Abstract P5-06-14: Integrating CD8, FOXP3 and PD-L1 expression in prognostic models for triple negative breast cancer (TNBC): An analysis of 265 patients treated with standard therapy for stage I-III disease

Background: Tumor infiltrating lymphocytes (TILs) are strong prognostic biomarkers for early TNBC. We evaluated the role of CD8, FOXP3 and PD-L1 expression in refining prognostic models for non-metastatic TNBC in a large cohort of patients treated with standard therapy. Methods: Consecutive patients diagnosed with stage I-III TNBC (ER/PgR 20%) were all significantly associated with improved DFS (HR 0.36 95%CI 0.18-0.72, p=0.004 for CD8; HR 0.48 95%CI 0.28-0.80, p=0.005 for FOXP3; HR 0.52 95%CI 0.28-0.97, p=0.039 for PD-L1). FOXP3 and PD-L1 provided significant additional prognostic information beyond a model containing TILs and stage: likelihood ratio χ2 5.12, p=0.024 for FOXP3; likelihood ratio χ2 5.52, p=0.019 for PD-L1. CD8 did not add relevant prognostic information beyond TILs and stage (likelihood ratio χ2 2.76, p=0.097). Including both FOXP3 and PD-L1 did not add further prognostic information to models already containing TILs, stage and either FOXP3 or PD-L1. Conclusions: FOXP3 and PD-L1 expression evaluated with a software-assisted method were prognostic for stage I-III TNBC pts treated with standard therapy and may contribute to refine the prognostic stratification beyond stage and TILs. This study was supported by a grant from Merck KGaA. Citation Format: Maria Vittoria Dieci, Vassilena Tsvetkova, Gaia Griguolo, Federica Miglietta, Deborah Bacchin, Giulia Tasca, Carlo Alberto Giorgi, Enrico Cumerlato, Enrico Orvieto, Valentina Guarneri, Pierfranco Conte. Integrating CD8, FOXP3 and PD-L1 expression in prognostic models for triple negative breast cancer (TNBC): An analysis of 265 patients treated with standard therapy for stage I-III disease [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-06-14.