Irinotecan and cisplatin demonstrated promising outcomes in extensive-stage small-cell lung cancer. According to the dosage and schedule of irinotecan, efficacy and toxicity profiles showed subtle differences. This study was designed to evaluate efficacy and toxicity of 3-week schedule of irinotecan/cisplatin in patients with previously untreated extensive-stage small-cell lung cancer. The primary objective was to evaluate response rate and secondary objectives were overall survival and progression-free survival. Patients with previously untreated extensive-stage small-cell lung cancer were enrolled. Irinotecan 65 mg m À2 was administered on days 1 and 8 and cisplatin 60 mg m À2 on day 1. Treatment was repeated every 3 weeks. Seven out of 54 patients (13.0%) had complete response, and partial response was observed in 33 (61.1%). The overall response rate was 74.1% (95% CI; 62.0 -82.2%). Stable disease was observed in eight (14.8%) and no progressive disease was observed. After a median follow-up duration of 28.7 months, the median overall survival and progressive-free survival were 13.6 and 6.5 months, respectively. Major grade 3/4 toxicities were neutropenia (50.0%), anorexia (42.6%), diarrhoea (29.6%), fatigue (29.6%) and vomiting (13.0%). There was one treatment-related death owing to pneumonia. Three-week schedule of irinotecan/cisplatin showed effective antitumour activity and moderate toxicities in patients with previously untreated extensive-stage small-cell lung cancer. British Journal of Cancer (2006) (Jemal et al, 2004), and also in Korea (Shin et al, 2004). The proportion of histologic diagnosis with small-cell lung cancer (SCLC) in the United States is approximately 15% of patients with lung cancer (Jemal et al, 2004), and more than half of these patients are diagnosed with extensive-stage disease. Incidence of SCLC had paralleled trends in cigarette smoking, and smoking prevalence for the adult population is relatively high in Korea. During the last decade, most patients with extensivestage SCLC (ES-SCLC) have been treated with etoposide and platinum resulting in a median survival of 8 -10 months (Roth et al, 1992). Although several trials of platinum-based combination chemotherapy were performed, it failed to show a superiority to combination of etoposide and cisplatin (EP) (Mavroudis et al, 2001;Sundstrom et al, 2002).Irinotecan, which inhibits the function of topoisomerase I in cancer cells, demonstrated synergism and non-cross resistance when combined with platinum agents (Fukuda et al, 1996;Masuda et al, 1996). Kudoh et al (1998) reported that combination chemotherapy of irinotecan and cisplatin (IP) in patients with SCLC showed a promising response rate of 84 with 29% of complete responses and median survival over 13 months. Since then, several phase II/III trials of irinotecan-based combination chemotherapy with different dose and schedule were performed with varying results in SCLC patients (Noda et al, 2002;Kudoh et al, 2005;Hanna et al, 2006;Kinoshita et al, 2006;Schmittel et al, 2006). In...