Abstract A141: Health disparities among women who received treatment for 1L advanced and recurrent endometrial cancer in the United States

Abstract Introduction The burden of endometrial cancer in the United States is disproportionately higher among Black women than that in women of any other race or ethnicity, with disparities observed in risk factors, comorbidities, diagnosis, treatment, and outcomes. A comprehensive approach that simultaneously assesses how various factors contribute to the disparity is needed. Methods This retrospective study used data from the US-based electronic health record-derived deidentified Flatiron Health Research Database (2013-2025). Women aged ≥18 with advanced or recurrent endometrial cancer receiving first-line (1L) therapy were included. Descriptive and Kaplan-Meier analyses were conducted to present patient and clinical characteristics, 1L treatment patterns, and real-world outcomes by race. Hazard ratios for risk of all-cause mortality were estimated using Cox proportional hazard regression models adjusting for race, ethnicity, age, BMI, region, insurance status, socioeconomic status, histology, recurrent vs. de novo, ECOG performance status, and MMR status. Results A total of 3217 advanced or recurrent endometrial cancer patients received 1L therapy (White: 1886 (59%), Black: 588 (18%), Asian: 69 (2%), Other/Unknown: 674 (21%)). As compared to White women, Black women were more likely to be from the southern US (49.7% vs. 32.1%) and of lower socioeconomic status (lowest quintile of socioeconomic status: 39.5% vs. 12.7%). Black women were also more likely to present with advanced disease (56% vs. 48%), non-endometrioid histology (serous carcinoma (41% vs. 25%), carcinosarcoma/mixed Müllerian tumors (17% vs. 9%)), and pMMR tumors (49% vs. 43%) than White women. Overall, similar proportions of Black and White women were treated with 1L immunotherapy (monotherapy/combination). Black women had shorter time to second-line (2L) treatment indicating faster progression (Black: Median 6.9 months vs. White: 7.8 months), and had worse overall mortality (Black: Median (IQR) 17.9 (8.0-39.7) months vs. White: 22.9 (9.2-89.3) months). 3-year survival was 39.3% and 28.0%, and 5-year survival was 29.9% and 17.9%, for White and Black patients, respectively. After adjusting for other factors, being Black (HR: 1.016 (1.01-1.02) vs. White), having non-endometrioid histology (carcinosarcoma/MMT: HR: 1.74 (1.49-2.03); clear cell carcinoma: HR: 1.33 (1.04-1.70); serous carcinosarcoma: HR: 1.48 (1.32-1.67); endometrial cancer, NOS: HR: 1.70 (1.45-1.99); all vs. endometrioid carcinoma), worse ECOG performance status (ECOG 2-4: HR:1.89 (1.63-2.18) vs. ECOG 0-1), and pMMR status (HR: 1.26 (1.06-1.48) vs. dMMR) were associated with having significantly worse survival. Conclusion Disparities in health persist in endometrial cancer with histology, socioeconomic status, and shorter time to 2L treatment contributing to the increased mortality in the long-term among Black women vs. other races and ethnicities. Understanding the magnitude and source of these disparities will help us address them in a better way and improve outcomes for women who bear the highest burden of this disease. Citation Format: Kathleen M. McClain, Vimalanand S. Prabhu, Srujitha Marupuru, Ke Meng, Vy Tran, Kristina Woodhouse, Robin Meng, Angela K. Green, Vicky Makker. Health disparities among women who received treatment for 1L advanced and recurrent endometrial cancer in the United States abstract. In: Proceedings of the 18th AACR Conference on the Science of Cancer Health Disparities; 2025 Sep 18-21; Baltimore, MD. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2025;34(9 Suppl):Abstract nr A141.