Background and objective:

dihydropyridine dehydrogenase (DPD) deficiency has been associated with an increased risk of toxicity after exposure to fluoropyrimidines (FP). Determination of endogenous uracil (U) plasma concentrations is the recommended test to identify DPD deficiency. However, the value of U can be affected by various factors. The objective was to determine the serum concentration of U in a population candidate to receive treatment with FP and to verify if its distribution was compatible with the prevalence of partial DPD deficiency estimated in the Caucasian population.

Material and methods:

prospective observational study in which cancer patients candidates for FP treatment were included. For the analytical determination, a Dionex Ultimate 3000 UHPLC system coupled to a Q-exactive hybrid quadrupole-orbitrap mass spectrometer was used.

Results:

77 patients, with a mean age of 71 years, were included. The mean and median serum U concentrations were 30.4 and 24.0 ng/ml, respectively. The range was from 7.1 to 139.7 ng/ml. 79.2% of the patients presented a U level between 16 and 150ng/ml, showing a statistically significant difference when compared to the estimated prevalence in the Caucasian population (8%) (p-value <0.0001). The analytical method used has a correlation coefficient R2 > 0.99 and a detection limit <0.2 ng/ml.

Conclusions:

it is necessary to carry out more studies with a design aimed at establishing the optimal conditions related to the pretreatment of the samples in order to avoid or minimize the influence of these factors on the analyte values.