Zoledronic acid for hormone-naive prostate cancer with bone metastasis.

e16092 Background: The potency of zoledronic acid for hormone-naïve prostate cancer is unclear. We conducted a phase II study to investigate the benefit of administering zoledronic acid concomitant with androgen-deprivation therapy in treatment-naïve prostate cancer patients with bone metastases, in which the primary endpoint was skeleton-related event (SRE)-free survival at 24 months after treatment. Methods: Treatment-naïve male patients with histologically confirmed adenocarcinoma of the prostate and radiologic evidence of bone metastasis were eligible. Treatment consisted of bicalutamide 80 mg administered orally on Day 1 and every day, goserelin acetate 10.8 mg administered subcutaneously on Day 8 and every 12 weeks, and zoledronic acid 4 mg administered intravenously on Day 8 and every four weeks. Results: Between July 2008 and April 2010, a total of 53 patients were enrolled and 52 evaluable. Median age was 72 years (range, 55 - 86). Median primary PSA was 249.4 ng/ml (range, 2.19 –19201). Median follow-up period was 33.3 months. The SRE-free survival rate at 24 months after treatment was 82.7 %. Median time to PSA progression was 25.9 months (95% confidential interval, 17.97-24.43). The score of the extent of bone diseases was stable or decreased in 73 % of the patients at 24 months after treatment. The grade-3 osteonecrosis of the jaw was reported in three patients (5.8 %). Conclusions: Our results suggest the potency of the early introduction of zoledronic acid for prostate cancer patients with bone metastases. Future studies are certainly required to ascertain the most appropriate timing of the commencement of zoledronic acid for patients with bone-metastatic prostate cancer. Clinical trial information: UMIN000007548.