Phase II trial of recombinant beta interferon in advanced colorectal cancer.

Betaseron is a genetically altered recombinant beta interferon with in vitro properties equivalent to those of native beta interferon. Nineteen patients with measurable advanced colorectal carcinoma who had no previous chemotherapy were given 30 X 10(6) IU Betaseron by iv push on Days 1-5 and 8-12 of each 28-day cycle. One of 17 evaluable patients had a complete response after nine courses of treatment which has been sustained greater than 9 months. The overall response rate was 6% (95% confidence limits, 0%-18%). Treatment was well tolerated with toxic effects consisting of fever, flu-like symptoms, nausea and vomiting, and transient mild granulocytopenia and liver function abnormalities. All toxic effects were World Health Organization (WHO) grade less than or equal to 2. No interferon neutralizing antibody activity was detected. Phase I and preclinical data support further investigation of Betaseron with dose escalation to tolerance for individual patients, as well as investigation of concomitant therapy with 5-fluorouracil, in an attempt to improve the observed response rate in colorectal cancer.