Distinct Benefit of Overall Survival between Patients with Non-Small-Cell Lung Cancer Harboring EGFR Exon 19 Deletion and Exon 21 L858R Substitution.

Background: Exon 19 deletion (Del19) and exon 21 L858R substitution (L858R), which account for 90% of epidermal growth factor receptor (EGFR) mutations as common mutations, are associated with favorable outcomes with EGFR-tyrosine kinase inhibitors (TKIs) compared with other uncommon EGFR mutations in non-small-cell lung cancer (NSCLC). However, whether there are differences in overall survival (OS) between patients with these common EGFR mutations remains controversial. Methods: The subjects studied were 74 NSCLC patients with common EGFR mutations treated with gefitinib or erlotinib. Using univariate and multivariate analyses, we retrospectively compared the clinicopahological characteristics of patients harboring Del19 with those harboring L858R. Results: Compared with patients harboring L858R, EGFR-TKIs provided a significant OS benefit in patients harboring Del19 (p = 0.024), as well as favorable therapeutic responses (p = 0.045) and progression-free survival (PFS) benefits (p = 0.031). In multivariate analyses, Del19 was independently associated with PFS (p = 0.029) and OS (p = 0.009), whereas no parameters other than pleural dissemination at the initial treatment were associated with EGFR mutation types. Conclusion: Del19 and L858R have distinct prognostic implications and may require individual therapeutic strategies. (C) 2017 S. Karger AG, Basel