RT Journal Article SR Electronic T1 284 Obesity and type I endometrial carcinoma: an overly simplified model? JF International Journal of Gynecologic Cancer JO Int J Gynecol Cancer FD BMJ Publishing Group Ltd SP A115 OP A115 DO 10.1136/ijgc-2020-IGCS.244 VO 30 IS Suppl 3 A1 Liao, C A1 Richardson, M A1 Tran, K A1 Chan, C A1 Mann, AK A1 Maxwell, GL A1 Hamilton, CA A1 Tian, C A1 Darcy, K A1 Kapp, DS A1 Chan, JK YR 2020 UL http://ijgc.bmj.com/content/30/Suppl_3/A115.2.abstract AB Objective To evaluate the relationship between obesity and incidence of type I endometrial cancer in two large population cohorts.Methods From 2001 to 2016, incidence rates were estimated from United States Cancer Statistics data. Hysterectomy, pregnancy, and obesity rates were derived from the Behavioral Risk Factor Surveillance System (BRFSS). SEER*Stat and Joinpoint regression were used to calculate the incidence rate (per 100,000).Results A total of 531,481 patients were diagnosed with endometrial cancer, and 385,821 were diagnosed with grade 1 or 2 endometrioid histology (82% White, 6% Black, 8% Hispanic, 3% Asian). Women aged 65–69 had the highest incidence (80.31). Incidence was highest in White women (20.0), followed by Hispanics (15.1), Blacks (12.8), and Asians (9.9).The overall incidence of grade 1 and 2 endometrioid carcinoma decreased by 2% per year from 24.4 to 18.5 between 2001 and 2016 (p<0.001). Using survey data from BRFSS, from 2001 to 2016, the proportion of women with obesity increased from 21.1% to 30.2% (average annual increase of 2.3%, p<0.001). Black women had the highest proportion of obesity (47.5%), followed by Hispanics (33.7%), Whites (28.1%), and Asians (12.8%). However, there was no increase in either grade 1 or 2 endometrioid carcinoma incidence over the study period, and no association with the increase in obesity rate.Abstract 284 Figure 1 Conclusion Older and White women are at higher risk of grade 1 or 2 endometrial cancer. Our combined analyses suggest that the decreasing incidence of type I endometrial cancer is not correlated with the rise in obesity.