OBJECTIVES: To examine the effect of breast cancer and its treatment on fracture risk in older breast cancer survivors.

DESIGN: A 10-year prospective cohort study beginning 5 years after a diagnosis of breast cancer for survivors and match date for comparison women.

SETTING: Six integrated healthcare systems.

PARTICIPANTS: Women aged 65 and older (1,286 survivors, 1,286 comparison women, mean age 77.7 in both groups, white, non-Hispanic: survivors, 81.6%; comparison women, 85.2%) who were alive and recurrence free 5 years after a diagnosis of early-stage breast cancer and matched on age, study site, and enrollment year to a comparison cohort without breast cancer.

MEASUREMENTS: Cox proportional hazards models were used to estimate the association between fracture risk and survivor-comparison status, adjusting for drugs and risk factors associated with bone health. A subanalysis was used to evaluate the association between tamoxifen exposure and fracture risk.

RESULTS: No difference was observed in fracture rates between groups (hazard ratio (HR) = 1.1, 95% confidence interval (CI) = 0.9-1.3). The protective effect of tamoxifen was not statistically significant (HR = 0.9, 95% CI = 0.6-1.2).

CONCLUSION: Long-term survivors of early-stage breast cancer diagnosed at age 65 and older are not at greater risk of osteoporotic fractures than age-matched women without breast cancer. There appears to be no long-term protection from fractures with tamoxifen use. Geriatrics Society.