Abstract 148: Dietary fat intake and risk of epithelial ovarian cancer by tumor histology.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Differences in ovarian cancer incidence rates worldwide suggest an important role for lifestyle factors, including diet, that may influence disease risk. In the WHI dietary modification RCT, a low-fat diet reduced ovarian cancer risk. However, a pooled analysis of 12 cohort studies observed no association between total fat intake and ovarian cancer risk. We hypothesized that the association between dietary fat intake and ovarian cancer risk may vary between the histological subtypes, or that associations may differ depending on the type of fat consumed, such as saturated fat, which has deleterious health effects, and long-chain omega-3 fatty acids, which have anti-inflammatory properties. The study objective was to evaluate fat intake in a New England case-control study that included 1872 cases and 1978 population-based controls enrolled between 1992-2008. At the time of enrolment, participants were interviewed in-person about known and suspected ovarian cancer risk factors and diet was assessed using a validated self-administered, semi-quantitative FFQ. Unconditional logistic regression was used to estimate the association between fat intake and ovarian cancer risk overall and polytomous logistic regression was used to test whether risk associations varied across the histological subtypes of invasive ovarian cancer. Multivariate models were adjusted for study center and phase, age, number of pregnancies, oral contraceptive use, history of tubal ligation and family history of ovarian cancer. We observed a significantly decreased risk of ovarian cancer overall with higher intakes of omega-3 and omega-6 (long chain n-3, Q4 vs. Q1, OR = 0.79, 95% CI = 0.66 - 0.96; total n-6, Q4 vs. Q1, OR = 0.77, 95% CI = 0.64 - 0.94), and an increased risk with increased consumption of total trans fats (Q4 vs. Q1, OR = 1.30, 95% CI = 1.08 - 1.57). The protective effects for high intake of omega-3 were strongest for endometrioid invasive tumors (Q4 vs. Q1, OR = 0.58, 95% CI = 0.41 - 0.82, Ptrend = 0.003, Phet (differences in associations between all invasive histological subtypes) = 0.20). There was a suggestive increased risk for serous, endometrioid, and mucinous invasive tumors with high intake of trans fats although this association was significant only for serous tumors (Q4 vs. Q1, OR = 1.28, 95% CI = 1.02 - 1.62, Ptrend = 0.02, Phet = 0.83). The protective effects of omega-6 were no longer apparent in analyses of different histological subtypes of invasive ovarian cancer although we observed an inverse association with risk of serous borderline tumors (Q4 vs. Q1, OR = 0.56, 95% CI = 0.36 - 0.90, Ptrend = 0.05). These findings suggest that higher intakes of omega-3 may be protective for ovarian cancer, while high consumption of trans fats appeared to increase risk. To further evaluate the possible role for omega-3 in the prevention of ovarian cancer, additional studies are needed to confirm these findings and to investigate the mechanistic basis for these associations. Citation Format: Melissa A. Merritt, Daniel W. Cramer, Allison F. Vitonis, Stacey A. Missmer, Linda J. Titus, Kathryn L. Terry. Dietary fat intake and risk of epithelial ovarian cancer by tumor histology. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 148. doi:10.1158/1538-7445.AM2013-148