Purpose: Phase II studies have shown that the combination of interferon alfa-2b (IFN) and fluorouracil (5-FU) is active in patients with metastatic colon cancer. This study was designed to investigate whether treatment with the combination of IFN and 5-FU could improve the response rate, duration of response, or survival compared with treatment with 5-FU alone.
Patients and methods: Patients with histologically confirmed advanced colorectal cancer were randomized to receive 5-FU 750 mg/m2/d by continuous infusion for 5 consecutive days followed by weekly bolus 5-FU 750 mg/m2 either with or without IFN 10 MU subcutaneously three times weekly. Treatment was continued until disease progression or unacceptable toxicity for up to 12 months.
Results: Radiologic response was observed in 26 of 106 assessable patients (25%): 10 of 52 (19%) in the group that received 5-FU plus IFN (all partial responses [PRs]) and 16 of 54 (30%) in the 5-FU-alone group (three complete responses [CRs] and 13 PRs) (P = .21). There was similarly no significant difference between the two groups in progression-free survival (median, 3 months), 1-year survival, or overall survival (median, 8 months). However, patients who received IFN did experience significantly more toxicity in the form of leukopenia (P = .013), lymphopenia (P = .01), depression (P = .014), and alopecia (P = .002), and were significantly more likely to be withdrawn due to adverse events (P = .003). There were four toxic deaths, all of which occurred in patients who had received IFN.
Conclusion: At the doses and schedules used in this study, IFN affords no benefit to 5-FU in terms of response and survival and significantly increases toxicity for patients with advanced colorectal cancer.