Adjuvant chemotherapy in colorectal cancer patients is aimed at decreasing the relapse rate of the disease and increasing the disease-free and the overall survival of the patients. In a prospective study we evaluated the efficacy of 5-FU plus levamisole as an aduvant therapy for 153 patients with Dukes' B-2 or C colon or rectal cancer following a curative-intended surgery. Adjuvant chemotherapy was started within 4 to 6 weeks following the operation. Combination of 5-FU 375 mg/m(2)/day was given intravenously over 15-20 min for 5 consecutive days, every month for 1 year. Levamisole 50 mg t.i.d. was administered orally during the first 3 days of each course of chemotherapy. Rectal cancer patients were also irradiated to the tumor bed and pelvic lymphatics. The dose intensities (DI) of 5-FU and levamisole in our study were 432.6 mg/m(2)/w and 103.8 mg/m(2)/w, respectively. Failure analysis in Dukes' B and C patients showed that the rectum accounted for 47.5% of the relapses, of which only 3 cases were in the vicinity of the resected area. Almost half of the failures were observed within the year of adjuvant treatment. The liver was the most common site for first relapse (50%). The 3-year disease-free survival of Dukes' B-2 patients group was 84%, compared with 64% in Dukes' C. The main toxic manifestations were diarrhea, nausea and vomiting, weakness and mucositis. No dose reduction was needed. Our protocol, using lower DI of levamisole yielded similar results with a lower rate of toxicity than other common protocols.

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