Likewise, the finding that a small subset of NSCLC patients who have gain-of-function epidermal growth factor receptor (EGFR) mutations and response rates to gefitinib and erlotinib of over 80% must be viewed as a major advance in our understanding of lung cancer biology (Lynch et al, 2004; Paez et al, 2004; Mitsudomi et al, 2005; Tokumo et al, 2005). This evidence concerns the gene EGFR and lung carcinoma.