Non-small cell lung cancer (NSCLC) accounts for 80% of all lung cancer cases. The majority of NSCLC patients have advanced disease at the time of diagnosis, which usually requires treatment beyond standard first-line chemotherapy. Until recently, patients were limited in the number of options available for second-line treatment of NSCLC. In 2004, erlotinib was approved by the FDA for second and third-line treatment of NSCLC. Erlotinib is a cancer chemotherapy medication that slows the growth and spread of cancer cells in the body.