Alcohol and breast cancer risk in postmenopausal women: The PLCO experience.

Abstract

1521 Background: Moderate alcohol consumption is an established breast cancer (BC) risk factor. Invasive BC is a heterogeneous disease comprised of several histological subtypes with distinct biological features that suggest etiologic differences. Several studies show the alcohol link may be stronger for estrogen receptor-positive tumors (ER+/PR+ and ER+/PR-) and for lobular BC. Few have evaluated the role of alcohol consumption by BC histology and hormone receptor status combined. Methods: We evaluated the risk of BC by baseline alcohol consumption in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial cohort (54649 participants, 1786 incident invasive breast cancers) by histology and hormone receptor status. Histologic subtype-specific associations were evaluated using a recently developed Cox proportional hazards model to calculate multivariate hazards ratios (HR) and 95% confidence intervals (CI). Results: 1444 ductal (81%), 233 lobular (13%) and 109 mixed ductal lobular (6%) cases were identified. The majority were ER+/PR+ (ductal: 959 ER+/PR+, 136 ER+/PR-, 229 ER-/PR-; lobular: 179 ER+/PR+, 37 ER+/PR-, 6 ER-/PR-; mixed ductal/lobular: 88 ER+/PR+, 6 ER+/PR-, 5 ER-/PR-). For ductal and lobular BC, risks for alcohol consumption were modestly elevated; compared to never drinkers, women consuming 7-14 drinks/week had a 40% increase in HR in both histologic subtypes. Risks for mixed ductal lobular cancer were significantly higher, particularly for women consuming 7-14 drinks per week (HR=3.0; 95% CI=1.5, 6.1). For all histologies combined, alcohol risks were confined to ER+/PR+ cancers with HR=1. 6 (95% CI=1.3, 2.1) for women consuming 7-14 drinks/ week; p trend=0.0005. Similarly, for each histologic subtype, the risk for alcohol consumption was limited to ER+/PR+ tumors, and notably, very few cases with pure lobular or mixed ductal lobular cancer were either ER+/PR- or ER-/PR-. Conclusions: Moderate alcohol consumption is associated with risk of ER+/PR+ BC in each of the predominant histologic subtypes, but not with hormone receptor-negative cancer. Unlike other studies, we did not find a link between alcohol consumption and ER+/PR- BC.