Effect of Bisphosphonate on Bone Loss in Postmenopausal Women With Breast Cancer Initiating Aromatase Inhibitor Therapy

This double-blind, placebo-controlled, randomized clinical trial will test the hypothesis that risedronate 35 mg once weekly, a potent antiresorptive agent, will prevent bone loss or improve bone mass and decrease bone turnover in elderly, osteopenic, postmenopausal women (ages 55 and older) with breast cancer on aromatase inhibitor therapy. 110 subjects will be randomized to receive either oral risedronate 35 mg once weekly or placebo for two years. Our primary outcome variable will be change in PA spine bone mineral density (BMD). Secondary endpoints will be BMD at the total hip, femoral neck, trochanter, lateral spine, forearm, and total body, and markers of bone turnover. We will also assess if the improvements in BMD are greater at sites of trabecular bone (spine) versus cortical bone (wrist). BMD will be measured at six month intervals. Biochemical markers of bone turnover will be measured at baseline, 6 months, 12 months, and 24 months.