Treatment of colorectal cancer. Current guidelines and future prospects for drug therapy.

Colorectal carcinoma is one of the most common cancers in Western countries (yearly incidence rate of 1:3000), and represents, after lung cancer, the second leading cause of deaths due to cancer. During the past decades, knowledge about this carcinoma has considerably increased, but little progress has been made in improvement in patient survival. At least 40% of patients with colorectal cancer will have metastases sometime during the course of their illness. In colon cancer, the first therapeutic approach is surgery, but the important role of adjuvant chemotherapy in these patients, in terms of disease-free survival and overall survival benefit, is now well established. Until today, standard therapy was represented by fluorouracil plus levamisole and/or calcium folinate (folinic acid). Other strategies are represented by monoclonal antibodies (mAb), which improve survival, (with a decrease in mortality by 32%), and by portal vein fluorouracil, alone or in combination with systemic therapy. In rectal cancer, the best results have been obtained with a combination of radiotherapy and chemotherapy. In advanced colorectal cancer, a standard treatment has not yet been established. This disease is usually considered as poorly chemosensitive and for more than 30 years fluorouracil has been the standard drug. Tumour response rates (partial+complete) for patients treated with bolus intravenous fluorouracil are 10 to 15%, with a median survival about 1 year. Many attempts have been made to improve these results. Biochemical modulation of fluorouracil is one of the most interesting strategies developed in the last few years in an attempt to increase the therapeutic index of this compound. Another way has been to administer fluorouracil by continuous infusion. Further innovative compounds such as irinotecan and raltitrexed are now being evaluated in clinical trials. Preliminary data from phase II and III studies have provided encouraging results on the use of these new drugs. In metastatic disease confined to the liver, the possibility of locoregional therapy through implantable pumps should be taken into consideration.