DNA and RNA are extracted from tumor samples. Genomic DNA is analyzed using real-time PCR/ reverse transcriptase PCR analysis and/or FISH analysis in order to study resistance mechanisms such as secondary EGFR mutations and the c-MET and PI3K pathways. RNA is analyzed using TaqMan quantitative PCR in order to determine the copy number of EGFR expressed in these tissues. Peripheral blood samples are used to isolate peripheral blood mononuclear cells positive for epithelial cell adhesion molecule (EpCAM).