According to the FDA drug label, erlotinib is a tyrosine kinase inhibitor indicated for first-line treatment of patients with metastatic non-small cell lung cancer (NSCLC), whose tumors are characterized by epidermal growth factor receptor (EGFR) exon 19 deletions or exon 21 (p.L858R) missense mutations. This evidence concerns the gene EGFR and non-small cell lung carcinoma.