A novel large intragenic DPYD deletion causing dihydropyrimidine dehydrogenase deficiency: a case report.

BACKGROUND: Dihydropyrimidine dehydrogenase (DPD), is the initial and rate-limiting enzyme in the catabolic pathway of pyrimidines. Deleterious variants in the DPYD gene cause DPD deficiency, a rare autosomal recessive disorder. The clinical spectrum of affected individuals is wide ranging from asymptomatic to severely affected patients presenting with intellectual disability, motor retardation, developmental delay and seizures. DPD is also important as the main enzyme in the catabolism of 5-fluorouracil (5-FU) which is extensively used as a chemotherapeutic agent. Even in the absence of clinical symptoms, individuals with either complete or partial DPD deficiency face a high risk of severe and even fatal fluoropyrimidine-associated toxicity. The identification of causative genetic variants in DPYD is therefore gaining increasing attention due to their potential use as predictive markers of fluoropyrimidine toxicity. METHODS: A male infant patient displaying biochemical features of DPD deficiency was investigated by clinical exome sequencing. Bioinformatics tools were used for data analysis and results were confirmed by MLPA and Sanger sequencing. RESULTS: A novel intragenic deletion of 71.2 kb in the DPYD gene was identified in homozygosity. The deletion, DPYD(NM_000110.4):c.850 + 23455_1128 + 8811del, eliminates exons 9 and 10 and may have resulted from a non-homologous end-joining event, as suggested by in silico analysis. CONCLUSIONS: The study expands the spectrum of DPYD variants associated with DPD deficiency. Furthermore, it raises the concern that patients at risk for fluoropyrimidine toxicity due to DPYD deletions could be missed during pre-treatment genetic testing for the currently recommended single nucleotide polymorphisms.

Impact of renal impairment on dihydropyrimidine dehydrogenase (DPD) phenotyping.

BACKGROUND: The chemotherapeutic agent 5-fluorouracil (5-FU) is catabolized by dihydropyrimidine dehydrogenase (DPD), the deficiency of which may lead to severe toxicity or death. Since 2019, DPD deficiency testing, based on uracilemia, is mandatory in France and recommended in Europe before initiating fluoropyrimidine-based regimens. However, it has been recently shown that renal impairment may impact uracil concentration and thus DPD phenotyping. PATIENTS AND METHODS: The impact of renal function on uracilemia and DPD phenotype was studied on 3039 samples obtained from three French centers. We also explored the influence of dialysis and measured glomerular filtration rate (mGFR) on both parameters. Finally, using patients as their own controls, we assessed as to what extent modifications in renal function impacted uracilemia and DPD phenotyping. RESULTS: We observed that uracilemia and DPD-deficient phenotypes increased concomitantly to the severity of renal impairment based on the estimated GFR, independently and more critically than hepatic function. This observation was confirmed with the mGFR. The risk of being classified 'DPD deficient' based on uracilemia was statistically higher in patients with renal impairment or dialyzed if uracilemia was measured before dialysis but not after. Indeed, the rate of DPD deficiency decreased from 86.4% before dialysis to 13.7% after. Moreover, for patients with transient renal impairment, the rate of DPD deficiency dropped dramatically from 83.3% to 16.7% when patients restored their renal function, especially in patients with an uracilemia close to 16 ng/ml. CONCLUSIONS: DPD deficiency testing using uracilemia could be misleading in patients with renal impairment. When possible, uracilemia should be reassessed in case of transient renal impairment. For patients under dialysis, testing of DPD deficiency should be carried out on samples taken after dialysis. Hence, 5-FU therapeutic drug monitoring would be particularly helpful to guide dose adjustments in patients with elevated uracil and renal impairment.

Implementation of dihydropyrimidine dehydrogenase deficiency testing in Europe.

