A Randomized Study to Compare the Efficacy and Safety of Belotecan and Topotecan as Monotherapy for Sensitive-Relapsed Small Cell Lung Cancer

Inclusion Criteria: * At least 18 years of age * Histological or cytological diagnosis of SCLC * Limited disease (LD) or Extensive disease (ED) at time of study entry * Recurrent or progressive SCLC ≥ 90 days of duration of response for firstline therapy * Measurable disease defined by RECIST criteria * ECOG Performance Status of 0, 1, or 2 * Life expectancy ≥ 3 months * Adequate bone marrow, Renal, Hepatic reserve: absolute neutrophil (segmented and bands) count (ANC) ≥ 1500 cells/mm3 platelet count ≥ 100,000 cells/ mm3 hemoglobin ≥ 9 g/dL Total bilirubin ≤ 1.5 mm3 Alanine aminotransferase (ALT) and aspartate aminotransferase(AST) ≤ 2.0 X ULN Alkaline Phosphatase (ALP) ≤ 2.0 X ULN Serum creatinine ≤ 1.5mg/dL or calculated creatinine clearance \> 60mL/min \- Signed a written informed consent Exclusion Criteria: * Active infection * Symptomatic brain lesion * Any other type of cancer during the previous 5 years * Severe concurrent diseases * Prior anticancer therapy within 4 weeks before enroll * Active pregnancy test and Pregnant or nursing women * Participation in any investigational drug study within 28 days prior to study entry