The Dihydrouracil/Uracil Ratios in Plasma and Toxicities of 5-Fluorouracil-Based Adjuvant Chemotherapy in Colorectal Cancer Patients

Background: This study was designed to measure the dihydrouracil (UH 2 )/uracil (U) ratio in plasma as a surrogate marker for dihydropyrimidine dehydrogenase (DPD) activity and to investigate the relationships of the UH 2 /U ratios in plasma with the toxicities of 5-fluorouracil (5-FU)-based adjuvant chemotherapy and 5-FU plasma concentrations in colorectal cancer patients. Methods: Thirty colorectal cancer patients received adjuvant chemotherapy of leucovorin plus 5-FU after operations. The concentrations of UH 2 , U and 5-FU were assayed by the high-performance liquid chromatography method. The relationships of the UH 2 /U ratios with the 5-FU toxicities and 5-FU plasma concentrations were analyzed.Results: There was a negative relationship between the UH 2 /U ratios and 5-FU plasma concentrations (p