Expression of PD-L1 Attenuates the Positive Impacts of High-level Tumor-infiltrating Lymphocytes on Prognosis of Triple-negative Breast Cancer

Background: Among all breast cancer subtypes, triple-negative breast cancer (TNBC) has aggressive clinical manifestations including more frequent relapses and metastases. The roles of PD-L1 expression and tumor-infiltrating lymphocytes (TILs) in TNBC clinicopathological behaviors and patients’ survival outcomes remain unclear. Methods: TNBC (108 cases) patients with at least 5-year follow-up were analyzed for PD-L1 expression and TILs by immunohistochemistry. We also analyzed the relationships between PD-L1 expression, TILs and clinicopathological characteristics. Furthermore, we explored the effect of PD-L1 expression and TILs on prognosis as illustrated by disease-free survival (DFS). Results: The expression of PD-L1 was related to more aggressive clinicopathological behaviors in TNBC patients including a larger tumor size, higher incidence of PL-1-ALN, more frequent distant metastasis, and a reduced disease-free survival. In contrast, patients with high-level TILs showed less aggressive disease progression hence a better prognosis compared to patients with low-level TILs. Among patients with high-level TILs, PD-L1 expression was correlated with adverse prognosis. Conclusions: Expression of PD-L1 and low-level TILs in TNBC patients were associated with adverse clinical outcomes. However, the positive impact of high-level TILs was attenuated by PD-L1 expression. Our results suggest potential biomarkers for a selection of indicated cases in the TNBC patients for anti-PD-L1/anti-PD1 immunotherapy.