Phase II study of S-1 and irinotecan combination chemotherapy as a first-line therapy for patients with advanced gastric cancer. Korean Cancer Study Group Protocol ST05-02

Background: Irinotecan plus intravenous 5-fluorouracil (5-FU) with leucovorin is effective against gastrointestinal cancer. S-1 is an oral fluoropyrimidine derivative and has a high response rate of about 40% for patients with advanced gastric cancer (AGC). We evaluated the antitumor activity and toxicities of an S-1 and irinotecan combination as a first-line therapy for patients with AGC. Methods: Patients with histologically confirmed unresectable or metastatic AGC were treated with S-1 40 mg/m² PO twice daily on days 1-14 and irinotecan 150 mg/m² i.v. on day 1 every 3 weeks until disease progression or unacceptable toxicities resulted. Results: A total of 45 patients were enrolled between September 2005 and March 2007. After a median of seven cycles of chemotherapy (range: 1-20, total: 350), 42 and 44 patients were evaluable for response and toxicity, respectively. On the intention-to-treat analysis, the overall response rate was 48.9% (95% C.I. 34.3-63.5%). The median time to progression was 5.7 months (95% C.I. 4.3-7.1) and the median overall survival was 10.4 months (95% C.I. 6.1-14.7). The commonly observed grade 3/4 adverse events were neutropenia (29.5% of patients) and vomiting (13.6%). Conclusion: An S-1 and irinotecan combination chemotherapy is active and tolerable as a first-line therapy for AGC.