Background: Analgesic use has been implicated in the chemoprevention of a number of solid tumors, but thus far, no previous research has focused on the role of aspirin in endometrial cancer etiology. Methods: We conducted a hospital-based case-control study of 427 women with primary, incident endometrial cancer, and 427 age- and residence-matched controls without benign or malignant neoplasms. All participants received medical services at Roswell Park Cancer Institute in Buffalo, NY, and completed a comprehensive epidemiologic questionnaire. Women who reported analgesic use at least once a week for at least 6 months were classified as regular users and served as the reference group throughout the analyses. We used unconditional logistic regression analyses to compute crude and adjusted odds ratios (OR) with corresponding 95% confidence intervals (CI). Results: Compared with nonusers, regular aspirin users were not at reduced risk of endometrial cancer (adjusted OR, 0.91; 95% CI, 0.66-1.26), nor were women with the highest frequency, duration, or cumulative lifetime aspirin use. When the sample was divided by body mass index status, regular aspirin use was not associated with risk among women classified as normal weight or overweight, but a significant risk reduction was seen for obese women (adjusted OR, 0.50; 95% CI, 0.27-0.92). Significant decreases in risk were also observed for obese women with the greatest frequency, duration, and cumulative aspirin use. No significant associations in the overall sample or among obese women were noted for acetaminophen use. Conclusion: We observed no evidence of an overall chemoprotective effect of aspirin on endometrial cancer risk, but the significant risk reductions among obese women warrant further investigation.
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