A clinical and pharmacological study of 5-fluorouracil, leucovorin and interferon alfa in advanced colorectal cancer.

Modulation of 5-fluorouracil (FUra) using leucovorin (LV) is a standard treatment approach in patients with metastatic colorectal cancer. Modulation of FUra with interferon alfa has also shown some promise. Laboratory data have demonstrated increased cytotoxicity when FUra is combined with both LV and interferon. The current study examined the effects of double modulation of FUra using LV and interferon. Patients with measurable advanced colorectal cancer received bolus FUra 375 mg/m2 plus LV 20 mg/m2 daily for 5 days, repeated every 28 days. Recombinant human interferon alfa-2a, 3 million IU/m2 subcutaneously, was given daily on the days of chemotherapy then three times weekly. There was one complete response and nine partial responses (10/41) seen for an overall response rate of 24% (95% CI 12.0-40.0%). Overall, 70% of patients experienced one or more episodes of nonhematologic toxicity of grade 3 or more. Weight loss was common, with a mean decrease of 2.9 kg over the first two months (P < 0.0001). Improvements in tumor-related symptoms were balanced by increased fatigue and a deterioration in body weight and performance status. There was no evidence of progressive changes in FUra metabolism from interferon usage.