Phase II study of combination therapy with S-1 and irinotecan in patients with advanced colorectal cancer

A combination of irinotecan with continuous intravenous infusions of 5-fluorouracil (5-FU) and leucovorin (LV) is often used to treat advanced colorectal cancer. However, recent concerns about safety and convenience have prompted the development of new oral fluoropyrimidine derivatives and improved regimens. This phase II study evaluated the efficacy and safety of the oral fluoropyrimidine S-1 plus irinotecan in patients with previously untreated advanced or recurrent colorectal cancer.

Forty eligible patients with histologically confirmed colorectal adenocarcinoma received this treatment. S-1 was administered orally on days 1 to 14 of a 21-day cycle. Patients were assigned on the basis of body surface area (BSA) to receive one of the following oral doses twice daily: 40 mg (BSA < 1.25 m(2)), 50 mg (BSA > or = 1.25 to < 1.50 m(2)), or 60 mg (BSA > or = 1.50 m(2)). Irinotecan (150 mg/m(2)) was administered by intravenous infusion on day 1.

A total of 327 courses of treatment were administered to 40 patients. Five patients had complete responses, and 20 had partial responses. The overall response rate was 62.5% (95% confidential interval, 47.5%-77.5%). Median progression-free survival was 8.0 months (95% confidential interval, 5.2-11.4 months). The rates of grade 3 or 4 toxicity were as follows: neutropenia, 15%; anemia, 7.5%; anorexia, 12.5%; and diarrhea, 7.5%.

Combined treatment with S-1 and irinotecan is an effective, well tolerated, and convenient regimen in patients with advanced colorectal cancer. Our findings suggest that combined treatment with S-1 and irinotecan is a promising regimen, offering benefits in terms of safety and survival as compared with conventional regimens in patients with advanced colorectal cancer.