Prognostic significance of PD-L1 in solid tumor

BACKGROUND An increasing number of studies have examined the ability of programmed death-ligand 1 (PD-L1) to function as a marker for tumor prognosis. However, whether PD-L1 expression is a prognostic factor for the poor outcomes in many human cancers remains controversial. This study aims to investigate the prognostic role of PD-L1 expression through a meta-analysis update of 60 studies. METHODS The studies were identified by searching PubMed, Embase, Google Scholar, and Cochrane Library, and were assessed by further quality evaluation. The pooled hazard ratios (HRs) with 95% confidence intervals (CIs) for total and stratified analyses were calculated to investigate the association between the PD-L1 expression and the overall (OS) and disease-free (DFS) or progression-free survivals (PFS) of cancer patients. Heterogeneity and publication bias were also investigated. RESULTS The results indicated that PD-L1 overexpression can predict a poor OS (HR = 1.58, 95% CI = 1.38-1.81, P <.000) and DFS/PFS (HR = 1.72, 95% CI = 1.26-2.33, P = .001). Subgroup analyses showed that PD-L1 overexpression was significantly related to the poor OS in patients with breast (HR = 1.98, 95% CI = 1.15-3.41, P = .014), urothelial (HR = 2.24, 95% CI = 1.61-3.12, P <.000), renal (HR = 3.30, 95% CI = 2.23-4.86, P <.000), and gastric cancers (HR = 1.56, 95% CI = 1.02-2.37, P = .040). Furthermore, PD-L1 overexpresion was significantly associated with poor DFS/PFS in patients with hepatocellular carcinoma (HCC) (HR = 1.72, 95% CI = 1.21-2.46, P = .003), melanoma (HR = 3.39, 95% CI = 2.02-5.69, P <.000), and renal carcinoma, (HR = 5.04, 95% CI = 2.87-8.86, P <.000). The adverse prognostic impact of PD-L1 was observed in patients of different ethnicities. CONCLUSIONS The findings of this meta-analysis suggest the correlation of PD-L1 overexpression with worse OS in patients with solid tumors. However, the correlations differed according to tumor types.