Aspirin use and mammographic density as a marker of breast cancer risk in postmenopausal women.

B211

Background: Many epidemiologic studies have shown that women who take aspirin have a lower risk of developing breast cancer but results vary markedly. Objective: We examined whether current aspirin use in postmenopausal women is inversely associated with mammographic breast density, a widely recognized marker of breast cancer risk. Design : Postmenopausal women, not currently on hormone replacement therapy and with no prior diagnosis of cancer, were recruited from a large radiological clinic for our cross-sectional study in Buffalo, New York from March 2005 through August 2005. Aspirin use and covariate data were collected from interviews and questionnaires. Screening mammograms and anthropometric measures were conducted during the clinic visit. Mammographic breast density was measured for 267 women from digitized images utilizing a validated computer-assisted method. Results : In a linear model adjusted for traditional risk factors related to breast density and breast cancer risk, we did not observe a significant association between aspirin pills-per-week as a continuous variable and percentage mammographic density. In general linear models categorical current aspirin (non-use/use) was marginally significant (p 0.051). Stratified analysis of aspirin use and non-use yielded a 10% reduction in percentage mamamographic density among nulliparous women in the aspirin group (adjusted mean percent density 32.7, 95% CI: 29.9-36.1) compared to non-aspirin users (mean 43.4, 95% CI: 36.7-50.2). Conclusion: The beneficial effect of aspirin use on mammographic breast density appeared to be greater for nulliparous women compared to parous women. The potential inverse association between aspirin use and breast density observed in our sample of postmenopausal women warrants further investigation.