EGFR and non-small cell lung carcinoma: Gefitinib, which is one of the epidermal growth factor receptor (EGFR) small molecule tyrosine kinase inhibitor tyrosine kinase inhibitors (TKIs), is widely used for patients with non-small cell lung cancer (NSCLC) harboring EGFR mutations20, including exon 19 deletion and exon 21 L858R mutation.