Real-time follow-up of 5-fluorouracil metabolism in the liver of tumor patients by means of F-19 MR spectroscopy.

Intraarterial 5-fluorouracil (5-FU) chemotherapy in eight patients, one with primary and seven with secondary liver tumors, was monitored by means of in vivo fluorine-19 magnetic resonance (MR) spectroscopy. F-19 MR spectra were obtained with surface coils and included signal contributions from both liver and tumor tissue. The time course of the relative concentrations of 5-FU and its major catabolite, alpha-fluoro-beta-alanine (FBAL), was followed for up to 100 minutes after the start of drug administration. The time constants for the kinetics of 5-FU ranged from 8 to 75 minutes, whereas the time constants for FBAL were either approximately 15 or 50 minutes. A broad peak comprising nucleoside and nucleotide anabolites of 5-FU was detected in one patient. These investigations demonstrate the feasibility of short-term therapy monitoring with F-19 MR spectroscopy and that catabolites and anabolites of 5-FU can be observed separately. However, since no F-19 MR spectroscopy localization sequence is available at present, the contributions to the total MR signal from normal liver and tumor tissue cannot be discriminated.