Biochemical modulation of 5-fluorouracil by leucovorin with or without interferon-alpha-2c in patients with advanced colorectal cancer: final results of a randomised phase III study.

5-Fluorouracil (5-FU) remains the mainstay of treatment for advanced colorectal carcinoma, although response rates are generally less than 20%. Improved therapeutic efficacy has been reported using biochemical modulation of 5-FU by leucovorin (LV) or interferon alpha (IFN), the combination of 5-FU/LV frequently considered as standard therapy in metastatic colorectal cancer. In an attempt to enhance the cytotoxicity of 5-FU, a prospective randomised trial was initiated to compare 5-FU/LV with 5-FU/LV plus IFN. Patients were randomised to receive either LV, 100 mg/m2 intravenously (i.v.), followed by 5-FU, 500 mg/m2 as a 1-h i.v. infusion, daily for 4 days, followed by weekly infusions until week 8, or the same regimen of 5-FU/LV plus IFN-alpha-2c, 30 micrograms subcutaneously (s.c.), three times weekly. Cycles were repeated after a 2-week rest period. Among 269 enrolled patients, 219 were available for response and 243 for toxicity. An objective tumour response was observed in 38 of 107 (36%) and 28 of 112 (25%) patients in the treatment arms with and without IFN, respectively (difference not significant). There was no significant difference between the two groups in response duration (median 8.4 versus 12.1 months), time to treatment failure (median 6.5 versus 4.9 months), or overall survival (median 10.0 versus 12.6 months). However, patients in the IFN arm experienced significantly more haematological and gastrointestinal toxicity and more frequent alopecia. In conclusion, the addition of IFN to 5-FU/LV in the schedules and doses used in the study did not provide any clinical benefit over 5-FU/LV alone and cannot be recommended for routine use in the treatment of advanced colorectal cancer.