Programmed death ligand-1 expression and its prognostic role in esophageal squamous cell carcinoma

AIM: To investigate the expression and prognostic role of programmed death ligand-1 (PD-L1) in locally advanced esophageal squamous cell carcinoma (ESCC). METHODS: A total of 200 patients with ESCC who underwent radical esophagectomy with standard lymphadenectomy as the initial definitive treatment in Seoul National University Hospital from December 2000 to April 2013 were eligible for this analysis. Tissue microarrays were constructed by collecting tissue cores from surgical specimens, and immunostained with antibodies directed against PD-L1, p16, and c-Met. Medical records were reviewed retrospectively to assess clinical outcomes. Patients were divided into two groups by PD-L1 status, and significant differences in clinicopathologic characteristics between the two groups were assessed. RESULTS: Tumor tissues from 67 ESCC patients (33.5%) were PD-L1-positive. Positive p16 expression was observed in 21 specimens (10.5%). The H-score for c-Met expression was ≥ 50 in 42 specimens (21.0%). Although PD-L1-positivity was not significantly correlated with any clinical characteristics including age, sex, smoking/alcoholic history, stage, or differentiation, H-scores for c-Met expression were significantly associated with PD-L1-positivity (OR = 2.34, 95%CI: 1.16-4.72, P = 0.017). PD-L1 expression was not significantly associated with a change in overall survival (P = 0.656). In contrast, the locoregional relapse rate tended to increase (P = 0.134), and the distant metastasis rate was significantly increased (HR = 1.72, 95%CI: 1.01-2.79, P = 0.028) in patients with PD-L1-positive ESCC compared to those with PD-L1-negative ESCC. CONCLUSION: PD-L1 expression is positively correlated with c-Met expression in ESCC. PD-L1 may play a critical role in distant failure and progression of ESCC.