Is uracil enough for effective pre-emptive DPD testing?
-
Niels Heersche
,
Maja Matic
To the Editor,
With great interest, we read the article by Launay et al. [1], which compared results of pre-emptive dihydropyrimidine dehydrogenase (DPD) deficiency testing for fluoropyrimidine treatment using both DPYD genotyping and plasma uracil levels. The impressive sample size demonstrates that routine pre-treatment DPD deficiency testing is feasible and has been fully adapted into clinical practice in France. However, we have several comments and concerns regarding the data and its interpretation.
Firstly, the authors opted to use a genotyping panel that omits haplotype B3 (HapB3; c.1129–5923C>G (rs75017182) and the commonly tested variant in linkage p.E412E; c.1236G>A (rs56038477)). Although indeed conflicting results regarding the adequate dose for HapB3 carriers exist, its association with increased toxicity rates, such as severe neutropenia and diarrhea, remains undisputed. In meta-analysis a relative risk rate for severe grade ≥3 fluoropyrimidine related toxicity of 1.72 (1.22–2.42) was found [2], and even among 51 patients treated at a 75 % dose intensity, an increased incidence of grade ≥3 adverse events of 39 % persisted [3]. The exclusion of HapB3 from the current analysis therefore hampers adequate comparison between both tests.
Secondly, the authors argue that targeted genotyping is not sufficiently reliable in the detection of patients who have a complete and profound DPD deficiency. In support of this argument, details are provided of five patients who had a complete DPD deficiency according to French health authority recommendations, with only one of them having a DPYD variant genotype (see ref [1], table 1, patient C: homozygous *2A genotype). Interestingly, this is also the only patient who had unmeasurable dihydrouracil levels. Reliable measurement of uracil and dihydrouracil levels, as noted by the authors, is heavily dependent on pre-analytical handling. Lack of adherence to recommendations regarding sample handling can result in false positive DPD deficiency diagnoses and subsequent undertreatment due to unnecessary dose-reductions. Moreover, renal impairment and abnormal liver function may also result in false positive results. Notably, one of the five described patients (i.e. patient B) had a very high dihydrouracil level, resulting in legitimate concerns of the authors regarding the reliability of the completely deficient status in this specific case. Regrettably, data on sample handling as well as clinical data relating to kidney and liver function were unavailable to the authors, making a final conclusion regarding the patient’s DPD status difficult. Nonetheless, we have concerns regarding the validity of the diagnosis of a completely deficient DPD status in the remaining three patients as well, suggesting that, in contrast to the authors’ conclusion, both genotyping and phenotyping are able to identify completely deficient patients. Literature on patients with a complete DPD deficiency is sparse. However, case-reports of four completely DPD deficient patients (genotype confirmed) show that these patients not only share the inability to form 5-FU metabolites (DHFU, FUPA or FBAL being not quantifiable), but also have undetectable levels of dihydrouracil [4], [5], [6]. Since the remaining three patients who were identified as being completely DPD deficient (i.e. patients A, D, and E) had detectable dihydrouracil levels, with two of the patients even having dihydrouracil levels within the physiological range, we consider it unlikely that these patients are truly completely DPD deficient. Although the patients match the criteria for a complete DPD deficiency based on uracil testing guidelines, we believe they are more likely to be partially deficient patients, in which case a major treatment line (i.e. fluoropyrimidines) has been unnecessarily withheld from them. Still, the absence of common DPYD variants in these patients highlights an important limitation of targeted DPYD genotyping: its inability to detect rare or unknown genetic variants. In that regard, DPYD sequencing of these patients would greatly aid interpretation of the results, as presence of rare DPYD variants could support diagnosis of a DPD deficiency. Consequently, this would demonstrate the added value of combining DPYD genotyping with uracil-based phenotyping, especially for patients with extremely elevated uracil levels. For now however, hard conclusions cannot be drawn from these cases due to the absence of additional data.
Finally, the lack of clinical outcomes or a corresponding DPD enzyme activity measured in peripheral blood mononuclear cells greatly hampers the interpretation of the results. Currently, prospective evidence for dose-reductions based on pre-emptive DPD testing is only available for genotyping [3, 7]. The evidence for uracil-based dosing is largely retrospective [7]. Unfortunately, based on the current data, it is not possible to answer the question of which of the pre-emptive DPD deficiency tests (i.e. genotyping vs. phenotyping) performs better. At best, it gives insight into the concordance between both tests. However, it is with the authors’ interpretation of the concordance that we disagree with most.
