Complete DPYD genotyping combined with dihydropyrimidine dehydrogenase phenotyping to prevent fluoropyrimidine toxicity: A retrospective study

INTRODUCTION

In April 2019, French authorities mandated dihydropyrimidine dehydrogenase (DPD) screening, specifically testing uracilemia, to mitigate the risk of toxicity associated with fluoropyrimidine-based chemotherapy. However, this subject is still of debate as there is no consensus on a standardized DPD deficiency screening test. We conducted a real-life retrospective study with the aim of assessing the impact of DPD screening on the occurrence of severe toxicity and exploring the potential benefits of complete genotyping using next-generation sequencing.

METHODS

All adult patients consecutively treated with 5-fluorouracil (5-FU) or its oral prodrug at six cancer centers between March 2018 and February 2019 were considered for inclusion. Dihydropyrimidine dehydrogenase deficiency screening included gene encoding DPD (DPYD) genotyping using complete genome sequencing and DPD phenotyping (uracilemia or dihydrouracilemia/uracilemia ratio) or both tests. Associations between each DPD screening method and (i) severe (grade ≥3) early toxicity and (ii) fluoropyrimidine dose reduction in the second chemotherapy cycle were evaluated using multivariable logistic regression analysis. Furthermore, we assessed the concordance between DPD genotype and phenotype using Cohen's kappa.

RESULTS

A total of 551 patients were included. Most patients were tested for DPD deficiency (86%) including DPYD genotyping only (6%), DPD phenotyping only (8%), or both (72%). Complete DPD deficiency was not detected in the study population. Severe early toxicity events were observed in 73 patients (13%), with two patients (0.30%) presenting grade 5 toxicity. Despite the numerically higher toxicity rate in untested patients, the occurrence of severe toxicity was not significantly associated with the DPD screening method (p = 0.69). Concordance between the DPD genotype and phenotype was weak (Cohen's kappa of 0.14).

CONCLUSION

Due to insufficient numbers, our study was not able to demonstrate any added value of DPYD genotyping using complete genome sequencing to prevent 5-FU toxicity. The optimal strategy for DPD screening before fluoropyrimidine-based chemotherapy requires further clinical evaluation.

Determination of plasma uracil as a screening for dihydropyrimidine dehydrogenase deficiency: clinical application in oncological treatments

AIMS

Treatment with dihydropyrimidines poses a significant risk of serious adverse reactions for patients with dihydropyrimidine dehydrogenase (DPD) deficiency. This study seeks to analyse the correlation between DPD deficiency and plasmatic uracil values in patients who are candidates for a fluoropyrimidine scheme. It also studies the incidence of adverse events (AEs) in patients with DPD deficiency established with plasmatic uracil determination.

METHODS

This was a retrospective observational study conducted in a tertiary level establishment from September 2020 to April 2021. Patients included were diagnosed with gastrointestinal tumours, were of good status, and were initiated into a fluoropyrimidine-based regimen. The incidence and grade of AEs, according Common Terminology Criteria for Adverse Events (CTCAE), were collected and compared in patients with and without DPD deficiency.

RESULTS

119 patients diagnosed with gastrointestinal cancer met the inclusion criteria. In 92 (77%) patients there was no DPD deficiency according to plasmatic uracil thresholds. In the group of patients without deficit, dose reductions oscillated between 10-25% (mean 17.4%). In the no DPD deficiency group, 43 (46%) patients experienced AEs. Patients who had a DPD deficiency according to plasmatic uracil measurements were started on a 5-fluorouracil (5-FU) regimen with a dose reduction of 15-50% (mean 35%). In this group, 12 patients (44%) experienced some AEs.

CONCLUSION

New research is needed to clarify the correlation between plasma uracil values and DPD deficiency to achieve an optimal balance between clinical benefit and toxicity.

Patient and healthcare professional acceptability of pharmacogenetic screening for DPYD and UGT1A1: A cross sectional survey

