High PD-L1 Expression Is Closely Associated With Tumor-Infiltrating Lymphocytes and Leads to Good Clinical Outcomes in Chinese Triple Negative Breast Cancer Patients

Background: To investigate the role of Programmed death ligand 1 (PD-L1) expression and tumor-infiltrating lymphocytes (TILs) in tumor recurrence and metastasis of Chinese patients suffering from triple negative breast cancer (TNBC). Methods: PD-L1 immunohistochemistry was performed on 215 TNBCs. Also, the prevalence of TILs correlated the expression of PD-L1 and TILs with clinical outcomes. Kaplan-Meier and the model analyses of univariate Cox proportional hazards were utilized to compare the survival of patients with positive PD-L1 expression with those with negative PD-L1 expression. Results: The median follow-up time was 67.7 months (range: 7-159 months). PD-L1-positive breast cancer patients had significantly longer disease-free survival (DFS) and Overall survival (OS) compared with PD-L1-negative patients (P=0.046; P=0.019) in TNBC. The presence of increased stromal lymphocytic infiltrates (STILs) was significantly associated with overall survival (P=0.026). The model analysis of univariate Cox proportional hazards showed that PD-L1 and STILs were independent prognostic factors for tumor prognosis. Conclusions: Our study found that high levels of PD-L1 could be expressed in TNBC, which was correlated with the prevalence of TILs.