title: Clinicopathological and prognostic significance of programmed cell death ligand 1 (PD-L1) expression in patients with esophageal squamous cell carcinoma: a meta-analysis.
abstract: BACKGROUND
  The clinicopathological and prognostic significance of programmed cell death ligand 1 (PD-L1) expression in patients with esophageal squamous cell carcinoma (ESCC) remains controversial. To investigate this question, we conducted a meta-analysis.
  
  
  METHODS
  A comprehensive literature search of electronic databases (up to July 10, 2016) was performed for relevant studies using multiple search strategies. Correlation between PD-L1 expression and clinicopathological features/overall survival (OS) was analyzed.
  
  
  RESULTS
  A total of 1,350 ESCC patients from eight studies were included. The pooled odds ratios (ORs) indicated that none of the clinicopathological characteristics was correlated with PD-L1 expression, including gender [OR =0.84; 95% confidence interval (CI): 0.59-1.18; P=0.31], histological differentiation (OR =1.33; 95% CI: 0.95-1.85; P=0.09), tumor depth (OR =0.66; 95% CI: 0.33-1.35; P=0.26), status of lymph node metastasis (OR =0.67; 95% CI: 0.30-1.52; P=0.34), distal metastasis (OR =0.66; 95% CI: 0.40-1.09; P=0.10) and tumor node metastasis (TNM) stage (OR =0.93; 95% CI: 0.49-1.75; P=0.82). The combined hazard ratio (HR) for OS showed a trend that overexpression of PD-L1 might be associated with the survival outcome of ESCC, though the difference was not statistically significant (HR =1.65; 95% CI 0.95-2.85; P=0.07).
  
  
  CONCLUSIONS
  Based on the published studies, PD-L1 overexpression in ESCC was not associated with common clinicopathological characteristics. PD-L1 might be a poor prognostic biomarker for ESCC. Further large-scale research should be performed to reveal the precise clinicopathological and prognostic significance of PD-L1 in ESCC by unified testing standard.
authors.affiliation: Department of Gastroenterology, Qingdao Municipal Hospital, School of Medicine, Qingdao University, Qingdao 266071, China.
authors.forename: Hai-Xia
authors.initials: HX
authors.lastname: Qu
authors.affiliation: Department of Gastroenterology, Qingdao Municipal Hospital, Qingdao 266071, China.
authors.forename: Li-Ping
authors.initials: LP
authors.lastname: Zhao
authors.affiliation: Department of Gastroenterology, Qingdao Municipal Hospital, Qingdao 266071, China.
authors.forename: Shu-Hui
authors.initials: SH
authors.lastname: Zhan
authors.affiliation: Department of Gastroenterology, Qingdao Municipal Hospital, Qingdao 266071, China.
authors.forename: Chang-Xin
authors.initials: CX
authors.lastname: Geng
authors.affiliation: Department of Gastroenterology, Qingdao Municipal Hospital, Qingdao 266071, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Xu
authors.affiliation: Department of Gastroenterology, Qingdao Municipal Hospital, School of Medicine, Qingdao University, Qingdao 266071, China.
authors.forename: Yong-Ning
authors.initials: YN
authors.lastname: Xin
authors.affiliation: Department of Gastroenterology, Qingdao Municipal Hospital, School of Medicine, Qingdao University, Qingdao 266071, China.
authors.forename: Xiang-Jun
authors.initials: XJ
authors.lastname: Jiang
keywords: Meta-analysis; esophageal squamous cell carcinoma (ESCC); prognosis; programmed cell death ligand 1 (PD-L1)