Abstract 2298: Endometrial cancer incidence by age across Asian/Pacific Islander ethnic subgroups

Abstract Introduction: Endometrial cancer is the most common gynecologic cancer in the U.S. Although late-onset endometrial cancer (LOEC, diagnosed age 50+) is more common, the incidence of early-onset endometrial cancer (EOEC, age <50) is rising, with recent data showing EOEC incidence increasing twice as fast as LOEC incidence during 1995-2017. Interestingly, when these findings were looked at by race/ethnicity, only Asian/Pacific Islander (APIs) showed incidence of LOEC increasing faster than that observed for EOEC. However, because APIs constitute unique ethnic subgroups that differ in culture, socioeconomic status, and access to care, we have examined EOEC and LOEC incidence for the seven largest API subgroups. Methods: The Surveillance, Epidemiology, and End Results Program (SEER-9) specialized database with Asian population denominators was used to examine EOEC and LOEC incidence from 1995 to 2014 for the following API subgroups: Asian Indian/Pakistani, Chinese, Filipino, Hawaiian/Pacific Islander, Japanese, Korean, and Vietnamese. Incidence rate ratios (IRRs) were calculated for each API subgroup, with NHW as the reference. Joinpoint Regression Program version 5.2.0.0 was used to calculate the average percent change (APC) of incidence rates in 4-year groups. All statistical tests were 2-sided, and statistical significance was defined as P<0.05. Results: The analysis included 14, 803 EOEC (2, 365 API; 12, 438 NHW) and 119, 637 LOEC cases (8, 213 API; 111, 424 NHW). The proportion of EOEC was higher in all API subgroups than in NHW (10%), with the highest among Hawaiian/Pacific Islander (35%) and the lowest among Chinese (15%). EOEC incidence was 6-20 times lower than LOEC incidence. EOEC incidence rates among API subgroups range from 2.11 (Asian Indian/Pakistani) to 16.72 per 100, 000 (Hawaiian/Pacific Islander). LOEC incidence rate ranged from 0.24 (Korean) to 93.94 per 100, 000 (Hawaiian/Pacific Islander). Hawaiian/Pacific Islander is the only subgroup with both EOEC and LOEC incidence rates higher than NHWs (IRRs=3.64 and 1.18, respectively). There was an increasing trend in EOEC and LOEC incidence during 1995-2014 for most API subgroups. The APCs for EOEC were lower than LOEC in most API subgroups, except for Hawaiian/Pacific Islander. In contrast, the APC for EOEC was greater than LOEC among NHW. Among the API subgroups, the APCs for EOEC ranged from -0.80 (Japanese) to 3.73 (Hawaiian/Pacific Islander). The APCs for LOEC ranged from 1.46 (Japanese) to 3.72 (Asian Indian/Pakistani). Conclusions: There was heterogeneity in incidence rates and trends of EOEC and LOEC by API subgroups. Both EOEC and LOEC incidence rates increased across nearly all API subgroups, and the increases were greater for LOEC, which is different from NHW. These differential increases underscore the need to monitor risk factor trends and develop tailored interventions to reduce endometrial cancer burden by age and API subgroups. Citation Format: Minh Tung Phung, Elizabeth Gehrig, Alice W. Lee. Endometrial cancer incidence by age across Asian/Pacific Islander ethnic subgroups [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2298.