Phase II clinical study of combination therapy with irinotecan and S-1(IRIS) for inoperable recurrent advanced colorectal cancer (2nd report): For Hokkaido Gastrointestinal Cancer Study Group (HGCSG)

Abstract

4105 Background: We planned to conduct a phase II clinical study of combination therapy with irinotecan and S-1, a new oral anticancer drug of the fluorinated pyrimidine type. We reported the interim reports of this study in colorectal cancer patients at ASCO 2006. Methods: The antitumor effect was the primary endpoint, while the safety, progression-free survival time, and median survival time were the secondary endpoints. The subjects were untreated patients with inoperable advanced colorectal cancer aged 20–75 years. Irinotecan was administered at a dose of 100 mg/m2 (on days 1 and 15) as an intravenous infusion over 90 minutes, and oral S-1 (40 mg/m2) was administered after breakfast and dinner and then withdrawn for 2 weeks. Results: Forty patients were enrolled in the present study. There were 23 men and 17 women. The median age was 62 years (range: 34 to 74 years). Two patients showed grade 4 neutropenia, but the next course could be given safely after dose reduction. Three patients had grade 3 diarrhea, but therapy could be continued with addition of an antidiarrhea drug. No other serious adverse reactions occurred (either hematological or non-hematological), and all patients could receive therapy safely on an outpatient basis. Forty pts. are evaluable for efficacy: RR was 52.5% (CR 1, PR 20, SD 17, PD 2, 95% CI, 37–68%) and Disease Control Rate (CR+PR+SD) was seen in 96.0% of pts. PFS of this regimen is 311 days. MST is not reached. Conclusions: IRIS therapy achieved a high response rate and could be given safely. These findings suggest that the therapy has potential as first-line treatment for inoperable advanced recurrent colorectal cancer. It seems that IRIS is a good treatment equal to FOLFIRI. Non-inferiority randomized phase III trial of IRIS vs. mFOLFOX6 (IFOX study) was planned, and it has been already started now. The latest data will be reported at the meeting. No significant financial relationships to disclose.