Background: A complex interplay between immune cells and abnormal tumor vasculature in the tumor microenvironment has been previously shown in preclinical studies, while clinical data suggest that angiogenesis biomarkers may be useful as predictors of prognosis and treatment response in immunotherapy-treated solid tumors, including non-small cell lung cancer (NSCLC). Our primary aim was to investigate the prognostic and predictive value of baseline and post-treatment levels of serum vascular endothelial growth factor-A and –B (VEGF-A and VEGF-B, respectively), soluble programmed cell death-1 (sPD-1) and programmed cell death-ligand 1 (sPD-L1) in patients with advanced NSCLC treated with immune checkpoint inhibitors (ICIs). Methods: 55 patients with advanced NSCLC eligible to receive ICIs (as monotherapy or in combination with chemotherapy) were prospectively enrolled. A group of sex- and age-matched healthy controls (n=16) was also recruited, for determination of the optimal cut-offs and the potential diagnostic value of the examined biomarkers. Serum VEGF-A, VEGF-B, sPD-1 and sPD-L1 levels were measured in peripheral blood samples using ELISA, both at baseline and at the time of treatment response evaluation, and were correlated with treatment response, prognosis (PFS, OS), and the remaining clinicopathological features of patients. Results: Mean age of patients was 66.5 years (SD=8.0 years); 65,5% of patients received chemo-therapy and pembrolizumab combination while the remaining patients received pembrolizumab monotherapy. VEGF-B and sPD-1 levels were significantly decreased and increased, respectively, after treatment (p=0,028 and p