Abstract PO-102: Racial disparities in outcomes following neoadjuvant chemotherapy by breast cancer subtype: Analyses from the National Cancer Database, 2010- 2016

Introduction: Pathologic complete response (pCR) following neoadjuvant chemotherapy for breast cancer is associated with improved prognosis in patients with aggressive subtypes. Our purpose was to describe racial disparities in pCR rate and overall survival among breast cancer patients treated with neoadjuvant chemotherapy. Methods: We conducted a retrospective cohort study of women with stages I-III breast cancer in the National Cancer Database who received neoadjuvant chemotherapy between 2010 and 2016. We collected demographic information, clinical characteristics, county-level socioeconomic factors, insurance status, type of treatment facility and overall survival. Breast cancer subtypes were categorized according to joint hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) status. Response to neoadjuvant therapy was categorized as (i) pathologic complete response (absence of invasive carcinoma in the breast and ipsilateral axillary lymph nodes) and (ii) partial or no response. Associations between race/ethnicity and rates of pCR by subtype were determined using modified Poisson regression models to estimate rate ratios (RR) and 95% confidence intervals (CI) with robust standard errors adjusted for age, T and N status, grade, histology, county- level education and median income, comorbidity score, facility type, geographic region and insurance status. Racial differences in overall survival by pCR status were determined using Kaplan-Meier survivor functions and multivariable Cox proportional hazards models to estimate adjusted hazard ratios and 95% CI. Results: A cohort of 73,950 breast cancer patients with a median follow up of 36 months included 70% non-Hispanic white, 16% non-Hispanic black, 8% Hispanic and 4% non- Hispanic Asian/Pacific Islander. Overall, 35% of women had pCR, which differed according to subtype (luminal A, HR+/HER2- 17%; luminal B, HR+/HER2+ 44%; triple negative, HR-/HER2- 44%; HER2-enriched, HR-/HER2+ 64%). Compared to whites, black women with aggressive subtypes had significantly lower rates of pCR (triple- negative, RR 0.92, 95% CI 0.88-0.96; HER2-enriched, RR 0.87, 95% CI 0.82-0.92), but no significant differences in pCR rate for luminal A (RR 1.07, 95% CI 0.99-1.16) and B (RR 0.95, 95% CI 0.89-1.02) tumors. Racial disparities in overall mortality were observed among black women without a pCR following neoadjuvant chemotherapy (hazard ratio 1.17, 95% CI 1.09-1.25) but there were no differences among those who achieved a pCR (hazard ratio 1.00, 95% CI 0.86-1.18). Conclusions: Racial disparities in pCR rate are limited to aggressive breast cancer subtypes. Independent of subtype, black women who do not experience pCR following neoadjuvant chemotherapy are at greater risk for all-cause mortality. These results should inform risk-stratified treatment decisions following neoadjuvant chemotherapy, and future clinical studies of neoadjuvant therapy should investigate potential racial differences in chemoresistance. Citation Format: Gregory S. Calip, Kent F. Hoskins, Naomi Y. Ko. Racial disparities in outcomes following neoadjuvant chemotherapy by breast cancer subtype: Analyses from the National Cancer Database, 2010- 2016 [abstract]. In: Proceedings of the AACR Virtual Conference: Thirteenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2020 Oct 2-4. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(12 Suppl):Abstract nr PO-102.