Abstract PS4-09-10: Geographic Barriers are Key Predictors of Clinical Trial Enrollment in Breast Cancer: A National Cancer Database Analysis

Abstract Background: Clinical trials are essential to improving cancer outcomes, yet racial and ethnic minorities remain underrepresented. Structural and social barriers such as limited access to care, geographic distance, financial burden, lack of information, and cultural mistrust contribute to this persistent underrepresentation. Despite longstanding initiatives to improve inclusivity, recent data show most clinical trial participants continue to be White (W). An understanding of the factors that influence trial enrollment, including both sociodemographic and geographic determinants, is essential to designing more equitable and representative research. In this study, we used the National Cancer Database (NCDB) to evaluate disparities in clinical trial enrollment among patients (pts) with breast cancer (BC), with a particular focus on the impact of race, income, education, and geographic access. Method: We conducted a retrospective cohort study using data from the NCDB including pts with complete data on race/ethnicity, clinical trial enrollment status, clinical stage, sociodemographic variables, and survival time. Race/ethnicity in the NCDB may be based on self-report, administrative data, or observation. Education and income quartiles were assigned based on ZIP code-level U.S. Census data, per NCDB methodology. Descriptive statistics were used to compare enrollment rates across racial and ethnic groups. Multivariable logistic regression was performed to estimate adjusted odds ratios (AORs) for clinical trial enrollment, with race/ethnicity as the primary predictor and adjustment for age, stage, grade, Charlson-Deyo comorbidity index, income, education level, facility type, and geographic location. A p-value of < 0.05 was considered statistically significant. All analyses were conducted using SAS software version 9.4. Results: A total of 1,798,690 BC pts were included in the analysis. The median age was 62 years. The cohort was 79.7% W, 10.9% Black, 4.9% Hispanic, and 4.6% other races/ethnicities. The majority of pts resided in metro areas (84.7%), followed by urban (13.3%) and rural (2.0%). Only 1,645 (<1%) were documented as enrolled in clinical trials. In multivariable logistic regression, rural residence was independently associated with lower clinical trial enrollment (AOR= 0.381; 95% CI: 0.24-0.60; p< 0.0001) as was travel distance > 50 miles to the treating facility (AOR= 0.44-0.52; p< 0.0001). Treatment at non-academic center was associated with a higher enrollment compared to academic centers (AOR 1.438, 95% CI 1.15-1.80; p<0.0012). After adjustment for clinical and sociodemographic variables, race/ethnicity, income and education level were not significant predictors of clinical trial participation. Conclusion: In this large national cohort of BC pts, clinical trial enrollment was strikingly low, with fewer than 1% of pts documented as participants. Rural residence and long travel distances to treatment facilities were significantly associated with lower enrollment, underscoring the critical role of geographic and structural barriers in accessing research opportunities. Unexpectedly, patients treated at non-academic centers had higher odds of trial enrollment, a finding that may reflect variation in reporting practices rather than true differences in access. Race, income, and education were not independent predictors after adjustment, suggesting access may be the primary driver of disparities. A key limitation is the NCDB’s underreporting of trial participation. The very low number of patients identified as enrolled highlights the urgent need for improved and standardized reporting mechanisms. Enhanced data accuracy is essential to guide equity-focused interventions and ensure representative participation in cancer research. Citation Format: A. Sandoval-Leon, Y. Chamorro, M. Roy, M. Rubens, N. Dempsey, L. Carcas, M. Ahluwalia, L. Dumeny, R. Mahtani. Geographic Barriers are Key Predictors of Clinical Trial Enrollment in Breast Cancer: A National Cancer Database Analysis [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 PS4-09-10.