Fracture risk and adjuvant hormonal therapy among a population-based cohort of older female breast cancer patients

Summary The risk of hip and other fractures was examined among a population-based group of older women with breast cancer. Women using aromatase inhibitors (AIs) were found to be over three times more likely to have a hip fracture over approximately 3 yearsپf follow-up. Other fracture risk factors were also identified. Introduction Aromatase inhibitors have been shown in randomized trials to increase total fracture risk compared with tamoxifen, but the fracture risks in the trials were relatively low, and no difference in hip fracture has been demonstrated. Methods A population-based cohort of 2003 breast cancer survivors .65 were followed prospectively for a median of 36 months. Patient survey information regarding adjuvant breast cancer therapies, prescription osteoporosis treatments, and other factors potentially associated with fracture was supplemented with cancer registry information. Hip and total nonvertebral fractures were determined using a validated Medicare algorithm, and the association of these fractures with adjuvant hormonal therapies was examined using Cox models. Results The cohort of 2,748 women with a mean age of 72.8 (SD 5.4) included 28.2%who took an aromatase inhibitor and 27.8%tamoxifen. There were 41 hip fractures (1.5%) and 218 nonvertebral fractures (7.9%) among the cohort. Subjects using AIs (adjusted hazard ratio 3.24 (1.05, 9.98)) and subjects not using hormone therapy (3.32 (1.14, 9.65)) were more likely than users of tamoxifen to have a hip fracture. Bisphosphonate use was more common among AI users but did not explain these results. Users of AIs were more likely to have nonvertebral fractures, but this result did not reach statistical significance (adjusted hazard 1.34 (0.92, 1.94)). Conclusions Hip and other fractures were common in an older population-based cohort of breast cancer survivors, and aromatase inhibitor use was associated with an increase in the short-term risk of hip fractures not detected in randomized controlled trials