Expression of Programmed Death Receptor Ligand 1 with High Tumor-Infiltrating Lymphocytes Is Associated with Better Prognosis in Breast Cancer

PURPOSE: The interaction of programmed death receptor 1 (PD-1) and its ligand, programmed death receptor ligand 1 (PD-L1), negatively regulates immune responses. This study aimed to clarify PD-L1 expression levels in breast cancer through immunohistochemistry (IHC) and to evaluate associations between these findings and clinicopathologic variables, including prognosis. METHODS: PD-L1 expression was analyzed using IHC on tissue microarrays of 465 invasive breast carcinomas. RESULTS: =0.003). CONCLUSION: PD-L1 protein expression in breast cancer is associated with better DFS and OS, but is not an independent prognostic factor. High PD-L1 expression was significantly associated with high TIL levels. This finding has important implications for antibody therapies targeting the PD-1/PD-L1 signaling mechanism in breast cancer.