Dietary Fats and All-cause and Breast Cancer-specific Mortality among Women with Breast Cancer: The Western New York Exposures and Breast Cancer Study.

Background: Study results of prediagnostic 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 study. Usual intake before diagnosis of total fat and subtypes were estimated from a food frequency questionnaire completed at baseline. HRs 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 with 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: Prediagnostic 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.