PD-L1 expression in immune cells is a favorable prognostic factor for nasopharyngeal carcinoma

Background: Programmed death-ligand 1 (PD-L1) has been determined as a reliable prognostic factor for various malignancies. In this study, we aimed to determine the prognostic effect of PD-L1 expression in tumor-infiltrating immune cells (TIICs) of nasopharyngeal carcinoma (NPC) patients. Methods: Seventy patients diagnosed with non-metastatic NPC were included in the study. PD-L1 expression on immune cells was analyzed by immunohistochemical method. Patients were categorized into two groups according to the PD-L1 expression level in TIICs (level of PD-L1 staining ≥5% positive vs