Abstract 966: Coffee consumption and invasive breast cancer incidence among postmenopausal women in the Cancer Prevention Study II Nutrition Cohort

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Abstract Accumulating evidence suggests that coffee consumption may be inversely associated with breast cancer risk among postmenopausal women, with growing evidence of a stronger association for caffeinated than for decaffeinated coffee. However, few studies have examined this association by hormone receptor status or minimized confounding due to cigarette smoking. Recently, we found that caffeinated, but not decaffeinated coffee consumption was inversely associated with breast cancer mortality among nonsmoking women enrolled in the Cancer Prevention Study-II (CPS-II). Subsequently, the 2018 WCRF/AICR Diet, Nutrition, Physical Activity and Cancer Third Expert Report drew no conclusion regarding the association between coffee consumption and breast cancer risk. To provide further evidence, we examined total, caffeinated and decaffeinated coffee consumption in relation to postmenopausal invasive breast cancer incidence, overall, among nonsmokers and by estrogen and/or progesterone receptor (ER/PR) status among women enrolled in the CPS-II Nutrition Cohort, a subcohort of CPS-II. This analysis included 57,120 postmenopausal women who were cancer-free and reported coffee intake in 1999, and who were followed for cancer incidence through June 2013. During follow-up, 2,848 (2,349 ER or PR positive, and 252 ER and PR negative) women with a verified invasive breast cancer were identified. Cox proportional hazards regression was used to estimate multivariable-adjusted hazard ratios (HR) and 95% confidence intervals (CI). Neither total nor decaffeinated coffee consumption was associated with risk of invasive breast cancer among all women or in any subgroup. For caffeinated coffee consumption, the HR (95% CI) for consumption of 2 or more cups/day, compared to less than 1 cup/month, was 0.90 (0.82-1.00) among all women, and 0.88 (0.80-0.98) among nonsmokers. Similarly, caffeinated coffee consumption was associated with a statistically significantly lower risk of ER+ or PR+ breast cancer (HR=0.88, 95% CI 0.79-0.99) and a nonsignificant lower risk of ER- and PR- breast cancer (HR=0.83, 95% CI 0.59-1.16) among all women. These findings underscore the importance of stratifying on type of coffee in studies examining the association between coffee consumption and risk of invasive postmenopausal breast cancer. Additionally, to better understand the role of caffeinated vs. decaffeinated coffee in breast cancer etiology we will examine the potential mediating effects of coffee metabolites on this association. Citation Format: Susan M. Gapstur, Marjorie L. McCullough, Rebecca A. Hodge, Ying Wang, Caroline Y. Um, Terryl J. Hartman, Mia M. Gaudet. Coffee consumption and invasive breast cancer incidence among postmenopausal women in the Cancer Prevention Study II Nutrition Cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 966.