Abstract C045: Outcomes of hormone-receptor positive, HER2-negative breast cancers by race and tumor biologic features

Abstract

Abstract Background: Black women have higher breast cancer mortality than white women, particularly within the hormone receptor positive, human epidermal growth factor receptor 2 negative (HR+/HER2-) clinical subtype. Interactions between tumor biology and treatment factors are complex and racial disparities in early events (such as 5-year recurrence risk) are not well characterized. Methods: Using data from the Carolina Breast Cancer Study (Phase 3, 2008-2013), a large population-based study enrolling 50% black and 50% white women from 44 counties in North Carolina, we estimated associations between race and recurrence among non-metastatic HR+/HER2- tumors, overall and within subgroups defined by PAM50 Risk of Recurrence score (ROR-PT, calculated from subtype, proliferation level, and tumor size), PAM50 intrinsic subtype, and tumor grade. We also compared treatment patterns by race among HR+/HER2- patients with high-risk disease. Relative frequency differences (RFD), interpretable as the percentage difference between index and referent groups, were estimated using multivariable linear regression. Recurrence risk was estimated using survival curves standardized for age and stage and inverse probability-weighted Cox models. Results: Among 1,775 eligible women, black women had higher recurrence risk relative to white women (crude hazard ratio: 1.8, 95% confidence interval [CI]: 1.3, 2.5), which remained elevated after standardizing for age and clinical covariates (hazard ratio: 1.4, CI: 1.0, 1.9). In stratified analyses, racial disparities persisted among women with high ROR-PT score (5-year standardized recurrence risk 18.9% in black vs. 12.5% in white women) and in high grade patients (5-year standardized recurrence risk 16.6% in black vs. 12.0% in white women). Black women with high grade tumors were significantly less likely to initiate endocrine therapy (RFD: -8.4%, CI: -15.9, -1.0) and experienced treatment delay more often than white women (RFD: +10.4%, CI: 1.8, 19.0). Conclusions: Racial disparities in HR+/HER2- breast cancer recurrence persist within high-risk subgroups. Efforts to identify treatment inequities and other causes of variation in cancer treatment are critical to reducing outcome disparities. Note: This abstract was not presented at the conference. Citation Format: H. Shelton Earp, Andrew F Olshan, Lisa A Carey, Charles M Perou, Melissa A Troester, Halei C. Benefield, Katherine E Reeder-Hayes, Hazel B Nichols, Benjamin C Calhoun, Michael I Love, Xuezheng Sun, Erin L Kirk, Joseph Geradts, Katherine A Hoadley, Stephen R Cole. Outcomes of hormone-receptor positive, HER2-negative breast cancers by race and tumor biologic features [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr C045.