Inclusion Criteria:

• Pathologically confirmed diagnosis of NSCLC of adenocarcinoma histology
• Stage IA-B, IIA-B, or IIIA by the American Joint Committee on Cancer 6th edition staging criteria
• Patients must have undergone surgical resection with curative intent within 6 months of enrollment
• Sufficient tumor tissue available for EGFR mutation analysis
• At least ONE of the following patient characteristics: previously detected deletion 19 or L858R EGFR mutation, female sex, history of never smoking, or Asian/Pacific Rim ethnicity (to be enrolled in the screening portion of trial).
• 18 years of age or older
• Tumor samples must have either exon 19 deletion mutations or the exon 21 L858R point mutation
• ECOG Performance status of 0,1, or 2
• Adequate organ function as outlined in protocol

Exclusion Criteria:

• Radiographic evidence of recurrent NSCLC prior to erlotinib treatment
• Confirmed T790M resistance mutation in the primary tumor sample
• Prior exposure to EGFR tyrosine kinase inhibitors
• Known hypersensitivity to erlotinib, gefitinib, or any closely related drug
• Pregnant or breastfeeding women
• Any evidence of clinically active interstitial lung disease
• Current use of enzyme-inducing anti-epileptic drugs, including carbamazepine, oxcarbazepine, phenytoin, fosphenytoin, phenobarbital, and primidone
• Evidence of any other significant clinical disorder or laboratory finding that makes it undesirable for the patient to participate in the study
• Use of any non-FDA approved or investigational agent within 2 weeks of enrolling onto the trial, or failure to recover from the side effects of any of these agents