The epidermal growth factor receptor (EGFR) protein activation leads to TK activation and results in cell proliferation, motility, adhesion, invasion, survival, and angiogenesis. The EGFR is over expressed in many solid tumors, including non-small cell lung cancer (NSCLC), and multiple studies have suggested a shortened survival in NSCLC patients whose tumor over expresses EGFR . Although studies using small-molecule TK inhibitors (TKIs) in NSCLC did not meet efficacy endpoints, a phase III trial demonstrated the benefit of EGFR TKI monotherapy. Patients with advanced NSCLC who have received 2 or 3 prior therapies were randomized to erlotinib or placebo, and those receiving erlotinib demonstrated a survival benefit that led to FDA approval of this drug in 2004.