Macro-nutrient intake and risk for endometrial cancer.

B68 Objective: To estimate the association between intakes of individual macro-nutrients and endometrial cancer occurrence in endometrial cancer cases and controls in Alberta, Canada. Rationale: The two main risk factors for endometrial cancer are prolonged exposure to unopposed estrogen therapy and obesity. In addition to its role in energy balance, diet has been hypothesized to influence endometrial cancer development by modifying the endogenous hormonal milieu.A high-fat diet or a low-carbohydrate diet may increase endometrial cancer risk, however, the results from epidemiologic studies have been inconsistent. Hence, we investigated the influence of intake of individual macro-nutrients on the risk for endometrial cancer in a population-based case-control study conducted in Alberta, Canada from 2002 to 2006. Methods: Women aged 28-79 years with incident, histologically-confirmed, primary endometrial cancer were identified from the Alberta Cancer Registry. Population-based controls were ≥30 years old, identified through random-digit dialling, and frequency-matched to cases on age and urban/rural residence in a 2:1 ratio. Lifestyle and dietary exposures were assessed with an in-person interview and the Diet History Questionnaire (DHQ). The DHQ captured self-reported frequency of use of 124 foods and beverages during the year before diagnosis and corresponding reference date from 525 endometrial cancer cases and 1002 controls. Daily intakes of selected macro-nutrients were estimated from the DHQ using DietCalc diet analysis software. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) for endometrial cancer risk associated with the highest quartile of nutrient intake compared to the lowest referent quartile, with quartile cut-points based on the intake distribution in controls. Results: After excluding 43 women with extreme total energy intakes of 5000 kcal/day, and adjusting for age (years), urban/rural residence, daily total caloric intake (kcal/day), body mass index (kg/m2), history of hypertension (never/ever) and parity (number of full-term pregnancies) endometrial cancer risk was elevated for the highest versus lowest quartile of total fat intake (OR=1.69, 95% CI 1.01-2.82). When fat intake was analysed as saturated fat, monounsaturated fat and polyunsaturated fat intake, no elevations in endometrial cancer risk were found (OR=1.31, 95% CI 0.81-2.12; OR=1.42, 95% CI 0.86-2.33; and OR=1.08, 95% CI 0.68-1.69, respectively); and similar results were observed for cholesterol intake (OR=1.28, 95% CI 0.83-1.96). We found no statistically significant association between greater daily intakes of total energy (OR=1.04, 95% CI 0.53-2.02), protein (OR=1.14, 95% CI 0.68-1.92), carbohydrate (OR=1.04, 95% CI 0.62-1.77) and dietary fiber (OR=1.12, 95% CI 0.73-1.71). Conclusion: These results support the hypothesis that a high-fat diet may increase the risk for endometrial cancer. However, a low-carbohydrate diet did not increase the risk for this cancer in this study population. Future analyses of food groups, glycemic index and glycemic load are planned with these data, to determine if any associations exist with these other dietary components.