Purpose: Androgen deprivation therapy in patients with prostate cancer is associated with bone loss and an increased risk of fractures. Zoledronic acid protects against bone mineral density loss when initiated concurrently with androgen deprivation therapy. We evaluated the effect of zoledronic acid initiated subsequent to androgen deprivation therapy on bone mineral density and biochemical markers of bone turnover. Materials and Methods: Patients with prostate cancer without bone metastases who had received androgen deprivation therapy for 12 months or less were randomized to 4 mg zoledronic acid or placebo intravenously every 3 months for 1 year. Patients were stratified according to androgen deprivation therapy duration (less than 6 vs 6 to 12 months). The primary end point was the change in femoral neck and lumbar spine bone mineral density in the 2 groups. The secondary end point was the change in serum bone specific alkaline phosphatase and urine N-telopeptide levels. Total hip bone mineral density was also measured. Results: The 120 patients with prostate cancer received zoledronic acid (61) or placebo (59). Compared with placebo, zoledronic acid increased femoral neck, total hip and lumbar spine bone mineral density yearly by 3.6% (p = 0.0004), 3.8% (p <0.0001) and 6.7% (p <0.0001), respectively. The effects of zoledronic acid on bone mineral density at these 3 sites were not differentiated according to androgen deprivation therapy duration. Additionally, mean bone specific alkaline phosphatase and N-telopeptide levels were decreased in the zoledronic acid group (each p <0.0001) and were increased in the placebo group (p <0.0001 and p = 0.004, respectively). Conclusions: Zoledronic acid increased bone mineral density and suppressed bone turnover markers in patients with prostate cancer without bone metastases when initiated during year 1 of androgen deprivation therapy.
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