PDCD1 and small cell lung carcinoma: In this regard, immunotherapy targeting programmed cell death-1 (PD-1) and programmed cell death-ligand 1 (PD-L1) has markedly improved the overall survival (OS) of patients, not only in those with metastatic NSCLC, but also in patients with locally advanced disease and extensive-stage small-cell lung cancer [8,9,10,11,12,13].