 Amplification of wild-type Kras has also been observed in ovarian, gastric, uterine, and lung cancers.Whether a patient is positive or negative for a mutation in the epidermal growth factor receptor (EGFR) will predict how patients will respond to certain EGFR antagonists such as erlotinib (Tarceva) or gefitinib (Iressa).Patients who harbor an EGFR mutation have a 60% response rate to erlotinib.