Postmenopausal breast cancer risk and dietary patterns in the E3N-EPIC prospective cohort study.

Since evidence relating diet to breast cancer risk is not sufficiently consistent to elaborate preventive proposals, the authors examined the association between dietary patterns and breast cancer risk in a large French cohort study. The analyses included 2,381 postmenopausal invasive breast cancer cases diagnosed during a median 9.7-year follow-up period (1993-2005) among 65,374 women from the E3N-EPIC cohort. Scores for dietary patterns were obtained by factor analysis, and breast cancer hazard ratios were estimated by Cox proportional hazards regression for the highest quartile of dietary pattern score versus the lowest. Two dietary patterns were identified: "alcohol/Western" (essentially meat products, French fries, appetizers, rice/pasta, potatoes, pulses, pizza/pies, canned fish, eggs, alcoholic beverages, cakes, mayonnaise, and butter/cream) and "healthy/Mediterranean" (essentially vegetables, fruits, seafood, olive oil, and sunflower oil). The first pattern was positively associated with breast cancer risk (hazard ratio = 1.20, 95% confidence interval (CI): 1.03, 1.38; P = 0.007 for linear trend), especially when tumors were estrogen receptor-positive/progesterone receptor-positive. The "healthy/Mediterranean" pattern was negatively associated with breast cancer risk (hazard ratio = 0.85, 95% CI: 0.75, 0.95; P = 0.003 for linear trend), especially when tumors were estrogen receptor-positive/progesterone receptor-negative. Adherence to a diet comprising mostly fruits, vegetables, fish, and olive/sunflower oil, along with avoidance of Western-type foods, may contribute to a substantial reduction in postmenopausal breast cancer risk.