BACKGROUND: The objective of this study was to investigate the efficacy of belotecan, a new camptothecin analog, combined with cisplatin for the treatment of chemotherapy-naive patients with extensive-disease small cell lung cancer (ED SCLC). METHODS: Treatment consisted of belotecan 0.5 mg/m(2) daily on Days I through 4 and cisplatin 60 mg/m(2) on Day 1 of a 3-week cycle for up to 6 cycles unless there was disease progression, unacceptable toxicity, or patient refusal. Response assessment was done every 2 cycles using the Response Evaluation Criteria in Solid Tumors, and toxicity assessment was done every cycle using the National Cancer Institute Common Terminology Criteria for Adverse Events, version 3.0. RESULTS: Between September 2006 and March 2008, 30 patients participated in the study. Among them, 21 patients achieved a partial response, and the response rate was 70% (95% confidence interval [CI], 50.6%-85.3%); and, after a median follow-up of 20.2 months, the median progression-free survival was 6.9 months (95% Cl, 6.3-7.5 months), and the overall survival was 19.2 months (95% Cl, 13.3-25.2 months). Grade 3 and 4 adverse events included neutropenia in 23 patients, thrombocytopenia in 8 patients, febrile neutropenia in 9 patients, nausea in 3 patients, and pneumonia in 3 patients. There was 1 treatment-related death from pneumonia. However, nonhematologic toxicity generally was mild and manageable. CONCLUSIONS: The belotecan and cisplatin combination that was studied demonstrated promising response rates and survival outcomes with a manageable toxicity profile for chemotherapy-naive patients who had ED SCLC. The authors concluded that the combination warrants further randomized trials. Cancer 2010;116:132-6. (C) 2010 American Cancer Society.