Chemotherapy and Erlotinib for Lung Cancer With Low Abundance Epidermal Growth Factor Receptor Mutation

Inclusion Criteria:Patients with histologically documented, locally advanced or recurrent (stage IIIb and not amenable to combined modality treatment) or metastatic (stage IV) non-small cell lung cancer. Low abundant activating EGFR mutation: EGFR exon 19 deletion or exon 21 L858R, which are positive by real-time PCR methods and negative by standard sequencing methods. Uncommon EGFR mutations are included excluding exon 20 mutations. ECOG performance status of ≤ 2. Patients can administer first line setting of platinum based chemotherapy. Patients must have measurable disease according to the RECIST (version 1.1) criteria. * Life expectancy of at least 12 weeks. * Age ≥ 18 years. * Written (signed) informed Consent to participate in the study. * Adequate organ function as defined by the following criteria: Liver function: SGOT (AST) and SGPT (ALT) ≤ 2.5 X ULN in the absence of liver metastases or up to 5 X ULN in case of liver metastases. Total bilirubin ≤ 1.5ULN. Bone marrow function: Granulocyte count ≥ 1,500/mm3 and platelet count ≥100,000/mm3 and hemoglobin ≥90g/dl. Renal function: serum creatinine ≤ 1.5 ULN or creatinine clearance ≥ 60 ml/min. (based on modified Cockcroft-Gault formula). * For all females of childbearing potential a negative serum/urine pregnancy test must be obtained within 48 hours before enrollment. Postmenopausal women must have been amenorrhoeic for at least 12 months to be considered of non-childbearing potential. Exclusion Criteria:Patients with prior chemotherapy or systemic anti-cancer therapy including target therapy targeting HER family members (such as erlotinib, gefitinib, cetuximab, trastuzumab, etc). Previous adjuvant or neo-adjuvant treatment for non-metastatic disease is permitted if completed ≥ 6 months before the enrollments. * Patients with history of any other malignancies within 5 years (except for adequately treated carcinoma in situ of the cervix or basal or squamous cell skin cancer). * Patients who have brain metastasis or spinal cord compression. It is permitted if the patient has been treated with surgery and/or radiation with evidence of stable disease for at least 4 weeks. * Patients who are at risk (in the investigator's opinion) of transmitting human immunodeficiency virus (HIV) through blood or other body fluids. * Nursing or lactating women. * Sexually active males and females (of childbearing potential) unwilling to practice contraception during the study. * Unwilling to write informed consent to participate in the study. * Patients who is unwilling to accept the follow-up.