DPYD genotype-guided dose individualization to improve patient safety of fluoropyrimidine therapy: call for a drug label update

Pharmacogenetic Testing or Therapeutic Drug Monitoring: A Quantitative Framework

BACKGROUND

Pharmacogenetic profiling and therapeutic drug monitoring (TDM) have both been proposed to manage inter-individual variability (IIV) in drug exposure. However, determining the most effective approach for estimating exposure for a particular drug remains a challenge. This study aimed to quantitatively assess the circumstances in which pharmacogenetic profiling may outperform TDM in estimating drug exposure, under three sources of variability (IIV, inter-occasion variability [IOV], and residual unexplained variability [RUV]).

METHODS

Pharmacokinetic models were selected from the literature corresponding to drugs for which pharmacogenetic profiling and TDM are both clinically considered approaches for dose individualization. The models were used to simulate relevant drug exposures (trough concentration or area under the curve [AUC]) under varying degrees of IIV, IOV, and RUV.

RESULTS

Six drug cases were selected from the literature. Model-based simulations demonstrated that the percentage of patients for whom pharmacogenetic exposure prediction is superior to TDM differs for each drug case: tacrolimus (11.0%), tamoxifen (12.7%), efavirenz (49.2%), vincristine (49.6%), risperidone (48.1%), and 5-fluorouracil (5-FU) (100%). Generally, in the presence of higher unexplained IIV in combination with lower RUV and IOV, exposure was best estimated by TDM, whereas, under lower unexplained IIV in combination with higher IOV or RUV, pharmacogenetic profiling was preferred.

CONCLUSIONS

For the drugs with relatively low RUV and IOV (e.g., tamoxifen and tacrolimus), TDM estimated true exposure the best. Conversely, for drugs with similar or lower unexplained IIV (e.g., efavirenz or 5-FU, respectively) combined with relatively high RUV, pharmacogenetic profiling provided the most accurate estimate for most patients. However, genotype prevalence and the relative influence of genotypes on the PK, as well as the ability of TDM to accurately estimate AUC with a limited number of samples, had an impact. The results could be used to support clinical decision making when considering other factors, such as the probability for severe side effects.

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.

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.

Updated DPYD HapB3 haplotype structure and implications for pharmacogenomic testing

The DPYD gene encodes dihydropyrimidine dehydrogenase, the rate-limiting enzyme for the metabolism of fluoropyrimidines 5-fluorouracil and capecitabine. Genetic variants in DPYD have been associated with altered enzyme activity, therefore accurate detection and interpretation is critical to predict metabolizer status for individualized fluoropyrimidine therapy. The most commonly observed deleterious variation is the causal variant linked to the previously described HapB3 haplotype, c.1129-5923C>G (rs75017182) in intron 10, which introduces a cryptic splice site. A benign synonymous variant in exon 11, c.1236G>A (rs56038477) is also linked to HapB3 and is commonly used for testing. Previously, these single-nucleotide polymorphisms (SNPs) have been reported to be in perfect linkage disequilibrium (LD); therefore, c.1236G>A is often utilized as a proxy for the function-altering intronic variant. Clinical genotyping of DPYD identified a patient who had c.1236G>A, but not c.1129-5923C>G, suggesting that these two SNPs may not be in perfect LD, as previously assumed. Additional individuals with c.1236G>A, but not c.1129-5923C>G, were identified in the Children's Mercy Data Warehouse and the All of Us Research Program version 7 cohort substantiating incomplete SNP linkage. Consequently, testing only c.1236G>A can generate false-positive results in some cases and lead to suboptimal dosing that may negatively impact patient therapy and prospect of survival. Our data show that DPYD genotyping should include the functional variant c.1129-5923C>G, and not the c.1236G>A proxy, to accurately predict DPD activity.

Upfront DPYD Genotype-Guided Treatment for Fluoropyrimidine-Based Chemotherapy in Advanced and Metastatic Colorectal Cancer: A Cost-Effectiveness Analysis

OBJECTIVES

Fluoropyrimidines are the most widely used chemotherapy drugs for advanced and metastatic colorectal cancer (CRC). Individuals with certain DPYD gene variants are exposed to an increased risk of severe fluoropyrimidine-related toxicities. This study aimed to evaluate the cost-effectiveness of preemptive DPYD genotyping to guide fluoropyrimidine therapy in patients with advanced or metastatic CRC.

METHODS

Overall survival of DPYD wild-type patients who received a standard dose and variant carriers treated with a reduced dose were analyzed by parametric survival models. A decision tree and a partitioned survival analysis model with a lifetime horizon were designed, taking the Iranian healthcare perspective. Input parameters were extracted from the literature or expert opinion. To address parameter uncertainty, scenario and sensitivity analyses were also performed.

