The History, Mechanism and Clinical Use of Oral 5-Fluorouracil Derivative Chemotherapeutic Agents

The role of oral chemotherapy has been getting expanded because of the potential advantage in patients' convenience and better quality of life as well as in cost-effectiveness as compared with intravenous chemotherapy. In this article, the history, mechanism of anti-tumor activity, and clinical use of oral chemotherapy using 5-fluorouracil (5-FU) derivative chemotherapeutic agents are reviewed. Pharmacological analysis has revealed that 5-FU, a basic chemotherapeutic agent widely used against a variety of malignant tumors, shows a time dependent anti-tumor activity, and that continuous maintenance of 5-FU concentration in blood is the optimal method in 5-FU administration. UFT, a combination drug of ftorafur (tetrahydrofuranyl-5-fluorouracil, tegafur, FT) and uracil, has been developed to have potent anti-tumor activity by maintaining higher 5-FU concentration in blood and tumor tissues for a long time. FT is a pro-drug that releases 5-FU continuously, and uracil is added to inhibit degradation of the released 5-FU. Clinically, oral administration of UFT has proved to be effective as an adjuvant therapy after surgery for some malignant tumors such as non-small cell lung cancer. Moreover, UFT has proved to be effective for inoperable advanced malignancies such as colorectal cancer, especially in combination with leucovorin or cisplatin. Recently, S-1, a more active oral 5-FU derivative chemotherapeutic agent has been developed in Japan. Several factors to affect anti-tumor effects and/or toxicities of 5-FU and the derivatives, such as thymidylate synthase activity, dehydropyrimidine dehydrogenase activity and p53 status, are also discussed in the article. In conclusion, oral administration of 5-FU derivatives such as UFT may have several clinical advantages over intravenous 5-FU administration.