Third-line Treatment of Gefitinib in NSCLC Patients

Inclusion Criteria: 1. The subject or legal guardian could understand and sign informed consent form. 2. Male or female aged 18 years or older; 3. Subjects were diagnosed with stage IIIB or IV NSCLC before starting the first dose of gefitinib third-line treatment; 4. EGFR exon 19 deletion or exon 21 L858R substitution mutation confirmed; 5. ECOG performance status 0-2; 6. Life expectancy of at least 12 weeks or longer; 7. Has at least one measureable lesion by RECIST 1.1; 8. NSCLC of enrolled subjects previously progressed after first-line gefitinib treatment (PFS ≥ 6 months) and progressed again after second-line chemotherapy (not limited for chemotherapy regimen, ≥ 4 cycles of chemotherapy). Investigator considers adopting third-line gefitinib retreatment; 9. Criteria for laboratory examinations: * Total bilirubin (TB) ≤ 1.5 times upper limit of normal * Aspartate aminotransferase(AST), alanine aminotransferase (ALT) ≤2 times upper limit of normal; for subjects with hepatic metastasis, AST,ALT≤ 5 times upper limit of normal * Creatinine clearance≥45ml/min Exclusion Criteria: 1. Known severe hypersensitivity to gefitinib or any ingredients of the product; 2. Patients with prior exposure to agents directed at the EGFR axis except gefitinib (e.g. erlotinib, cetuximab, trastuzumab) ; 3. Pre-existing interstitial lung disease or pulmonary fibrosis evidenced by CT scan at baseline; 4. Neutrophil count \<1.0×109/L or platelet count \<50×109/L; 5. Severe infection, uncontrolled systemic disease (e.g cardiopulmonary insufficiency, fatal arrhythmias, hepatitis, etc); 6. Pregnancy or breast-feeding; 7. Women of childbearing age refuse to take adequate contraception measures during gefitinib treatment 8. Subjects with other malignant tumors combined; 9. Known or suspected brain metastases or spinal cord compression, unless treated with surgery and/or radiation and stable without steroid treatment for at least 4 weeks prior to the first dose of study medication; 10. Subjects are unable to take medications orally or have digestive malabsorption; 11. Investigators consider subjects should not be involved in the study.