Phase II study of 5-fluorouracil plus leucovorin and interferon alpha 2b in advanced colorectal cancer.

15 untreated patients with advanced measurable colorectal cancer along with other 29 patients in progression after failing first line chemotherapy with fluoropyrimidines received 5-fluorouracil (5FU) 500 mg/m2 given as a weekly bolus at mid-infusion of leucovorin (LV), 500 mg/m2 administered intravenously over 2 h and interferon alpha 2b (IFN) 3 x 10(6) U given intramuscularly every other day. All patients had their previous chemotherapy at least 4 weeks prior to 5FU-LV-IFN. 5 patients discontinued the three drug regimen due to toxicity (intense weakness, fever and influenza-like symptoms in 4 patients; diarrhoea in 1 patient) however no grade IV toxicity was observed. IFN administration was reduced to twice/weekly in 5 patients due to influenza-like symptoms. 1 complete response and 5 partial responses were observed (13.6% response rate); the complete response was obtained in a patient resistant to 5FU: the response rate was only twice as much in untreated patients (3/15 patients, 20%) compared with that in patients previously treated with fluoropyrimidines (3/29 patients, 10.3%). Therefore, modulation of 5FU with LV plus IFN at the doses and schedules employed in this study may rarely overcome clinical resistance to the fluoropyrimidine and the addition of IFN does not appear to enhance the activity of 5FU plus LV.