Biological therapy of colon cancer

Levamisole is a synthetic phenylimidazothiazole oral antihelminth that exhibited non-specific immunostimu-latory properties in animal models [82]. Interest in this agent as a cancer therapy dates back to 1971. Small exploratory clinical studies were inconclusive, but considered encouraging enough to lead to randomized phase III trials in colon cancer. Two randomized trials failed to demonstrate a benefit for levamisole alone compared to placebo in the adjuvant setting. In one small double-blind U.S. trial 78 patients were randomized to receive 18 months of levamisole 2.5 mg/kg/day given on days 1 and 2 of each week, or placebo following resection of Dukes B or C colorectal cancer [8]. No benefit for levamisole was observed. In a double-blind randomized European trial comparing levamisole at 100 to 250 mg twice a week to placebo as adjuvant therapy for 297 patients with node-positive colon cancer, there again was no demonstrable benefit for levamisole [1].