In Reply In our review of previous prospective studies of aspirin use and total cancer incidence, we focused on analyses conducted among both women and men in which aspirin use was the primary exposure of interest. The study by Bardia et al and the analysis of the Women’s Health Initiative cohort by Brasky et al included only women. A second study by Brasky et al of the Vitamins and Lifestyle (VITAL) cohort used combined intake of nonsteroidal anti-inflammatory drugs and/or aspirin as the main exposure. We appreciate Brasky and colleagues highlighting their previous results. Although they argue that their prior data, as well as our recent findings, together suggest a lack of benefit for aspirin use for total cancer among women, we believe that interpretation is premature. Among women, we did observe that regular aspirin use was associated with a nonsignificant 2% reduced risk of total cancer, a significant 16% reduction in risk of colorectal cancer, and a significant 29% reduction in risk of gastroesophageal cancers. As we noted in our original article, the impact of aspirin use on total cancer incidence depends on the distribution of specific cancer sites in the underlying population. Thus, studies may yield inconsistent results for total cancer based on variation in the relative prevalence of site-specific cancers in their baseline population. Within our study, the differences that we observed for women and men in overall cancer risk reduction may largely reflect the fact that gastrointestinal cancers were more common in men (~25%) than in women (~12%). In addition, comparison across studies is hindered by variation in the definition of aspirin exposure, doses evaluated, length of follow-up, and timing of aspirin assessment. Zhou et al defined regular users as individuals who took aspirin at least 3 times/wk for more than 3 months. On the basis of this definition, 19% were regular users. In our analysis, regular aspirin users were defined as those who reported aspirin use at least 2 times/wk, which led to 42% being defined as regular users, a prevalence that more closely reflects usage in the general US population.1 Thus, we encourage additional research using a consistent definition of exposure among other cohorts of men and women, as well as other races and ethnicities.
Cao Y, Chan AT. Aspirin and Cancer Risk—Reply. JAMA Oncol. 2016;2(10):1372–1373. doi:10.1001/jamaoncol.2016.2295
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