[Neoadjuvant therapy for colorectal cancer].

To assess the role of neoadjuvant therapy in the treatment of colorectal cancer, we reviewed the literature investigating the effects of chemotherapy and/or radiotherapy given prior to surgery. Rationales for enteral administration of fluoropyrimidines preoperatively, in terms of pharmacokinetic and antitumor effects, have been demonstrated in clinical studies. For instance, the concentration of 5-FU in cancer tissue was shown to be significantly higher than in normal tissue, and a dose-response relationship between the cumulative doses of the agent and the histological antitumor effect was observed. Among several comparative studies, there were reports suggesting the efficacy of preoperative chemotherapy. The treatment group had a slight, but insignificant, improvement in disease-free interval or long-term survival. On the other hand, some randomized trials for rectal cancer demonstrated that preoperative radiotherapy could decrease local failure, and that patients who underwent curative surgery appeared to have an improved 5-year survival compared to the controls, although overall survival was not improved. Recent reports on combined modality treatment with chemotherapy and radiotherapy clearly showed a downstaging effect on the primary tumor and the decreased prevalence of regional involved lymph node. Further developments through rationally designed study are necessary to ascertain the efficacy of neoadjuvant therapy for colorectal cancer.