Epidermal Growth Factor Receptor Exon 20 Insertion in Early Resected Non-Small Cell Lung Cancer: A Retrospective, Single-Center Study in Taiwan.

Background: EGFR exon 20 insertions account for 1% to 10% of EGFR mutations in non-small-cell lung cancer (NSCLC) and are known to confer resistance to traditional tyrosine kinase inhibitors. However, the prognostic significance of these mutations in early-stage resected NSCLC remains unclear. This study assesses outcomes in patients with resected NSCLC harboring EGFR exon 20 insertions, comparing them to patients with common EGFR mutations and those with wild-type EGFR.

Methods: We retrospectively reviewed 3,235 patients who underwent resection for NSCLC at Tri-Service Hospital between 2008 and 2021. After excluding cases lacking EGFR testing, incomplete data, or advanced-stage disease, 44 patients with exon 20 insertions were matched to 602 patients with common EGFR mutations and 729 with wild-type EGFR. Clinical characteristics, disease-free survival (DFS), and overall survival (OS) were analyzed using the Kaplan-Meier method, with statistical comparisons performed using the log-rank test. Cox proportional hazards models were used to identify independent prognostic factors.

Results: Patients with exon 20 insertions were younger and more frequently presented with stage IA disease. The 5-year DFS was 79% in the exon 20 insertion group, compared to 81% in the common mutation group and 83.9% in the wild-type group. The 5-year OS was 78.5% for exon 20, 91.9% for common mutations, and 91% for wild-type. While no significant differences in DFS or OS were observed between groups, the exon 20 insertion group had a higher incidence of secondary cancers. Multivariable analysis indicated that exon 20 insertion was independently associated with worse OS, but not with DFS.

Conclusion: EGFR exon 20 insertions do not significantly shorten DFS, but are associated with inferior OS in early-stage resected NSCLC. Given the limited treatment options, the role of adjuvant therapy warrants further investigation.