Phase I/II trial of irinotecan and S-1 combination chemotherapy as a second-line treatment for advanced colorectal cancer.

Background: This study attempted to determine the therapeutic dosage of irinotecan and S-1 (IRIS) as a second-line treatment for colorectal cancer (CRC). Methods: S-1 was administered on days 1-14 of a 28-day cycle. Irinotecan was administered on days 1 and 15. The irinotecan dose was then escalated to determine the maximum-tolerated dose and the recommended dose at a fixed dosage of S-1 (80 or 65 mg.m(-2).day(-1)). The S-1 dose was reduced to 65 mg.m(-2).day(-1) when dose-limiting toxicities were observed at 80 mg.m(-2).day(-1) and the irinotecan dose was increased. Results: The recommended dose was 65 mg/m(2) for S-1 and 75 mg/m(2)for irinotecan. Twenty-one patients were treated at the recommended dose. The overall response rate was 28.6%. Condusion: This modified IRIS regimen is considered effective with acceptable toxicities for advanced CRC resistant to treatment with 5-fluorouracil/leucovorin or uracil and tegafur/leucovorin. (C) 2014 S. Karger AG, Basel