Abstract A77: Weight gain and weight cycling and risk of endometrial cancer

Abstract

Abstract Background: Obesity, as measured by BMI, is an established risk factor for endometrial cancer in postmenopausal women. However, whether weight gain and weight cycling, both which occur frequently, are associated with risk of endometrial cancer independent of BMI is not clear. Previous studies of weight gain have found mixed results, but there was considerable variation in how the potential influence of BMI on this association was accounted for. Some studies did not adjust for BMI at all while others adjusted for BMI from different points during life. Similarly, inconsistent findings have been reported from studies of weight cycling and risk of endometrial cancer. Because weight cycling has been suggested to influence fat distribution and the ability to lose weight, it may affect risk of endometrial cancer. Methods: The associations of weight gain and weight cycling with endometrial cancer risk were investigated in a large, well characterized prospective study, the American Cancer Society's Cancer Prevention Study II (CPS-II) Nutrition Cohort. Included in this analysis were 38,152 women with an intact uterus who provided information on weight history and weight cycling on the 1992 baseline questionnaire. Of these, 560 were diagnosed with endometrial cancer between 1992 and June 30, 2007. Adult weight change was calculated from the reported weight at age 18 and current weight on the 1992 baseline questionnaire. Number of lifetime weight cycles was assessed based on responses to the 1992 baseline questions asking how many times 10 or more pounds were intentionally lost and later regained. Multivariate-adjusted hazards ratios (HR) and 95% confidence intervals (CI) were estimated using Cox proportional hazards regression. Results: Total weight gain during adulthood was statistically significantly positively associated with risk of endometrial cancer (HR=3.93, 95% CI:2.73–5.65 for gained 61+ lbs versus stable weight, p<0.0001). This association was attenuated by adjustment for BMI in 1992 but remained statistically significant (HR=1.92, 95% CI:1.20–3.07, p-trend<0.0001). Similarly, weight cycling was associated with increased risk of endometrial cancer (HR=2.10, 95% CI:1.61–2.74 for 10+ weight cycles versus no weight cycles, p-trend<0.0001). However, after adjustment for BMI in 1992, this association was null (HR=1.02, 95% CI:0.75–1.39, p-trend=0.95). Weight cycling was not associated with endometrial cancer in analyses stratified by BMI or by weight change after adjustment for BMI in 1992. Conclusions: Our finding that adult weight gain is positively associated with risk of endometrial cancer even after adjustment for BMI suggests that both adult weight gain and BMI might have independent effects on the risk of endometrial cancer. The absence of association of weight cycling with endometrial cancer incidence after adjustment for BMI suggests that cycles of intentional weight loss followed by regain do not contribute to risk of this cancer. These findings underscore the importance of avoiding adult weight gain and indicate that encouraging women to try to lose weight is unlikely to increase risk of endometrial cancer even if weight is lost and subsequently regained. Citation Information: Cancer Prev Res 2011;4(10 Suppl):A77.