Cancer Letters

Cancer Letters

Volume 249, Issue 2, 8 May 2007, Pages 271-282
Cancer Letters

5-Fluorouracil-related severe toxicity: A comparison of different methods for the pretherapeutic detection of dihydropyrimidine dehydrogenase deficiency

https://doi.org/10.1016/j.canlet.2006.09.006Get rights and content

Abstract

5-Fluorouracil (5-FU)-related early toxicity, due to a metabolic deficiency, is rare but is potentially severe and even lethal (0.1%). It is due to dihydropyrimidine dehydrogenase (DPYD) gene polymorphism or some epigenetic factors. The detection of metabolic change could prevent severe toxicity, but until now it has not been carried out in clinical practice.

Purpose

To find the simplest and most accurate pretherapeutic test to predict DPD deficiency in patients treated with 5-FU by comparing different approaches.

Results

Two hundred and fifty two French Caucasian patients treated by 5-FU infusion were studied. A two-step strategy, combining firstly SNP detection and uracil plasma measurement, followed, in cases where metabolic deficiency was suspected, by dihydrouracil/uracil ratio determination to confirm deficiency and to determine the optimum 5-FU dosage, appeared the best approach, with 83% and 82% sensitivity and specificity, respectively.

Conclusion

These data support the future use of this approach, suitable to clinical practice, as screening test to identify DPD deficiency before 5-FU-based therapy.

Introduction

5-Fluorouracil can result in severe toxic side-effects, including death, in advanced or adjuvant setting, due to catabolic pathway deficiency [1], [2], [3]. Dihydropyrimidine dehydrogenase (DPD), the rate-controlling enzyme of endogenous pyrimidine and fluoropyrimidine catabolism, is subject to a genetic polymorphism and its activity shows a wide range of individual variation [4], [5], [6]. This results in a broad range of enzymatic deficiency from partial (3–5% of the population) to complete loss (0.2% of the population) of enzyme activity and consequently to severe polyvisceral 5-FU-induced toxicity [7], [8].

Considering the common use of 5-FU, and oral fluoropyrimidines, pretreatment detection of DPD deficiency could prevent severe toxicity.

To date, different techniques have been reported. They can be arranged according to their check point, from the gene encoding the DPD enzyme to the 5-FU catabolic pathway: (1) the detection of relevant DPYD gene SNPs; (2) the level of DPYD mRNA expression; (3) the evaluation of DPD activity in lymphocytes with radio-enzymatic techniques; (4) the measurement of uracil, a natural substrate of DPD, in plasma or urine; (5) the UH2/U ratio in plasma catabolite (dihydrouracil) and substrate (uracil) of DPD; (6) the more recently the [2-C13]uracil breath test; (7) the evaluation of 5-FU plasma clearance during treatment for a pharmacokinetic follow-up and an individual 5-FU dosage adjustment.

These last approaches allow for the use of individual dose adjustment but cannot detect major DPD deficiency prior to treatment, and thus cannot prevent immediate severe toxicity [9]. It is suitable for the avoidance of toxicity in patients with a known DPD deficiency, and for dose intensification in underdosed patients [10].

The determination of uracil in plasma or urine has been reported previously [11]. However, its levels can be influenced by factors other than DPD activity, such as nutrition and pyrimidine production; no threshold has been reported in the literature to date, and the correlation between uracil levels and 5-FU plasma clearance remains to be measured. To get rid of potential interfering factors, we simultaneously measured both plasma uracil and its dihydrogenated metabolite and characterized the dihydrouracil/uracil ratio (UH2/U) prior to treatment. We found a good correlation with 5-FU plasma clearance and this ratio was later correlated with DPD activity [12], [13].

DPD activity measured in peripheral mononuclear cells by radio-enzymatic assay has been considered by some authors as the reference technique to detect severe DPD deficiency [14], [15]. Nevertheless, it is clearly a tedious, time-consuming technique, requiring large volumes of blood and radiolabelled materials, and is hence not suitable for clinical practice.

Genotyping techniques can be used for DPYD gene polymorphism detection [16]. Thus far, at least thirty variant DPYD alleles have been published, with or without a deleterious impact upon DPD activity [17]. Splice-site mutation IVS14 + 1G > A is considered as the most common mutation (52%) [18]. For most of the other ones, their location and hypothetical interference with the functional status of enzymes has been described, but frequently no correlation to toxicity was looked for and their respective frequencies often remain unknown [19]. A few genotyping methods such as RFLP, and DHPLC have been reported, though they are often not suitable for the rapid detection of different DPYD gene mutations within an acceptable timeframe for routine practice.

The uracil breath test has been recently correlated with DPD deficiency but [2-C13]uracil is not currently available in many countries [20].

Therefore, the objective of the present study was to determine the most accurate and simple method to predict DPD deficiency before 5-FU-based treatment.

We compared 4 different methods in a population of French Caucasian patients:

  • 1.

    Uracil plasma measurement, by liquid chromatography [21],

  • 2.

    Dihydrouracil/uracil ratios in plasma, by liquid chromatography [22],

  • 3.

    Quantification of DPD mRNA in lymphocytes, in real-time quantitative RT-PCR,

  • 4.

    Detection of DPD genes SNPs in lymphocytes, using a minisequencing method via pyrosequencing techniques [23].

These parameters were correlated to individual 5-FU metabolism, the 5-FU plasma clearance at the first cycle, and to tolerance to the treatment.

We selected neither the radio-enzymatic method since it obviously cannot be used on a large scale nor the breath test because [2-C13]uracil is not available everywhere.

Section snippets

Patients and treatments

This prospective study was conducted on 252 French Caucasian patients treated for advanced colorectal carcinomas or in the adjuvant setting by 5-FU – leucovorin chemotherapy regimen. To be eligible, patients had to be naïve of 5-FU, have a WHO performance status (PS) < 2, a life-expectancy of at least 3 months, an age lower than 80 years, and adequate hematological and cardiac status.

Treatment consisted of two types of regimens:

  • 1.

    Biweekly 5-FU 400 mg/m2 bolus + 2500 mg/m2 46 h infusion plus 400 mg/m2

Number and clinical characteristics and outcomes of the patients

Two hundred and fifty two patients were studied, 112 females and 140 men, their mean age being 67 ± 11.4 years old, (30–80). Their performance status was 220 PS 0-1, and 32 PS 2. Ninety-nine out of 168 in the LV5FU2 group were treated for metastatic cancer, vs 27 out of 84 in the FuFol group.

5-FU-induced toxic side-effects were graduated (Table 1). Early toxic side effect frequency was 11.3%, with 6.3% at toxicity grades III–IV. We found no difference between the two kinds of 5-FU

Discussion

In the present study, we compared different approaches for DPD deficiency detection prior to 5-FU-based therapy. Acute polyvisceral toxicity, after high and prolonged 5-FU plasma levels due to DPD deficiency, can occur as early as the first cycle of treatment with a frequency of about 3–5%; it is sometimes lethal (0.5%) [4], [7], [8], [9]. Considering its frequent use, it would be important to detect patients with complete or partial deficiency prior to treatment, but no detection strategy and

Acknowledgement

We thank the Comité Départemental du Maine et Loire de la Ligue Contre Le Cancer for their financial support.

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