BACKGROUND: The main cause for fluoropyrimidine-related toxicity is deficiency of the metabolizing enzyme dihydropyrimidine dehydrogenase (DPD). In 2020, the European Medicines Agency (EMA) recommended two methods for pre-treatment DPD deficiency testing in clinical practice: phenotyping using endogenous uracil concentration or genotyping for DPYD risk variant alleles. This study assessed the DPD testing implementation status in Europe before (2019) and after (2021) the release of the EMA recommendations. METHODS: The survey was conducted from 16 March 2022 to 31 July 2022. An electronic form with seven closed and three open questions was e-mailed to 251 professionals with DPD testing expertise of 34 European countries. A descriptive analysis was conducted. RESULTS: We received 79 responses (31%) from 23 countries. Following publication of the EMA recommendations, 87% and 75% of the countries reported an increase in the amount of genotype and phenotype testing, respectively. Implementation of novel local guidelines was reported by 21 responders (27%). Countries reporting reimbursement of both tests increased in 2021, and only four (18%) countries reported no coverage for any testing type. In 2019, major implementation drivers were 'retrospective assessment of fluoropyrimidine-related toxicity' (39%), and in 2021, testing was driven by 'publication of guidelines' (40%). Although the major hurdles remained the same after EMA recommendations-'lack of reimbursement' (26%; 2019 versus 15%; 2021) and 'lack of recognizing the clinical relevance by medical oncologists' (25%; 2019 versus 8%; 2021)-the percentage of specialists citing these decreased. Following EMA recommendations, 25% of responders reported no hurdles at all in the adoption of the new testing practice in the clinics. CONCLUSIONS: The EMA recommendations have supported the implementation of DPD deficiency testing in Europe. Key factors for successful implementation were test reimbursement and clear clinical guidelines. Further efforts to improve the oncologists' awareness of the clinical relevance of DPD testing in clinical practice are needed.

Implementation and clinical benefit of DPYD genotyping in a Danish cancer population.

BACKGROUND: In 2020, the European Medicines Agency recommended testing patients for dihydropyrimidine dehydrogenase (DPD) deficiency before systemic treatment with fluoropyrimidines (FP). DPD activity testing identifies patients at elevated risk of severe FP-related toxicity (FP-TOX). The two most used methods for DPD testing are DPYD genotyping and DPD phenotyping (plasma uracil concentration). The primary objective of this study was to compare the overall frequency of overall grade ≥3 FP-TOX before and after the implementation of DPYD genotyping. PATIENTS AND METHODS: Two hundred thirty Danish, primarily gastrointestinal cancer patients, were DPYD-genotyped before their first dose of FP, and blood was sampled for post hoc assessment of P-uracil. The initial dose was reduced for variant carriers. Grade ≥3 FP-TOX was registered after the first three treatment cycles of FP. The frequency of toxicity was compared to a historical cohort of 492 patients with post hoc determined DPYD genotype from a biobank. RESULTS: The frequency of overall grade ≥3 FP-TOX was 27% in the DPYD genotype-guided group compared to 24% in the historical cohort. In DPYD variant carriers, DPYD genotyping reduced the frequency of FP-related hospitalization from 19% to 0%. In the control group, 4.8% of DPYD variant carriers died due to FP-TOX compared to 0% in the group receiving DPYD genotype-guided dosing of FP. In the intervention group, wild-type patients with uracil ≥16 ng/ml had a higher frequency of FP-TOX than wild-type patients with uracil <16 ng/ml (55% versus 28%). CONCLUSIONS: We found no population-level benefit of DPYD genotyping when comparing the risk of grade ≥3 FP-TOX before and after clinical implementation. We observed no deaths or FP-related hospitalizations in patients whose FP treatment was guided by a variant DPYD genotype. The use of DPD phenotyping may add valuable information in DPYD wild-type patients.

Awareness and attitudes of oncology specialists toward dihydropyrimidine dehydrogenase testing in Saudi Arabia.

