Continuing benefit of zoledronic acid for the prevention of skeletal complications in men with advanced prostate cancer

4575 Background: We previously reported the efficacy and safety of 4 mg zoledronic acid (Zol) at 15 months compared with placebo in patients with bone metastases from prostate cancer (Saad et al. J Natl Cancer Inst. 2002;94:1458–1468). We report here the results of an exploratory analysis of the 15- to 24-month extension phase of this study to evaluate the benefit of Zol treatment beyond 15 months.Methods: Data were collected during months 15 to 24 for patients who chose to enter the 9-month extension phase. Endpoints included the percentage of patients with a skeletal-related event (SRE), time to first SRE, skeletal morbidity rate (SMR), and multiple event analysis using the method of Andersen and Gill. Results: Of 422 patients randomized to the 4-mg or placebo treatment arms, 147 completed the 15-month core phase, and 133 elected to enter the extension phase. Among these patients, multiple event analysis revealed a 53% reduction in the risk of developing an SRE for patients treated with 4 mg Zol compare...