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