and 7 months in the placebo group (P < 0.001). Six patients treated with pamidronate discontinued treatment due to drug‐related adverse events. Pain and analgesic scores were significantly worse in the placebo group compared with those patients in the pamidronate group.

In the current study, monthly infusions of 90 mg of pamidronate as a supplement to antineoplastic therapy were found to be well tolerated and superior to antineoplastic therapy alone in preventing skeletal complications and palliating symptoms for at least 24 months in breast carcinoma patients with osteolytic bone metastases. Cancer 2000;88:1082–90. © 2000 American Cancer Society.