The Study of Gemcitabine in the Maintenance Treatment of Advanced Non-small Cell Lung Cancer

Inclusion Criteria: 18\~75 years Patients who were diagnosed by the histologic, cytologic diagnosis of IIIb-IV non-small cell lung cancer patients who have acceptted combination chemotherapy based on platinum 4 course,SD OR PR,the CR patients should accept 6 course of combination chemotherapy. 3\~8 weeks after patients complete first line chemotherapy(include radiotherapy) Ecog0-2 Expected life time longer than 3 monthes Normal laboratory values: * leucocyte ≥ 4×109/L * neutrophil ≥ 1.5×109/L * platelet ≥ 100×109/L * Hemoglobin ≥ 10g/L * ALT and * AST ≤ 2.5×ULN (≤ 5×ULN if liver metastasis) Signed written informed consent Exclusion Criteria: * Patients have used drugs according to protocol * Uncontrolled infection of Bacterial or virus or fungal * Patients with other malignant tumor * Uncontrolled brain metastases * Female patients during their pregnant and lactation period, or patients without contracep