Abstract 1567: Race, RNA-based recurrence scores, and survival of early hormone receptor-positive breast cancer: A population-based study

Abstract

Abstract Introduction: Compared with white women, black American women are less likely to develop hormone receptor-positive breast cancer, but experience higher mortality of the disease. The 21-gene recurrence scores (RS) predict individualized benefit of chemotherapy for early hormone receptor-positive breast cancer. We hypothesize that the RS scores in early hormone receptor-positive breast cancer are higher in black women than in white women and this contributes to the worse outcomes among black women with hormone receptor-positive breast cancer. Methods: Utilizing the Surveillance, Epidemiology, and End Results database, we identified 75,861 women (75.7% non-Hispanic white, 7.9% non-Hispanic black, 8.0% Asian/Pacific Islander, and 8.5% Hispanic) with stage I-III hormone receptor-positive breast cancer diagnosed between 2004 and 2014. RS scores were categorized into low, medium, and high groups using traditional cutoffs (18 and 30) and the cutoffs used in the TAILORx clinical trial (11 and 25). We performed multivariable logistic regression to evaluate odds ratios (ORs) of RS categories, and Cox proportional hazard regression to estimate hazard ratios (HRs) for breast cancer-specific mortality and overall mortality. Results: The multivariable adjusted least square mean of RS was significantly higher in black (23.2) than other racial/ethnic groups (white 22.9, Asian/PI 22.5, Hispanic 22.4; p<0.0001). Compared with white women, black women were more frequently in the high RS category defined by a cutoff of 30 (case-only OR=1.24, 95% CI: 1.11-1.39), Asian/PI (OR=0.88, 95% CI: 0.79-0.98) and Hispanic (OR=0.80, 95% CI: 0.72-0.89) were less frequently in the high RS category defined by a cutoff of 25. Compared with white women, the HR of breast cancer-specific mortality was 1.37 (95% CI: 1.10-1.69) in black women, and 0.65 (95% CI: 0.48-0.90) in Asian/PI women, after adjustment for demographic factors, RS categories and other tumor characteristics, and treatment. This association did not significantly vary by RS categories. The multivariable-adjusted associations between race/ethnicity and overall mortality were similar to those for breast cancer-specific mortality. Conclusions: Racial/ethnic differences in early hormone receptor-positive breast cancer outcomes could not be explained by RS scores. Potential differences in tumor biology that are not related to the genes in the 21-gene assay may contribute to the worse prognosis of black women with hormone receptor-positive breast cancer. Citation Format: Yunan Han, Graham A. Colditz, Ying Liu. Race, RNA-based recurrence scores, and survival of early hormone receptor-positive breast cancer: A population-based study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1567.