Phase I trials of uracil-tegafur (UFT) using 5 and 28 day administration schedules: demonstration of schedule-dependent toxicities.

We conducted two consecutive phase I clinical trials to identify the qualitative and quantitative toxic effects of uracil-tegafur (UFT) [Taiho Pharmaceutical Co. Ltd, Tokyo, Japan; (BMS-200604) Bristol-Myers Squibb, Princeton, NJ] administered either on a 5 or 28 day schedule and to determine the phase II trial starting doses for both schedules. Nineteen patients were entered in the 5 day schedule and 23 patients were entered on the 28 day schedule; a minimum of three patients were entered at each dose level studied. In both phase I trials, the daily UFT dose was divided into three doses administered every 8 h. Dose levels examined with the 5 day schedule were 360, 720, 900 and subsequent de-escalation to 800 mg/m2/day. Dose levels studied with the 28 day schedule were 180, 360, 450 and subsequent de-escalation to 400 mg/m2/day. With the 5 day schedule, the dose-limiting toxicity (DLT) was granulocytopenia, with four of five patients experiencing grade 4 granulocytopenia at the 900 mg/m2/day dose level. With the 28 day schedule, the DLT was diarrhea, which was noted in three of eight patients treated at 400 mg/m2/day and in three of six patients treated at 450 mg/m2/day. At these dose levels, four of these patients required prolonged hospitalizations for their diarrhea. The toxic effects of UFT are schedule dependent, with marked differences in the toxic effect profile (neutropenia versus diarrhea). With the 5 day schedule, the phase II UFT starting dose is 800 mg/m2/day. On the 28 day schedule, the suggested phase II UFT starting dose is 360 mg/m2/day. Future clinical trials examining the combination the UFT plus oral folinic acid are being conducted to develop oral regimens of therapy for advanced colorectal carcinoma and adjuvant therapy for colon carcinoma.