Renal impairment and abnormal liver function tests in pre-therapeutic phenotype-based DPD deficiency screening using uracilemia: a comprehensive population-based study in 1138 patients

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.

Integrating rare genetic variants into DPYD pharmacogenetic testing may help preventing fluoropyrimidine-induced toxicity

Variability in genes involved in drug pharmacokinetics or drug response can be responsible for suboptimal treatment efficacy or predispose to adverse drug reactions. In addition to common genetic variations, large-scale sequencing studies have uncovered multiple rare genetic variants predicted to cause functional alterations in genes encoding proteins implicated in drug metabolism, transport and response. To understand the functional importance of rare genetic variants in DPYD, a pharmacogene whose alterations can cause severe toxicity in patients exposed to fluoropyrimidine-based regimens, massively parallel sequencing of the exonic regions and flanking splice junctions of the DPYD gene was performed in a series of nearly 3000 patients categorized according to pre-emptive DPD enzyme activity using the dihydrouracil/uracil ([UH2]/[U]) plasma ratio as a surrogate marker of DPD activity. Our results underscore the importance of integrating next-generation sequencing-based pharmacogenomic interpretation into clinical decision making to minimize fluoropyrimidine-based chemotherapy toxicity without altering treatment efficacy.

Case report: 5-Fluorouracil treatment in patient with an important partial DPD deficiency

Esophageal cancer is a cancer with poor prognosis and the standard 1^st line treatment for metastatic or recurrent EC is systemic chemotherapy with doublet chemotherapy based on platinum and 5-fluorouracil (5-FU). However, 5-FU could be a source of severe treatment-related toxicities due to deficiency of dihydropyrimidine dehydrogenase (DPD). In this case report, a 74-year-old man with metastatic esophageal cancer was found to have partial DPD deficiency based on uracilemia measurements (about 90 ng/mL). Despite this, 5-FU was safely administered thanks to therapeutic drug monitoring (TDM). The case report highlights the importance of TDM in administering 5-FU to patients with partial DPD deficiency, as it allows individualized dosing and prevents severe toxicity.

Benzoylaconitine Alleviates Progression of Psoriasis via Suppressing STAT3 Phosphorylation in Keratinocytes

Psoriasis is a chronic and multifactorial skin disease which is caused by inflammatory infiltrates, keratinocyte hyperproliferation, and accumulation of immune cells. As part of the Aconitum species, Benzoylaconitine (BAC) shows potential antiviral, anti-tumor, and anti-inflammatory effects. In this study, we investigated the effects and mechanisms of BAC on tumor necrosis factor-alpha (TNF-α)/LPS-induced HaCaT keratinocytes in a imiquimod(IMQ)-induced mice model. The results showed that BAC could relieve the symptoms of psoriasis by inhibiting cell proliferation, the release of inflammatory factors, and the accumulation of Th17 cells, while no obvious effect on cell viability and safety was observed both in vitro and in vivo. Additionally, BAC can markedly inhibit the protein and mRNA levels of inflammatory cytokines in TNF-α/LPS-induced HaCaT keratinocytes by inhibiting the phosphorylation of STAT3. In brief, our data indicated that BAC could alleviate the progression of psoriasis and may be a potential therapeutic agent for treating psoriasis in clinical practice.

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.

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].