BACKGROUND: Fluoropyrimidines (FP) are among the most common class of prescribed anti-neoplastic drugs. This class has severe to moderate toxicity in around 10%-40% of those who take 5-fluorouracil (5-FU) or capecitabine for the treatment of cancer. In practice many patients with severe toxicities from FP use had dihydropyrimidine dehydrogenase (DPD) enzyme deficiency. Several studies have proposed DPD screening before treatment with 5-fluorouracil (5-FU) and capecitabine or other drugs belonging to the FP group. This study aims to assess the level of awareness and attitudes of oncology specialists in Saudi Arabia toward genetic screening for DPD prior to giving FP. This highlights the importance of health guidelines required for implementation in our health care system, as a framework to adopt testing as a regular practice in clinical care. Based on the findings in this study, guidelines have been suggested for the Middle East North Africa region. METHODS: A cross-sectional survey study was conducted during 2021 targeting oncologists and clinical pharmacists working in the oncology departments across Saudi Arabia. RESULTS: A total of 130 oncologists and pharmacists completed the questionnaire representing a response rate of 87%. Most of the respondents indicated that they prescribe FP in clinical practice, but 41% of respondents reported that they have never ordered a specific molecular test during their practice. Only 20% of respondents reported that they often screen for DPD deficiency prior to prescribing FP. Significantly higher rates of awareness of potential dihydropyrimidine dehydrogenase gene (DPYD) mutation were observed among respondents in governmental hospitals (81.1% vs. 47.4% in private hospitals), and among those with more years of practice (80.6% if 5 or more years of practice vs. 59.3% if less than 5 years of practice). Also, higher rates of observing the impact of DPD testing were present among respondents with a PharmD (35% vs. 11% for oncologists and 18% for other professions) and among those with 5 or more years of practice (24.6% vs. 7.7% among those with less than 5 years). CONCLUSION: While in some institutions there is a high level of awareness among oncology specialists in Saudi Arabia regarding the effect of the potentially serious DPD enzyme deficiency as a result of gene mutations, screening for these mutations prior to prescribing FP is not a routine practice in hospitals across the country. The findings of this study should promote personalized medicine with recognition of interpatient variability via DPD testing to manage the risks of FP prescribing more effectively in the Kingdom of Saudi Arabia.

Cost-effectiveness of DPYD Genotyping Prior to Fluoropyrimidine-based Adjuvant Chemotherapy for Colon Cancer.

BACKGROUND: Adjuvant fluoropyrimidine-based chemotherapy substantially reduces recurrence and mortality after resection of stage 3 colon cancer. While standard doses of 5-fluorouracil and capecitabine are safe for most patients, the risk of severe toxicity is increased for the approximately 6% of patients with dihydropyimidine dehydrogenase (DPD) deficiency caused by pathogenic DPYD gene variants. Pre-treatment screening for pathogenic DPYD gene variants reduces severe toxicity but has not been widely adopted in the United States. METHODS: We conducted a cost-effectiveness analysis of DPYD genotyping prior to fluoropyrimidine-based adjuvant chemotherapy for stage 3 colon cancer, covering the c.1129-5923C>G (HapB3), c.1679T>G (*13), c.1905+1G>A (*2A), and c.2846A>T gene variants. We used a Markov model with a 5-year horizon, taking a United States healthcare perspective. Simulated patients with pathogenic DPYD gene variants received reduced-dose fluoropyrimidine chemotherapy. The primary outcome was the incremental cost-effectiveness ratio (ICER) for DPYD genotyping. RESULTS: Compared with no screening for DPD deficiency, DPYD genotyping increased per-patient costs by $78 and improved survival by 0.0038 quality-adjusted life years (QALYs), leading to an ICER of $20,506/QALY. In 1-way sensitivity analyses, The ICER exceeded $50,000 per QALY when the cost of the DPYD genotyping assay was greater than $286. In probabilistic sensitivity analysis using a willingness-to-pay threshold of $50,000/QALY DPYD genotyping was preferred to no screening in 96.2% of iterations. CONCLUSION: Among patients receiving adjuvant chemotherapy for stage 3 colon cancer, screening for DPD deficiency with DPYD genotyping is a cost-effective strategy for preventing infrequent but severe and sometimes fatal toxicities of fluoropyrimidine chemotherapy.

Cancer genomic profiling identified dihydropyrimidine dehydrogenase deficiency in bladder cancer promotes sensitivity to gemcitabine.

