Effectiveness of EGFR tyrosine kinase inhibitors in advanced non‐small cell lung cancer patients with uncommon EGFR mutations: A multicenter observational study

BACKGROUND: Epidermal growth factor receptor‐tyrosine kinase inhibitor (EGFR‐TKI) therapy is the standard treatment for advanced non‐small cell lung cancer (NSCLC) harboring common EGFR mutations, such as exon 19 deletion or L858 point mutation. However, the effectiveness of EGFR‐TKIs for patients with uncommon EGFR mutations remains unclear. METHODS: We retrospectively surveyed a consecutive database of NSCLC patients with EGFR mutations at five participating institutions. Data from NSCLC patients with uncommon mutations (including single or compound mutations), who were treated with systemic therapy between May 2016 and October 2018, were collected and analyzed. RESULTS: A total of 23 of the 524 patients whose data were collected had uncommon EGFR mutations. Of these, 22 received EGFR‐TKIs (gefitinib = 6, erlotinib = 4, and afatinib = 12). Patients who received first EGFR‐TKIs had overall response and disease control rates of 59.1% and 81.8%, respectively. The median progression‐free survival (PFS) of patients with G719X mutation (n = 13, median PFS = 32.9 months) was favorable, compared with those of patients with L861Q mutation (n = 4, median PFS = 6.4 months) and compound mutations (n = 4, median PFS = 7.3 months). The PFS of patients who received first‐ and second‐generation EGFR‐TKIs was 14.0 months (n = 10) and 7.3 months (n = 12), respectively. The median cumulative duration of treatment (DOT) with EGFR‐TKIs was 30.4 months, which was longer than those of cytotoxic chemotherapy (median DOT = 10.7 months) or immune checkpoint inhibitors (median DOT = 6.6 months). CONCLUSIONS: EGFR‐TKIs elicit favorable responses and contribute to long‐term disease control in NSCLC patients with uncommon EGFR mutations. KEY POINTS: Significant findings of the study: Our results demonstrate that both first‐ and second‐generation EGFR‐TKIs elicit favorable responses in NSCLC patients with uncommon EGFR mutations. What this study adds This study revealed all clinical courses for NSCLC patients with uncommon EGFR mutations. In addition to EGFR‐TKIs, CCT and ICIs were found to contribute to long‐term disease control in this cohort.