Establishing peripheral PD-L1 as a prognostic marker in hepatocellular carcinoma patients: how long will it come true?

Abstract

The prognostic role of intratumoral programmed cell death ligand 1 (PD-L1) expression in hepatocellular carcinoma (HCC) has been investigated by several meta-analyses. However, the prognostic value of pretreatment peripheral PD-L1 (PPPD-L1) level in HCC remains undetermined. Thus, this systemic review aimed to establish PPPD-L1 as a new prognostic marker in HCC according to available evidence. Case-control studies investigating the prognostic role of PPPD-L1 in HCC were systemically sought in the database of PubMed and Web of Science until March 25th, 2020. Our main concern is survival results, including overall survival (OS), disease-free survival (DFS), and progression-free survival (PFS). The combined results were summarized in narrative form according to data extracted from each included study. Finally, nine studies published from 2011 to 2019, were incorporated into this systemic review. Among these, six studies evaluated the PD-L1 expression by enzyme-linked immunosorbent assay (ELISA) from blood serum, and three studies evaluated the PD-L1 expression by flow cytometric analysis from peripheral blood mononuclear cells (PBMC). According to the extracted evidence, high PPPD-L1 expression, measured in either blood serum or PBMC, is associated with poor OS, poor DFS, and poor PFS. Meanwhile, PPPD-L1 was also correlated with enlarged tumor size and more likely with advanced tumor stage as well as vascular invasion. High PPPD-L1 level is associated with increased mortality rate and increased recurrence rate in HCC. As a convenient serum marker, PPPD-L1 could be a promising marker of prognosis in HCC patients.