Chemotherapy is a standard therapy for muscle-invasive bladder cancer (MIBC). However, genomic alterations associated with chemotherapy sensitivity in MIBC have not been fully explored. This study aimed to investigate the genomic landscape of MIBC in association with the response to chemotherapy and to explore the biological role of genomic alterations. Genomic alterations in MIBC were sequenced by targeted exome sequencing of 409 genes. Gene expression in MIBC tissues was analyzed by western blotting, immunohistochemistry, and RNA microarray. Cellular sensitivity to gemcitabine and gemcitabine metabolite was examined in bladder cancer cells after modulation of candidate gene. Targeted exome sequencing in 20 cases with MIBC revealed various genomic alterations including pathogenic missense mutation of DPYD gene encoding dihydropyrimidine dehydrogenase (DPD). Conversely, high DPYD and DPD expression were associated with poor response to gemcitabine-containing chemotherapy among patients with MIBC, as well as gemcitabine resistance in bladder cancer cells. DPD suppression rendered cells sensitive to gemcitabine, while DPD overexpression made cells gemcitabine-resistant through reduced activity of the cytotoxic gemcitabine metabolite difluorodeoxycytidine diphosphate. This study revealed the novel role of DPD in gemcitabine metabolism. It has been suggested that DPYD genomic alterations and DPD expression are potential predictive biomarkers in gemcitabine treatment.

Dihydropyrimidine Dehydrogenase Deficiency and Implementation of Upfront DPYD Genotyping.

Fluoropyrimidines (FP; 5-fluorouracil, capecitabine, and tegafur) are a commonly prescribed class of antimetabolite chemotherapies, used for various solid organ malignancies in over 2 million patients globally per annum. Dihydropyrimidine dehydrogenase (DPD), encoded by the DPYD gene, is the critical enzyme implicated in FP metabolism. DPYD variant genotypes can result in decreased DPD production, leading to the development of severe toxicities resulting in hospitalization, intensive care admission, and even death. Management of toxicity incurs financial burden on both patients and healthcare systems alike. Upfront DPYD genotyping to identify variant carriers allows an opportunity to identify patients who are at high risk to suffer from serious toxicities and allow prospective dose adjustment of FP treatment. This approach has been shown to reduce patient morbidity, as well as improve the cost-effectiveness of managing FP treatment. Upfront DPYD genotyping has been recently endorsed by several countries in Europe and the United Kingdom. This review summarizes current knowledge about DPD deficiency and upfront DPYD genotyping, including clinical and cost-effectiveness outcomes, with the intent of supporting implementation of an upfront DPYD genotyping service with individualized dose-personalization.

Dihydropyrimidine Dehydrogenase Phenotyping Using Pretreatment Uracil: A Note of Caution Based on a Large Prospective Clinical Study.

In clinical practice, 25-30% of the patients treated with fluoropyrimidines experience severe fluoropyrimidine-related toxicity. Extensively clinically validated DPYD genotyping tests are available to identify patients at risk of severe toxicity due to decreased activity of dihydropyrimidine dehydrogenase (DPD), the rate limiting enzyme in fluoropyrimidine metabolism. In April 2020, the European Medicines Agency recommended that, as an alternative for DPYD genotype-based testing for DPD deficiency, also phenotype testing based on pretreatment plasma uracil levels is a suitable method to identify patients with DPD deficiency. Although the evidence for genotype-directed dosing of fluoropyrimidines is substantial, the level of evidence supporting plasma uracil levels to predict DPD activity in clinical practice is limited. Notwithstanding this, uracil-based phenotyping is now used in clinical practice in various countries in Europe. We aimed to determine the value of pretreatment uracil levels in predicting DPD deficiency and severe treatment-related toxicity. To this end, we determined pretreatment uracil levels in 955 patients with cancer, and assessed the correlation with DPD activity in peripheral blood mononuclear cells (PBMCs) and fluoropyrimidine-related severe toxicity. We identified substantial issues concerning the use of pretreatment uracil in clinical practice, including large between-center study differences in measured pretreatment uracil levels, most likely as a result of pre-analytical factors. Importantly, we were not able to correlate pretreatment uracil levels with DPD activity nor were uracil levels predictive of severe treatment-related toxicity. We urge that robust clinical validation should first be performed before pretreatment plasma uracil levels are used in clinical practice as part of a dosing strategy for fluoropyrimidines.

