Previous studies have shown that the first-generation EGFR-TKIs gefitinib and erlotinib lead to better outcomes in approximately 5–15% of NSCLC patients with sensitizing EGFR mutations (exon 19 deletions and exon 21 L858R substitution) than in those with wild-type EGFR [24,25,26]. This evidence concerns the gene EGFR and non-small cell lung carcinoma.