RESULTS

Compared with no screening, the genotype-guided treatment strategy was cost-saving ($41.7). Nevertheless, due to a possible reduction in the survival of patients receiving reduced-dose regimens, it was associated with fewer quality-adjusted life-years (9.45 vs 9.28). In sensitivity analyses, the prevalence of DPYD variants had the most significant impact on the incremental cost-effectiveness ratio. The genotyping strategy would remain cost-saving, as long as the genotyping cost is < $49 per test. In a scenario in which we assumed equal efficacy for the 2 strategies, genotyping was the dominant strategy, associated with less costs (∼$1) and more quality-adjusted life-years (0.1292).

CONCLUSIONS

DPYD genotyping to guide fluoropyrimidine treatment in patients with advanced or metastatic CRC is cost-saving from the perspective of the Iranian health system.

DPD deficiency in an Irish oncology centre: Prevalence and clinical implications

INTRODUCTION

Fluorouracil (5FU) and capecitabine are metabolised by dihydropyrimidine dehydrogenase (DPD). Up to 9% of people have low levels of a working DPD enzyme and are at risk of severe toxicity from 5FU/capecitabine. In April 2020, the EMEA recommended patients undergo prospective screening for DPD deficiency before starting treatment, and this was introduced in our hospital.

METHODS

We retrospectively reviewed records of all patients receiving 5FU/capecitabine in a tertiary Irish cancer centre from May 2020 to April 2021 (n = 197), and those starting first-line treatment in May 2019-April 2020 (n = 97). Our primary outcome was to estimate the prevalence of DPYD variant genes by prospective genotypic screening, with secondary outcomes including variant prevalence by prospective and reactive screening in patients receiving first-line treatment, and 5FU toxicity/tolerability in those with detected variants.

RESULTS

In those treated 2020-2021, cancer subtypes included colorectal (n = 120, 61%), breast (n = 34, 17%), and biliary/pancreatic cancers (n = 21, 11%). Median patient age was 62 (range 25-86 years); 40% (n = 79) of patients were screened overall, with a prospective-screening deficiency prevalence of 6.8% (n = 3 of 44). Three patients had pathogenic DPYD-variants detected by prospective screening and tolerated treatment with 50% up-front dose reduction of 5FU, two had variants of uncertain significance detected by reactive screening.

DISCUSSION

Other Irish studies estimated prevalence at 11-12%. As the number of variants detected was small, and screening rates were incomplete, our study may have underestimated prevalence.

CONCLUSIONS

Approximately 6.8% of Irish patients may carry DPD deficiencies, prospective screening is essential to reduce the risk of life-threatening toxicity in these 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.

Assessment of the Clinical Utility of Pretreatment DPYD Testing for Patients Receiving Fluoropyrimidine Chemotherapy

PURPOSE

Patients who carry pathogenic variants in DPYD have higher systemic fluoropyrimidine (FP) concentrations and greater risk of severe and fatal FP toxicity. Pretreatment DPYD testing and DPYD-guided FP dosing to reduce toxicity and health care costs is recommended by European clinical oncology guidelines and has been adopted across Europe, but has not been recommended or adopted in the United States. The cochairs of the National Comprehensive Cancer Network Guidelines for colon cancer treatment explained their concerns with recommending pretreatment DPYD testing, particularly the risk that reduced FP doses in DPYD carriers may reduce treatment efficacy.

METHODS

This special article uses previously published frameworks for assessing the clinical utility of cancer biomarker tests, including for germline indicators of toxicity risk, to assess the clinical utility of pretreatment DPYD testing, with a particular focus on the risk of reducing treatment efficacy.

RESULTS

There is no direct evidence of efficacy reduction, and the available indirect evidence demonstrates that DPYD-guided FP dosing results in similar systemic FP exposure and toxicity compared with standard dosing in noncarriers, and is well calibrated to the maximum tolerated dose, strongly suggesting there is minimal risk of efficacy reduction.

CONCLUSION

This article should serve as a call to action for clinicians and clinical guidelines committees in the United States to re-evaluate the clinical utility of pretreatment DPYD testing. If clinical utility has not been demonstrated, further dialogue is needed to clarify what additional evidence is needed and which of the available study designs, also described within this article, would be appropriate. Clinical guideline recommendations for pretreatment DPYD testing would increase clinical adoption and ensure that all patients receive maximally safe and effective FP treatment.