This study explored the acceptability of a novel pharmacist-led pharmacogenetics (PGx) screening program among patients with cancer and healthcare professionals (HCPs) taking part in a multicenter clinical trial of PGx testing (PACIFIC-PGx ANZCTR:12621000251820). Medical oncologists, oncology pharmacists, and patients with cancer from across four sites (metropolitan/regional), took part in an observational, cross-sectional survey. Participants were recruited from the multicenter trial. Two study-specific surveys were developed to inform implementation strategies for scaled and sustainable translation into routine clinical care: one consisting of 21 questions targeting HCPs and one consisting of 17 questions targeting patients. Responses were collected from 24 HCPs and 288 patients. The 5-to-7-day PGx results turnaround time was acceptable to HCP (100%) and patients (69%). Most HCPs (92%) indicated that it was appropriate for the PGx clinical pharmacist to provide results to patients. Patients reported equal preference for receiving PGx results from a doctor/pharmacist. Patients and HCPs highly rated the pharmacist-led PGx service. HCPs were overall accepting of the program, with the majority (96%) willing to offer PGx testing to their patients beyond the trial. HCPs identified that lack of financial reimbursements (62%) and lack of infrastructure (38%) were the main reasons likely to prevent/slow the implementation of PGx screening program into routine clinical care. Survey data have shown overall acceptability from patients and HCPs participating in the PGx Program. Barriers to implementation of PGx testing in routine care have been identified, providing opportunity to develop targeted implementation strategies for scaled translation into routine practice.

Screening for dihydropyrimidine dehydrogenase deficiency by measuring uracilemia in chronic kidney disease patients is associated with a high rate of false positives

BACKGROUND

Pretherapeutic screening for dihydropyrimidine dehydrogenase (DPD) deficiency based on the measurement of plasma uracil ([U]) is recommended prior to the administration of fluoropyrimidine-based chemotherapy. Cancer patients frequently have impaired kidney function, but the extent to which kidney function decline impacts [U] levels has not been comprehensively investigated.

METHODS

We assessed the relationship between DPD phenotypes and estimated glomerular filtration rate (eGFR) in 1751 patients who benefited on the same day from a screening for DPD deficiency by measuring [U] and [UH₂]:[U], and an evaluation of eGFR. The impact of a kidney function decline on [U] levels and [UH₂]:[U] ratio was evaluated.

RESULTS

We observed that [U] was negatively correlated with eGFR, indicating that [U] levels increase as eGFR declines. For each ml/min of eGFR decrease, [U] value increased in average by 0.035 ng/ml. Using the KDIGO classification of chronic kidney disease (CKD), we observed that [U] values >16 ng/ml (DPD deficiency) were measured in 3.6 % and 4.4 % of stage 1 and 2 CKD (normal-high eGFR, >60 ml/min/1.73m²) patients, but in 6.7 % of stage 3A CKD patients (45 to 59 ml/min/1.73m²), 25% of stage 3B CKD patients (30 to 44 ml/min/1.73m²), 22.7% of stage 4 CKD patients (15 to 29 ml/min/1.73m² and 26.7% of stage 5 CKD patients (<15 ml/min/1.73m²). [UH2]:[U] ratios were not impacted by kidney function.

CONCLUSION

DPD phenotyping based on the measurement of plasma [U] in patients with decreased eGFR is associated with an exceedingly high rate of false positives when kidney function decline reaches 45 ml/minute/1.73m² of eGFR or lower. In this population, an alternative strategy that remain to be evaluated would be to measure the [UH₂]:[U] ratio in addition to [U].

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.

Current diagnostic and clinical issues of screening for dihydropyrimidine dehydrogenase deficiency

Fluoropyrimidine drugs (FP) are the backbone of many chemotherapy protocols for treating solid tumours. The rate-limiting step of fluoropyrimidine catabolism is dihydropyrimidine dehydrogenase (DPD), and deficiency in DPD activity can result in severe and even fatal toxicity. In this review, we survey the evidence-based pharmacogenetics and therapeutic recommendations regarding DPYD (the gene encoding DPD) genotyping and DPD phenotyping to prevent toxicity and optimize dosing adaptation before FP administration. The French experience of mandatory DPD-deficiency screening prior to initiating FP is discussed.

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.

Issues and limitations of available biomarkers for fluoropyrimidine-based chemotherapy toxicity, a narrative review of the literature

Fluoropyrimidine-based chemotherapies are widely used to treat gastrointestinal tract, head and neck, and breast carcinomas. Severe toxicities mostly impact rapidly dividing cell lines and can occur due to the partial or complete deficiency in dihydropyrimidine dehydrogenase (DPD) catabolism. Since April 2020, the European Medicines Agency (EMA) recommends DPD testing before any fluoropyrimidine-based treatment. Currently, different assays are used to predict DPD deficiency; the two main approaches consist of either phenotyping the enzyme activity (directly or indirectly) or genotyping the four main deficiency-related polymorphisms associated with 5-fluorouracil (5-FU) toxicity. In this review, we focused on the advantages and limitations of these diagnostic methods: direct phenotyping by evaluation of peripheral mononuclear cell DPD activity (PBMC-DPD activity), indirect phenotyping assessed by uracil levels or UH2/U ratio, and genotyping DPD of four variants directly associated with 5-FU toxicity. The risk of 5-FU toxicity increases with uracil concentration. Having a pyrimidine-related structure, 5-FU is catabolised by the same physiological pathway. By assessing uracil concentration in plasma, indirect phenotyping of DPD is then measured. With this approach, in France, a decreased 5-FU dose is systematically recommended at a uracil concentration of 16 ng/ml, which may lead to chemotherapy under-exposure as uracil concentration is a continuous variable and the association between uracil levels and DPD activity is not clear. We aim herein to describe the different available strategies developed to improve fluoropyrimidine-based chemotherapy safety, how they are implemented in routine clinical practice, and the possible relationship with inefficacy mechanisms.

