Dietary fats and all-cause and breast cancer specific mortality among women with breast cancer: The Western New York Exposures and Breast Cancer (WEB) Study

Abstract Background: Study results of pre-diagnostic dietary fat intake and breast cancer mortality have been inconclusive. While dietary fat subtypes (saturated (SFA), polyunsaturated (PUFA) and monounsaturated (MUFA) fatty acids) may have different biological effects, there is little evidence regarding the association of dietary fat and fat subtype intake with mortality after breast cancer diagnosis. Methods: Women with incident, pathologically confirmed invasive breast cancer and complete dietary data (n=793) were followed in a population-based study, the Western New York Exposures and Breast Cancer (WEB) Study. Usual intake before diagnosis of total fat and subtypes were estimated from a food frequency questionnaire completed at baseline. Hazard ratios (HR) and 95% confidence intervals (CI) for all-cause and breast cancer-specific mortality were estimated with Cox proportional hazards models. Interactions by menopausal status, estrogen receptor (ER) status, and tumor stage were examined. Results: Median follow-up time was 18.75 years; 327 (41.2%) participants had died. Compared to lower intake, greater intake of total fat (HR 1.05, 95% CI 0.65-1.70), SFA (1.31, 0.82-2.10), MUFA (0.99,0.61-1.60), and PUFA (0.99, 0.56-1.75) was not associated with breast cancer-specific mortality. There was also no association with all-cause mortality. Results did not vary by menopausal status, ER status, or tumor stage. Conclusions: Pre-diagnostic intake of dietary fat and fat subtypes was not associated with either all-cause or breast cancer mortality in a population-based cohort of breast cancer survivors. Impact: Understanding factors affecting survival among women diagnosed with breast cancer is critically important. Dietary fat intake prior to diagnosis may not impact that survival.