Distinct Benefit of Overall Survival between Patients with Non-Small-Cell Lung Cancer Harboring <b><i>EGFR</i></b> Exon 19 Deletion and Exon 21 L858R Substitution

Abstract

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