Impact of Guidelines Regarding Dihydropyrimidine Dehydrogenase (DPD) Deficiency Screening Using Uracil-Based Phenotyping on the Reduction of Severe Side Effect of 5-Fluorouracil-Based Chemotherapy: A Propension Score Analysis

Dihydropyrimidine dehydrogenase (DPD) deficiency is associated with severe fluoropyrimidines-induced toxicity. As of September 2018, French recommendations call for screening for DPD deficiency by plasma uracil quantification prior to all fluoropyrimidine-based chemotherapy. A dose reduction of fluoropyrimidine is recommended when uracil concentration is equal to or greater than 16 ng/mL. This matched retrospective study assessed the impact of DPD screening on the reduction of severe side effects and on the management of DPD-deficient patients. Using a propensity score, we balanced the factors influencing 5-Fluorouracil (5-FU) toxicity. Then, the severity scores (G3 and G4 severity as well as their frequency) of patients who did not benefit from DPD screening were compared with those of patients who benefited from DPD screening for each treatment cycle (from 1 to 4). Among 349 screened patients, 198 treated patients were included. Among them, 31 (15.7%) had DPD deficiency (median uracilemia 19.8 ng/mL (range: 16.1−172.3)). The median toxicity severity score was higher in the unscreened group for each treatment cycle (0 vs. 1, p < 0.001 at each cycle from 1 to 4) as well as the cumulative score during all courses of treatment (p = 0.028). DPD-deficient patients received a significantly lower dose of 5-FU (p < 0.001). This study suggests that pretherapeutic plasmatic uracil assessment, along with 5-FU dosage adjustment, may be beneficial in reducing 5-FU toxicity in real-life patients.

Introducing a simple and cost-effective RT-PCR protocol for detection of DPYD*2A polymorphism: the first study in Kurdish population

PURPOSE

Fluoropyrimidines, the major chemotherapeutic agents in various malignancies treatment, are metabolized by dihydropyrimidine dehydrogenase (DPD). DPD deficiency can lead to severe and sometimes fatal toxicity. In the present study, we developed a simple protocol to detect the DPYD*2A variant. Common side effects in patients treated with these drugs were also evaluated in a Kurdish population.

METHOD

We established a reverse-transcriptase polymerase chain reaction (RT-PCR) technique for detection of DPYD*2A. Sanger sequencing was used to confirm the results. 121 Kurdish patients receiving fluoropyrimidine derivatives were enrolled, and clinical information regarding the dosage and toxicity was analyzed.

RESULTS

Our RT-PCR method was able to detect one patient with heterozygous state for DPYD*2A (0.8%). The most observed adverse drug reactions were tingling, nausea, and hair loss. The frequency of patients with the toxicity of grade 3 or worse was 6.6%.

CONCLUSION

This was the first study that detect DPYD*2A polymorphism in the Kurdish population. Our method was successfully able to detect the DPYD*2A variant and, due to its simplicity and cost-effectiveness, it may be considered as an alternative to the current methods, especially in developing countries. Our detected polymorphism rate at 0.8% is comparable with other studies. Despite the low rate of DPYD*2A polymorphism, pharmacogenetics assessment before beginning the treatment process is highly recommended due to its association with a high risk of severe toxicity.

Testing for Dihydropyrimidine Dehydrogenase Deficiency to Individualize 5-Fluorouracil Therapy

Simple Summary

5-Fluorouracil (5-FU) is a chemotherapy drug that is commonly used to treat multiple cancers. Many people who are treated with 5-FU experience severe toxicity to the drug, and in severe cases, patients can die. This review discusses current methods for identifying people who are at high risk for severe side effects to 5-FU therapy.

Abstract

Severe adverse events (toxicity) related to the use of the commonly used chemotherapeutic drug 5-fluorouracil (5-FU) affect one in three patients and are the primary reason cited for premature discontinuation of therapy. Deficiency of the 5-FU catabolic enzyme dihydropyrimidine dehydrogenase (DPD, encoded by DPYD) has been recognized for the past 3 decades as a pharmacogenetic syndrome associated with high risk of 5-FU toxicity. An appreciable fraction of patients with DPD deficiency that receive 5-FU-based chemotherapy die as a result of toxicity. In this manuscript, we review recent progress in identifying actionable markers of DPD deficiency and the current status of integrating those markers into the clinical decision-making process. The limitations of currently available tests, as well as the regulatory status of pre-therapeutic DPYD testing, are also discussed.

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.

