Abstract B62: Racial disparities in endometrial cancer incidence and mortality are limited to non-Hispanic black women
Authors: Cote Michele L. , Ruterbusch Julie J. , Olson Sara H. , Lu Karen H. , Ali-Fehmi Rouba 
Published: October 2015

Background: Unlike the decreasing incidence seen for most cancers, incidence rates of endometrial cancer have been increasing in the United States over the last decade. Earlier studies have shown that mortality rates from endometrial cancer are significantly higher for non-Hispanic black women compared to non-Hispanic white women, but this has not been established for other racial/ethnic groups. Our objective was to determine whether the increasing incidence and mortality from endometrial cancer are equally distributed by race/ethnicity and tumor histologic subtype.

Methods: Data from the Surveillance, Epidemiology and End Results (SEER) registry were used to identify women diagnosed with endometrial cancer from 2000-2011. A total of 120,513 women, including 90,621 non-Hispanic white (NHW) women (75.2%), 11,386 Hispanic women (9.4%), 10,365 non-Hispanic black women (NHB) (8.6%) and 8,141 Asian women (6.8%) comprised the study population. Age-adjusted incidence and incidence-based mortality rates, with 95% confidence intervals and annual percent changes (APC), were calculated by race/ethnicity (4 groups) overall and for 7 histologic subtypes (low grade endometrioid, high grade endometrioid, clear cell, mixed, MMMT, serous, and other), along with rate ratios to compare racial/ethnic groups, using NHW as the referent group. In addition, 5-year survival rates were calculated by race/ethnic group, histologic subtype, and stage at diagnosis (localized, regional, distant). Differences between NHW and NHB women in the percentage surviving 5 years were described by calculating (%NHW-%NHB)/%NHW) overall and for each histologic subtype and each stage at diagnosis (21 comparisons).

Results: Incidence rates for endometrial cancers are rising across all racial/ethnic groups, with the greatest annual percent change (APC) seen among NHB and Asian women (APC=2.5 for both). Low-grade endometrioid endometrial cancers are the most commonly diagnosed subtype among all women, with highest rates in NHW women, but these rates have stabilized or decreased over the last decade for all women with the exception of NHB women (APC=1.0). High grade endometrioid endometrial cancers have significantly decreased incidence rates over the last decade, particularly among NHW women (APC=-2.5). NHB women have the highest incidence rates of this and other aggressive subtypes of endometrial cancers (clear cell, serous, and malignant mixed Mullerian tumors) compared to NHW women. Hispanic and Asian women had incidence rate ratios equal to or lower than NHW women for all tumor subtypes. For every subtype and stage of disease, the 5-year survival for NHB women is lower than for NHW women, and significantly lower for nearly each comparison. The smallest percent difference seen is for women with localized endometrioid cancers, where NHB women have 6% lower survival, and the largest is 59% lower survival for distant stage clear cell cancers. Hispanic and Asian women have the same or slightly better survival rates compared to NHW women across all stages and subtypes.

Conclusions: The lower survival rates among NHB women with endometrial cancer persist at nearly every stage and histologic subtype examined. Various factors, including socioeconomic status (SES), comorbid conditions, access to care, and treatment decisions may all impact this disparity to some extent, yet Hispanic women who have many of the same challenges are at lower risk of occurrence and have outcomes similar to NHW women after diagnosis. Additionally, the most aggressive types of endometrial cancer are also more common among NHB women, and are among the endometrial cancer subtypes with largest increasing incidence rates. We have yet to fully account for these disparities seen primarily in NHB women and, without intervention, they are likely to persist and potentially widen as endometrial cancer emerges as a significant cause of morbidity and mortality in the decades to come.

Citation Format: Michele L. Cote, Julie J. Ruterbusch, Sara H. Olson, Karen H. Lu, Rouba Ali-Fehmi. Racial disparities in endometrial cancer incidence and mortality are limited to non-Hispanic black women. [abstract]. In: Proceedings of the Seventh AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 9-12, 2014; San Antonio, TX. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2015;24(10 Suppl):Abstract nr B62.