Real-world efficacy of atezolizumab combined with etoposide and platinum chemotherapy in extensive-stage small cell lung cancer: a retrospective cohort study.

Background: Small cell lung cancer (SCLC) is a highly aggressive thoracic malignancy for which immune checkpoint inhibitors (ICIs) combined with chemotherapy have become standard first-line therapy according to recent randomized clinical trials. However, real-world data on the efficacy of atezolizumab-based regimens remain limited, especially in patients with high tumor burden or brain metastases. The aim of this study was to evaluate the real-world effectiveness of atezolizumab plus etoposide and platinum (EP) chemotherapy compared to EP alone as first-line treatment in patients with extensive-stage SCLC (ES-SCLC). Methods: This retrospective cohort study included patients diagnosed with ES-SCLC at Tianjin Chest Hospital between January 2019 and December 2024. Eligible patients received either atezolizumab plus EP or EP chemotherapy alone as first-line treatment, with at least four completed cycles. Inverse probability of treatment weighting (IPTW) was used to balance the baseline covariates. The primary outcomes were overall survival (OS) and progression-free survival (PFS), which were analyzed with Kaplan-Meier curves and Cox proportional hazards models with robust variance estimation. Results: A total of 95 patients were included (42 in the atezolizumab group and 53 in the EP-only group). After IPTW adjustment, the combination group demonstrated improved OS as compared to the EP-only group [median 9.7 Conclusions: In this real-world cohort of patients with ES-SCLC, atezolizumab combined with EP chemotherapy was associated with improved survival outcomes as compared to EP alone, even in a clinically heterogeneous population. These findings support the broader applicability of immune-chemotherapy in routine practice and underscore the potential benefit for patients without brain metastases.