In vivo monitoring of fluoropyrimidine metabolites: magnetic resonance spectroscopy in the evaluation of 5-fluorouracil.

Since 5-fluorouracil (5-FU) was synthesized in the late 1950s it has become an important component of many anticancer treatment regimens. The increasing volume of literature accumulating about this drug is evidence that the optimal administration schedule and its combination with modulators has yet to be determined. Much of the investigation of 5-FU, particularly in the clinical setting, has been in the development of administration schedules based on plasma pharmacokinetic data. Particularly with the development of modulators of 5-FU, investigators are looking more closely at its intracellular tissue pharmacology and metabolism. To study the tissue metabolism of 5-FU (and other drugs), patients often have to be willing to undergo invasive procedures, sometimes with significant discomfort, usually with little direct benefit to their management. The ability to conduct an investigation of the cellular effects of a drug in both tumor and normal tissue non-invasively will not only be more acceptable to patients, resulting in better compliance to protocols, but will give information about the in situ tissue which is not subject to the problems of invasive sampling techniques. Magnetic resonance spectroscopy is a non-invasive technique that has recently started to show potential in the area of investigating 5-FU metabolism and its impact on tumor and patient outcome. Further development of this method may ultimately have an impact on the investigation of any new anticancer agent.