Reversible Toxic Encephalopathy Involving the Cerebellum and Subcortical White Matter Attributed to Capecitabine

Capecitabine is an anticancer drug related to 5-fluorouracil (5-FU) that is used to treat multiple cancers. Little is known about the central nervous system toxicity of capecitabine owing to the low frequency of occurrence. In this report we describe a rare case of capecitabine-related toxic encephalopathy involving the cerebellum and subcortical white matter. A review of the literature showed that most reported cases have shown excellent recovery within a few days of capecitabine termination. Whether uridine triacetate is a reasonable treatment choice for patients with life-threatening toxic encephalopathy depends on the availability of reliable clinical data. Prescreening for dihydropyrimidine dehydrogenase genotype variants and detection of 5-FU degradation rate prior to capecitabine treatment may become an effective way to avoid toxic reactions by regulating the therapeutic dose for each patient, which remains to be investigated and needs more clinical data to support.

Ethnic Diversity of DPD Activity and the DPYD Gene: Review of the Literature

Pharmacogenomic screening can identify patients with gene variants that predispose them to the development of severe toxicity from fluoropyrimidine (FP) chemotherapy. Deficiency of the critical metabolic enzyme dihydropyrimidine dehydrogenase (DPD) leads to excessive toxicity on exposure to fluoropyrimidine chemotherapy. This can result in hospitalisation, intensive care admissions and even death. Upfront screening of the gene that encodes for DPD (DPYD) has recently been implemented in regions throughout Europe and the United Kingdom. Current screening evaluates DPYD variants that are well described within Caucasian patient populations and provides genotyped-guided dose adjustment recommendations based upon the presence of these variants. This article reviews the differences in DPYD gene variants within non-Caucasian populations compared to Caucasian populations, with regard to the implications for clinical tolerance of fluoropyrimidine chemotherapies and genotype guided dose adjustment guidelines.

Pathogenic DPYD Variants and Treatment-Related Mortality in Patients Receiving Fluoropyrimidine Chemotherapy: A Systematic Review and Meta-Analysis

BACKGROUND

Pathogenic variants of the DPYD gene are strongly associated with grade ≥3 toxicity during fluoropyrimidine chemotherapy. We conducted a systematic review and meta-analysis to estimate the risk of treatment-related death associated with DPYD gene variants.

MATERIALS AND METHODS

We searched for reports published prior to September 17, 2020, that described patients receiving standard-dose fluoropyrimidine chemotherapy (5-fluorouracil or capecitabine) who had baseline testing for at least one of four pathogenic DPYD variants (c.1129-5923C>G [HapB3], c.1679T>G [*13], c.1905+1G>A [*2A], and c.2846A>T) and were assessed for toxicity. Two reviewers assessed studies for inclusion and extracted study-level data. The primary outcome was the relative risk of treatment-related mortality for DPYD variant carriers versus noncarriers; we performed data synthesis using a Mantel-Haenszel fixed effects model.

RESULTS

Of the 2,923 references screened, 35 studies involving 13,929 patients were included. DPYD variants (heterozygous or homozygous) were identified in 566 patients (4.1%). There were 14 treatment-related deaths in 13,363 patients without identified DPYD variants (treatment-related mortality, 0.1%; 95% confidence interval [CI], 0.1-0.2) and 13 treatment-related deaths in 566 patients with any of the four DPYD variants (treatment-related mortality, 2.3%; 95% CI, 1.3%-3.9%). Carriers of pathogenic DPYD gene variants had a 25.6 times increased risk of treatment-related death (95% CI, 12.1-53.9; p < .001). After excluding carriers of the more common but less deleterious c.1129-5923C>G variant, carriers of c.1679T>G, c.1905+1G>A, and/or c.2846A>T had treatment-related mortality of 3.7%.

CONCLUSION

Patients with pathogenic DPYD gene variants who receive standard-dose fluoropyrimidine chemotherapy have greatly increased risk for treatment-related death.

IMPLICATIONS FOR PRACTICE

The syndrome of dihydropyrimidine dehydrogenase (DPD) deficiency is an uncommon but well-described cause of severe toxicity related to fluoropyrimidine chemotherapy agents (5-fluorouracil and capecitabine). Patients with latent DPD deficiency can be identified preemptively with genotyping of the DPYD gene, or with measurement of the plasma uracil concentration. In this systematic review and meta-analysis, the authors study the rare outcome of treatment-related death after fluoropyrimidine chemotherapy. DPYD gene variants associated with DPD deficiency were linked to a 25.6 times increased risk of fluoropyrimidine-related mortality. These findings support the clinical utility of DPYD genotyping as a screening test for DPD deficiency.

