In this review, we summarise studies conducted to assess the prevalence of PD-L1 expression on CTCs from patients with metastatic/non-metastatic NSCLC, evaluate the prognostic value of PD-L1 positive CTCs to inform risk stratification, and explore its utility as a predictive biomarker for selecting patients for immunotherapy. The gene discussed is CD274; the disease is non-small cell lung carcinoma.