Inclusion Criteria:

• Histologically or cytologically diagnosed small cell lung cancer
• Extensive disease (distant metastasis, contralateral hilar lymph node involvement, or cytologically confirmed malignant pleural effusion)
• If patients have brain metastasis with neurological symptom, they should be stabilized neurologically with prior radiotherapy or surgery for the brain metastasis (no neurologic symptom in progress and without further steroid treatment)
• No prior chemotherapy, immunotherapy, surgery or radiotherapy for small cell lung cancer (Local radiotherapy for brain or bone metastasis with symptom is permitted, in which case patients can be enrolled in this study when they have recovered from toxicity of radiotherapy)
• One or more measurable disease by RECIST criteria
• at least 18 years of age
• Performance status of 0, 1 and 2 on the Eastern Cooperative Oncology Group (ECOG) criteria
• Adequate hematologic (neutrophil count >= 1,500/uL, platelets >= 100,000/uL), hepatic (transaminase =< upper normal limit(UNL)x2.5, bilirubin level =< UNLx1.5), and renal (creatinine =< UNL) function
• Informed consent from patient which conforms to Institutional Review Board

Exclusion Criteria:

• History of cured basal cell carcinoma or cured uterine cervical malignancy except for carcinoma in situ within 5 years
• Medically uncontrolled serious heart, lung, neurological, psychological, metabolic disease
• Uncontrolled serious infection
• Enrollment in other study within 30 days