Phase I and II studies of the combination of recombinant human interferon-gamma and 5-fluorouracil in patients with advanced colorectal carcinoma.

Based on the in vitro and in vivo data suggesting synergistic cytolysis by the combination of 5-fluorouracil and interferon-gamma against a variety of malignant cell lines including a human colon carcinoma cell line (HT-29), we initiated studies in patients with advanced colon or rectal carcinoma. Forty-six patients received 5-fluorouracil as an intravenous injection on days 1-5 and recombinant human interferon-gamma as an intramuscular injection on days 1-14, followed by a rest period of 14 days; courses were repeated every 28 days. In the phase I study, cohorts of two patients received a stepwise dose level increase to achieve the maximum tolerated dose (MTD), at which a total of six patients were studied. The dose levels constituting the MTD were as follows: 5-fluorouracil (500 g/m2/day) and recombinant gamma-interferon (0.5 mg/m2/day). Four patients achieved a partial response in the phase I study. In the phase II study, 30 patients received therapy at the MTD. Among 29 evaluable patients in the phase II study, two patients achieved a partial response. Common toxicities included malaise, fever, anorexia, nausea and vomiting, and diarrhea. Transient severe myelosuppression was common but did not result in significant morbidity. Our data suggest that the combination of 5-fluorouracil and recombinant gamma-interferon did not have the same antitumor effect in patients as it had in the preclinical experiments.