In addition to KRAS and EGFR T790 mutations, the expression of oncogenes, including MET [5–7], HER2 (ERBB2) [8], and epidermal growth factor receptor 3 (HER3, ERBB3) [5, 9, 10], is associated with drug resistance against EGFR-TKIs and leads to tumor recurrence in lung cancers. The gene discussed is KRAS; the disease is lung cancer.