Survey of US Medical Oncologists' Practices and Beliefs Regarding DPYD Testing Before Fluoropyrimidine Chemotherapy.

PURPOSE: Patients who carry reduced-activity DPYD polymorphisms have increased fluoropyrimidine (FP) toxicity risk. Although pretreatment DPYD testing is recommended throughout most of Europe, it is not recommended in the United States, and adoption has been limited. The objective of this survey was to describe the current practice in the United States regarding pretreatment DPYD testing and understand the factors deterring oncologists from ordering testing. METHODS: Survey invitations were e-mailed to 325 medical oncologists practicing in the United States who are members of the SWOG Cancer Research Network Gastrointestinal Cancer, Breast Cancer, or Early Therapeutics Committees. Descriptive statistics were used to evaluate survey responses. RESULTS: Responses were collected from 59 (18.2%) US medical oncologists, of whom 98% strongly or somewhat agree that patients with dihydropyrimidine dehydrogenase (DPD) deficiency have increased toxicity risk and 96% would modify FP dosing for a patient with known DPD deficiency. However, only 32% strongly or somewhat agree that pretreatment DPYD testing is useful to inform FP treatment, 20% have ever ordered pretreatment testing, and 3% order testing for at least 10% of their FP-treated patients. The most important factors that deter oncologists from ordering testing were low prevalence of DPD deficiency (54%) and lack of clinical practice guideline recommendations (48%). CONCLUSION: Clinical adoption of pretreatment DPYD testing is extremely limited in the United States. Utilization may be substantially increased by inclusion in the oncology clinical practice guideline recommendations, coverage through health insurance, and potentially education of medical oncologists regarding available treatment modification guidelines.

Severe Gastrointestinal Disorder Due to Capecitabine Associated with Dihydropyrimidine Dehydrogenase Deficiency: A Case Report and Literature Review.

Dihydropyrimidine dehydrogenase (DPD) deficiency induces severe adverse events in patients receiving fluoropyrimidines. We encountered a 64-year-old DPD-deficient man with a severe capecitabine-related gastrointestinal disorder. He received capecitabine-containing chemotherapy after rectal cancer resection. During the first course of chemotherapy, he developed severe diarrhea, a fever, and hematochezia. Endoscopy revealed mucosal shedding with bleeding throughout the gastrointestinal tract. DPD deficiency was suspected because he developed many severe adverse events of capecitabine early and was finally confirmed based on the finding of a low DPD activity level in peripheral blood mononuclear cells. After one month of intensive care, hemostasis and mucosal healing were noted, although his gastrointestinal function did not improve, and he had persistent nutritional management issues.

Treating patients with dihydropyrimidine dehydrogenase (DPD) deficiency with fluoropyrimidine chemotherapy since the onset of routine prospective testing-The experience of a large oncology center in the United Kingdom.

BACKGROUND: Fluoropyrimidine chemotherapy is used across many tumor types and settings. The incidence of severe adverse events (SAEs) is around 20%. Mortality is 0.5%-1%. Dihydropyrimidine dehydrogenase (DPD) plays a key role in fluoropyrimidine inactivation. Key DPYD mutations are linked to a high risk of SAEs. Pretreatment DPD screening was mandated by EMA guidelines in April 2020 and widely adopted thereafter. Uncertainty remains regarding optimal dosing practice. METHODS: We retrospectively examined records of all 23 patients with DPYD mutation who started chemotherapy between April and November 2020. Our center tests for the mutations considered clinically actionable by Clinical Pharmacogenetics Implementation Consortium and uses the Gene Activity Score (GAS) to guide dose reduction. RESULTS: Most patients started on a 50% dose. One started on 100% and experienced mild diarrhea after cycle 2; DPD was tested belatedly, subsequent cycles were reduced to 50% and he remained well. Three patients receiving chemo-radiotherapy started on 76% dose; 50% was felt to be subtherapeutic. One of them had no toxicities; another had grade 2 nausea and a hospital attendance with non-neutropenic fever; the third was admitted for 6 weeks with pancolitis. Seven patients did not have toxicities above grade 1 and no hospital attendances. Five patients had further dose reductions. None had dose escalation. CONCLUSION: As our experience shows, patients with DPD deficiency are heterogeneous. Worryingly, SAEs occur despite dose reduction according to GAS. Others had minimal toxicity and may be under-dosed by GAS. There are clearly many factors at play other than the 4 DPYD variants. The DPD result must be available and inform first cycle dosing. Dose should be cautiously titrated up if tolerated; this was not done at our center due to clinician caution. Further research is needed to guide this. Patients should be reviewed frequently, counselled regarding their DPD status, and empowered to seek advice promptly when they feel unwell.

