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Background: Both irinotecan and oxaliplatin are active agents in the treatment of patients with metastatic colorectal cancer (MCC). There is a strong preclinical rationale for combining these two agents. We sought to determine the dose-limiting toxicity (DLT) and the maximum tolerated dose (MTD) of combined irinotecan and oxaliplatin given every three weeks., Methods: Cohorts of patients with MCC previously treated with 5-fluorouracil received escalating doses of irinotecan (150, 175, and 200 mg/m(2)) and a fixed dose of oxaliplatin (130 mg/m(2)), both given intravenously every 3 weeks. DLT was evaluated within the first course of treatment. Objective responses were evaluated every two courses and were confirmed at least four weeks later., Results: Fourteen patients were treated and evaluated for toxicity. The DLT was neutropenia, with or without fever, and delayed recovery of neutrophil counts was frequent (13 courses in six patients). Other toxic effects (peripheral neuropathy, nausea, vomiting, diarrhea, and fatigue) were mild to moderate. Among 13 patients evaluable for activity, four achieved partial responses and nine had stable disease., Conclusion: The combination of irinotecan and oxaliplatin is safe and apparently active in the treatment of MCC patients. The recommended dose for phase II studies is 175 mg/m(2) irinotecan plus 130 mg/m(2) oxaliplatin, given every 3 weeks. Neutropenia and delayed recovery of neutrophil counts are the predominant early toxicities with this schedule.

We previously reported results of a Phase II trial of UFT [Taiho Pharmaceutical Ltd., Tokyo, Japan; (BMS-200604) Bristol-Myers Squibb, Princeton, NJ], an oral 4:1 molar concentration of uracil and tegafur, plus oral leucovorin for metastatic colorectal carcinoma (Pazdur et al., J. Clin. Oncol. 12:2296-2300, 1994]. Our results demonstrated that a 28-day schedule of this combination produced a response rate similar to that obtained with conventional intravenous fluorouracil (5-FU)-plus-leucovorin regimens but without the severe or life-threatening neutropenia or oral mucositis that complicates intravenous 5-FU regimens. The current Phase I trial examines the dose-limiting toxic effects and maximum tolerated dose of a 14-consecutive-day schedule of UFT plus oral leucovorin in 14 patients who had histologically proven cancer and had received prior chemotherapy. The daily UFT plus leucovorin dose was divided into three doses administered orally every 8 hours. In this study, the UFT dose was escalated while the leucovorin dose remained at 150 mg/day. Of the 14 patients, 4 were initially treated at the 350-mg/m2/day UFT level for 14 days without any dose-limiting toxic reactions. Subsequently, another 7 patients were treated at the 400-mg/m2/day level; grade 3 diarrhea developed in 3 of these 7 (with severe abdominal cramping in 2 cases and severe nausea and vomiting unresponsive to antiemetics in the third). To better define the starting dose for phase II studies, an additional 3 patients were treated at the 350-mg/m2/day dose level. Of the total 7 patients treated at 350 mg/m2/day, grade 3 toxic events (diarrhea) developed in 2 patients. Grade 1-2 toxic effects noted at this level included fatigue, stomatitis, skin rash, abdominal pain, nausea, and vomiting. Neither partial nor complete responses were observed in this trial. The maximum tolerated dose of this schedule is 350 mg/m2/day UFT plus 150 mg/day oral leucovorin. However, because of this schedule's inferior dose intensity compared with that of the 28-day schedule of UFT plus leucovorin, subsequent development of UFT in the United States has focused on the 28-day regimen.