PDCD1 and small cell lung carcinoma: Among the PD-1 inhibitors, nivolumab and pembrolizumab [29,30,31,32,33,34], and the PD-L1 inhibitors atezolizumab and durvalumab [21,31], are already approved by the U.S. Food and Drug Administration (FDA) for immunotherapy in SCLC, being currently recommended for disease therapy, according to NCCN guidelines.