Real-World Comparative Survival Outcomes of First-Line Serplulimab Plus Chemotherapy in Extensive-Stage Small-Cell Lung Cancer: A Single-Center Retrospective Cohort Study

Background: Extensive-stage small-cell lung cancer (ES-SCLC) remains an aggressive malignancy with poor survival despite platinum-etoposide chemotherapy.Although serplulimab plus chemotherapy has demonstrated a survival benefit in randomized trials, comparative real-world evidence remains limited.We therefore evaluated survival outcomes with first-line serplulimab plus chemotherapy versus chemotherapy alone in patients with ES-SCLC. Methods:We conducted a single-center retrospective cohort study at Tianjin Chest Hospital.Patients with ES-SCLC who initiated first-line platinum-etoposide-based chemotherapy between January 2020 and December 2024 were screened, with follow-up censored on May 1, 2025.Patients were classified according to whether serplulimab was incorporated into first-line treatment.The primary endpoint was overall survival (OS), and the secondary endpoint was real-world progression-free survival (rwPFS).Treatment effects were estimated using Kaplan-Meier analyses and Cox proportional hazards models.Because of the limited sample size and event count, the primary adjusted Cox model was restricted to prespecified clinical covariates.Sensitivity analyses included treatment-year adjustment, restriction to patients treated during 2022-2024, reduced propensity score overlap weighting, and stabilized trimmed inverse probability of treatment weighting (IPTW).Results: The final cohort included 112 patients, of whom 30 received serplulimab plus chemotherapy and 82 received chemotherapy alone.Median OS was 18.69 months with serplulimab plus chemotherapy and 11.86 months with chemotherapy alone (HR = 0.49, 95% CI: 0.27-0.90;P = 0.021; log-rank P = 0.017).The association remained significant after parsimonious clinical adjustment (adjusted HR = 0.50, 95% CI: 0.27-0.93;P = 0.028).Sensitivity analyses yielded directionally similar OS estimates across treatment-year adjustment, 2022-2024 restriction, overlap weighting, and stabilized trimmed IPTW.Median rwPFS was also numerically longer with serplulimab plus chemotherapy, although the difference was not statistically significant (10.64 vs 8.18 months; HR = 0.76, 95% CI: 0.48-1.20;P = 0.244).Conclusions: In this single-center real-world cohort, first-line serplulimab plus chemotherapy was associated with longer OS than chemotherapy alone in patients with ES-SCLC, whereas the rwPFS difference was not statistically significant.The findings were directionally supported by multiple sensitivity analyses but should be interpreted cautiously because of the limited sample size, potential calendar-time confounding, and incomplete standardized safety assessment.Larger prospective studies are needed for confirmation.