Gefitinib is a selective small molecule inhibitor of the epidermal growth factor receptor (EGFR) tyrosine kinase (TK); it is an effective treatment for patients with advanced non small cell lung cancer (NSCLC, stage IIIb/IV, new TNM classification stage IV [1]) and activating mutations of the EGFR TK [2-5]. This evidence concerns the gene TKT and non-small cell lung carcinoma.