A phase I trial of interferon alpha-2b with folinic acid and 5-fluorouracil administered by 4-hour infusion in metastatic colorectal carcinoma.

Preclinical data suggest that both folinic acid and interferon may enhance the efficacy of 5-fluorouracil (5-FU) in colorectal carcinoma. We therefore initiated a phase I trial evaluating the doses, safety, and pharmacokinetics of the combination of recombinant interferon (IFN) alpha-2b with folinic acid (FA) and 5-FU. Seventeen patients with colorectal cancer who failed local chemotherapy received 5-FU as a 4-hour infusion, preceded by a bolus of FA and IFN. The 5-FU dose was escalated over the range of 400 to 650 mg/m2/d for a period of 7 days. Folinic acid was administered as a bolus in a fixed dose of 200 mg/m2/d and IFN as 5 million U/d subcutaneously on days 1 to 7. A total of 89 courses of therapy were completed for the 17 patients, of which there were 10 paired courses with a combination of 5-FU and IFN or 5-FU alone, being performed to analyze the pharmacokinetics and modulation of 5-FU by IFN. The maximum tolerated dose of 5-FU using this combination and a 4-hour schedule was 600 mg/m2/d for 7 days. The dose-limiting toxicity of this regimen was diarrhea. Mucositis and myelosuppression was not a marked problem at dose levels of 400 and 500 mg/m2/d for 7 days. However, at a dose level of 600 to 650 mg/m2/d for 7 days, grade 3 and 4 (WHO) leukopenia occurred in 50% and mucositis occurred in 33%. At a given dose of 5 million U, IFN did not significantly influence 5-FU serum levels. Mean steady-state serum levels of 5-FU at 500 mg/m2 given as a 4-hour infusion were 16.55 +/- 9.34 mumol/L and 18.23 +/- 12.77 mumol/L with and without IFN, respectively. Mean area under the curve (mumol/L x min) was 4,008 +/- 2,133 and 5,114 +/- 2,567 with and without interferon, respectively. Objective responses were seen in one of 17 of these heavily pretreated patients and stable disease was seen in seven of 17 patients. The recommended dose of 5-FU for use of phase II studies is 500 mg/m2/d for 7 days. We conclude that the toxicity of 5-FU plus FA with and without IFN alpha-2b can be reduced by using a 4-hour infusion instead of a bolus.