Additive effect of zoledronic acid on serum prostate-specific antigen changes for hormone-sensitive prostate cancer patients with bone metastasis treated by combined androgen blockade.

Combined androgen blockade is widely used to treat patients with advanced prostate cancer. Recently, zoledronic acid was proven to be effective in preventing skeletal-related events for prostate cancer patients with bone metastases. Aim of the present study was to assess the effect of adding zoledronic acid to combined androgen blockade in the treatment of hormone-naïve metastatic prostate cancer patients by analyzing the changes of biomarker levels. Patients were treated with either a combination of combined androgen blockade and zoledronic acid (n=23) or combined androgen blockade alone (historical control combined androgen blockade group, n=42). Zoledronic acid was injected intravenously at 4 mg every 4 weeks for 2 years. Prostate-specific antigen and bone turnover markers (alkaline phosphatase and pyridinoline cross-linked carboxyterminal telopeptide of type 1 collagen) were examined before treatment and at 3, 6, and 12 months after treatment. Sequential changes of prostate-specific antigen, alkaline phosphatase and pyridinoline cross-linked carboxyterminal telopeptide of type 1 collagen for the two groups versus pretreatment levels were compared. Prostate-specific antigen values in both groups significantly declined at 3, 6 and 12 months compared with pretreatment levels. However, the decline of the prostate-specific antigen was lower in the combined androgen blockade group. Alkaline phosphatase significantly declined at 6 and 12 months in the combination of combined androgen blockade and zoledronic acid group, with no significant changes seen in the combined androgen blockade group. The addition of zoledronic acid to combined androgen blockade showed prostate-specific antigen and bone turnover markers response compared with combined androgen blockade therapy only, suggesting a potential antitumor effect of zoledronic acid in the management of metastatic prostate cancer patients.