Joint Belgian recommendation on screening for DPD-deficiency in patients treated with 5-FU, capecitabine (and tegafur).

OBJECTIVES: Fluoropyrimidines such as 5-Fluorouracil (5-FU), capecitabine and tegafur are drugs that are often used in the treatment of maliginancies. The enzyme dihydropyrimidine dehydrogenase (DPD) is the first and rate limiting enzyme of 5-FU catabolism. Genetic variations within the DPYD gene (encoding for DPD protein) can lead to reduced or absent DPD activity. Treatment of DPD deficient patients with fluoropyrimidines can result in severe and, rarely, fatal toxicity. Screening for DPD deficiency should be implemented in practice. METHODS: The available methods in routine to screen for DPD deficiency were analyzed and discussed in several group meetings involving members of the oncological, genetic and toxicological societies in Belgium: targeted genotyping based on the detection of 4 DPYD variants and phenotyping, through the measurement of uracil and dihydrouracil/uracil ratio in plasma samples. RESULTS: The main advantage of targeted genotyping is the existence of prospectively validated genotype-based dosing guidelines. The main limitations of this approach are the relatively low sensitivity to detect total and partial DPD deficiency and the fact that this approach has only been validated in Caucasians so far. Phenotyping has a better sensitivity to detect total and partial DPD deficiency when performed in the correct analytical conditions and is not dependent on the ethnic origin of the patient. CONCLUSION: In Belgium, we recommend phenotype or targeted genotype testing for DPD deficiency before starting 5-FU, capecitabine or tegafur. We strongly suggest a stepwise approach using phenotype testing upfront because of the higher sensitivity and the lower cost to society.

[Phenotype- or genotype test for dihydropyrimidin dehydrogenase deficiency before treatment with a fluoropyrimidine].

Some patients may have partial or complete deficiency of dihydropyrimidin dehydrogenase (DPD) and be more likely to experience severe toxicity with 5-fluorouracil. Since the spring of 2020, the Danish Medicines Agency has recommended genotype or phenotype testing before treatment with a fluoropyrimidine, but the most appropriate test strategy is debated. In this review, we present polymorphisms in the genes coding for DPD and summarise the evidence for DPD-enzyme deficiency testing and pharmacokinetic guided dosing.

An Application of Machine Learning in Pharmacovigilance: Estimating Likely Patient Genotype From Phenotypical Manifestations of Fluoropyrimidine Toxicity.

Dihydropyrimidine dehydrogenase (DPD)-deficient patients might only become aware of their genotype after exposure to dihydropyrimidines, if testing is performed. Case reports to pharmacovigilance databases might only contain phenotypical manifestations of DPD, without information on the genotype. This poses a difficulty in estimating the cases due to DPD. Auto machine learning models were developed to train patterns of phenotypical manifestations of toxicity, which were then used as a surrogate to estimate the number of cases of DPD-related toxicity. Results indicate that between 8,878 (7.0%) and 16,549 (13.1%) patients have a profile similar to DPD deficient status. Results of the analysis of variable importance match the known end-organ damage of DPD-related toxicity, however, accuracies in the range of 90% suggest presence of overfitting, thus, results need to be interpreted carefully. This study shows the potential for use of machine learning in the regulatory context but additional studies are required to better understand regulatory applicability.

[Dihydropyrimidine dehydrogenase deficiency screening for management of patients receiving a fluoropyrimidine: Results of two national practice surveys addressed to clinicians and biologists]. / Intérêts et limites de la recherche du déficit en dihydropyrimidine déshydrogénase dans le suivi des patients traités par fluoropyrimidines : résultats de deux enquêtes nationales de pratiques réalisées auprès des médecins et des biologistes.

