 In this study, the investigators will collect blood from NSCLC patients who harbor EGFR mutation in biopsy specimens. Buffy coat and serumplasma will be separated and DNA will be extracted. The investigators will check the EGFR mutation by next generation sequencing or digital PCR. Blood from volunteers without lung cancer patient will be also collected as standard. Serial follow-up the change of EGFR mutation every month in cancer patient will be correlated with clinical course. The Investigators hope the detection of EGFR mutation and serial change in the patient blood could offer as a marker for early diagnosis and early relapse. 