Abstract 1269: Alcohol intake in relation to lethal breast cancer
Authors: Boeke Caroline E. , Eliassen A. Heather , Chen Wendy Y. , Holmes Michelle D. , Rosner Bernard , Willett Walter C. , Tamimi Rulla M. 
Published: May 2015

Abstract
Background: Increasing evidence suggests that many breast cancers may be “overdiagnosed” due to intensive screening and would not cause harm if left untreated. More research is needed on risk factors for the most harmful tumors that go on to become lethal. Alcohol is the strongest dietary risk factor for breast cancer, but whether alcohol consumption increases risk of lethal breast cancer specifically is unknown.
Methods: We assessed alcohol intake (drinks/week) in 88,759 women in the Nurses' Health Study (NHS; 1980-2010) and 93,911 women in the NHSII (1991-2009). Women reported beer, wine, and liquor intake on semi-quantitative food frequency questionnaires administered every four years. The main exposure was cumulative average alcohol consumption in grams/day; we also assessed baseline and updated current consumption. Breast cancer cases were confirmed with pathology reports and deaths were confirmed by next of kin or the National Death Index. We defined lethal cases as women with invasive breast cancer for whom the primary cause of death was breast cancer or a metastasis from breast cancer. Person-time for each participant was calculated from the date of return of the baseline questionnaire to the date of breast cancer diagnosis, date of any other cancer diagnosis, death from any cause, or the end of follow-up, whichever came first. We pooled the NHS and NHSII data and used Cox proportional hazards models adjusted for breast cancer risk factors. To determine whether the association differed for lethal versus nonlethal breast cancer, competing risks models were used; we conducted likelihood ratio tests to compare models assuming different versus the same associations of alcohol (defined continuously) with lethal and nonlethal tumors. We tested for an interaction between alcohol and folate intake using a likelihood ratio test.
Results: 1,452 women developed lethal breast cancer over follow-up. Cumulative average alcohol intake was associated with higher risk of lethal breast cancer [hazard ratio (HR) per 10 g increase: 1.13 (95% CI: 1.07, 1.18, p-trend&lt;0.0001)]; the HR with total incident breast cancers was 1.07 [(95% CI: 1.05, 1.09, p-trend&lt;0.0001)]. Compared to non-drinkers, women who consumed 30+ grams of alcohol per day had a HR of 1.66 (95% CI: 1.33, 2.08) for lethal breast cancer and 1.33 (95% CI: 1.21, 1.46) for any breast cancer. However, the association with alcohol was not statistically different for lethal vs. nonlethal breast cancer [p-heterogeneity=0.45]. There was not a statistically significant interaction with folate intake [p-interaction=0.26].
Conclusions: In these two prospective cohort studies, alcohol intake was positively associated with lethal breast cancer, but the association was not significantly different for lethal versus nonlethal breast cancer.
Citation Format: Caroline E. Boeke, A. Heather Eliassen, Wendy Y. Chen, Michelle D. Holmes, Bernard Rosner, Walter C. Willett, Rulla M. Tamimi. Alcohol intake in relation to lethal breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1269. doi:10.1158/1538-7445.AM2014-1269