The current evidence of S-1 and irinotecan hydrochloride combination chemotherapy with tri-weekly schedule

A combination therapy of irinotecan hydrochloride (CPT-11) with continuous intravenous infusions of (infusional) 5-fluorouracil (5-FU) and Leucovorin (LV) is often used to treat advanced colorectal cancer. However, recent concerns on safety and convenience have prompted the development of new oral fluoropyrimidine derivatives which improved regimens. Yamada et al conducted a phase I study to assess the maximum tolerated dose and recommended dose of S-1 combined with CPT-11. The study recommended that 150 mg/m2 of CPT-11 be given on day 1 and 80 mg/m2 of S-1 daily on days 1 to 14 every 3 weeks. Recently, several phase I/II studies assessed the efficacy and safety of the combined therapy with S-1 and CPT-11 in patients with advanced colorectal cancer. Some of the studies which were ongoing assessed a tri-weekly schedule regimen. Our results showed that S-1 plus CPT-11 was very effective, with a response rate of 63% and PFS of 8 months. Toxicity was generally mild and manageable on an outpatient basis. The current evidence showed that a combination of S-1 and CPT-11 was more convenient and easier to administer than a combination of CPT-11 plus infusional 5-FU and LV. It will be essential to prove that the combination of S-1 plus CPT-11 can replace the combination of infusional 5-FU and LV plus CPT-11 without negatively affecting efficacy and toxicity.