Abstract PS4-12-13: Real-world comparison of tumor-infiltrating lymphocytes and survival in advanced triple-negative breast cancer across racial groups in brazil

Abstract Background: TNBC is an aggressive breast cancer subtype affecting younger, non-white women in Brazil, associated with higher recurrence and lower survival. Although chemotherapy remains the primary treatment for advanced TNBC, recent advances in immunotherapy highlight the importance of immune biomarkers such as tumor-infiltrating lymphocytes (TILs) and programmed death-ligand 1 (PD-L1) expression in predicting treatment response. TIL subtypes and PD-L1 are important in tumor immunity and treatment response. Their prognostic value and racial differences in Brazil require further investigation. Methods: A retrospective database query was performed within the Brazilian National Cancer Institute to identify women with recurrent or metastatic TNBC treated between 2018 and 2022. Patients were categorized as White or Black/Mixed-race. Biopsy specimens obtained before chemotherapy underwent immunohistochemistry (IHC) assessment using the PD-L1 CPS by 22C3 pharmDx assay, along with markers including CD3, CD4, CD8, CD68, FOXP3, and PD-1. Associations between the prevalence of TILs subtypes and ethnicity were evaluated. Progression-free survival (PFS) and overall survival (OS) were estimated with the Kaplan–Meier method. Results: A total of 148 patients with advanced TNBC were included: 44 (29.7%) White and 104 (70.3%) Black/Mixed-race. Median age was similar—White 52.0 years (SD 12.6) and Black/Mixed 51.5 years (SD 13.4). De novo disease was present in 31 (70.5%) White and 81 (77.9%) Black/Mixed patients. Immune marker expressions showed modest differences: median CD3 was 5.0 (IQR 1.0–16.2) in White and 5.0 (1.0–30.0) in Black/Mixed; CD4 median was 10.0 (1.0–16.2) vs. 10.0 (1.0–30.0); CD8 median was 5.0 (1.0–20.0) in both groups. CD68 median was higher in White patients—12.5 (1.0–75.0) vs. 10.0 (1.0–40.0). FOXP3 median was 0.0 (0.0–1.0) in White and 0.0 (0.0–3.0) in Black/Mixed; PD-1 median was 0.0 (0.0–1.0) in White and 1.0 (0.0–1.0) in Black/Mixed. PD-L1 CPS distribution was similar: CPS