Study of Small Doses of Etoposide as Maintenance Treatment in Small Cell Lung Cancer(SCLC)

Inclusion Criteria: * Pathological diagnosis of small cell lung cancer * Extensive stage according to American Veteran Staging System * At least one measurable lesion according to Response Evaluation Criteria in Solid Tumors (RECIST )1.1 * Eastern Cooperative Oncology Group (ECOG) scores for performance status of 0 to 2 * Age≥18 years * Adequate organ function * Consent form according with Guideline for Good Clinical Practice of the International Conference on Harmonisation (ICH-GCP)guidelines * The expected survival≥2 months Exclusion Criteria: * Pathological diagnosis of mixed small cell lung cancer * Limited stage according to American Veteran Staging System * Other preexisting or existing malignant tumors,not including non-melanoma skin cancer with effective treatment,cervical cancer in situ or tumor response has been 3 years which is considered cured by the investigator * Known pre-existing interstitial lung disease * Pre-existing or uncontrolled gastrointestinal disease which may affect drug absorption or worsen existing disease believed by the investigator * Any other medical history or coexisting disease that may affect compliance of patients or the assessment of safety and effectiveness of the drug believed by the investigator * Pregnant or lactating women * Active phase of hepatitis B virus infection,Active phase of hepatitis C virus infection or known HIV carriers