Abstract PS3-01-22: Targeting Disparities: Impact of Mammographic Screening and Social Drivers on Advanced-Stage Triple-Negative Breast Cancer in Vulnerable Populations Across US Counties

Abstract Background: Triple-negative breast cancer (TNBC) is an aggressive subtype with disproportionate mortality among underserved populations. Mammographic screening reduces breast cancer mortality, but disparities in access and utilization persist, particularly in African American (AA) communities and socioeconomically vulnerable areas. This study aims to quantify the relationship between mammography uptake, demographic factors, and social determinants of health (SDOH) with advanced-stage TNBC (AS-TNBC) across diverse U.S. populations. Methods: We conducted a cross-sectional analysis of 593 counties across multiple states using data from the CDC PLACES database (2020 release, representing 2018 data), the American Community Survey (ACS 2014-2018), and county-level SDOH indicators. Communities were aggregated using the Max-P Regions method to balance TNBC case counts and socioeconomic indices (adjusted for area deprivation index, ADI). Descriptive statistics were used to summarize key characteristics across regions. Then, multivariable Poisson and negative binomial regression models were used to evaluate associations between AS-TNBC diagnoses mammographic screening uptake, demographic (% AA, % Hispanic, % aged <45 years), and social vulnerabilities, including limited English proficiency, rurality, and insurance status. Results: The median percentage of AS-TNBC diagnoses across counties was 38.8% (IQR: 34.9-43.6%). Counties with higher AS-TNBC incidence exhibited significantly lower mammography use (71.5% vs. 72.6%, p 0.001), higher uninsured rates (18.7% vs. 15.7%, p <0.001), and increased proportions of AA residents (14.0% vs. 7.9%, p <0.001), limited English proficiency (1.7% vs. 1.5%, p 0.005), higher socioeconomic deprivation (ADI top quartile: 33.7% vs. 16.4%, p <0.001), and greater rurality (41.5% vs. 30.2%, p 0.006). Multivariable Poisson regression modeling demonstrated a protective effect of mammographic screening, where a 10% increase in screening uptake correlated with a 5.2% decrease in AS-TNBC diagnoses (RR 0.95, 95% CI 0.91-0.99, p 0.007). Conversely, higher proportions of AA residents (RR 1.04, p <0.001), rural populations (RR 1.05, p 0.02), and Hispanic residents (RR 1.002, p <0.001) significantly correlated with increased AS-TNBC rates. Negative binomial regression (adjusting for total breast cancer cases) reaffirmed the robust protective role of screening (RR 0.91, 95% CI 0.89-0.93, p <0.001). In the negative binomial model (adjusted for total breast cancer cases), mammographic screening remained a strong protective factor (RR 0.91, 95% CI: 0.89-0.93, p <0.001), indicating a 9.1% reduction in AS diagnosis per 10% increase in screening. Higher proportions of AA residents (RR 1.04, p <0.001), uninsured individuals (RR 1.04, p <0.001), and those in the most deprived areas (ADI top quartile, RR 1.04, p <0.001) were significantly associated with higher AS diagnosis rates, as well as younger population composition (age 18-44; RR 1.03, p 0.004). Conclusions: Mammographic screening disparities and adverse social determinants significantly influence the prevalence of advanced-stage TNBC. High-risk populations, particularly AA communities, rural areas, and regions with elevated socioeconomic vulnerabilities, face disproportionate impacts. These findings highlight the urgent need for targeted interventions aimed at enhancing access to culturally sensitive and linguistically appropriate screening and healthcare services to mitigate disparities and improve breast cancer outcomes. Citation Format: R. Abou Zeidane, C. Pisano, F. Hussain, W. Dong, T. Lal, L. Vu, N. Mehta, S. Koroukian, J. Rose, C. Speers. Targeting Disparities: Impact of Mammographic Screening and Social Drivers on Advanced-Stage Triple-Negative Breast Cancer in Vulnerable Populations Across US Counties [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS3-01-22.