Two Different Dosages of Irinotecan Combined With Cisplatin Scheme in Extensive Disease-Small Cell Lung Cancer

Inclusion Criteria: * Histologic or cytologic diagnosis of small-cell lung cancer * Extensive-stage disease, defined as disease extending beyond one hemithorax involving contralateral mediastinal, hilar or supraclavicular lymph nodes, and/or pleural effusion. * Males or females between 18 to 75 years * No prior chemotherapy, if the surgery or radiotherapy has been administered, the interval is at least above four weeks. * Performance status of 0-2 on the ECOG criteria. Expected survival is above three months. * At least one unidimensional measurable lesion meeting Response Evaluation Criteria in Solid Tumors (RECIST. 2000). * Patient compliance that allow adequate follow-up. Informed consent from patient or patient's relative. * Adequate hematologic (neutrophil count \>= 1,500/uL, platelets \>= 100,000/uL), hepatic (transaminase =\< upper normal limit(UNL)x2.5, bilirubin level =\< UNL x 1.5), and renal (creatinine =\< UNL) function * The gene type of UGT1A1 \*28 is 6/6 and 6/7. * If female: childbearing potential either terminated by surgery, radiation, or menopause, or attenuated by use of an approved contraceptive method (intrauterine device \[IUD\], birth control pills, or barrier device) during and for 3 months after trial. If male, use of an approved contraceptive method during the study and 3 months afterwards. Females with childbearing potential must have a urine negative HCG test within 7 days prior to the study enrollment. * No concomitant prescriptions including cyclosporin A, valproic acid, phenobarbital, phenytoin, ketoconazole. Exclusion Criteria: * Non small cell lung cancer and carcinoid * Medically uncontrolled severe diarrhea in recent three weeks. * Inability to comply with protocol or study procedures. * Medically uncontrolled serious heart, lung, neurological, psychological, metabolic disease * Second primary malignancy that is clinically detectable at the time of consideration for study enrollment. * Pregnant or breast-feeding. * Enrollment in other study within 30 days * Brain metastasis with symptoms