Page 273 - Personalised medicine of fluoropyrimidines using DPYD pharmacogenetics Carin Lunenburg

plasma using a high-performance liquid chromatography ultra-violet (HPLC-UV) method in the laboratory of the Department of Pharmacy at the Scheper Hospital in Emmen.
2-13C-uracil breath test8-10
A personalized dose of 6 mg/kg 2-13C uracil was administered to patients after overnight fasting (minimum eight hours) and alcohol abstaining (minimum 24 hours). Food and drinks had to be abstained for the duration of the assay as well. The 2-13C uracil was dissolved in hot water and administered between 8 and 9 am, to minimize effects of circadian rhythm. Just prior to the administration of the 2-13C uracil solution the patients had to ingest two tablets of Alka-Seltzer Gold® (containing anhydrous citric acid, potassium bicarbonate and sodium bicarbonate) with water, to stimulate uniform and fast absorption of the 2-13C uracil solution. Breath samples (300 ml in a Otsuka Pharmaceuticals breath bag, Japan®) and blood samples (4 ml in a heparin tube) were taken pre-dose and 50 minutes after administration of uracil. Blood samples were centrifuged immediately at 4°C at 1,500g for ten minutes. Plasma was kept at -80°C until analysis. Quantification of 13C-uracil and 13C-dihydrouracil levels was done using the same UPLC-MS/MS method as for the endogenous DHU/U ratio at the Netherlands Cancer Institute, Amsterdam, but with uracil-13C4,15N2 and dihydrouracil- 13C4,15N2 as internal standards. 13CO2 and 12CO2 concentrations were determined in the exhaled breath samples by infrared spectrometry using the FDA approved POCone IR spectrometer (Photal Electronics, Japan®) at the laboratory of the department of Clinical Pharmacy and Toxicology at the Leiden University Medical Center or at the Division of Pharmacology at the Netherlands Cancer Institute, Amsterdam. A delta-over-baseline (DOB) ratio at 50 minutes was calculated that represents a change in the 13CO2/12CO2 ratio of two breath samples.
Supplementary results
Supplementary Table 1. Toxicity data of patients who underwent three or four DPD phenotyping assays and the main study cohort
10
Supplement
Type of event
Overall grade ≥3 toxicity
Grade ≥3 gastrointestinal toxicity
Grade ≥3 hematological toxicity
Grade 3 hand-foot syndrome
Grade ≥3 cardiological toxicity
Grade ≥3 other treatment-related toxicity
Fluoropyrimidine-related hospitalization
Stop of fluoropyrimidines due to adverse events Fluoropyrimidine-related death
Phenotyping assays (N=92)
19 (21%) 6 (7%) 10 (11%) 4 (4%)
0
3 (3%)
7 (8%) 20 (22%) 0
Main study cohort (N=1,103)
264 (24%) 103 (9%) 78 (7%) 37 (3%) 10 (1%) 87 (8%) 156 (14%) 190 (17%) 2 (0%)
P-valuea
0.477 0.367 0.180 0.389 0.447 0.106 0.079 0.133 ND
four DPD phenotyping test.
a All p-values represent a comparison of 92 patients who underwent three or assays to patients from the main study cohort. We used χ2 test or Fisher exact Abbreviations: ND: not done.
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