Expression of programmed death ligand-1 predicts poor outcome in nasopharyngeal carcinoma

Abstract

Programmed death ligand-1 (PD-L1) is a potentially important tumor immunotherapy target. However, whether PD-L1 expression is associated with survival in nasopharyngeal carcinoma (NPC) remains controversial. The aim of the present study was to investigate the association between PD-L1 expression and prognosis in NPC. The expression of PD-L1 was assessed in tumor specimens from 120 patients with NPC using immunohistochemistry. Staining was evaluated using the H-score method. The associations between PD-L1 expression and clinical characteristics and prognosis were analyzed. Overall, 78% of the patients had stage I-III and 22% had stage IV disease. The estimated 5-year overall survival (OS) and disease-free survival (DFS) rates for the entire cohort were 87.5 and 70.1%, respectively. PD-L1 expression was detected in 85 (71%) patients and was localized to the tumor cells. High tumor expression of PD-L1 (median H-score ≥5) was associated with significantly poorer OS (P=0.023) and DFS (P=0.002). Univariate analysis indicated that low PD-L1 expression was associated with better DFS compared with high PD-L1 expression (HR=0.163, 95% CI: 0.044-0.600, P=0.006 for DFS). Multivariate analysis revealed that T stage (HR=8.190, 95% CI: 1.355-18.152; P=0.023) and PD-L1 expression level (HR=0.124, 95% CI: 0.031-0.509; P=0.001) served as independent prognostic factors for DFS. In conclusion, tumor PD-L1 expression was found to be a significant prognostic factor in NPC, and high PD-L1 expression may be of prognostic value for recurrence and metastasis following conventional treatments.

Keywords: expression; nasopharyngeal carcinoma; prognosis; programmed death ligand-1.

Figure 1.

Representative images of immunohistochemical staining for programmed death ligand 1 (PD-L1) in nasopharyngeal carcinoma (NPC). (A) PD-L1 was expressed in the cell membrane of the primary tumor cells (magnification, ×40). (B and C) The PD-L1 protein was expressed in NPC cells, but not the surrounding normal nasopharyngeal epithelial cells (magnification, ×40). (D) PD-L1 was expressed in the germinal center of lymph nodes (magnification, ×40).

Figure 2.

Kaplan-Meier overall survival (OS) and disease-free survival (DFS) curves for the 62 patients eligible for survival analysis. (A) OS and (B) DFS curves for the 62 patients. (C) OS and (D) DFS curves for patients stratified by high and low PD-L1 expression. PD-L1, programmed death ligand 1.