PDCD1 and small cell lung carcinoma: The results of the meta-analysis showed that the combination of PD-1/PD-L1 inhibitors significantly improved the OS (HR: 0.73, 95% CI: 0.66-0.80; <i>P</i><0.0001), prolonged PFS (HR: 0.66,95% CI: 0.55-0.79; <i>P</i><0.0001) and did not increase overall incidence of treatment-related adverse events (TRAEs) (RR: 1.03, 95% CI: 0.97-1.09; <i>P</i>=0.330) in ES-SCLC patients compared with chemotherapy alone.