Extended Follow‐Up Analysis of First‐Line Atezolizumab in Extensive‐Stage Small Cell Lung Cancer: A Real‐World Multicenter Prospective Cohort Study

Background We previously reported the short‐term real‐world effectiveness and safety of first‐line atezolizumab combined with chemotherapy in patients with extensive‐stage small cell lung cancer (ES‐SCLC). This study provides an updated analysis of the effectiveness, prognostic factors, and subsequent treatment patterns in first‐line immunochemotherapy. Methods This prospective multicenter observational study enrolled patients with ES‐SCLC, diagnosed at seven university hospitals throughout Korea, between June 2021 and August 2022. Primary outcomes were 1‐year overall survival (OS) and progression‐free survival (PFS), whereas secondary outcomes included OS, objective response rate, disease control rate, second progression‐free survival, and safety, evaluated based on established clinical guidelines. Results A total of 100 ES‐SCLC patients (median age, 69 years) were enrolled, with a median follow‐up duration of 26.0 months. The median PFS and OS were 6.2 and 17.1 months, respectively, with a 1‐year OS rate of 62.5%. Favorable prognostic factors for OS included partial response (PR) and stable disease (SD) as the best responses (SD: hazard ratio (HR), 0.79; PR: HR, 0.38) and a longer platinum‐free interval (HR 0.84). Brain radiotherapy significantly improved OS in patients with brain metastases, whereas thoracic radiotherapy during first‐line treatment tended to prolong survival in patients who responded to systemic treatment. Patients receiving second‐line treatment after progression presented a significantly longer OS than did those receiving only best supportive care. Conclusion This study outlined the real‐world effectiveness and safety of first‐line atezolizumab immunochemotherapy for ES‐SCLC patients over an extended follow‐up, noting that local treatment and post‐progression therapy were associated with improved survival.