PDCD1 and small cell lung carcinoma: With the Food and Drug Administration (FDA) approval of carboplatin, etoposide, and the anti-programmed death-ligand-1 (PD-L1) antibodies atezolizumab or durvalumab, as first-line therapy options, and the anti-programmed cell death protein-1 (PD-1) antibodies pembrolizumab and nivolumab as monotherapies in third-line settings, ES-SCLC treatment has entered the era of immunotherapy (9, 10).