The effect of aspirin on colorectal cancer incidence in African Americans.

4085 Background: From 2011 to 2016, the incidence and mortality rate of colorectal cancer(CRC) were highest among African Americans(AA), compared to other US racial/ethnic groups. Long-term aspirin use is recommended as a strategy to reduce the risk of CRC. Yet, there is scant information on the chemopreventive effect of aspirin among AA. It is imperative to assess whether the reported chemo-preventive effect also occurs in AA. Our central hypothesis is that aspirin use in AA is associated with a lower incidence of CRC, irrespective of race/ethnicity. Methods: We conducted a secondary analysis, using data from AA participants in the Atherosclerosis Risk in Communities(ARIC) longitudinal study, who did not have CRC at enrollment, from 1987 to 1998. We extracted demographic, clinical and mortality data to compare the incidence of CRC among participants taking aspirin compared to those who were not taking aspirin, stratified by age, tobacco use, and body mass index. All-cause mortality and CRC mortality will also be assessed, and we will use Cox proportional hazard regression to determine the relationship between aspirin use and CRC incidence, and mortality. Results: At baseline in 1987, 15,026 participants enrolled in the ARIC study, 25% of whom were AA, median age 54(range 44-66), including 46.7% who reported using aspirin. We analyzed follow-up data from 10,960 participants in 1996-1998, 20% of whom were AA, and 56.9% of whom were taking aspirin. Non-AA participants were more likely to report using aspirin at baseline and follow-up, compared to AA, 53% vs 30% and 59% vs 50% respectively. After 10years, the total incidence of CRC in AA participants was 1% compared with 1.1% in non-AA(p = 0.7). There was no difference in CRC incidence by aspirin use among all participants, and when stratified by race(among all participants p = 0.81, amongAA p = 0.68, among non-AA p = 0.94). Conclusions: We found no difference in the incidence of CRC among AA compared to Caucasians, by aspirin use. Investigation of consistency and/or dose of aspirin use by race may provide further insights on the relationship between aspirin use and CRC incidence, comparing AA to Caucasians.