Phase II Study of Combined Treatment with Irinotecan and S-1 (IRIS) in Patients with Inoperable or Recurrent Advanced Colorectal Cancer (HGCSG0302)

Objectives: This phase II study was designed to evaluate the efficacy and safety of oral fluoropyrimidine S-1 plus irinotecan (IRIS regimen) in patients with previously untreated metastatic colorectal cancer. Methods: The response rate was the primary endpoint. Safety, progression-free survival time, and median survival time were secondary endpoints. The subjects were untreated patients with inoperable advanced colorectal cancer. Irinotecan was administered at a dose of 100 mg/m 2 (on days 1 and 15). S-1 (40 mg/m 2 ) was administered for 2 weeks (on days 1 to 14) and followed by a 2-week rest. Results: Forty patients were enrolled. Four patients had grade 4 neutropenia, and six patients had grade 3 diarrhea. No other serious hematologic or nonhematologic adverse reactions occurred, and all patients received IRIS safely on an outpatient basis. The response rate was 52.5% (95% confidence interval [CI], 36.1–68.5%). Median progression-free survival was 8.6 months (95% CI, 5.3–11.9), and median survival time was 23.4 months (95% CI, 15.9–30.8). Conclusions: IRIS produced a high response rate and could be given safely. IRIS may become a first-line treatment for inoperable or recurrent advanced colorectal cancer.