e15512 Background: Programmed death ligand 1 (PD-L1) expression has become a promising biomarker in predicting the efficacy of immune checkpoint inhibitors in various advanced cancers, including gastric cancer (GC). However, the prognostic value and clinicopathological significance of PD-L1 in GC is still not clearly identified. Hence, we carried out a meta-analysis to investigate the potential role of PD-L1 in GC, expecting to provide new clues for the judgement of prognosis in resected gastric cancer. Methods: A literature search strategy was performed from the PubMed, Web of Science, EMBASE, and the Cochrane Library database as of December 1, 2018. Relevant data was rigorously extracted from the included literatures. Hazard ratios (HRs) and Odds ratios (ORs) along with 95% confidence intervals (95% CIs) were used to evaluate the prognostic value or clinicopathological significance of PD-L1 expression in GC. Results: A total of 21 studies containing 6021 patients fitted into our meta-analysis. The pooled HRs indicated that PD-L1 high-expression accompanied with a worse overall survival (OS) (HR=1.28, 95% CI: 1.01-1.62, P=0.04) in GC, while no correlation with disease-free survival (DFS) (HR=0.88, 95%CI: 0.53-1.45, P=0.61). Subgroup analysis showed that PD-L1 high-expression was negatively associated with distant metastasis groups (OR=0.66, 95%CI:0.48-0.89, P=0.01), but was positively related to elderly(OR=1.19, 95%CI: 1.01-1.40, P=0.04), lymph-node metastasis(OR=1.63, 95%CI: 1.08-2.46, P=0.02), deeper tumor infiltration(OR=1.73, 95%CI: 1.08-2.79, P=0.02), Epstein-Barr virus infection positive (EBV+) (OR=8.01, 95%CI: 3.10-20.72, P<0.0001), and MET positive (MET+) groups (OR=1.78, 95%CI: 1.05-3.00, P=0.03). Conclusions: Our meta-analysis found that the high-expression of PD-L1 accompanied with a poor OS. Moreover, PD-L1 high-expression was related to age, lymph-node metastasis, depth of infiltration, distant metastasis, EBV infection, and MET status.
