The epidermal growth factor receptor (EGFR) is a transmembrane protein that transduces growth factor signaling from the extracellular milieu to the cell.
1 Oncogenic
EGFR (OMIM 131550) mutations—either a deletion in exon 19 or an amino acid substitution at codon 858 in exon 21 (L858R)
2,3—induce constant phosphorylation of EGFR and activation of downstream signals that induce carcinogenesis.
1 Mutations in
EGFR—present in 16.6% of Spanish patients with non–small-cell lung cancer (NSCLC)
4—confer sensitivity to the EGFR tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib hydrochloride.
5-7 In 2 randomized trials based on clinical—but not molecular—selection of patients, comparing chemotherapy with gefitinib, a significant improvement in progression-free survival (PFS) with gefitinib therapy was observed in patients harboring
EGFR mutations.
8,9 Several randomized clinical trials of patients with
EGFR-mutant NSCLC comparing chemotherapy with gefitinib,
10,11 erlotinib,
12,13 or afatinib dimaleate (a second-generation EGFR TKI)
14,15 also identified a significant improvement in PFS with EGFR TKI therapy. However, no differences in overall survival (OS) were observed, likely due to crossover at the time of progression. We had previously reported no differences in PFS with erlotinib as first-line or second-line therapy in patients with
EGFR mutations.
4