Aims of the present study were 1) to investigate PD-L1 expression in CTCs isolated from patients with NSCLC treated with the PD-L1 inhibitor Nivolumab 2) to monitor any change in PD-L1(+) CTCs during the course of treatment and 3) to clarify whether PD-L1(+) CTCs might represent a predictive biomarker to anti-PD-1 directed therapies. Here, PDCD1 is linked to non-small cell lung carcinoma.