Historical cohort
Using the electronic medical record system of Peking Union Medical College Hospital, ES-SCLC patients who received ICIs combined with chemotherapy as the first-line treatment were retrospectively reviewed. Among them, patients who received EP/EC combined with PD-L1 blockades (atezolizumab or durvalumab) were selected as the historical control. Information of baseline characteristics, treatment pattern, efficacy and safety profiles of patients were reviewed.