Phase I trial of high-dose infusional hydroxyurea, high-dose infusional 5-fluorouracil and recombinant...

The ribonucleotide reductase inhibitor, hydroxyurea (HU), augments the cytotoxic effects of 5-fluorouracil (5FU) in vitro; both drugs are synergistic with interferon-alpha (IFN) in vitro. The aim of this phase I study was to determine the maximal duration of HU, 4.3 g/m2, administered as a parenteral infusion in combination with 5FU, 2.6 g/m2 administered over 24 hrs each week, + IFN, 9 MU, subcutaneously three times per week. There were 26 patients enrolled and evaluable. This included 14 patients with colorectal cancer of whom 13 had been previously treated, and 12 patients with other refractory malignancies (pancreas, cholangiocarcinoma, hepatocellular carcinoma, renal cell carcinoma, and others), of whom 10 were previously untreated. The dose-limiting toxicity of this regimen was myelosuppression. This prohibited dose escalation of HU above the starting dose (24 hrs) on a 6-weeks-on, 2-weeks-off therapy schedule. When filgrastim, 480 microg, was administered subcutaneously on days 3-6, the duration of HU could be extended to 48 hrs on a 2-weeks-on, 1-week-off therapy schedule. There were two instances of fatal infection, one in a patient with a rectovaginal fistula with neutropenic sepsis and the second in a patient with non-neutropenic Clostridium septicum sepsis. All therapy was administered in the ambulatory setting. There were three responders, all among previously untreated patients. High-dose parenteral hydroxyurea, 4.3 g/m2 administered over 24 hrs, can be safely combined with high-dose weekly 5FU, 2.6 g/m2 over 24 hrs + IFN, 9 MU subcutaneously three times per week, without filgrastim in the ambulatory setting. Parenteral hydroxyurea, 4.3 g/m2 over 24 hrs daily x 2 can also be combined with high-dose 5FU + IFN, but requires the addition of filgrastim to avoid severe myelosuppression.