Alarmingly, the majority of patients (66 %) carrying one of the four tested variants (*2A, *7, *13 and D949V) within the analysis, had uracil levels below 16 ng/mL and were thus incorrectly identified as DPD proficient. At best, the uracil test was able to detect ∼50 % of the *2A and *13 carriers, whereas only ∼22 % of the D949V and *7 carriers was detected as DPD deficient. All of these patients are expected to have a highly increased risk of fluoropyrimidine-related severe – and potentially fatal – toxicity based on literature. Whilst the authors proceed to conclude that both approaches may be complementary, the results demonstrated by Launay et al., lead us to conclude that when physicians opt to employ pre-treatment DPD testing using uracil, they must also perform genotyping for the most common DPYD variants, as uracil testing alone does not suffice for identification of patients carrying deleterious DPYD variants.
We want to stress that proper identification of DPYD variant carriers is of utmost importance in fluoropyrimidine treatment, even despite its limitations. We therefore urge medical societies and regulatory organizations to refrain from recommending fluoropyrimidine dosing strategies based on uracil levels alone. Conversely, further analysis of the presented cases of severe uracilemia could demonstrate the added value of uracil testing when solely performing DPYD genotyping.
-
Research ethics: Not applicable.
-
Informed consent: Not applicable.
-
Author contributions: The authors have accepted responsibility for the entire content of this manuscript and approved its submission. Writing – original draft: NH; Writing – review & editing: MM, RHJM, MJHC, RHNvS.
-
Competing interests: RHJM reports unrestricted grants for investigator-initiated trials (all paid to the institute) from Astellas, Bayer, Boehringer-Ingelheim, Cristal Therapeutics, Deuter Oncology, Echo Pharmaceuticals, Nordic Pharma, Novartis, Pamgene, Pfizer, Roche, Sanofi, and Servier. All of the other authors state no conflicts of interest.
-
Research funding: None declared.
-
Data availability: Not applicable.
References
1. Launay, M, Raymond, L, Guitton, J, Loriot, MA, Chatelut, E, Haufroid, V, et al.. Can we identify patients carrying targeted deleterious DPYD variants with plasma uracil and dihydrouracil? A GPCO-RNPGx retrospective analysis. Clin Chem Lab Med 2024;62:2415–24. https://doi.org/10.1515/cclm-2024-0317.Search in Google Scholar PubMed
2. Meulendijks, D, Henricks, LM, Sonke, GS, Deenen, MJ, Froehlich, TK, Amstutz, U, et al.. Clinical relevance of DPYD variants c.1679T>G, c.1236G>A/HapB3, and c.1601G>A as predictors of severe fluoropyrimidine-associated toxicity: a systematic review and meta-analysis of individual patient data. Lancet Oncol 2015;16:1639–50. https://doi.org/10.1016/s1470-2045(15)00286-7.Search in Google Scholar PubMed
3. Henricks, LM, Lunenburg, CATC, de Man, FM, Meulendijks, D, Frederix, GWJ, Kienhuis, E, et al.. DPYD genotype-guided dose individualisation of fluoropyrimidine therapy in patients with cancer: a prospective safety analysis. Lancet Oncol 2018;19:1459–67. https://doi.org/10.1016/s1470-2045(18)30686-7.Search in Google Scholar PubMed
4. Thomas, F, Hennebelle, I, Delmas, C, Lochon, I, Dhelens, C, Garnier Tixidre, C, et al.. Genotyping of a family with a novel deleterious DPYD mutation supports the pretherapeutic screening of DPD deficiency with dihydrouracil/uracil ratio. Clin Pharmacol Ther 2016;99:235–42. https://doi.org/10.1002/cpt.210.Search in Google Scholar PubMed
5. Henricks, LM, Kienhuis, E, de Man, FM, van der Veldt, AAM, Hamberg, P, van Kuilenburg, ABP, et al.. Treatment algorithm for homozygous or compound heterozygous DPYD variant allele carriers with low-dose capecitabine. JCO Precis Oncol 2017;1:1–10. https://doi.org/10.1200/po.17.00118.Search in Google Scholar
6. Henricks, LM, Siemerink, EJM, Rosing, H, Meijer, J, Goorden, SMI, Polstra, AM, et al.. Capecitabine-based treatment of a patient with a novel DPYD genotype and complete dihydropyrimidine dehydrogenase deficiency. Int J Cancer 2018;142:424–30. https://doi.org/10.1002/ijc.31065.Search in Google Scholar PubMed
7. Etienne-Grimaldi, MC, Pallet, N, Boige, V, Ciccolini, J, Chouchana, L, Barin-Le Guellec, C, et al.. Current diagnostic and clinical issues of screening for dihydropyrimidine dehydrogenase deficiency. Eur J Cancer 2023;181:3–17. https://doi.org/10.1016/j.ejca.2022.11.028.Search in Google Scholar PubMed
© 2024 the author(s), published by De Gruyter, Berlin/Boston
This work is licensed under the Creative Commons Attribution 4.0 International License.
