A simple and rapid UPLC-UV method for determining DPD functional status in patients with cancer.

Detecting patients with DPD deficiency is becoming a major concern in clinical oncology. Monitoring physiological plasma uracil and/or plasma uracil-to-dihydrouracil metabolic ratio is a common surrogate frequently used to determine DPD phenotype without direct measurement of the enzymatic activity. With respect to the rising number of patients to be analyzed, developing simple, rapid and affordable methods suitable to routine screening is critical. We have developed and validated a simple and robust UPLC-UV method with shorten (i.e., 12 minutes) analytical run times, compatible with these requirements of large-scale upfront screening. The method enabled detection of U over a 5-500 ng.mL-1 range (265 nm) and of UH2 over a 40-500 ng.mL-1 range (210 nm) in plasma with no chromatographic interference. When used as part of routine screening for DPD deficiency, this method was fully able to discriminate non-deficient patients (i.e., with U levels below 16 ng.mL-1 ) from deficient patients at risk of severe toxicities (i.e., U > 16 ng.mL-1 ). Results from one month of routine testing are presented and although no complete deficit were detected, 10,7% of the screened patients presented DPD deficiency and would thus require cut in dosing. Overall, this new method, using a simple pre-analytical solid-phase extraction procedure and based upon the use of standard UPLC apparatus is both cost- and time-effective and can be easily implemented at low cost in any laboratory about to start DPD testing in routine.