Iressa Pan Asian Study demonstrated that an EGFR was the most appropriate biomarker for the use of EGFR TKI inhibitors in stage IV non-small cell lung carcinomas and with a significant improvement in PFS and quality of life, gefitinib became standard of care first-line option for NSCLC patients with EGFR-mutated tumor. This evidence concerns the gene EGFR and non-small cell lung carcinoma.