Prognostic value of programmed cell death ligand (PD-L1) for hepatocellular carcinoma: a meta-analysis

The prognostic role of programmed death ligand-1 (PD-L1) expression in hepatocellular carcinoma (HCC) has been widely studied but the results are controversial. In this comprehensive meta-analysis, we elucidated the clinical value of PD-L1 in HCC. Relevant studies were systematically searched in the Cochrane Library, EMBASE, and PubMed until June 27, 2019. Eligible studies were validated for the prognostic effect of PD-L1 on the overall survival (OS), disease-free survival (DFS), and relapse-free survival (RFS) in HCC using a hazard ratio (HR) and its 95% confidence interval (95% CI). Twenty-three studies with 3529 patients were involved in this meta-analysis. The pooled results revealed that high membrane-bound PD-L1 (mPD-L1) expression was associated with poor OS (HR: 1.42; 95% CIl: 1.12-1.80; P = 0.004) and had no significant correlation with RFS (HR: 1.14; 95% CI: 0.85-1.54; P = 0.39), and DFS (HR: 1.36; 95% CI: 0.81-2.28; P = 0.25). The results also indicated that high soluble PD-L1 (sPD-L1) levels were associated with worse OS (HR: 2.93; 95% CI: 2.20-3.91; P = 0.00001). In addition, high mPD-L1 expression was associated with high alpha-fetoprotein levels (AFP; OR = 1.46; 95% CI: 1.16-1.84; P = 0.001), hepatitis (OR = 0.72; 95% CI: 0.54-0.98; P = 0.03), poor tumor differentiation (OR = 0.68; 95% CI: 0.55-0.84; P = 0.03), and tumor-infiltrating lymphocytes (OR = 3.39; 95% CI: 1.06-10.91; P = 0.04). The mPD-L1 expression had no significant correlation with age, number of tumors, gender, tumor size, liver cirrhosis, vascular invasion, tumor encapsulation, or TNM stage. The study revealed that high mPD-L1 expression in the tumor tissue and high sPD-L1 levels were associated with shorter OS in HCC. Moreover, overexpression of mPD-L1 was significantly associated with poor tumor differentiation, hepatitis, AFP elevation, and tumor-infiltrating lymphocytes.