Abstract PO2-09-08: Biological and non-biological predictors of breast cancer disease-free survival among young Black females

Abstract Introduction: Young Black females bear a disproportionate burden of breast cancer (BC) deaths compared to White females yet remain underrepresented in clinical studies. We sought to discover predictors of disease-free survival (DFS) in a cohort of young Black females with BC. Methods: Black females diagnosed with invasive BC ≤ age 50 from 2005 to 2016 were recruited through the Florida and Tennessee state cancer registries. Participants were asked to complete a questionnaire, medical records release, and tissue/tumor release. Saliva was also requested for germline DNA extraction. For the primary outcome of BC DFS, univariate analyses were conducted using the following variables: proportion of West African ancestry, RNA expression based on PAM50 analyses, body mass index (BMI), social determinants of health (i.e., employment and insurance), immunohistochemistry (IHC) subtype, treatment category (i.e., chemotherapy, radiation, and surgery), and BC family history. Multivariate analyses were conducted using backward selection among these variables to analyze in the reduced model. Results: Of 701 consented, 687 participants with early-stage disease were included in the analysis; 14 participants with stage 4 disease at diagnosis were excluded. Among the 687 participants, the median age at diagnosis was 44, 28% had triple-negative breast cancer (TNBC), 13% were deceased, and 5% had recurrent disease. Clinically, participants with TNBC and lymph node involvement had worse BC DFS (p=0.001 and p=0.0002, respectively). Socio-economically, full-time employement was associated with higher BC DFS (p=0.0003). Among those for whom global ancestry data were available (n=551), multivariate analysis showed an association between increased percent of West African ancestry and worse BC DFS with HRIQR=1.23*, which approached significance (p=0.085). Additional subgroup analyses among those with hormone receptor-positive (HR+) (estrogen and/or progesterone receptor positive) BC (n=431) showed that participants with private insurance had better BC DFS (HR=0.45; p=0.05), while those with lymph node involvement had worse BC DFS (HR=2.07; p=0.001). Among HR+ participants with available ancestry data (n=349), worse BC DFS was associated with increased West African ancestry (p=0.05) and lymph node involvement (p=0.08). When ancestry was included in the model, private insurance was no longer associated with BC DFS in this HR+ subgroup (p=0.31). Other predictors analyzed did not reach statistical significance. Conclusion: Our findings confirm prior established adverse predictors of BC DFS, such as TNBC with lymph node involvement and the protective effect of full-time employment. We also found a novel association with West African ancestry among patients with HR+ breast cancer. Although further large-scale studies are needed, results from this cohort of young Black females with BC and highlight the critical need to support research to understand biological and non-biological factors contributing to BC DFS and develop targeted strategies to improve survival outcomes. * HRIQR is the ratio of hazard rates corresponding to upper and lower quartiles of percent West African (interquartile range (IQR): 70.0%-80.8%). Citation Format: Sonya Reid, Run Fan, Lindsay Venton, Anne Weidner, Ann Tezak, Mya Roberson, Susan Vadaparampil, Xuefeng Wang, Sean Yoder, Marilin Rosa, Jibril Hirbo, Jennifer Whisenant, Jennifer Pietenpol, Sheila Rajagopal, Brian Lehmann, Fei Ye, Tuya Pal. Biological and non-biological predictors of breast cancer disease-free survival among young Black females [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-09-08.