Real-World Evaluation of Universal Germline Screening for Cancer Treatment-Relevant Pharmacogenes

The purpose of this study was to determine the frequency of clinically actionable treatment-relevant germline pharmacogenomic variants in patients with cancer and assess the real-world clinical utility of universal screening using whole-exome sequencing in this population. Cancer patients underwent research-grade germline whole-exome sequencing as a component of sequencing for somatic variants. Analysis in a clinical bioinformatics pipeline identified clinically actionable pharmacogenomic variants. Clinical Pharmacogenetics Implementation Consortium guidelines defined clinical actionability. We assessed clinical utility by reviewing electronic health records to determine the frequency of patients receiving pharmacogenomically actionable anti-cancer agents and associated outcomes. This observational study evaluated 291 patients with cancer. More than 90% carried any clinically relevant pharmacogenetic variant. At least one disease-relevant variant impacting anti-cancer agents was identified in 26.5% (77/291). Nine patients with toxicity-associated pharmacogenomic variants were treated with a relevant medication: seven UGT1A1 intermediate metabolizers were treated with irinotecan, one intermediate DPYD metabolizer was treated with 5-fluorouracil, and one TPMT poor metabolizer was treated with mercaptopurine. These individuals were more likely to experience treatment-associated toxicities than their wild-type counterparts (p = 0.0567). One UGT1A1 heterozygote died after a single dose of irinotecan due to irinotecan-related adverse effects. Identifying germline pharmacogenomic variants was feasible using whole-exome sequencing. Actionable pharmacogenetic variants are common and relevant to patients undergoing cancer treatment. Universal pharmacogenomic screening can be performed using whole-exome sequencing data originally obtained for quality control purposes and could be considered for patients who are candidates for irinotecan, 5-fluorouracil, capecitabine, and mercaptopurine.

How I treat stage II colon cancer patients

Stage II colon cancer (CC) is probably one of the best prognosis gastrointestinal tumors seen in our consultations, but often takes a lot of time for physicians to determine appropriate treatment because of the limited benefit of adjuvant chemotherapy (CT) in these patients, together with the limited evidence in this situation. How to choose the best treatment for each individual patient is thus dependent on molecular (microsatellite instability/microsatellite stability status) and clinico-pathological features relevant enough to classify these tumors into low-, intermediate- and high-risk stage II disease and to choose an appropriate attitude for each of these subgroups. In practice, the first step in treatment decision making must be to assess the patient's status and comorbidities to see if the patient is eligible for an adjuvant treatment. Then, as fluoropyrimidines (FPs) are the corner stone of CC adjuvant treatment, screening for dihydropyrimidine dehydrogenase deficiency is mandatory in western countries. Finally, depending on the patient's characteristics and tumor risk stage, the strategy may be surveillance, adjuvant FP alone or oxaliplatin-based adjuvant CT. In the near future, new tools such as Immunoscore® (HalioDx; Luminy Biotech Enterprises, Marseille Cedex, France) and circulating tumor DNA may help to identify more precisely patients with minimal residual disease for more personalized adjuvant treatment approaches.

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Stage II CC is a heterogeneous disease with a complex management due to the limited data and benefit of adjuvant CT.

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Risk stratification through prognostic parameters is crucial to aid clinicians in determining the appropriate therapy.

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Lymph node sampling <12 and pT4 are currently recognized as the major prognostic features associated with worse survival.

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Adjuvant CT should be considered by incorporating prognostic features and balanced against patient's age and comorbidities.

Prognostic implications of chemotherapy-induced neutropenia in stage III colorectal cancer

BACKGROUND

Previous studies have reported chemotherapy-induced neutropenia (CIN) as a prognostic factor in stage IV colorectal cancer (CRC). However, only few reports analyzed the prognostic value of CIN in patients with stage III CRC who received adjuvant chemotherapy with oxaliplatin, 5-fluorouracil, and leucovorin (FOLFOX). We aimed to investigate the prognostic implications of CIN in patients with stage III CRC who received adjuvant chemotherapy with FOLFOX.

MATERIALS AND METHODS

We retrospectively analyzed patients with stage III CRC who received adjuvant chemotherapy with FOLFOX at a tertiary hospital between January 2007 and December 2017. Severe CIN was defined as an absolute neutrophil count of less than 1000/mm³. Three-y disease-free survival (DFS) and overall survival (OS) were analyzed as primary endpoints.

RESULTS

Among the 199 patients included in this study, 110 patients (55.3%) experienced severe CIN. There were no significant differences in survival outcomes between the control and CIN groups (control group versus CIN group: 3-y OS, 82.0 % versus 72.7 %; log rank, P = 0.250 and 3-y DFS, 71.9 % versus 62.7; log rank, P = 0.294). Univariate and multivariate analyses revealed that CIN did not affect DFS and OS in patients with stage III CRC who received adjuvant FOLFOX chemotherapy.

