In the first-line treatment of ES-SCLC, IMpower133 and CASPAIN studies have demonstrated the survival benefit of PD-L1 inhibitor atezolizumab or durvalumab plus chemotherapy, while KEYNOTE-604 study of PD-1 inhibitor pembrolizumab plus chemotherapy only showed a PFS benefit but failed to show an OS benefit (5–8, 19). This evidence concerns the gene PDCD1 and small cell lung carcinoma.