Gefitinib Long-term Survivor Study

Inclusion Criteria: For inclusion in the long-term survivors group, the study subjects must fulfil the following criteria at the time of screening: 1. Provision of informed consent or EC approve informed consent waiver prior to any study specific procedures 2. Histological or cytological confirmed locally advanced NSCLC (stage III B) or metastatic (stage IV) NSCLC, not amenable to curative surgery or radiotherapy 3. EGFR mutation positive 4. Patients who continuously received gefitinib for at least 3 years without evidence of PD 5. Patients with OS ≥ 5 years from NSCLC diagnosis will be preferred 6. Collect archival tumour tissue before gefitinib treatment (blood and re-biopsy tumour tissue are optional); tumor tissue samples requirements: 1) slices requirements: \>1 cm2, thickness 4-5 μm, ≥ 15 slices. or, whole FFPE block; 2) tumor percentage \> 20% and necrosis \< 30% by pathology QC. For inclusion in the rapid PD group, the study subjects must fulfil the following criteria: 1. Provision of informed consent or EC approve informed consent waiver prior to any study specific procedures 2. Histological or cytological confirmed locally advanced NSCLC (stage III B) or metastatic (stage IV) NSCLC, not amenable to curative surgery or radiotherapy 3. EGFR mutation positive 4. Patients who had undergone PD after gefitinib treatment≤3 months (Rapid PD) 5. Collect archival tumour tissue before gefitinib treatment (blood and re-biopsy tumour tissue samples are optional) ; tumor tissue samples requirements: 1) slices requirements: \>1 cm2, thickness 4-5 μm, ≥ 15 slices. or, whole FFPE block; 2) tumor percentage \> 20% and necrosis \< 30% by pathology QC. Exclusion Criteria: For the active patients, who must not enter the study if any of the following exclusion criteria are fulfilled 1. Patients who disagree to participate this study. For the terminated patients, who must not enter the study if any of the following exclusion criteria are fulfilled 1\. Patients in whose medical objection was recorded to use the existing data from medical practice for scientific research.