Comparison of Sequencing and PNA Clamping of EGFR Gene in Patients With Non-Small Cell Type Lung Cancer

Single arm, open label, prospective, observational study of gefitinib treatment for locally advanced (stage IIIB) or IV (metastatic) or relapsed NSCLC patients. Using DNA acquired from tumor tissue, sequencing and PNA-clamping for EGFR gene will be performed. The detection rates of EGFR mutation will be compared using paired samples.