CONCLUSIONS

Severe CIN occurring during adjuvant FOLFOX chemotherapy did not play a significant role in the prognosis of patients with stage III CRC.

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.

An Evaluation of the Diagnostic Accuracy of a Panel of Variants in DPYD and a Single Variant in ENOSF1 for Predicting Common Capecitabine Related Toxicities

Simple Summary

5-Fluorouracil (5-FU) is a chemotherapy drug that can cause severe toxicity in some patients. A protein, an action molecule in our cells, called dihydropyrimidine dehydrogenase, or DPD for short, is important in clearing 5-FU from the body. Some people have versions of DPD that do not clear 5-FU very well. This causes active drug to stay in the body too long, causing toxicities such as diarrhoea or low levels of blood cells important for fighting infections. Current guidelines identify four sequence changes in the gene that encodes DPD with high level evidence of an impact on protein activity. Our study aims to calculate the frequency of a set of variants identified in patients with DPD deficiency in patients that were part of a clinical trial called QUASAR 2. We go on to test how well the DPD deficiency variants and a set of common variants previously shown to be associated with 5-FU toxicity can predict a person’s risk of 5-Fluorouracil induced toxicity. Our research is important for working out the best way to identify patients at risk of toxicity so high risk patients can be given lower doses of 5-Fluorouracil or be treated with a different drug all together.

Abstract

Efficacy of 5-Fluorouracil (5-FU)-based chemotherapy is limited by significant toxicity. Tests based upon variants in the Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines with high level evidence of a link to dihydropyrimidine dehydrogenase (DPD) phenotype and 5-FU toxicity are available to identify patients at high risk of severe adverse events (AEs). We previously reported associations between rs1213215, rs2612091, and NM_000110.3:c.1906-14763G>A (rs12022243) and capecitabine induced toxicity in clinical trial QUASAR 2. We also identified patients with DPD deficiency alleles NM_000110.3: c.1905+1G>A, NM_000110.3: c.2846C>T, NM_000110.3:c.1679T>G and NM_000110.3:c.1651G>A. We have now assessed the frequency of thirteen additional DPYD deficiency variants in 888 patients from the QUASAR 2 clinical trial. We also compared the area under the curve (AUC)—a measure of diagnostic accuracy—of the high-level evidence variants from the CPIC guidelines plus and minus additional DPYD deficiency variants and or common variants associated with 5-FU toxicity. Including additional DPYD deficiency variants retained good diagnostic accuracy for serious adverse events (AEs) and improved sensitivity for predicting grade 4 haematological toxicities (sensitivity 0.75, specificity 0.94) but the improvement in AUC for this toxicity was not significant. Larger datasets will be required to determine the benefit of including additional DPYD deficiency variants not observed here. Genotyping two common alleles statistically significantly improves AUC for prediction of risk of HFS and may be clinically useful (AUC difference 0.177, sensitivity 0.84, specificity 0.31).

Higher ETV5 Expression Associates With Poor 5-Florouracil-Based Adjuvant Therapy Response in Colon Cancer

Discovery of markers predictive for 5-Fluorouracil (5-FU)-based adjuvant chemotherapy (adjCTX) response in patients with locally advanced stage II and III colon cancer (CC) is necessary for precise identification of potential therapy responders. PEA3 subfamily of ETS transcription factors (ETV1, ETV4, and ETV5) are upregulated in multiple cancers including colon cancers. However, the underlying epigenetic mechanism regulating their overexpression as well as their role in predicting therapy response in colon cancer are largely unexplored. In this study, using gene expression and methylation data from The Cancer Genome Atlas (TCGA) project, we showed that promoter DNA methylation negatively correlates with ETV4 expression (ρ = -0.17, p = 5.6 × 10^-3) and positively correlates with ETV5 expression (ρ = 0.22, p = 1.43 × 10^-4) in colon cancer tissue. Further, our analysis in 1,482 colon cancer patients from five different cohorts revealed that higher ETV5 expression associates with shorter relapse-free survival (RFS) of adjCTX treated colon cancer patients (Hazard ratio = 2.09-5.43, p = 0.004-0.01). The present study suggests ETV5 expression as a strong predictive biomarker for 5-FU-based adjCTX response in stage II/III CC patients.

