Association between serum level soluble programmed cell death ligand 1 and prognosis in patients with non-small cell lung cancer treated with anti-PD-1 antibody

Background Programmed cell death ligand 1 (PD-L1) is known to have soluble forms aside from its membrane-bound forms. The aim of this study was to evaluate the predictive and prognostic values of serum soluble PD-L1 (sPD-L1) in patients with non-small cell lung cancer (NSCLC) who were treated with anti-PD-1 antibody. Methods A total of 233 patients were enrolled in this study. We assessed the level of serum sPD-L1 before anti-PD-1 antibody treatment (pembrolizumab or nivolumab) and evaluated the correlation with PD-L1 expression on tumor cells, the response to anti-PD-1 antibody treatment, and patient outcome. Results The median serum sPD-L1 concentration was 67.7 (range, 25 to 223) pg/mL. A weak correlation between serum sPD-L1 and tumor PD-L1 expression was observed. The disease control rate in the high sPD-L1 group (>= 90 pg/mL) was significantly lower than that in the low sPD-L1 group (<90 pg/mL) (37% vs. 57%, P = 0.0158). The progression-free survival (PFS) and overall survival (OS) in the high sPD-L1 group were significantly shorter than those in the low sPD-L1 group (median PFS, 57 days vs. 177 days, P = 0.011; median OS, 182 days vs. not reached, P < 0.001). The high level of serum sPD-L1 was independently associated with a shorter PFS (hazard ratio [HR], 1.910; P = 0.061) and OS (HR, 2.073; P = 0.034) in multivariate analysis. Conclusions The serum sPD-L1 level, which was only weakly correlated with the tumor PD-L1 expression level, was an independent predictive and prognostic biomarker for NSCLC patients receiving anti-PD-1 antibody. Key points Significant findings of the study The disease control rate in the high sPD-L1 group was significantly lower than that in the low sPD-L1 group. The progression-free survival (PFS) and overall survival (OS) in the high sPD-L1 group were significantly shorter than those in the low sPD-L1 group. The high level of serum sPD-L1 was independently associated with a shorter PFS and OS in multivariate analysis. What this study adds This study demonstrated that serum sPD-L1 level was an independent predictive and prognostic biomarker for NSCLC patients receiving anti-PD-1 antibody.