Abstract
PURPOSE: Anti-programmed cell death-1 (PD-1)/programmed cell death-ligand 1 (PD-L1) therapy has shown promise in tumor immunotherapy. Our objectives were to measure pre-treatment serum-soluble PD-L1 (sPD-L1) levels and to assess the relationships between sPD-L1 levels and clinical characteristics, prognosis, and tumor tissue PD-L1 expression in patients with hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). METHODS: Pre-treatment serum sPD-L1 levels were measured with an enzyme-linked immunosorbent assay (ELISA) in 81 patients with HBV-related HCC and compared to those in 49 healthy controls. The association between serum sPD-L1 levels and prognosis was assessed using survival analysis. The correlation between paired serum sPD-L1 levels and tumor PD-L1 expression (in resected tissue homogenates) was assessed in a separate group of 20 patients with HBV-related HCC. RESULTS: Median sPD-L1 concentration in patients with HBV-related HCC was 5.129 (range 0.140-12.391) ng/mL and in healthy controls was 0.836 (range 0.105-2.168) ng/mL (p < 0.001). On multivariate analysis, sPD-L1 levels were significant independent predictors of disease-free survival (hazard ratio [HR] 3.503; 95% confidence interval [CI], 1.559-7.871; p = 0.002) and overall survival (HR 3.399; 95% CI 1.308-8.831; p = 0.012). Positive correlation (r = 0.527, p = 0.017) between serum sPD-L1 and tumor PD-L1 expression was observed. Tumor expression of PD-L1 was significantly higher in those with serum sPD-L1 concentrations above vs. below the median level of 5.471 ng/ml (p = 0.012). CONCLUSIONS: In patients with HBV-related HCC, serum sPD-L1 concentrations were elevated, and positively correlated with tumor PD-L1 expression. Lower pre-treatment serum sPD-L1 levels were predictors of more favorable disease-free and overall survival. Serum sPD-L1 testing has a potential role in HBV-related HCC disease assessment, systemic therapy choices and survival prediction.