Real-world long-term efficacy of chemoimmunotherapy in advanced stage small cell lung cancer

Introduction: Since IMPOWER-133 and CASPIAN phase 3 trials, chemoimmunotherapy has become the first-line systemic treatment for advanced stage small-cell lung carcinoma (SCLC). We conducted a study on the long-term efficacy. Methods: A retrospective cohort study was performed on advanced stage SCLC patients who initiated treatment with first-line carboplatin-etoposide-atezolizumab between January 2018 and December 2022 at the University Hospitals Leuven. Follow-up data were collected until February 2025. The Kaplan Meier method was used for estimating survival outcomes, and Cox regression models were used to assess the association between baseline clinical characteristics (age, ECOG Performance Status, metastatic sites, s-albumin, s-LDH, s-CRP, s-NSE, Neutrophil-Lymphocyte Ratio (NLR), modified Glasgow Prognostic Score (mGPS) and LIPI score) and survival outcomes. Results: A total of 74 patients were included. The median progression-free survival (PFS) was 4.8 months (95%CI 4.5-5.0) and median overall survival (OS) was 11.5 months (95%CI 8.9-14.6). The 1-year, 2-year and 5-year PFS and OS rates were 16.2% (95%CI 8.9-25.5), 9.5% (95%CI 4.2-17.4) and 8.1% (95%CI 3.3-15.7), and 47.3% (95%CI 35.6-58.1), 18.9% (95%CI 11.0-28.5) and 8.9% (95%CI 3.2-18.2%), respectively. In multivariable analysis, bone metastasis (HR 2.21; 95%CI 1.26-3.87), age (+1yr, HR 1.03; 95%CI 1.00-1.07), s-NSE >250 µg/L (HR 4.55; 95%CI 2.13-9.72), and s-albumin ≥35g/dl (HR 0.49; 95%CI 0.25-0.99) were significantly associated with OS. During induction phase, chemotherapy dose reduction and discontinuation occurred in 31% and 8%, respectively. Overall, irAEs occurred in 21 patients (28%) leading to discontinuation of atezolizumab in 7 patients (10%). Conclusion: Our study provides long-term safety and efficacy outcomes of first-line chemoimmunotherapy in a real-world cohort of advanced stage SCLC. In multivariable analysis, we found that baseline conventional biomarkers (age, bone metastasis, s-albumin, and s-NSE) did significantly predict overall survival, while systemic inflammation scores (NLR, mGPS and LIPI) did not.