Fluoropyrimidines, such as 5-fluorouracil (5-FU) and capecitabine, are among the most frequently prescribed anticancer drugs. They are inactivated by the enzyme dihydropyrimidine dehydrogenase (DPD... Show moreFluoropyrimidines, such as 5-fluorouracil (5-FU) and capecitabine, are among the most frequently prescribed anticancer drugs. They are inactivated by the enzyme dihydropyrimidine dehydrogenase (DPD). Up to 5% of the population is DPD deficient and these patients have a significantly increased risk of severe and potentially lethal toxicity when treated with regular doses of 5-FU or capecitabine. DPD is encoded by the gene DPYD and variants in DPYD can lead to a decreased DPD activity. Although prospective DPYD genotyping is a valuable tool to identify patients with DPD deficiency, and thus those at risk for severe and potential life-threatening toxicity, prospective genotyping has not yet been implemented in daily clinical care.With this thesis we improved knowledge on different aspects of DPYD genotyping and DPD phenotyping, in order to better predict DPD deficient patients and personalize their therapy. In addition, we improved clinical implementation of DPYD genotyping, and reduced the risk of severe fluoropyrimidine-induced toxicity in DPYD variant allele carriers. Show less
Lunenburg, C.A.T.C.; Henricks, L.M.; Dreussi, E.; Peters, F.P.; Fiocco, M.; Meulendijks, D.; ... ; Gelderblom, H. 2018
Fluoropyrimidines are being used in the treatment of different types of cancer. The most common fluoropyrimidine is 5-flourouracil (5-FU), which is administered intravenously as a bolus or as... Show moreFluoropyrimidines are being used in the treatment of different types of cancer. The most common fluoropyrimidine is 5-flourouracil (5-FU), which is administered intravenously as a bolus or as prolonged infusion. Many tissues throughout the body express thymidine phosphorylase. Dihydropyrimidine Dehydrogenase (DPD) is involved in the degradation of endogenous pyrimidine nucleosides, but also in the degradation of fluoropyrimidines. More than 80% of the amount of 5-FU administered is catabolized primarily in the liver where DPD is abundantly expressed. DPD is encoded by the DPYD gene for which 567 coding variants are known to date, some of them being pathogenic by reducing enzyme capacity. Interindividual variability in the activity of DPD influences 5-FU pharmacokinetics and a reduced DPD activity can lead to severe toxicity and even death following administration of 5-FU or capecitabine. Knowledge regarding the clinical impact of reduced DPD activity on the pharmacokinetics and pharmacodynamics of fluoropyrimidines may be useful to dose individualize therapy. In this thesis, an in depth overview is given of methods and their potential to optimize fluoropyrimidine dosing based on individual DPD enzyme activity. Furthermore an oral uracil loading dose as probe for DPD deficiency in cancer patients treated with fluoropyrimdines for this purpose is studied. Show less
Treatment for advanced colorectal cancer (ACC) consists primarily of systemic treatment, mostly without curative intent. Systemic therapies are associated with potentially severe side effects.... Show moreTreatment for advanced colorectal cancer (ACC) consists primarily of systemic treatment, mostly without curative intent. Systemic therapies are associated with potentially severe side effects. Furthermore, treatment is not effective in all patients. Currently, pre-treatment predictors for efficacy and toxicity in systemic treatment of ACC are scarce. Germline genetic variation in genes encoding for enzymes involved in pharmacokinetics or pharmacodynamics of cytotoxic drugs could explain intra-patient differences in treatment effects. Pharmacogenetic studies aim at finding such germline genetic predictors. This thesis focusses on pharmacogenetics of capecitabine and oxaliplatin in treatment of ACC. First, it is established that results derived from DNA in archived tumor samples can be reliably compared to those using DNA from peripheral blood leukocytes. Then, germline genetic markers in MTHFR and MTRR, as well as markers derived from an in vitro genome-wide association study (GWAS) are tested for their association with capecitabine toxicity. Next, effects of ERCC1 genotype on oxaliplatin cytotoxicity in vitro and in clinical association analysis are addressed. The influence of genetic variation in organic cation transporters on oxaliplatin-induced neurotoxicity is examined. Lastly, the results of a GWAS searching for germline predictors of treatment efficacy of capecitabine, oxaliplatin and bevacizumab, with or without cetuximab, are presented. Show less
Even though treatment of several types of solid tumors has improved in the past few years with the introduction of the monoclonal antibodies against the epidermal growth factor receptor (EGFR) and... Show moreEven though treatment of several types of solid tumors has improved in the past few years with the introduction of the monoclonal antibodies against the epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF), the clinical benefit of these targeted therapies is modest. Pharmacogenetics has the potential to select patients with higher chance of response to agents that target these pathways. In the thesis, we describe the association of the FCGR3A Phe158Val polymorphism with progression-free survival in advanced colorectal cancer patients treated with cetuximab added to chemotherapy and bevacizumab. Following this finding, we found that cetuximab activates type 2 macrophages, which could have a negative effect on the clinical efficacy of cetuximab. Furthermore, we detected a genetic interaction profile consisting of the VEGF +405G>C and TYMS TSER polymorphisms, that was associated with the efficacy of capecitabine, oxaliplatin and bevacizumab in advanced colorectal cancer patients. Finally, we performed a genome wide association study with the same treatment, in which polymorphisms in the proximity of the AGPAT5 gene were associated with progression-free survival Show less
