Abstract PS4-10-10: Trends in Neoadjuvant Pembrolizumab Use in Triple Negative Breast Cancer

Abstract Introduction: Since its trial demonstrating efficacy in February 2020 and FDA approval for its use in the neoadjuvant setting occurred in July 2021, the integration of pembrolizumab with neoadjuvant chemotherapy (NAC) has significantly improved prognosis and treatment efficacy in triple-negative breast cancer (TNBC) (1,2). Our study investigated national rates of NAC-pembrolizumab use for TNBC, focusing on how patient factors and socioeconomic status affected adoption of pembrolizumab. Methods: We utilized the Epic Cosmos national database to analyze pembrolizumab use among patients with TNBC who received NAC between 1/1/2021 - 12/31/2024. We studied how race/ethnicity and the area of deprivation index (ADI), a standardized score highlighting the social economic designation of a geographic region derived from census variables (3), correlated with pembrolizumab use. Results: To define our population, we used breast cancer ICD-10 codes that included a new diagnosis of estrogen receptor (ER)-negative disease and/or triple negative disease. We excluded those with listing of ER-positive, progesterone receptor-positive, or HER2-positive disease, and those with Stage 0, I, or IV disease documented. In addition, we included only those patients who had an encounter with an oncologist and who received paclitaxel without trastuzumab as a component of neoadjuvant treatment prior to a breast surgical procedure. A total of 6,689 unique patients were identified. Overall rate of pembrolizumab use over the course of the study was 76.2%. This rate increased from 35.9% in 2021, 79.9% in 2022, 84.1% in 2023, and 87.1% in 2024. There were no differences in pembrolizumab according to race or ethnicity. Patients with the highest quartile (highest risk) of ADI scores had significantly lower rates of use compared to the rest of the population (77.4% vs. 74.0%, p=0.04). Investigating rates of adoption of pembrolizumab by year revealed a trend toward lower rate of use in Black patients compared to White patients in 2021 (32.1% vs, 36.9%, p=0.08), but these differences were negligible in subsequent years. Similarly, the differences in use according to ADI was more pronounced in the earlier years relative to the later. Conclusion: This study reveals high rates of pembrolizumab utilization within a year of FDA approval for its use with NCT treatment of triple negative breast cancer. Overall, we did not find significant differences in its use according to race and ethnicity. Patients who live in areas of higher social economic deprivation had lower rates of use. There was a suggestion that adoption rates were slower in those with higher ADI. References: 1. Schmid, P., Cortes, J., Pusztai, L., et al. Pembrolizumab for Early Triple-Negative Breast Cancer. New England Journal of Medicine, 2020. 382(9), 810-821. https://doi.org/10.1056/nejmoa1910549 2. Center for Drug Evaluation and Research. (2021, July 27). FDA approves pembrolizumab for high-risk early-stage triple-negative breast cancer. U.S. Food and Drug Administration. Retrieved from https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-pembrolizumab-high-risk-early-stage-triple-negative-breast-cancer. 3. Kind AJH, Buckingham W. Making Neighborhood Disadvantage Metrics Accessible: The Neighborhood Atlas. New England Journal of Medicine, 2018. 378: 2456-2458. DOI: 10.1056/NEJMp1802313. PMCID: PMC6051533. Citation Format: E. Li, S. R. Spierling Bagsic, R. F. Belasco, C. H. Nguyen, S. Ali, N. Liloia, A. A. Aguayo, D. Lindsay, T. A. Buchholz. Trends in Neoadjuvant Pembrolizumab Use in Triple Negative Breast Cancer [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 PS4-10-10.