Programmed cell death-ligand 1 expression and its prognostic significance in completely resected primary small cell carcinoma of esophagus

Background: Programmed cell death-ligand-1 (PD-L1) has been highly up-regulated in various malignancies. The present study was intended to explore the frequency of PD-L1 expression and understand its role as a prognostic factor for overall survival in primary small cell carcinoma of esophagus (SCCE). Methods: Immunohistochemistry was employed for evaluating the expression of PD-L1 in 78 specimens of SCCE at Zhejiang Cancer Hospital. Tumors with staining in over 5% of tumor cells were scored as positive for PD-L1 expression. Survival outcome was evaluated by the Kaplan-Meier method and multivariate regression was performed with a Cox proportional hazard model. Results: PD-L1 expression was detected in 53.8% (42/78) of all patients and it was not correlated with gender (P=0.34), age (P=0.39), stage (P=0.87), smoking history (P=0.34), lymph node metastasis (P=0.56), tumor length (P=0.49) or histology (P=0.13). Their median disease-free and overall survivals were 13.0 and 27.5 months, respectively. The median disease-free survivals in PD-L1 positive and negative SCCE patients were 19.0 and 8.8 months, respectively (P=0.001). The median overall survival was longer in PD-L1 expression positive patients than that in negative counterparts (34.0 vs. 21.0 months, P=0.019). Multivariate analyses indicated PD-L1 was a significant prognostic factor for more favorable survival (HR=0.85; P=0.041). Conclusions: Over half of SCCE patients expressed PD-L1 and its positive expression was associated with more favorable survival.