Relationship between immune‐related adverse events and treatment effectiveness in extensive disease small cell lung cancer

Abstract Background This study aimed to assess the relationship between immune response adverse events (irAEs) and treatment efficacy in patients with extensive disease small cell lung cancer (ED‐SCLC). Methods We retrospectively evaluated the clinical effects in 40 ED‐SCLC patients who had received immune‐checkpoint inhibitors (ICIs), platinum agents, and etoposide between September 2019 and September 2021. We identified and compared patients belonging to two groups: irAE and non‐irAE. Results Fifteen patients experienced irAEs, and 25 did not. The median progression‐free survival in patients with irAE was longer than that in patients without irAE (12.6 months [95% CI: 6.3–19.3 months] vs. 7.2 months [95% CI: 5.8–7.9 months], p = 0.0108). However, the median overall survival (OS) was similar between irAE and non‐irAE groups (27.6 months [95% CI: 15.4–NA] vs. 24.9 months [95% CI: 13.7–NA], p = 0.268). Seven (46.7%) in the irAE group and 20 (80%) in the non‐irAE group received sequential therapy. The median OS was prolonged in patients who received first‐ and second‐line therapy than in those who received first‐line therapy alone (27.6 months [95% CI: 19.2–NA] vs. 6.6 months [95% CI: 0.3–NA], p = 0.053). Grade ≧ 3 irAEs occurred in five (12.5%) patients. Among them, grade 5 irAEs were observed in two patients, including exacerbation of polymyositis and pulmonary arterial embolism. Conclusion In this study, the development of irAEs did not affect OS in patients with ED‐SCLC who received platinum‐based agents, etoposide, or ICI therapy. We determined that managing irAEs and administering first‐ and second‐line therapies could contribute to prolonged OS.