To the Editor,
With great interest, we read the article by Launay et al. [1], which compared results of pre-emptive dihydropyrimidine dehydrogenase (DPD) deficiency testing for fluoropyrimidine treatment using both DPYD genotyping and plasma uracil levels. The impressive sample size demonstrates that routine pre-treatment DPD deficiency testing is feasible and has been fully adapted into clinical practice in France. However, we have several comments and concerns regarding the data and its interpretation.
Firstly, the authors opted to use a genotyping panel that omits haplotype B3 (HapB3; c.1129–5923C>G (rs75017182) and the commonly tested variant in linkage p.E412E; c.1236G>A (rs56038477)). Although indeed conflicting results regarding the adequate dose for HapB3 carriers exist, its association with increased toxicity rates, such as severe neutropenia and diarrhea, remains undisputed. In meta-analysis a relative risk rate for severe grade ≥3 fluoropyrimidine related toxicity of 1.72 (1.22–2.42) was found [2], and even among 51 patients treated at a 75 % dose intensity, an increased incidence of grade ≥3 adverse events of 39 % persisted [3]. The exclusion of HapB3 from the current analysis therefore hampers adequate comparison between both tests.
Secondly, the authors argue that targeted genotyping is not sufficiently reliable in the detection of patients who have a complete and profound DPD deficiency. In support of this argument, details are provided of five patients who had a complete DPD deficiency according to French health authority recommendations, with only one of them having a DPYD variant genotype (see ref [1], table 1, patient C: homozygous *2A genotype). Interestingly, this is also the only patient who had unmeasurable dihydrouracil levels. Reliable measurement of uracil and dihydrouracil levels, as noted by the authors, is heavily dependent on pre-analytical handling. Lack of adherence to recommendations regarding sample handling can result in false positive DPD deficiency diagnoses and subsequent undertreatment due to unnecessary dose-reductions. Moreover, renal impairment and abnormal liver function may also result in false positive results. Notably, one of the five described patients (i.e. patient B) had a very high dihydrouracil level, resulting in legitimate concerns of the authors regarding the reliability of the completely deficient status in this specific case. Regrettably, data on sample handling as well as clinical data relating to kidney and liver function were unavailable to the authors, making a final conclusion regarding the patient’s DPD status difficult. Nonetheless, we have concerns regarding the validity of the diagnosis of a completely deficient DPD status in the remaining three patients as well, suggesting that, in contrast to the authors’ conclusion, both genotyping and phenotyping are able to identify completely deficient patients. Literature on patients with a complete DPD deficiency is sparse. However, case-reports of four completely DPD deficient patients (genotype confirmed) show that these patients not only share the inability to form 5-FU metabolites (DHFU, FUPA or FBAL being not quantifiable), but also have undetectable levels of dihydrouracil [4], [5], [6]. Since the remaining three patients who were identified as being completely DPD deficient (i.e. patients A, D, and E) had detectable dihydrouracil levels, with two of the patients even having dihydrouracil levels within the physiological range, we consider it unlikely that these patients are truly completely DPD deficient. Although the patients match the criteria for a complete DPD deficiency based on uracil testing guidelines, we believe they are more likely to be partially deficient patients, in which case a major treatment line (i.e. fluoropyrimidines) has been unnecessarily withheld from them. Still, the absence of common DPYD variants in these patients highlights an important limitation of targeted DPYD genotyping: its inability to detect rare or unknown genetic variants. In that regard, DPYD sequencing of these patients would greatly aid interpretation of the results, as presence of rare DPYD variants could support diagnosis of a DPD deficiency. Consequently, this would demonstrate the added value of combining DPYD genotyping with uracil-based phenotyping, especially for patients with extremely elevated uracil levels. For now however, hard conclusions cannot be drawn from these cases due to the absence of additional data.
Finally, the lack of clinical outcomes or a corresponding DPD enzyme activity measured in peripheral blood mononuclear cells greatly hampers the interpretation of the results. Currently, prospective evidence for dose-reductions based on pre-emptive DPD testing is only available for genotyping [3, 7]. The evidence for uracil-based dosing is largely retrospective [7]. Unfortunately, based on the current data, it is not possible to answer the question of which of the pre-emptive DPD deficiency tests (i.e. genotyping vs. phenotyping) performs better. At best, it gives insight into the concordance between both tests. However, it is with the authors’ interpretation of the concordance that we disagree with most.
