Increased programmed death ligand-1 expression predicts poor prognosis in hepatocellular carcinoma patients

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.

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.

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.

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.