To determine the effectiveness and safety of the bisphosphonate risedronate in preventing bone loss in young women with breast cancer and early menopause induced by chemotherapy who are at major risk for the development of postmenopausal osteoporosis.

Fifty-three white women, aged 36 to 55 years, with breast cancer and artificially induced menopause were stratified according to prior tamoxifen use. Thirty-six patients received tamoxifen (20 mg/d). Within each stratum, patients were randomly assigned to receive risedronate (n = 27) or placebo (n = 26). Treatment consisted of eight cycles oral risedronate 30 mg/d or placebo daily for 2 weeks followed by 10 weeks of no drug (12 weeks per cycle). Patients were monitored for a third year without treatment.

Main outcomes of the study were changes in lumbar spine and proximal femur (femoral neck, trochanter, and Ward's triangle) bone mineral density (BMD), and biochemical markers of bone turnover. In contrast to a significant decrease of BMD at the lumbar spine and hip in the placebo group, there was an increase in BMD in the risedronate group. On treatment withdrawal, bone loss ensued, which suggests that treatment needs to be continuous to maintain a protective effect on bone mass. At 2 years, the mean difference (+/- SEM) between groups was 2.5% +/- 1.2%, (95% confidence interval [CI], 0.2 to 4.9) at the lumbar spine (P = .041) and 2.6% +/- 1.1%, (95% CI, 0.3 to 4.8) at the femoral neck (P = .029). Similar results were observed at the hip trochanter. Results by stratum indicate a beneficial, although partial, effect of tamoxifen in reducing bone loss. Risedronate was well tolerated and showed a good safety profile, with no evidence of laboratory abnormalities.

Risedronate appears to be a safe treatment that prevents both trabecular and cortical bone loss in women with menopause induced by chemotherapy for breast cancer.