A Japanese Patient with Gastric Cancer and Dihydropyrimidine Dehydrogenase Deficiency Presenting with DPYD Variants

A 63-year-old Japanese male with stomach adenocarcinoma received oral 5-fluorouracil derivative, cisplatin and trastuzumab chemotherapy. On day 8, severe diarrhea and mucositis developed; chemotherapy was stopped. On day 14, the patient developed renal dysfunction and febrile neutropenia. He also suffered from pneumonia due to Candida albicans. Systemic symptoms improved after intensive conservative treatment. Best supportive care was continued until the patient died from gastric cancer. The dihydropyrimidine dehydroge-nase protein level was low at 3.18 U/mg protein. The result of DPYD genotyping revealed three variants at posi-tions 1615 (G > A), 1627 (A > G), and 1896 (T > C) in exons 13, 13, and 14, respectively.

[PHARMACOGENOMICS AND PERSONALIZED MEDICINE: TOWARDS A SYSTEMATIC GENOMIC SCREENING?]

Recent advances in medical genomics open new perspectives for personalized medicine through the identification of genetic variants that influence drug response and/or the risk of side effects. Today, the clinical applications of pharmacogenetics remain scarce as a consequence of the cost and turn-around-time of genetic tests. However, a few tests are recommended, for instance before the prescription of some anti-cancer agents or the anti-retroviral agent abacavir. In the future, we will probably move either towards rapid targeted tests or towards a large screening, before any diagnosis, of all the genetic factors influencing the therapeutic response. In that case, physicians will have to consult the patient genomic data before drug prescription in order to personalize the choice of the therapeutic agent or its dosage. However, such a genomic approach brings economical and ethical questions and will require further progress in our capacity to interpret and store the personal genomic data without compromising their confidentiality.

Clinical Pharmacogenetics Implementation Consortium guidelines for dihydropyrimidine dehydrogenase genotype and fluoropyrimidine dosing

The fluoropyrimidines are the mainstay chemotherapeutic agents for the treatment of many types of cancers. Detoxifying metabolism of fluoropyrimidines requires dihydropyrimidine dehydrogenase (DPD, encoded by the DPYD gene), and reduced or absent activity of this enzyme can result in severe, and sometimes fatal, toxicity. We summarize evidence from the published literature supporting this association and provide dosing recommendations for fluoropyrimidines based on DPYD genotype (updates at http://www.pharmgkb.org).

[Dihydropirymidine dehydrogenase (DPD)--a toxicity marker for 5-fluorouracil?]

In proceedings relating to patients suffering from cancer, an important step is predicting response and toxicity to treatment. Depending on the type of cancer, physicians use the generally accepted schema of treatment, for example pharmacotherapy. 5-fluorouracil (5-FU) is the most widely used anticancer drug in chemotherapy for colon, breast, and head and neck cancer. Patients with dihydropyrimidine dehydrogenase (DPD) deficiency, which is responsible for the metabolism of 5-FU, may experience severe side effects during treatment, and even death. In many publications the need for determining the activity of DPD is discussed, which would protect the patient from the numerous side effects of treatment. However, in practice these assays are not done routinely, despite the high demand. In most cases, a genetic test is used to detect changes in the gene encoding DPD (such as in the USA), but because of the large number of mutations the genetic test cannot be used as a screening test. Dihydropyrimidine dehydrogenase activity has been shown to have high variability among the general population, with an estimated proportion of at least 3-5% of individuals showing low or deficient DPD activity. In this publication we presents data about average dihydropirymidine dehydrogenase activity in various populations of the world (e.g. Japan, Ghana, Great Britain) including gender differences and collected information about the possibility of determination of DPD activity in different countries. Detection of reduced DPD activity in patients with planned chemotherapy will allow a lower dosage of 5-FU or alternative treatment without exposing them to adverse reactions.

