Dietary fat intake and risk of epithelial ovarian cancer by tumour histology

Background: Studies of fat intake and epithelial ovarian cancer (EOC) risk have reported inconsistent findings, hence we hypothesised that associations may vary by histologic subtype. Methods: We evaluated fat intake in a New England case-control study including 1872 cases and 1978 population-based controls (1992-2008). Epithelial ovarian cancer risk factors and diet were assessed using a food frequency questionnaire at enrolment. Logistic regression was used to estimate associations between fat intake and EOC risk and polytomous logistic regression was used to test whether associations varied by histologic subtype. Results: We observed a decreased risk of EOC when comparing the highest vs lowest quartiles of intake of omega-3 (odds ratio (OR) = 0.79, 95% confidence interval (CI) 0.66-0.96, P-trend = 0.01) and omega-6 (OR = 0.77, 95% CI 0.64-0.94, P-trend = 0.02) and an increased risk with high consumption of trans fat (OR = 1.30, 95% CI 1.08-1.57, P-trend = 0.002). There was no significant heterogeneity by tumour histologic subtype; however, we observed a strong decreased risk for endometrioid invasive tumours with high intake of omega-3 (quartile (Q) 4 vs Q1, OR = 0.58, 95% CI 0.41-0.82, P-trend = 0.003). Conclusions: These findings suggest that higher intake of omega-3 may be protective for EOC overall and endometrioid tumours in particular, whereas greater consumption of trans fat may increase risk of EOC overall.