Posible influencia de factores no controlados en las concentraciones séricas de uracilo / Possible influence of uncontrolled factors on serum uracil concentrations

Antecedentes y objetivos: el déficit de dihidropirimidina deshidrogenasa (DPD) se ha asociado con un mayor riesgo de toxicidad tras exposición a fluoropirimidinas (FP). La determinación de las concentraciones plasmáticas de uracilo endógeno (U) es la prueba recomendada para identificar el déficit de DPD. Sin embargo, el valor de U puede verse afectado por diversos factores. El objetivo fue determinar la concentración sérica de U en una población candidata a recibir tratamiento con FP y comprobar si su distribución era compatible con la prevalencia del déficit parcial de DPD estimada en población caucásica. Material y métodos: estudio observacional prospectivo en el que se incluyeron pacientes oncológicos candidatos a tratamiento con FP. Para la determinación analítica se empleó un sistema Dionex Ultimate 3000 UHPLC, acoplado a un espectrómetro de masas cuadrupolo-orbitrap híbrido Q-exactive. Resultados: se incluyeron 77 pacientes con una edad media de 71 años. La media y la mediana de las concentraciones séricas de U fue 30,4 y 24,0 ng/ml, respectivamente. El rango fue de 7,1 a 139,7 ng/ml. Un 79,2% de los pacientes presentó un nivel de U comprendido entre 16 y 150 ng/ml, mostrando una diferencia estadísticamente significativa al compararlo con la prevalencia estimada en población caucásica (8%) (p-valor <0,0001). El método analítico empleado tiene un coeficiente de correlación R2 > 0,99 y un límite de detección <0,2 ng/ml. Conclusiones: es necesario llevar a cabo más estudios con un diseño dirigido a establecer las condiciones óptimas relativas al pretratamiento de las muestras a fin de evitar o minimizar la influencia de estos factores sobre los valores del analito. (AU)

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. (AU)

Toxicities associated with chemotherapy regimens containing a fluoropyrimidine: A real-life evaluation in France.

AIMS: Despite fluoropyrimidines (FPs) constituting the main component of the chemotherapy combination protocols in 50% of chemotherapies for solid tumour treatments, incidence data for FP-related toxicity are poorly documented in real life. This study evaluated the number of patients receiving FP-based chemotherapies in France, along with the true incidence of FP-related serious adverse effects (SAEs) before the recent mandatory dihydropyrimidine dehydrogenase (DPD)-screening was introduced by French health authorities, DPD being the rate-limiting enzyme of 5-fluorouracil (5-FU) catabolism. METHODS: Exhaustive data on the number of patients treated with FP-based chemotherapy in 2013-2014 were collected in the Centre-Val de Loire region of France. True incidence of SAEs was extracted from a cohort of 513 patients with incident solid tumours receiving first-line FP-based chemotherapy. RESULTS: After extrapolation at national level, we estimated that 76,200 patients are currently treated annually with 5FU (53,100 patients, 62% digestive system-related versus 26% breast cancers versus 12% head and neck cancers) or capecitabine (23,100 patients, 45% digestive system-related versus 37% breast cancers versus 18% non-documented). Earlier (in the first two cycles) the SAE incidence rate was 19.3% (95% confidence interval (CI) 16-23%) including one toxic death (0.2%, 95%CI 0-1%). SAE incidence rate was 32.2% (95%CI 28-36%) over the first 6 months of treatment. Incidence of death, life-threatening prognosis or incapacity/disability was 1.4% (95%CI 0.4-2.4%) and 1.6% (95%CI 0.5-2.6%) during first two cycles and first 6 months, respectively. CONCLUSION: These data highlight the significant public health issue related to FP toxicity, with around 1200 patients developing FP-related life-threatening prognosis or incapacity/disability annually in France, including 150 toxic deaths. It is hoped that DPD-deficiency screening will reduce such iatrogenic events and eradicate toxic deaths.