Alarmingly, the majority of patients (66 %) carrying one of the four tested variants (*2A, *7, *13 and D949V) within the analysis, had uracil levels below 16 ng/mL and were thus incorrectly identified as DPD proficient. At best, the uracil test was able to detect ∼50 % of the *2A and *13 carriers, whereas only ∼22 % of the D949V and *7 carriers was detected as DPD deficient. All of these patients are expected to have a highly increased risk of fluoropyrimidine-related severe – and potentially fatal – toxicity based on literature. Whilst the authors proceed to conclude that both approaches may be complementary, the results demonstrated by Launay et al., lead us to conclude that when physicians opt to employ pre-treatment DPD testing using uracil, they must also perform genotyping for the most common DPYD variants, as uracil testing alone does not suffice for identification of patients carrying deleterious DPYD variants.
We want to stress that proper identification of DPYD variant carriers is of utmost importance in fluoropyrimidine treatment, even despite its limitations. We therefore urge medical societies and regulatory organizations to refrain from recommending fluoropyrimidine dosing strategies based on uracil levels alone. Conversely, further analysis of the presented cases of severe uracilemia could demonstrate the added value of uracil testing when solely performing DPYD genotyping.
-
Research ethics: Not applicable.
-
Informed consent: Not applicable.
-
Author contributions: The authors have accepted responsibility for the entire content of this manuscript and approved its submission. Writing – original draft: NH; Writing – review & editing: MM, RHJM, MJHC, RHNvS.
-
Competing interests: RHJM reports unrestricted grants for investigator-initiated trials (all paid to the institute) from Astellas, Bayer, Boehringer-Ingelheim, Cristal Therapeutics, Deuter Oncology, Echo Pharmaceuticals, Nordic Pharma, Novartis, Pamgene, Pfizer, Roche, Sanofi, and Servier. All of the other authors state no conflicts of interest.
-
Research funding: None declared.
-
Data availability: Not applicable.
References
1. Launay, M, Raymond, L, Guitton, J, Loriot, MA, Chatelut, E, Haufroid, V, et al.. Can we identify patients carrying targeted deleterious DPYD variants with plasma uracil and dihydrouracil? A GPCO-RNPGx retrospective analysis. Clin Chem Lab Med 2024;62:2415–24. https://doi.org/10.1515/cclm-2024-0317.Search in Google Scholar PubMed
2. Meulendijks, D, Henricks, LM, Sonke, GS, Deenen, MJ, Froehlich, TK, Amstutz, U, et al.. Clinical relevance of DPYD variants c.1679T>G, c.1236G>A/HapB3, and c.1601G>A as predictors of severe fluoropyrimidine-associated toxicity: a systematic review and meta-analysis of individual patient data. Lancet Oncol 2015;16:1639–50. https://doi.org/10.1016/s1470-2045(15)00286-7.Search in Google Scholar PubMed
3. Henricks, LM, Lunenburg, CATC, de Man, FM, Meulendijks, D, Frederix, GWJ, Kienhuis, E, et al.. DPYD genotype-guided dose individualisation of fluoropyrimidine therapy in patients with cancer: a prospective safety analysis. Lancet Oncol 2018;19:1459–67. https://doi.org/10.1016/s1470-2045(18)30686-7.Search in Google Scholar PubMed
4. Thomas, F, Hennebelle, I, Delmas, C, Lochon, I, Dhelens, C, Garnier Tixidre, C, et al.. Genotyping of a family with a novel deleterious DPYD mutation supports the pretherapeutic screening of DPD deficiency with dihydrouracil/uracil ratio. Clin Pharmacol Ther 2016;99:235–42. https://doi.org/10.1002/cpt.210.Search in Google Scholar PubMed
5. Henricks, LM, Kienhuis, E, de Man, FM, van der Veldt, AAM, Hamberg, P, van Kuilenburg, ABP, et al.. Treatment algorithm for homozygous or compound heterozygous DPYD variant allele carriers with low-dose capecitabine. JCO Precis Oncol 2017;1:1–10. https://doi.org/10.1200/po.17.00118.Search in Google Scholar
6. Henricks, LM, Siemerink, EJM, Rosing, H, Meijer, J, Goorden, SMI, Polstra, AM, et al.. Capecitabine-based treatment of a patient with a novel DPYD genotype and complete dihydropyrimidine dehydrogenase deficiency. Int J Cancer 2018;142:424–30. https://doi.org/10.1002/ijc.31065.Search in Google Scholar PubMed
7. Etienne-Grimaldi, MC, Pallet, N, Boige, V, Ciccolini, J, Chouchana, L, Barin-Le Guellec, C, et al.. Current diagnostic and clinical issues of screening for dihydropyrimidine dehydrogenase deficiency. Eur J Cancer 2023;181:3–17. https://doi.org/10.1016/j.ejca.2022.11.028.Search in Google Scholar PubMed
© 2024 the author(s), published by De Gruyter, Berlin/Boston
This work is licensed under the Creative Commons Attribution 4.0 International License.
