Efficacy and Safety of Zoledronic Acid in Patients with Breast Cancer Metastatic to Bone: A Multicenter Clinical Trial

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Abstract
Purpose. This study evaluated the efficacy and safety of zoledronic acid in breast cancer patients with newly diagnosed bone metastases. Materials and Methods. Patients diagnosed with bone metastases ≤ 6 weeks prior to first visit were enrolled. Zoledronic acid (4 mg) was administered via a 15-minute infusion every 3 or 4 weeks for 12 infusions. Skeletal-related events (SREs) were defined as pathologic bone fractures, spinal cord compression, surgery to bone, radiation therapy to bone, and hypercalcemia of malignancy. Primary efficacy end points were the proportion of patients with at least one SRE and the time to first SRE. Secondary end points included pain, analgesic use, and quality of life. Results. Among 312 patients enrolled, 30% experienced at least one SRE during the 12-month study, and 22% experienced only one SRE. The median time to first SRE was not reached in the intent-to-treat population. Mean pain and analgesic scores declined from baseline, and quality-of-life scores remained stable to study end. The most frequently reported adverse events, regardless of relationship to study drug, were pyrexia (22%) and bone pain (10%). Serum creatinine levels did not significantly increase from baseline throughout the study. Conclusions. Breast cancer patients with newly diagnosed bone metastases who were treated with zoledronic acid had a low incidence of SREs compared with patients who received placebo in randomized phase III trials, and pain was decreased from baseline. This study demonstrated the favorable risk:benefit ratio of zoledronic acid for the prevention of skeletal complications.