Progres recents en chimiotherapie adjuvante des cancers du colon

Carcinoma of the large bowel is one of the most common malignant disease. In France, 15,000 died each year from the metastatic or locoregional progression of this cancer. In the past, effective surgical adjuvant therapy has been an elusive goal with no evidence of benefit from chemotherapy or immunotherapy. However, a meta-analysis published in 1988 showed that one-year adjuvant chemotherapy, using 5-fluorouracil (5-FU) containing regimens may slightly improve survival. Accelerated progress has been made since 1990: in colon cancer with regional nodal metastasis (stage C tumor), therapy with combined 5-FU and levamisole has resulted in a 33% reduction in tire death rate. Controlled clinical trials demonstrated improved tumor response rates when the combination of 5-FU and leucovorin was compared with single-agent 5-FU in patients with metastatic colorectal cancer. Recent results indicate that this combination is effective in preventing tumor relapse and improving survival in patients with high risk colon cancer (especially stage C tumor). The comparison of 5-FU and leucovorin to 5-FU and levamisole is ongoing; the preliminary results of these controlled trials showed that 6 months of adjuvant therapy, with 5-FU and leucovorin is as effective as the standard 12 months 5-FU and levamisole regimen and less toxic. No clear adjuvant benefit has been established in patients with Dukes' stage B2 colon cancer. The lack of statistical power of the trials and the 80% overall survival rate of these patients may explain these negative results. Almost all the specialists of these tumors considered that it is possible to select patients who are at sufficiently high risk of recurrence so that treatment can be justified. These patients are those who presented initially with tumor perforation or obstruction, adherence to or invasion of adjacent organs, young patients. Clinical trials suggest a survival benefit from the direct portal administration of the 5- FU in the immediate post-operative period, although the magnitude of the effect is less than that seen in the systemic therapy trials.