Abstract
BACKGROUND: The prognostic significance of circulating soluble programmed death ligand-1 (sPD-L1) in patients with solid tumors remains unclear. We performed a meta-analysis to address this issue. METHODS: Several electronic databases were searched from January 1970 to May 2017. The hazard ratios (HRs) and 95% confidence interval (95% CI) were calculated to determine the relationship between the level of soluble PD-L1 in peripheral blood and patient overall survival. RESULTS: A total of 1040 patients with solid tumors from 8 eligible studies were included in the present meta-analysis. The pooled HR suggested that a high level of soluble PD-L1 (sPD-L1) in peripheral blood was significantly correlated with a worse overall survival (HR = 2.26, 95% 1.83-2.80, Z = 7.51, P < .001). CONCLUSION: The present meta-analysis demonstrated that a high level of soluble PD-L1 in peripheral blood significantly predicts poor prognosis in patients with solid tumors, suggesting that high level of sPD-L1 may serve as a predictive biomarker for poor prognosis.