This is a randomized controlled trial to compare efficacy and safety between erlotinib and gefitinib in advanced NSCLC harboring EGFR exon 19 or 21 mutations.Eligible patients were randomized to receive erlotinib or gefitinib in any line settings.The primary endpoint was progression-free survival (PFS).

Patients with stage IV NSCLC who have EGFR exon 19 or 21 mutations will randomized to received oral erlotinib 150mg or gefitinib 250mg once daily until disease progression or unacceptable toxicity. Method of direct DNA sequencing of tumor tissue is used to analysis EGFR mutation status of exons 18-21. The response will be evaluated by RECIST criteria first month,second month and then repeat every 3 months after the beginning of the treatment weeks.

Inclusion Criteria:

• Histologically or cytologically confirmed stage IIIB (wet) or IV NSCLC.
• Patients with positive EGFR exon19 or exon21 mutation as confirmed by direct sequencing histologically.
• Signing the informed consent form.
• The vital organ functions are tolerant to therapy.
• Have recovered to CTCAE2 grade below from toxicity of previous chemotherapy and radiotherapy
• PS 0-2 scores.
• Functional reserve of bone marrow is adequate, e.g. white blood cell count ≥3.0×109/L, planet count ≥90×109/L, and HB≥80×109/L.
• Serum bilirubin is 2 times less than the upper limit of normal (ULN), ALT and AST are 3 times less than ULN; for liver metastases, ALT and AST need to be 5 times less than ULN; creatinine should be 2 times less than ULN.

Exclusion Criteria:

• Informed consent is not provided.
• Women of pregnancy or breastfeeding.
• Have difficulty in swallowing.