title: Increased programmed death ligand-1 expression predicts poor prognosis in hepatocellular carcinoma patients.
abstract: OBJECTIVE
  Accumulating studies have investigated the prognostic and clinical significance of programmed death ligand-1 (PD-L1) expression in patients with hepatocellular carcinoma (HCC); however, the results were conflicting and inconclusive. We conducted a meta-analysis to combine controversial data to precisely evaluate this issue.
  
  
  METHODS
  Relevant studies were thoroughly searched on PubMed, Web of Science, and Embase until April 2016. Eligible studies were evaluated by selection criteria. Hazard ratio (HR) with 95% confidence interval (CI) was used to estimate the prognostic role of PD-L1 for overall survival (OS) and disease-free survival (DFS)/recurrence-free survival (RFS). Odds ratio (OR) with 95% CI were selected to assess the relationship between PD-L1 and clinicopathological features of HCC patients. Publication bias was tested using Begg's funnel plot.
  
  
  RESULTS
  A total of seven studies published from 2009 to 2016 were included for meta-analysis. The data showed that high PD-L1 expression was correlated to shorter OS (HR =2.09, 95% CI: 1.66-2.64, P<0.001) as well as poor DFS/RFS (HR =2.3, 95% CI: 1.46-3.62, P<0.001). In addition, increased PD-L1 expression was also associated with tumor differentiation (HR =1.51, 95% CI: 1-2.29, P=0.05), vascular invasion (HR =2.16, 95% CI: 1.43-3.27, P<0.001), and α-fetoprotein (AFP; HR =1.46, 95% CI: 1-2.14, P=0.05), but had no association with tumor stage, tumor size, hepatitis history, sex, age, or tumor multiplicity. No publication bias was found for all analyses.
  
  
  CONCLUSIONS
  This meta-analysis revealed that overexpression of PD-L1 was predictive for shortened OS and DFS/RFS in HCC. Furthermore, increased PD-L1 expression was associated with less differentiation, vascular invasion, and AFP elevation.
authors.affiliation: Department of Radiation Oncology, Peking University First Hospital, Peking University, Beijing, People's Republic of China.
authors.forename: Xiaobin
authors.initials: X
authors.lastname: Gu
authors.affiliation: Department of Radiation Oncology, Peking University First Hospital, Peking University, Beijing, People's Republic of China.
authors.forename: Xian-Shu
authors.initials: XS
authors.lastname: Gao
authors.affiliation: Department of Oncology, Tangshan People's Hospital, Hebei, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Xiong
authors.affiliation: Graduate School of Medicine, Hebei North University, Zhangjiakou, Hebei, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Guo
authors.affiliation: Graduate School of Medicine, Hebei North University, Zhangjiakou, Hebei, People's Republic of China.
authors.forename: Linjun
authors.initials: L
authors.lastname: Han
authors.affiliation: Department of Radiation Oncology, Peking University First Hospital, Peking University, Beijing, People's Republic of China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Bai
authors.affiliation: Department of Radiation Oncology, Peking University First Hospital, Peking University, Beijing, People's Republic of China.
authors.forename: Chuan
authors.initials: C
authors.lastname: Peng
authors.affiliation: Department of Radiation Oncology, Peking University First Hospital, Peking University, Beijing, People's Republic of China.
authors.forename: Ming
authors.initials: M
authors.lastname: Cui
authors.affiliation: Department of Radiation Oncology, Peking University First Hospital, Peking University, Beijing, People's Republic of China.
authors.forename: Mu
authors.initials: M
authors.lastname: Xie
keywords: hepatocellular carcinoma; meta-analysis; prognosis; programmed death ligand-1