Prognostic value of programed death ligand 1 in patients with solid tumors: A meta-analysis

Background: A great deal of research have been performed to explore the prognostic value of programed death ligand 1 (PD-L1) in solid tumors in last decades. However, the results still remain inconsistent. To clarify a precise determinant of the clinical significance of PD-L1, we conducted a meta-analysis to evaluate the overall risk of PD-L1 on survival for patients with solid tumors. Materials and Methods: Related studies were identified through multiple search strategies from PubMed, Embase, and Cochrane databases. Data were collected from studies comparing overall survival (OS) in patients with positive PD-L1 and those having a negative expression. The meta-analysis was performed by Stata version 11.0 (Stata Corporation, College Station, TX, USA). The pooled hazard ratios (HRs) and 95% confidence intervals (95% CIs) were calculated employing fixed-or random-effects models depending on the heterogeneity of the included trials. Results: A total of 14 eligible studies involved 2916 patients were included in our meta-analysis. A summary HRs of all studies and subgroup HRs were calculated. The combined HRs suggested that a positive PD-L1 expression had an unfavorable impact on OS (1.67, 95% CI 1.30-2.16; P < 0.001). Similar results were also observed in subgroup analysis, according to tumor types, regions, patients' number, and publication year. Conclusion: With the available evidence, PD-L1 might serve as an efficient prognostic indicator in solid tumor and may represent the important new therapeutic target. More prospective studies are now needed to confirm the clinical utility of PD-L1 as an independent prognostic marker.