Impact of EGFR Mutation Subtypes on Response to Chemoimmunotherapy and Chemotherapy in Non-Small-Cell Lung Cancer After EGFR-TKI Failure

Background: The efficacy of immune checkpoint inhibitor (ICI) monotherapy on non-small-cell lung cancer (NSCLC) varies by epidermal growth factor receptor (EGFR) mutation subtypes. However, the impact of these subtypes on the clinical outcomes of chemoimmunotherapy (Chemo+ICI) or platinum-based chemotherapy (Chemo) in real-world practice remains unclear. Objective: This study evaluated the impact of EGFR mutation subtypes on NSCLC treatment outcomes of Chemo and Chemo+ICI. Patients and Methods: We retrospectively analyzed patients with advanced or recurrent EGFR-mutant NSCLC from 20 institutions between January 2017 and July 2022. Patients received Chemo with or without ICI after failure of EGFR-tyrosine kinase inhibitors. Common EGFR mutations were categorized as exon 19 deletions and exon 21 L858R mutations. Results: Among the 403 patients, 205 (50.9%) had exon 19 deletions, and 198 (49.1%) had L858R mutations. For patients with L858R mutations, Chemo+ICI significantly improved progression-free survival (PFS) compared with Chemo (7.0 vs 5.3 months; p = 0.04). However, no significant difference in PFS was observed between treatments for patients with exon 19 deletions (6.7 vs 6.0 months; p = 0.96). Multivariate analysis identified Chemo+ICI as an independent predictor of PFS in patients with L858R mutations (hazard ratio 0.63; 95% confidence interval 0.43–0.92; p = 0.02). Conclusions: Among patients with common EGFR mutation subtypes, those with L858R mutations demonstrated significantly improved PFS with Chemo+ICI than with Chemo. These findings suggest that Chemo+ICI may offer a more effective treatment option for patients with L858R-mutant NSCLC, warranting further investigation in prospective studies.