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 <5% negative). Results: Median follow-up period was 34 months (range = 1 - 188). 1 and 2 years survival rate were found as 75% and 63% in PD-L1 negative TIICs group (47%), and 85% and 83% in PD-L1 positive TIICs group (53%), respectively. PD-L1 positivity in immune cells (ICs) was detected in 53% of the patients. The survival rate was found better in the PD- L1 positive group compared to the negative group (P = 0.049). Discussion: In conclusion, the survival rate was found significantly better in the PD-L1 positive TIICs group, compared to the negative group.