Chalita Lagampan, MD¹

Background: Patients with non-small cell lung cancer (NSCLC) harboring uncommon epidermal growth factor receptor (EGFR) mutations often exhibit variable responses to EGFR tyrosine kinase inhibitors (TKIs).

Objective: To evaluate the clinical outcomes of first-line erlotinib in patients with advanced NSCLC harboring uncommon EGFR mutations, compared to those with common mutations.

Materials and Methods: The present study was a retrospective study conducted on 193 patients with advanced NSCLC and documented EGFR mutations, treated with erlotinib at Chonburi Hospital, Thailand, between January 1, 2020, and December 31, 2023. The authors collected data on patient demographics, mutation types, treatment regimens, progression-free survival (PFS), overall survival (OS), and physician-assessed objective response rates.

Results: Patients with uncommon EGFR mutations, which include 10.3%, had significantly shorter median OS of 7.6 months (95% CI 3.2 to 12.0) and PFS of 5.7 months (95% CI 0.0 to 11.4) compared to those with common EGFR mutations with a median OS of 19.5 months (95% CI 15.8 to 23.2) and a median PFS of 11.0 months (95% CI 9.2 to 12.7). The objective response rate to erlotinib was lower in patients with uncommon mutations (33.3% had partial responses) compared to those with common mutations (78.1% for exon 19 deletion and 82.4% for L858R). Multivariate analysis identified ECOG performance status as a significant prognostic factor for survival in patients with uncommon EGFR mutations.

Conclusion: Patients with advanced NSCLC harboring uncommon EGFR mutations exhibit poorer survival outcomes with first-line erlotinib treatment compared to those with common mutations. Alternative treatment strategies and personalized approaches are warranted for these patients.

Received 16 May 2025 | Revised 17 January 2026 | Accepted 19 January 2026

DOI: 10.35755/jmedassocthai.2026.3.03126