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Exploring Differences in the Aspirin–Colorectal Cancer Association by Sex and Race/Ethnicity: The Multiethnic Cohort Study

Background: Evidence has accumulated that long-term use of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) protects against colorectal cancer. We tested whether the inverse associations between NSAIDs and colorectal cancer is similarly observed across sexes and five racial/ethnic groups (Japanese, Latino, African American, Native Hawaiian, and white) in the Multiethnic Cohort (MEC) Study. Methods: During a mean follow-up of 16.1 years, we identified 4,882 invasive incident colorectal cancer cases among 183,199 eligible participants. Cox proportional hazards models were used to calculate HRs and 95% confidence intervals (CI). Results: Use of aspirin and other NSAIDs was associated with a lower incidence of colorectal cancer in men (HR = 0.77; 95% CI, 0.69–0.86 for current vs. never users of aspirin) but not in women (Pinteraction = 0.005). Among male current users, a reduced risk was observed with ≥6 years of aspirin or total NSAID use. The inverse association with current NSAID use in men was observed in all racial/ethnic groups, except for Native Hawaiians, and was stronger in whites. Conclusions: Our findings suggest that the benefit of NSAIDs for colorectal cancer may be strongest for white men and generalizes to African American, Japanese, and Latino, but not to Native Hawaiian men. The lack of inverse association observed in women and Native Hawaiian men in the MEC should be interpreted with caution. Impact: As only very few ethnic/racial groups are likely to be represented in trials of NSAIDs and colorectal cancer, it is important to conduct prospective observational studies in various populations to test the generalizability of their results. Cancer Epidemiol Biomarkers Prev; 26(2); 162–9. ©2016 AACR.