In a study of 65 NSCLC cell lines, the growth inhibitory potency of afatinib varied markedly; it was most potent in cell lines harbouring overexpressed wild-type, mutated or amplified EGFR or HER2 and much less potent in those expressing normal levels of EGFR or mutated BRAF, KRAS or NRAS (Pfeifer et al. 2010). This evidence concerns the gene EGFR and non-small cell lung carcinoma.