Background: The efficacy of zoledronic acid in patients with treatment-naïve prostate cancer is unclear. We conducted a phase II study to investigate the benefits of combined zoledronic acid and androgen deprivation therapy in treatment-naïve prostate cancer with bone metastasis. The primary endpoint was skeletal-related event-free survival at 24 months.
Methods: Subjects were treatment-naïve patients with histologically confirmed adenocarcinoma of the prostate and radiological evidence of bone metastasis. Treatment consisted of bicalutamide 80 mg daily, goserelin acetate 10.8 mg every 12 weeks, and zoledronic acid 4 mg every 4 weeks. Zoledronic acid was continued for 24 months.
Results: Of the patients enrolled between July 2008 and April 2010, 52 were included in the analyses. The median age of the patients was 72 years. The median baseline prostate-specific antigen level was 249.4 ng/mL. The median follow-up period was 33.3 months. The 24-month skeletal-related event-free survival rate was 84.4 % (95 % confidence interval 71.2-91.9). The median time to prostate-specific antigen progression was 25.9 months (95 % confidence interval 14.7-36.3). The median overall survival time was not reached. Improvement in pain or maintenance of no pain during the first 12 weeks was observed in 70 % of patients and the extent of bone disease was decreased in 10 % of patients at 12 months. Grade 3 osteonecrosis of the jaw was observed in three patients (5.8 %).
Conclusion: Zoledronic acid concomitant with androgen deprivation therapy as initial treatment in patients with treatment-naïve prostate cancer with bone metastasis resulted in an encouraging skeletal-related event-free survival rate at 24 months.