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-L1 in PDAC.Data sources: Electronic search of the Pub Med, Cochrane Library and Web of Science was performed until December 2016. Through database searches, we identified articles describing the relationship between PD-L1 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-L1 expression analysis. And 5 studies with 688 PDAC patients were included in the prognostic analysis. The PD-L1 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-L1 had significantly reduced OS(HR = 2.34;95% CI: 1.78–3.08). Subgroup analysis showed that the prognostic effect of PD-L1 levels was similar between the IHC and PCR methods. The PD-L1 positive rate was associated with PDAC T stages; the PD-L1 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-L1 expression levels predicted a poor prognosis in PDAC patients. Thus, PD-L1 status helps determine treatment in PDAC patients.