Abstract:Objective To investigate the choice between chemotherapy and combined immunotherapy in second-line treatment for extensive-stage small cell lung cancer. Methods A retrospective analysis was conducted on the medical records of 117 patients with extensive-stage small cell lung cancer who underwent second-line treatment at Jiangsu Cancer Hospital from November 30, 2018 to November 30, 2023. Based on their second-line treatment choices, the study cases were divided into a chemotherapy group (n=79) and a combined immunotherapy group (n=38). Adverse events were assessed using the Common Terminology Criteria for Adverse Events v5.0, and efficacy was evaluated according to the Response Evaluation Criteria in Solid Tumors (RECIST) v1.1. The Kaplan-Meier method and Cox proportional hazards regression analysis were used to estimate progression-free survival (PFS) and overall survival (OS), which were compared using the log-rank test. Results The median OS in the chemotherapy group was 7.9 months (95%CI: 6.9-8.9), compared to 8.3 months (95%CI: 7.7-10.3) in the combined immunotherapy group, with a statistically significant difference between the two groups (P＜0.05). The median PFS was 3.9 months (95%CI: 3.3-4.6) in the chemotherapy group and 5.0 months (95%CI: 3.8-6.2) in the combined immunotherapy group, with no statistically significant difference between the two groups (P＞0.05). The incidence of grade 3-4 toxicity was similar between the two groups (20.2% vs 18.4%; χ2=0.050, P=0.815). Conclusion For patients whose disease has progressed after first-line platinum based doublet therapy, the use of immunotherapy combined with chemotherapy in the second-line can prolong their OS.