Fluoropyrimidine-induced cardiotoxicity

Cardio-oncology is a discipline based on early screening, monitoring, and treating chemotherapy-induced cardiotoxicity. There are many chemotherapeutics known for their cardiac toxic effects, including fluoropyrimidines. Fluoropyrimidine represents the cornerstone of many types of cancer and each year almost two million cancer patients undergo this treatment. Fluoropyrimidine-induced cardiotoxicity can be manifested in several forms, from angina pectoris to sudden death. This paper is a review of how the cardiotoxicity of fluoropyrimidines is presented, the mechanisms of its occurrence, its diagnosis, and management.

Implementing DPYD*2A Genotyping in Clinical Practice: The Quebec, Canada, Experience

BACKGROUND

Fluoropyrimidines are used in chemotherapy combinations for multiple cancers. Deficient dihydropyrimidine dehydrogenase activity can lead to severe life-threatening toxicities. DPYD*2A polymorphism is one of the most studied variants. The study objective was to document the impact of implementing this test in routine clinical practice.

METHODS

We retrospectively performed chart reviews of all patients who tested positive for a heterozygous or homozygous DPYD*2A mutation in samples obtained from patients throughout the province of Quebec, Canada.

RESULTS

During a period of 17 months, 2,617 patients were tested: 25 patients tested positive. All were White. Twenty-four of the 25 patients were heterozygous (0.92%), and one was homozygous (0.038%). Data were available for 20 patients: 15 were tested upfront, whereas five were identified after severe toxicities. Of the five patients confirmed after toxicities, all had grade 4 cytopenias, 80% grade ≥3 mucositis, 20% grade 3 rash, and 20% grade 3 diarrhea. Eight patients identified with DPYD*2A mutation prior to treatment received fluoropyrimidine-based chemotherapy at reduced initial doses. The average fluoropyrimidine dose intensity during chemotherapy was 50%. No grade ≥3 toxicities were observed. DPYD*2A test results were available in an average of 6 days, causing no significant delays in treatment initiation.

CONCLUSION

Upfront genotyping before fluoropyrimidine-based treatment is feasible in clinical practice and can prevent severe toxicities and hospitalizations without delaying treatment initiation. The administration of chemotherapy at reduced doses appears to be safe in patients heterozygous for DPYD*2A.

IMPLICATIONS FOR PRACTICE

Fluoropyrimidines are part of chemotherapy combinations for multiple cancers. Deficient dihydropyrimidine dehydrogenase activity can lead to severe life-threatening toxicities. This retrospective analysis demonstrates that upfront genotyping of DPYD before fluoropyrimidine-based treatment is feasible in clinical practice and can prevent severe toxicities and hospitalizations without delaying treatment initiation. This approach was reported previously, but insufficient data concerning its application in real practice are available. This is likely the first reported experience of systematic DPYD genotyping all over Canada and North America as well.

The cancer patient and cardiology

Advances in cancer treatments have improved clinical outcomes, leading to an increasing population of cancer survivors. However, this success is associated with high rates of short- and long-term cardiovascular (CV) toxicities. The number and variety of cancer drugs and CV toxicity types make long-term care a complex undertaking. This requires a multidisciplinary approach that includes expertise in oncology, cardiology and other related specialties, and has led to the development of the cardio-oncology subspecialty. This paper aims to provide an overview of the main adverse events, risk assessment and risk mitigation strategies, early diagnosis, medical and complementary strategies for prevention and management, and long-term follow-up strategies for patients at risk of cancer therapy-related cardiotoxicities. Research to better define strategies for early identification, follow-up and management is highly necessary. Although the academic cardio-oncology community may be the best vehicle to foster awareness and research in this field, additional stakeholders (industry, government agencies and patient organizations) must be involved to facilitate cross-discipline interactions and help in the design and funding of cardio-oncology trials. The overarching goals of cardio-oncology are to assist clinicians in providing optimal care for patients with cancer and cancer survivors, to provide insight into future areas of research and to search for collaborations with industry, funding bodies and patient advocates. However, many unmet needs remain. This document is the product of brainstorming presentations and active discussions held at the Cardiovascular Round Table workshop organized in January 2020 by the European Society of Cardiology.

Pharmacogenetic profiling of dihydropyrimidine dehydrogenase (DPYD) variants in the Indian population

BACKGROUND

The present study aimed to delineate the pharmacologically relevant dihydropyrimidine dehydrogenase (DPYD) variants in the Indian population.

METHODS

We screened 2000 Indian subjects for DPYD variants using the Infinium Global Screening Array (GSA) (Illumina Inc., San Diego, CA, USA).

