In particular, the signaling pathway downstream of the Epidermal Growth factor Receptor (EGFR) has been investigated in advanced NSCLC patients harboring activating EGFR mutations (approximately 15% of Caucasian and 50% of Asian patients) treated with first-line tyrosine kinase inhibitors (TKIs), such as gefitinib, erlotinib, and afatinib. This evidence concerns the gene EGFR and non-small cell lung carcinoma.