For example, patients with lung cancer treated with Gefitinib, a first-generation epidermal growth factor receptor (EGFR) inhibitor, typically develop resistance after 9 to 15 months of progression-free survival.1 Genetic mechanisms, such as mutations in the T790M gene,2,3 have been partially attributed to the development of drug resistance. The gene discussed is EGFR; the disease is lung carcinoma.