De Novo Resistance to Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitors

This study is based on the following hypothesis "De novo resistance to EGFR-TKI in EGFR mutation positive patients is related with mutations in EGFR downstream genes". Investigators will prospectively collect genomic DNA and clinical data regarding treatment outcomes to EGFR-TKI in NSCLC patients with activating EGFR mutations. Investigators will sequence candidate mutations of EGFR downstream genes and analyze c-met gene amplification and protein expression in PTEN, HGF, and IGFR. To identify genetic mutations, amplification, and protein over expression as predictive markers of treatment outcomes, investigators analyzed the association of treatment outcomes with the presence of genetic alteration or protein over expression. Investigators will attempt to identify biomarkers that are able to predict de novo resistance to EGFR-TKI in EGFR mutated NSCLC.