Abstract
BACKGROUND: There is limited evidence concerning real-world efficacy of second-line (2L) treatment with immune checkpoint inhibitors (ICIs) in extensive-stage small-cell lung cancer (ES-SCLC). In this study, we evaluated the efficacy of 2L-ICIs therapy in patients with ES-SCLC. METHODS: In this retrospective study, we included patients with ES-SCLC who experienced disease progression following first-line (1L) therapy and received 2L treatment between March 2019 and December 2023. The primary endpoint of this study was progression-free survival (PFS), and the secondary endpoints included safety, the objective response rate (ORR), the disease control rate (DCR), and overall survival (OS). Survival analyses were conducted using Kaplan-Meier curves. One-to-one propensity score matching (PSM) was used to reduce confounding. Univariate and multivariate Cox regression analyses were conducted to identify factors associated with PFS and OS. RESULTS: We included 496 patients in this study; among them, 200 patients were in the 2L-ICIs group and 296 patients were in the 2L-non-ICIs group. The 2L-ICIs group demonstrated significantly longer PFS than the 2L-non-ICIs group (median PFS: 4.14 vs. 2.84 months; p < 0.001), and this benefit persisted after PSM (median PFS: 4.21 vs. 2.87 months; p < 0.001). The 2L-ICIs group also had a significantly higher ORR (ORR: 29.5% vs. 10.1%; p < 0.001) and DCR (DCR: 67.0% vs. 51.7%; p < 0.001). Treatment-related adverse events were comparable between the groups, with only one grade 3 rash reported in the 2L-ICIs group. Multivariate Cox regression identified liver metastases, the number of metastatic lesions, and the 1L-PFS as independent predictive factors for PFS. CONCLUSION: In this study, 2L-ICIs demonstrate significant clinical benefits with acceptable toxicity in ES-SCLC patients who progressed after 1L therapy, supporting their use as a clinically actionable option.