Use of Aspirin, Other Nonsteroidal Anti-inflammatory Drugs, and Acetaminophen and Risk of Breast Cancer Among Premenopausal Women in the Nurses' Health Study II

Background: The use of aspirin and other nonsteroidal anti-inflammatory drugs ( NSAIDs) is widespread for treatment of common symptoms such as headaches, muscular pain, and inflammation. In addition, the chemopreventive use of NSAIDs is increasingly common for heart disease and colon cancer. Evidence of a protective association with breast cancer risk has been inconsistent, and few data exist for premenopausal women. Methods: We assessed the associations for use of aspirin, other NSAIDs, and acetaminophen with breast cancer risk among premenopausal women in the prospective Nurses' Health Study II. In total, 112 292 women, aged 25 to 42 years and free of cancer in 1989, were followed up until June 2003. Multivariate relative risks and 95% confidence intervals were calculated by Cox proportional hazards models, adjusting for age and other important breast cancer risk factors. Results: Overall, 1345 cases of invasive premenopausal breast cancer were documented. Regular use of aspirin (>= 2 times per week) was not significantly associated with breast cancer risk ( relative risk, 1.07; 95% confidence interval, 0.89-1.29). Regular use of either non-aspirin NSAIDs or acetaminophen also was not consistently associated with breast cancer risk. Results did not vary by frequency ( days per week), dose ( tablets per week), or duration of use. Furthermore, associations with each drug category did not vary substantially by estrogen and progesterone receptor status of the tumor. Conclusion: These data suggest that the use of aspirin, other NSAIDs, and acetaminophen is not associated with a reduced risk of breast cancer among premenopausal women.