The clinicopathological and prognostic significance of PD-L1 expression in pancreatic cancer: A meta-analysis

Background: Immunotherapy has shown promise against solid tumors. However, the clinical significance of programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1) in pancreatic ductal adenocarcinoma (PDAC) remains unclear. This meta-analysis aimed to analyze the prognostic effect of PD-Ll in PDAC. Data sources: Electronic search of the PubMed, Cochrane Library and Web of Science was performed until December 2016. Through database searches, we identified articles describing the relationship between PD-Ll status and PDAC patient prognosis. Meta-analysis was performed to investigate the relationship between PD-1 and overall survival (OS). Results: Nine studies with 989 PDAC patients were included for PD-Ll expression analysis. And 5 studies with 688 PDAC patients were included in the prognostic analysis. The PD-Ll positive rate measured by immunohistochemistry (IHC) was higher than that measured by polymerase chain reaction (PCR) (P < 0.001). PDAC patients with high expression levels of PD-Ll had significantly reduced OS (HR =2.34; 95% CI: 1.78-3.08). Subgroup analysis showed that the prognostic effect of PD-Ll levels was similar between the IHC and PCR methods. The PD-Ll positive rate was associated with PDAC T stages; the PD-Ll positive rate in the T3-4 group was higher than that in the T1-2 group (OR= 0.37; P=0.001). Conclusions: High PD-Ll expression levels predicted a poor prognosis in PDAC patients. Thus, PD-Ll status helps determine treatment in PDAC patients. (C) 2018 First Affiliated Hospital, Zhejiang University School of Medicine in China. Published by Elsevier B.V. All rights reserved.