This is a study for patients with advanced non-small cell lung cancer with changes to their cancer cells called EGFR mutations. Mutated EGFR is important in the growth of cancer cells. Medical studies have shown that patients with EGFR mutation-positive lung cancer gain more benefit from targeted therapy drugs such as EGFR inhibitors than with standard chemotherapy. However, a significant proportion of patients carrying these sensitizing mutations do not respond well to the first-generation EGFR-TKIs (erlotinib and gefitinib), indicating the existence of intrinsic resistance mechanisms. Moreover, despite initial response to EGFR-TKIs, acquired resistance is inevitable in all patients.