Abstract PS5-11-30: Racial and ethnic differences in site of metastasis at presentation and treatment in de novo metastatic triple-negative breast cancer

Abstract Background: Triple-negative breast cancer (TNBC) is an aggressive disease that disproportionately affects Black patients in the U.S. Racial/ethnic minoritized patients are diagnosed at younger ages, later stages, face barriers in accessing oncology care, and overall experience worse outcomes, despite improvements in early detection and treatment. There remains limited data on racial/ethnic and socioeconomic disparities in disease presentation, treatment receipt, and initiation in metastatic TNBC nationally. Methods: Using the National Cancer Database (NCDB), we analyzed a retrospective cohort of patients diagnosed with de novo metastatic TNBC between 2010-2022. We evaluated 3 metastatic sites, including brain, bone only, and visceral (liver and/or lung). Three treatment modalities were assessed: immunotherapy, chemotherapy, and radiation. Immunotherapy use was restricted to patients treated with chemotherapy from 2019-2022, following the initial accelerated approvals for atezolizumab in 2019 and pembrolizumab in 2020 for metastatic TNBC. Treatment initiation delay (i.e., number of days) was defined as the time from initial diagnosis to treatment start and compared by metastatic disease presentation and across racial/ethnic groups. Multiple linear regression was used to examine racial/ethnic differences in treatment initiation, adjusting for clinical and socioeconomic factors. Regression coefficients (β) and 95% CIs were calculated. Results: Of 16,897 patients included, the mean age was 61.6 years; 62.9% were White, 26.3% Black, 6.9% Hispanic, 2.9% Asian or Pacific Islander (API), and 1.0% Other (per self-report); 12.0%, 24.5%, and 57.4% had brain, bone only, and visceral metastases at presentation, respectively; 55.8% received chemotherapy alone, 44.2% chemoimmunotherapy, and 31.8% radiotherapy as their first line of treatment. Higher percentages of White (12.6%) patients were diagnosed with brain metastasis at presentation compared to 9.2% API, 10.8% Black, and 11.4% Hispanic patients (P = .009). A higher proportion of API patients (27.5%) presented with metastatic bone only disease than White (25.7%), Hispanic (23.5%), or Black (21.8%) patients (P .001). Among patients with visceral metastases, a higher proportion were Black (59.1%) vs White (57.2%), API (56.4%) and Hispanic (53.3%) (P = .008). There was a shorter time to first-line radiotherapy initiation among patients with brain metastases compared to those without (median days: 29.0 vs 140.0; P .001). Treatment receipt and initiation varied across racial/ethnic groups. In the adjusted models, Black (β = 3.0; 95% CI, 0.6-5.3) and Hispanic (β = 6.8; 95% CI, 2.6-10.9) patients experienced a longer time to chemotherapy initiation than White patients. Immunotherapy was delayed, on average, for 7.8 days (95% CI, 0.6-15.1) in Black and for 16.6 days (95% CI, 6.0-27.2) in Hispanic as compared to White patients; however, these differences were not significant when further controlling for socioeconomic factors. API, Black, and Hispanic patients also had a longer time to radiotherapy initiation. Compared to private insurance, Medicare was associated with chemotherapy initiation delay (β = 3.0; 95% CI, 0.3-5.7) while Medicaid was associated with immunotherapy initiation delay (β = 12.9; 95% CI, 2.0-23.7). A shorter time to immunotherapy initiation was observed in areas with higher levels of education. Conclusions: This NCDB study found notable racial/ethnic and socioeconomic disparities in metastases at presentation and treatment initiation delays among patients diagnosed with de novo metastatic TNBC the U.S. More effort is needed to alleviate these disparities and to improve care equity and treatment outcomes for all patients with metastatic TNBC. Citation Format: J. Q. Freeman, W. Guo, S. Poland, A. Ravichandran, M. Hennessy, R. Nanda. Racial and ethnic differences in site of metastasis at presentation and treatment in de novo metastatic 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 PS5-11-30.