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Does Aspirin Prevent Breast Cancer? Maybe

In this case-control study, risk was significantly reduced among women who used aspirin at least seven times per week.

Over the past decade, results from several studies have suggested that aspirin and other nonsteroidal anti-inflammatory drugs may prevent certain cancers. Because prostaglandins appear to play a role in breast cancer development by affecting local hormone biosynthesis, use of NSAIDs to inhibit prostaglandin-driven production of estrogen or progesterone might be a means to prevent breast cancer.

Researchers with the Long Island Breast Cancer Study Project, a population-based case-control study, interviewed 1442 women with breast cancer and 1420 age-matched controls about their use of aspirin, ibuprofen, and acetaminophen 12 months before breast cancer diagnosis (or corresponding age for controls). The researchers adjusted for potential confounding variables in their analyses.

Ever use of aspirin (i.e., use at least once per week for at least 6 months) was significantly and inversely associated with breast cancer risk (odds ratio, 0.80), with the strongest associations in postmenopausal women (OR, 0.77) and women with hormone-receptor-positive tumors (OR, 0.74). Aspirin use did not reduce risk in women with hormone-receptor-negative tumors (OR, 0.97). The findings for ibuprofen showed similar trends but did not reach statistical significance; acetaminophen use did not affect breast cancer risk at all. When frequency of use was examined, reduced risk was limited to those who used aspirin at least seven times per week (OR, 0.72, vs. 0.95 among those who used aspirin less often).

Comment: Although this study satisfies many criteria for credible evidence of causation (i.e., dose-response gradient, biologic plausibility, consistent associations, and exposure preceding outcome), the relatively weak risk reductions are not sufficient to justify a change in practice. Clinicians must await confirmation of these results from randomized controlled trials before recommending routine aspirin use to prevent breast cancer.

— Jane E. Corboy, MD

Published in Journal Watch Women's Health July 8, 2004

Citation(s):

Terry MB et al. Association of frequency and duration of aspirin use and hormone receptor status with breast cancer risk. JAMA 2004 May 26; 291:2433-40.

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