Zoledronic acid is superior to pamidronate for the treatment of bone metastases in breast carcinoma patients with at least one osteolytic lesion

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Abstract
BACKGROUND Treatment with zoledronic acid (Zol) was compared with a dose of 90 mg of pamidronate (Pam) in breast carcinoma (BC) patients with at least 1 osteolytic lesion based on data from a Phase III, randomized trial. METHODS Overall, 1130 patients with breast carcinoma who had all types of bone metastases (osteolytic, mixed, or osteoblastic by radiology) were randomized to receive treatment with either 4 mg of Zol or 8 mg of Zol as a 15‐minute infusion or 90 mg of Pam as a 2‐hour infusion every 3–4 weeks for 12 months. A skeletal‐related event (SRE) was defined as a pathologic fracture, spinal cord compression, radiotherapy, or surgery to bone. RESULTS Among all patients with BC, the proportion of those who had an SRE (primary endpoint) was comparable between treatment groups (43% of patients who received 4 mg of Zol vs. 45% of patients who received Pam). Among patients who had breast carcinoma with at least 1 osteolytic lesion (n = 528 patients), the proportion with an SRE was lower in the 4‐mg Zol group compared with the Pam group (48% vs. 58%), but this did not reach statistical significance (P = 0.058). The time to first SRE was significantly longer in the 4‐mg Zol group compared with the Pam group (median, 310 vs. 174 days; P = 0.013). Moreover, multiple‐event analysis demonstrated significant further reductions in the risk of developing SREs over the reduction achieved with Pam (30% in the osteolytic subset [P = 0.010] and 20% for all patients with BC [P = 0.037]). CONCLUSIONS The current data indicate that treatment with 4 mg of Zol was more effective than 90 mg of Pam in reducing skeletal complications in a subset of patients with breast carcinoma who had at least 1 osteolytic lesion at study entry. Cancer 2004;100:36–43. © 2003 American Cancer Society.