Intravenous zoledronic acid to prevent osteoporosis in a veteran population with multiple risk factors for bone loss on androgen deprivation therapy.

PURPOSE: Androgen deprivation therapy for prostate cancer is associated with osteoporosis and increased fracture risk. Previous studies of zoledronic acid demonstrated bone loss prevention in patients initiating androgen deprivation therapy. There are limited data on patients on prolonged androgen deprivation therapy or in Veterans Affairs patients with multiple risk factors for osteoporosis.

METHODS: We randomized 93 patients with M0 prostate cancer in this placebo controlled trial in the Veterans Affairs health care system. Preplanned strata included 50 patients on androgen deprivation therapy for less than 1 year (stratum 1) and 43 on androgen deprivation therapy for greater than 1 year (stratum 2). In each stratum patients were randomized to 4 mg zoledronic acid intravenously every 3 months for 4 treatments or intravenous placebo. The primary end point was the percent change in bone mineral density at the lumbar spine at 12 months.

RESULTS: Age, race, body mass index and osteoporosis risk factors were similar for the 2 treatments. Most patients were former smokers, had moderate alcohol intake, were not on calcium/vitamin D supplements and were relatively sedentary at baseline. In stratum 1 spine bone mineral density increased 5.95% in the zoledronic acid arm and decreased 3.23% in the placebo arm (p = 0.0044). In stratum 2 spine bone mineral density increased 6.08% in the zoledronic acid arm and only increased 1.57% in the placebo arm (p = 0.0005). Treatment was well tolerated with minimal impact on renal function.

CONCLUSIONS: Zoledronic acid improved bone mineral density in patients with M0 prostate cancer on androgen deprivation therapy for 1 year or less, or greater than 1 year. This finding indicates that bisphosphonate therapy remains effective when initiated later in the course of androgen deprivation therapy and is efficacious in Veterans Affairs patients with multiple risk factors for osteoporosis.