Maintenance Therapy for Small-cell Lung Cancer

Inclusion Criteria: * 1\. Histopathologically confirmed patients with extensive small cell lung cancer; 2. Karnofsky performance status ≥60; 3. At least one lesion that can measured by CT; 4. Expected to survive for at least 3 months; 5. Peripheral blood and liver and kidney function within the following allowable range (tested within 7 days before treatment); 6. White blood cell (WBC) ≥3.0×109/L or Neutrophils (ANC) ≥1.5×109/L; Hemoglobin (HGB) ≥80 g/L；Platelet (PLT) ≥100×109/L; 7. Liver transaminases（AST/ALT）\<3.0 times the normal range limit; Total bilirubin（TBIL）\<1.5 times the normal range limit; Creatinine（CREAT）\<1.5 times the normal range limit; 8. Patients of childbearing age (including female and male patients' partner) must take effective contraception methods; Signed informed consent 9. Must be able to swallow tablets Exclusion Criteria: * 1\. Limited stage disease 2. Metastastic meningitis, spinal compression, Tumor to main vesicular less than 5mm 3. Other pathological types of tumor except for small cell lung cancer; 4. Patients with a history of severe allergies or allergies; 5. Pregnancy or breastfeeding women; 6. Patients who have previously participated in other clinical trials and have not yet terminated the trial; 7. Patients who have acute infection that difficult to control; 8. Subjects with difficulties in swallowing or known drug malabsorption.