Objectives: To study the effect of zoledronic acid on patients with pre-existing osteoporosis on androgen deprivation therapy (ADT), who are at highest risk for fracture. Zoledronic acid is a potent bisphosphonate that can prevent osteoporosis in patients with nonmetastatic (M0), prostate cancer (CaP) who are initiating ADT. The effect of zoledronic acid on patients with pre-existing osteoporosis on ADT, who are highest risk for fracture, has not been adequately studied.
Methods: We enrolled 28 patients with M0 CaP on ADT with severe osteopenia or osteoporosis (baseline bone-mineral density (BMD) T score < -2.0) in this open-label, single-arm trial to assess the effect of zoledronic acid on BMD. All patients also received supplemental calcium and vitamin D, and were counseled about lifestyle modifications. Patients received zoledronic acid (4 mg) intravenously every 3 months for 4 treatments. BMD was measured by dual energy X-ray absorptiometry scan at enrollment, 6 and 12 months. Primary endpoint was percent change in lumbar spine BMD.
Results: This was a high-risk patient population-primarily older Caucasians (mean age, 73 years), former smokers, and moderate users of alcohol. Mean duration of ADT was 2.4 years. Pre-existing osteopenia or osteoporosis was observed in a single site in 9 patients and multiple sites in 19 (68%). After 12 months of zoledronic acid, lumbar spine BMD increased 4.17% (P < .0001), and BMD increased significantly (P < .05) in both hips and the right femoral neck. Seven patients (25%) experienced improved BMD into the nonosteoporotic range (T score > -2.0). Zoledronic acid infusion was well tolerated and without substantial renal toxicity.
Conclusions: Zoledronic acid improves BMD in men with M0 CaP on ADT with severe osteopenia or osteoporosis (T scores < 2.0). This novel finding identifies a high-risk patient population that can potentially benefit from bisphosphonate therapy.
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