Recommendations for use of zoledronic acid (Z) for prevention and treatment of osteoporosis in men on androgen deprivation therapy (ADT) for prostate cancer (PC).

16060 Background: Prolonged ADT for men with PC increases risk of osteoporosis and fracture. Z is a potent IV bisphosphonate that can improve the bone mineral density (BMD) in patients on ADT. There are no established treatment guidelines for such patients. We propose treatment recommendations based on two recent VA studies - our main study evaluating Z for prevention of osteoporosis due to ADT, and its companion study evaluating Z for treatment of patients with pre-existing osteoporosis.,The main double blind, placebo (P) controlled trial randomized 93 patients to receive Z or P q3 mos. Preplanned strata (St) included 50 patients on ADT < 1 year (St 1) and 43 patients on ADT > 1 year (St 2). Baseline BMD T score was ≥ -2.0. The companion trial enrolled 27 patients with pre-existing osteoporosis (baseline BMD score < -2.0) on an open label, single arm trial to receive Z q3 mos. for 1 year. All patients in both trials received calcium, vitamin D, & counseling on lifestyle modification. BMD was measured by DEXA scan at enrollment, 6 and 12 mos. The primary endpoint was the % change in BMD at the lumbar spine at 12 mos.,In the main trial, patients were matched within the St across the treatment arms with respect to age, race, BMI, and osteoporosis risk factors. In St 1, spine BMD increased 5.95% in the Z arm and decreased 3.23% in the P arm (p=0.0044). In St 2, spine BMD increased 6.08% in the Z arm and increased only 1.57% in the P arm (p=0.0005). In the companion trial, lumbar spine BMD increased an average of 5.11% (p<0.0001) compared to baseline. In both trials, Z infusion was well tolerated with few side effects.,Zoledronic acid improves BMD in men with PC on ADT. Benefit can be seen even in patients on prolonged ADT or those with pre-existing osteoporosis. We propose the following: patients initiating ADT should be evaluated for osteoporosis risk factors and counseled on preventive lifestyle modifications. DEXA scans should be obtained at baseline and repeated annually if normal. Treatment with Z should be considered for prevention and/or treatment of osteopenia/osteoporosis in men with PC who are on ADT. Supported by a grant from Novartis Pharmaceuticals Corporation [Table: see text].