[Fluorinated pyrimidines--administration methods]

In spite of the fact that fluorinated pyrimidines have been in extensive clinical use for more than 25 years, the optimal dose, route of administration and schedule have yet to be determined. An adequate course is considered to be one that produces either an objective response or mild toxicity. However, modification of dose schedule have shown considerable variation in rate of response, drug toxicity, and drug mortality. In contrast to its rapid clearance from blood, 5-fluorouracil may persist for prolonged period in cancer tissue. More detailed measurements of their metabolites in cancer tissue may lead to an improved understanding of 5-fluorouracil treatment.