A phase I study of 5-fluorouracil, leucovorin and levamisole

The activity of 5-fluorouracil (5-FU) against colon cancer is enhanced by leucovorin and the combination of 5-FU and levamisole has activity in the adjuvant treatment of colonic malignancies. The combination of 5-FU with both leucovorin and levamisole may provide additional benefit in the treatment of colon cancer.

A phase I study to assess qualitative and quantitative toxicities of this three-drug combination and to determine a dose for further phase II testing was undertaken. The role of levamisole as an immunomodulator was also assessed.

A group of 38 patients with incurable metastatic malignancies received 119 cycles of treatment at eight dose levels. 5-FU (375 mg/m2 per day) and leucovorin (200 mg/m2 per day) were administered intravenously (days 1-5). Levamisole was administered orally (days 1-3 and 15-17) at doses from 30 to 470 mg/m2 per day. Patients received both 5FU/leucovorin and 5-FU/leucovorin/levamisole in random order for their initial two cycles. All subsequent treatments were with the three-drug combination. Toxicities included nausea, vomiting, stomatitis, thrombocytopenia and granulocytopenia. Diarrhea was the dose-limiting toxicity at 470 mg/m2 per day levamisole. The addition of levamisole resulted in more toxicity than 5-FU and leucovorin alone. No clinical responses were seen with this regimen. The addition of levamisole resulted in more immunomodulation than 5-FU and leucovorin alone as evidenced by release of neopterin from monocytes.

With this schedule and dose of 5-FU and leucovorin, the maximum tolerated dose of levamisole was 354 mg/m2. However, given the lack of response and the absence of dose-dependent immunomodulation, this may not be the appropriate dose for further phase 11 studies.