Dihydropyrimidine dehydrogenase (DPD) deficiency is the main cause of early severe toxicities induced by fluoropyrimidines (FP). The French Group of Clinical Oncopharmacology (GPCO)-Unicancer and the French Pharmacogenetics Network (RNPGx) initiated two surveys, one addressed to oncologists, the other to biologists, in order to evaluate routine practices regarding DPD deficiency screening at national level, as well as compliance, motivations and obstacles for implementation of these tests. These anonymized online surveys were performed with the logistic assistance of the Francophone Federation of Digestive Oncology (FFCD) and the support of numerous medical and biological societies. The surveys were conducted in 2016-2017 before the creation of the French INCa/HAS expert panel, which contributed to the drafting of rules and recommendations for DPD deficiency screening published in December 2018. In all, 554 questionnaires from clinicians were analyzed (23% participation) and 35 from biologists. The main arguments raised by clinicians for justifying the limited practice of DPD deficiency screening were: the lack of recommendations from medical societies or Health Authorities, delays in obtaining results, and the lack of adequate reimbursement by the health insurance system. The goal of these surveys was to provide the French Health Authorities with an overview on nationwide DPD-deficiency screening practices and thus help to design recommendations for the standardization and improvement of the management and safety of cancer patients receiving FP-based chemotherapy.

Successful use of uridine triacetate (Vistogard) three weeks after capecitabine in a patient with homozygous dihydropyrimidine dehydrogenase mutation: A case report and review of the literature.

5-fluorouracil and capecitabine are chemotherapeutic agents commonly used to treat solid malignancies. Increased susceptibility to 5-fluorouracil or capecitabine, caused by impaired clearance, dihydropyrimidine dehydrogenase deficiency, or other genetic mutations in the enzymes that metabolize 5-fluorouracil can lead to severe life-threatening toxicities and are typically manifested by an early onset of symptoms. We report and discuss the management and outcome of capecitabine toxicity with the recently FDA approved antidote, uridine triacetate (Vistogard), in a 57-year-old female breast cancer patient with homozygous dihydropyrimidine dehydrogenase deficiency who received treatment beyond the recommended 96 h window from the last dose of capecitabine.

Dihydropyrimidine dehydrogenase deficiency as a cause of fatal 5-Fluorouracil toxicity

5-Fluorouracil (5-FU), in combination with other cytotoxic drugs, is commonly used to treat a variety of cancers. Dihydropyrimidine dehydrogenase (DPD) catalyzes the first catabolic step of the 5-FU degradation pathway, converting 80% of 5-FU to its inactive metabolite. Approximately 0.3% of the population demonstrate complete DPD deficiency, translating to extreme toxicity of 5-FU. Here we present a case of a patient who had a fatal outcome after treatment with 5-FU who was found to have an unknown DPD deficiency discovered at autopsy.

Prompt treatment with uridine triacetate improves survival and reduces toxicity due to fluorouracil and capecitabine overdose or dihydropyrimidine dehydrogenase deficiency.

Uridine triacetate has been shown to be an effective antidote against mortality and toxicity caused by either overdoses or exaggerated susceptibility to the widely used anticancer agents 5-fluorouracil (5-FU) and capecitabine. However, a direct assessment of efficacy based on when emergency treatment was initiated was not clinically feasible. In this study we used mouse models of 5-FU overdose and of dihydropyrimidine dehydrogenase (DPD) deficiency to compare the efficacy of uridine triacetate in reducing toxicity and mortality when treatment was initiated at time points from 4 to 144 h after administration of 5-FU. We found that uridine triacetate was effective both in the 5-FU overdose and DPD deficiency models. Starting treatment within 24 h was most effective at reducing toxicity and mortality in both models, while treatment starting more than 96 to 120 h after 5-FU was far less effective. Uridine triacetate also reduced mortality in the DPD deficiency model when mice were treated with the 5-FU prodrug capecitabine. The results of this study are supportive of clinical observations and practice, indicating that efficacy declined progressively with later and later treatment initiation. Prompt treatment with uridine triacetate, within 24 h, conferred the greatest protection against 5-FU overexposure.