Erlotinib Re-Challenge for Recurrent EGFR-mutant Lung Cancer in Patients Who Previously Received Adjuvant Erlotinib or Gefitinib

Inclusion Criteria: * A history of stage I-IIIB NSCLC * Previously underdone definitive surgery or radiation * Received prior adjuvant treatment or neoadjuvant with erlotinib or gefitinib for a total of at least 3 months at any time * Stopped adjuvant erlotinib or neoadjuvant at least 2 months prior to date of first imaging demonstrating recurrence * Pathologic evidence of recurrent lung cancer, confirmed at MSKCC EGFR sensitizing mutation (point mutation in exons 18 or 21, or deletion in exon 19) must be documented in the primary or recurrent tumor * Tissue from their recurrent tumor must be submitted for EGFR mutation testing, and to evaluate for the presence of the T790M mutation (results do not need to have been reported to be eligible) * Measurable disease by RECIST; if received prior irradiation, then must have a target lesion outside the irradiated field * Signed informed consent * Age \> or = to 21 years old * Persons of reproductive potential must agree to use an adequate method of contraception throughout treatment and for at least 4 weeks after study drug is stopped Exclusion Criteria: * Prior progressive disease while receiving erlotinib or gefitinib therapy * Patients with known pre-existing interstitial lung disease * Total bilirubin greater than 1.8 mg/dl, excepting patients known to have Gilbert's syndrome * AST or ALT greater than five times the upper limit of normal * Pregnant or lactating women * Medically unfit for erlotinib therapy as determined by treating oncologist