Based upon analogous studies in other diseases with another kinase inhibitor, imatinib, a single amino acid substitution from threonine to methionine at position 790 in the wild-type EGFR kinase domain was predicted to lead to drug resistance, even before the association of exon 19 and 21 mutations of EGFR with drug responsiveness in NSCLC was reported. Here, EGFR is linked to non-small cell lung carcinoma.