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- Editorial
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- Analytical validation of the amplification refractory mutation system polymerase chain reaction-capillary electrophoresis assay to diagnose spinal muscular atrophy
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- Letters to the Editor
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- Use of the term “Bence-Jones proteinuria” in the EFLM European Urinalysis Guideline 2023
- Is uracil enough for effective pre-emptive DPD testing?
- Reply to: “Is uracil enough for effective pre-emptive DPD testing?”
- Accurate predictory role of monocyte distribution width on short-term outcome in sepsis patients
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Articles in the same Issue
- Frontmatter
- Editorial
- External quality assurance (EQA): navigating between quality and sustainability
- Reviews
- Molecular allergology: a clinical laboratory tool for precision diagnosis, stratification and follow-up of allergic patients
- Nitrous oxide abuse direct measurement for diagnosis and follow-up: update on kinetics and impact on metabolic pathways
- Opinion Papers
- A vision to the future: value-based laboratory medicine
- Point-of-care testing, near-patient testing and patient self-testing: warning points
- Navigating the path of reproducibility in microRNA-based biomarker research with ring trials
- Point/Counterpoint
- Six Sigma – is it time to re-evaluate its value in laboratory medicine?
- The value of Sigma-metrics in laboratory medicine
- Genetics and Molecular Diagnostics
- Analytical validation of the amplification refractory mutation system polymerase chain reaction-capillary electrophoresis assay to diagnose spinal muscular atrophy
- Can we identify patients carrying targeted deleterious DPYD variants with plasma uracil and dihydrouracil? A GPCO-RNPGx retrospective analysis
- General Clinical Chemistry and Laboratory Medicine
- Comparison of ChatGPT, Gemini, and Le Chat with physician interpretations of medical laboratory questions from an online health forum
- External quality assessment performance in ten countries: an IFCC global laboratory quality project
- Multivariate anomaly detection models enhance identification of errors in routine clinical chemistry testing
- Enhanced patient-based real-time quality control using the graph-based anomaly detection
- Performance evaluation and user experience of BT-50 transportation unit with automated and scheduled quality control measurements
- Stability of steroid hormones in dried blood spots (DBS)
- Quantification of C1 inhibitor activity using a chromogenic automated assay: analytical and clinical performances
- Reference Values and Biological Variations
- Time-dependent characteristics of analytical measurands
- Cancer Diagnostics
- Expert-level detection of M-proteins in serum protein electrophoresis using machine learning
- An automated workflow based on data independent acquisition for practical and high-throughput personalized assay development and minimal residual disease monitoring in multiple myeloma patients
- Cardiovascular Diseases
- Analytical validation of the Mindray CL1200i analyzer high sensitivity cardiac troponin I assay: MERITnI study
- Diabetes
- Limitations of glycated albumin standardization when applied to the assessment of diabetes patients
- Patient result monitoring of HbA1c shows small seasonal variations and steady decrease over more than 10 years
- Letters to the Editor
- Inaccurate definition of Bence Jones proteinuria in the EFLM Urinalysis Guideline 2023
- Use of the term “Bence-Jones proteinuria” in the EFLM European Urinalysis Guideline 2023
- Is uracil enough for effective pre-emptive DPD testing?
- Reply to: “Is uracil enough for effective pre-emptive DPD testing?”
- Accurate predictory role of monocyte distribution width on short-term outcome in sepsis patients
- Reply to: “Accurate predictory role of monocyte distribution width on short-term outcome in sepsis patients”
- Spurious parathyroid hormone (PTH) elevation caused by macro-PTH
- Setting analytical performance specifications for copeptin-based testing
- Serum vitamin B12 levels during chemotherapy against diffuse large B-cell lymphoma: a case report and review of the literature
- Evolution of acquired haemoglobin H disease monitored by capillary electrophoresis: a case of a myelofibrotic patient with a novel ATRX mutation
