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Background: Treatment with epidermal growth factor receptor (EGFR)‐tyrosine kinase inhibitors (TKIs) leads to initial response in most patients with EGFR‐mutated non‐small cell lung cancer (NSCLC). In contrast, little is known of the subpopulation of patients with NSCLC with EGFR mutations who exhibit clinical outcomes that require treatment with immune checkpoint inhibitors (ICIs). Therefore, to identify eligible cases to treat with ICIs, we retrospectively analyzed the correlation between clinical features and the efficacy of ICIs in patients with EGFR mutations. Patients and Methods: We retrospectively analyzed patients with advanced NSCLC harboring EGFR mutations who were treated with ICIs after developing resistance to EGFR‐TKIs between February 2016 and April 2018 at 6 institutions in Japan. The association between clinical outcomes and the efficacy of ICIs was investigated. Results: We enrolled 27 patients who harbored EGFR‐activating mutations. The objective response and disease control rates were higher in patients with uncommon EGFR mutations than in those with common EGFR mutations (71% vs 35.7% and 57% vs 7%, P = 0.14 and P < 0.01, respectively). Patients with uncommon EGFR mutations or without T790M mutations exhibited a significantly longer median progression‐free survival than those with common EGFR mutations or with T790M mutations (P = 0.003 and P = 0.03, respectively). Conclusion: Patients with uncommon EGFR mutations and without T790M mutations are associated with the best outcomes for treatment with immunotherapy among those with EGFR‐mutated NSCLC, based on retrospective analysis. Further research is needed to validate the clinical biomarkers involved in ICI responders with EGFR mutations. [ABSTRACT FROM AUTHOR]

Osimertinib is a mutant-selective EGFR inhibitor that is effective against non-small cell lung cancer (NSCLC) in patients with the EGFR-T790M mutation, who are resistant to EGFR-tyrosine kinase inhibitors (EGFR-TKIs). However, the factors affecting response to osimertinib treatment are unknown. In this retrospective study, 27 NSCLC patients with the EGFR-T790M mutation were enrolled at five institutions in Japan. Among several parameters tested, the progression-free survival (PFS) associated with the initial EGFR-TKIs was positively correlated with the PFS after osimertinib treatment (p = 0.021). The median PFS following osimertinib treatment and the overall survival (OS) were longer in patients who responded to osimertinib than in those who did not (17.7 months versus 3.5 months, p = 0.009 and 24.2 months versus 13.5 months, p = 0.021, respectively). A multivariate analysis demonstrated that the PFS with initial EGFR-TKIs was significantly related to the PFS with osimertinib treatment (p = 0.035), whereas osimertinib response was significantly related to the PFS and OS with osimertinib treatment (p = 0.016 and p = 0.006, respectively). Our retrospective observations indicate that PFS following the initial EGFR-TKI treatment and the response rate to osimertinib might be promising predictors for effective osimertinib treatment in NSCLC patients with the EGFR-T790M mutation. [ABSTRACT FROM AUTHOR]