Comparative Clinical Outcomes Between EGFR Ex20ins and Wildtype NSCLC Treated with Immune Checkpoint Inhibitors

The activity of immune checkpoint inhibitors (ICIs) in NSCLC harboring EGFR exon 20 insertion mutations (ex20ins) has not been extensively studied. In this real-world analysis, patients with EGFR ex20ins NSCLC had shorter median time to next therapy after first ICI treatment than patients with wildtype NSCLC, suggesting that ICIs may not be effective in EGFR ex20ins NSCLC. Introduction: The activity of immune checkpoint inhibitors (ICIs) in NSCLC harboring EGFR exon 20 insertion mutations (ex20ins) has not been closely examined due to the frequent exclusion of patients with EGFR mutations from large immunotherapy-based NSCLC trials. Patients and Methods: A real-world, retrospective study was conducted to compare outcomes of ICI-treated patients with EGFR ex20ins and wildtype NSCLC (wt-NSCLC; defined as EGFR and ALK test negative). Patients with advanced NSCLC from the Flatiron Health database (2015-2020) were included in the analysis. Real-world time to next therapy (rwTTNT) and overall survival (rwOS), stratified by ICI initiation line of therapy, were the prespecified primary and secondary endpoints, respectively. Results: Among 59 patients with EGFR ex20ins NSCLC and 5365 with wt-NSCLC, ICI treatment was received as first-line therapy in 25% and 39%, respectively. Patients with EGFR ex20ins had a 58% increased risk of shorter time to next-line therapy compared with wt-NSCLC (adjusted hazard ratio of 1.58 [95% confidence interval [CI], 1.2-2.1]; P =.0012). The median rwTTNT for first ICI line was 3.7 months (95% CI, 3.0-4.9) for EGFR ex20ins NSCLC compared with 5.8 months (95% CI, 5.6-6.0) for wt-NSCLC. No meaningful difference in rwOS between the groups was observed. Conclusions: ICI therapy may be less effective for patients with EGFR ex20ins compared with wt-NSCLC. Consistent with prior data on exon 19 deletion and L858R substitution, tumors harboring ex20ins appear to be less responsive to immune checkpoint inhibition than wt-NSCLC.