Dual diagnosis of dihydropyrimidine dehydrogenase deficiency and GM₁ gangliosidosis

An 8-month-old girl, born to consanguineous parents, presented with developmental delay, decreased muscle tone, disinterest in her surroundings, and sleepiness. Tests revealed a marked excretion of thymine with significantly increased uracil excretion in the urine, indicating a pyrimidine catabolic disorder, i.e., dihydropyrimidine dehydrogenase deficiency. Plasma endogenous purines confirmed elevated plasma thymine (21 μmol/L) and uracil (29 μmol/L), also consistent with dihydropyrimidine dehydrogenase deficiency. Purine mutation analysis confirmed complete dihydropyrimidine dehydrogenase deficiency with a 16 [ corrected] base pair homozygous deletion in exon 16, corresponding to DPYD c.2043-2058del. Cranial magnetic resonance imaging at 14 months indicated severe hypomyelination with gliosis. Her basal ganglia were also involved. At age 15 months, she was hospitalized for aspiration pneumonia and seizures, and also manifested hepatosplenomegaly. White cell enzymes revealed a marked deficiency of β-galactosidase activity (4 μmol/g/hour) in white cells and an elevated chitotriosidase activity (443 μmol/L/hour) in plasma indicating GM(1) gangliosidosis. Mutation analysis confirmed c.841C>T (p.His281Tyr) homozygosity for GM(1) gangliosidosis. She died at age 19 months.

[Review of methods for determination of dihydropyrimidine dehydrogenase and possible application in screening previous chemotheraphy with 5-fluorouracil]

5-fluorouracil (5-FU) and its prodrug capecitabine are one of the most commonly used chemotherapeutic drugs. DPD-deficient cancer patients may be at risk of severe and sometimes lethal toxicity after the administration of 5-FU. In 39-61% of the cases severe toxicity of 5-FU is caused by decreased DPD acivity. DPD is the initial and rate-limiting enzyme of the metabolism of pyrimidines. 80-90% of the administered 5-FU is catabolised by DPD. Mutation of the DPYD gene encoding DPD result in decreased enzyme activity--total (0.2% of population) or partial (3-5% of population). Determination of DPD activity can be used as a screening procedure to identify patients with a DPD deficiency, before the start of treatment with 5-FU. There are several methods for DPD activity determination: the detection of relevant DPYD gene single-nucleotide polymorphism (SNPs), measurement of the level of DPYDmRNA expression, the evaluation of DPD activity in PBMC, the measurement of uracil in plasma and urea, evaluation of the UH2/U (dihydrouracil/uracil) and THYH2/THY (dihydrothymine/tymine) ratio in plasma and urea, [2-C13]uracil breath test, the analysis of fluorouracil and dihydrofluorouracil in plasma after administered a test dose of fluorouracil and measurement of 2-fluoro-beta-alanine. So far more than 30 mutations of DPYD gene have been identified in patients with cancer. A large number of them limits introduction of simple genetic test, which could be used for detection of DPD deficiency. Therefore scientists in searching of the simplest, the cheapest and the most available technique for detection DPD deficiency, generally use methods associated with measurement of DPD activity.

Dihydropyrimidine dehydrogenase deficiency presenting with psychomotor retardation in the first Polish patient

Dihydropyrimidine dehydrogenase (DPD) deficiency is a rare defect of the first step of the pyrimidine catabolic pathway. Patients with a complete enzyme deficiency may be clinically asymptomatic or suffer from neurological abnormalities of various severity. We report a case of an 8-year-old girl with psychomotor retardation and mild course of the disease. Analysis of urine showed strongly elevated levels of uracil and thymine, and no DPD activity could be detected in peripheral blood mononuclear cells. Sequence analysis of the DPD gene (DPYD) revealed that our patient was homozygous for the common splice-site mutation IVS14+1G > A, which suggest that the carrier status for this mutation may be not rare in the Polish population.

[Clinical problems and prospects in laboratory chemical analysis]

The first subject of clinical problems is about uncertainty in measurement, but is now going be clarified by the standardization of reference measurement procedure and reference material. On the other hand, physiological uncertainty in samples is unable to be solved. So the establishment of evidence based diagnostic values is important in company with reference value, especially in the field of health examination. The life expectancy of the Japanese population is one of longest in the world. So the preventive medicine of lifestyle-related disease is important to perform an extensive research like as disease preventive biomarkers. Furthermore, we expect the progression of examinations in the pathophysiological diagnosis. I present the paper of development for the diagnostic method of dihydropyrimidine dehydrogenase-deficient as an example.