A population-based cohort of 26,580 postmenopausal women was linked to a SEER
Cancer Registry to identify incident breast cancers. Regular use of aspirin and other NSAIDs was
reported on a self-administered questionnaire mailed in 1992. Cox proportional hazards models
were used to estimate multivariate relative risks (RRs) and 95% confidence intervals (CIs) of
breast cancer incidence overall and by ER and PR status, adjusting for multiple breast cancer risk
factors.