Longitudinal trends in pembrolizumab uptake for triple-negative breast cancer (TNBC): A comparative analysis of Appalachian and non-Appalachian populations at a tertiary care center.

e23412 Background: Appalachian populations face unique barriers leading to cancer care disparities. As pembrolizumab becomes standard for triple-negative breast cancer (TNBC), equitable access for rural patients is critical. This study evaluates immunotherapy uptake between Appalachian and non-Appalachian patients at the University of Kentucky. Methods: A retrospective analysis using Epic SlicerDicer identified TNBC patients (July 2021- December 2025) at the University of Kentucky, segmented by Appalachian and non-Appalachian counties. Data on demographics, comorbidities, staging, and insurance were extracted. Chi-square tests compared groups; annual pembrolizumab uptake was calculated with confidence intervals. Results: 405 patients with TNBC were identified (220 Appalachian, 185 non-Appalachian). Groups were matched for age < 49 (p = 0.8) and gender (p = 0.91); median ages were 57 and 60 years, respectively. Appalachian patients demonstrated a higher prevalence of obesity (59.5% vs 50.3%; p = 0.06) and Type 2 Diabetes (20.0% vs 13.0%; p = 0.053) compared to the non-Appalachian cohort. Other comorbidities, including GERD (p = 0.19), depression (p = 0.11), hypertension (p = 0.21), and anxiety (p = 0.84), showed no significant regional differences. Non-Appalachian patients were significantly more likely to hold private insurance (40.5% vs 28.6%; p = 0.011), whereas Appalachian patients had significantly higher rates of Medicare enrollment (39.5% vs 29.2%; p = 0.029). Medicaid (p = 0.52) and self-pay (p = 0.2) rates were comparable between regions. Pembrolizumab uptake increased over time in both Appalachia and other counties, but consistently lagged in Appalachia. With an average of (29.7%) in the non-Appalachian cohort compared to the Appalachian cohort (21.4%), a difference that trended towards but did not reach statistical significance (p = 0.053). Despite this disparity in immunotherapy utilization, mortality rates remained similar between the two groups (p = 0.83), with 35 deaths in the Appalachian cohort and 28 in the non-Appalachian cohort. Conclusions: A persistent disparity in pembrolizumab uptake, with almost 15% gap in peak usage, suggests that systemic barriers to immunotherapy persist in rural Kentucky. Addressing insurance disparities and metabolic burden is critical. Further investigation into referral patterns and coverage is needed to ensure equitable access as standards of care evolve. Patient characteristics and insurance distribution. Variable Appalachian (n=220) Non-Appalachian (n=185) P-value Age < 49 63 55 0.8 Obesity 131 93 0.06 Type 2 DM 44 24 0.053 Pembro Use 47 55 0.053 Private Insurance 63 75 0.011 Medicare 87 54 0.029 Medicaid 36 26 0.52 Self Pay 13 17 0.2 Death 35 28 0.83 (P-values calculated via Chi-square analysis).