RESULTS

The GSA analysis identified seven coding, two intronic and three synonymous DPYD variants. Level 1A alleles (rs75017182, rs3918290, P633Qfs*5 and D949V) were found to be rare (minor allele frequency: 1.889%), whereas Level 3 alleles were observed to be predominant (C29R: 24.91%, I543V: 9.047%, M166V: 8.993% and V732I: 8.44%). In silico predictions revealed that all Level 1A alleles were deleterious, whereas three (M166V, S534N and V732I) of seven Level 3 alleles were damaging. CUPSAT analysis revealed that two Level 1A (P633Qfs*, D949V) and three Level 3 (I543V, V732I and S534N) variants were thermolabile. The pooled Indian data showed that V732I, S534N and rs3918290 variants were associated with 5-FU/capecitabine toxicity, whereas C29R, I543V and M166V variants exhibited the null association. A comparison of our data with other population data from the 'Allele Frequency Aggregator' (https://www.ncbi.nlm.nih.gov/snp/docs/gsr/alfa/) database showed similarities with the South Asian data.

CONCLUSIONS

We have identified four Level 1A (non-functional/dysfunctional) and seven Level 3 variants in the DPYD gene. The pooled Indian data revealed the association of V732I, S534N and rs3918290 variants with 5-FU/capecitabine toxicity. Clustering analysis revealed the similarities in the DPYD profiles of the Indian and South Asian populations.

The adjuvant use of capecitabine for residual disease following pre-operative chemotherapy for breast cancer: Challenges applying CREATE-X to a US population

INTRODUCTION

The CREATE-X study, conducted in Japan and South Korea, established capecitabine as an adjuvant treatment option for patients with triple negative breast cancer (TNBC) who have residual disease (RD) following neoadjuvant anthracycline or taxane-based chemotherapy. However, there are no reports on the tolerability and outcomes of adjuvant capecitabine in the US setting following publication of the CREATE-X data.

METHODS

We retrospectively collected treatment and tolerability data from the medical records of the first 23 TNBC patients who received adjuvant capecitabine for RD post neoadjuvant chemotherapy at our institution. Disease-free survival was assessed using the Kaplan-Meier method.

RESULTS

The median starting dosage of capecitabine was 1871 mg/m²/day, most commonly divided into two daily doses on days 1-14 of each 21 day cycle. 34.8% of patients completed the treatment as prescribed. Side effects associated with treatment were common with 69.6% of patients experiencing hand-foot syndrome, 39.1% of patients experiencing diarrhea, and 13.0% of patients requiring hospitalization for side effects. Of 23 patients treated with adjuvant capecitabine, 34.8% completed the planned dose, 30.4% completed with dose reduction, and 34.8% discontinued early. At a median follow-up time of 14 months, the median disease-free survival was 22 months, with 30.4% of patients experiencing recurrence.

CONCLUSION

Tolerability was poor overall compared to the CREATE-X cohort. Administering adjuvant capecitabine for TNBC patients with residual disease in the United States is challenging given differences in tolerability. More research is needed to understand how poor tolerability will affect the efficacy of this approach in the US population.

Dihydropyrimidine Dehydrogenase Testing prior to Treatment with 5-Fluorouracil, Capecitabine, and Tegafur: A Consensus Paper

BACKGROUND

5-Fluorouracil (FU) is one of the most commonly used cytostatic drugs in the systemic treatment of cancer. Treatment with FU may cause severe or life-threatening side effects and the treatment-related mortality rate is 0.2-1.0%.

SUMMARY

Among other risk factors associated with increased toxicity, a genetic deficiency in dihydropyrimidine dehydrogenase (DPD), an enzyme responsible for the metabolism of FU, is well known. This is due to variants in the DPD gene (DPYD). Up to 9% of European patients carry a DPD gene variant that decreases enzyme activity, and DPD is completely lacking in approximately 0.5% of patients. Here we describe the clinical and genetic background and summarize recommendations for the genetic testing and tailoring of treatment with 5-FU derivatives. The statement was developed as a consensus statement organized by the German Society for Hematology and Medical Oncology in cooperation with 13 medical associations from Austria, Germany, and Switzerland. Key Messages: (i) Patients should be tested for the 4 most common genetic DPYD variants before treatment with drugs containing FU. (ii) Testing forms the basis for a differentiated, risk-adapted algorithm with recommendations for treatment with FU-containing drugs. (iii) Testing may optionally be supplemented by therapeutic drug monitoring.

Genetic influence of DPYD*9A polymorphism on plasma levels of 5-fluorouracil and subsequent toxicity after oral administration of capecitabine in colorectal cancer patients of South Indian origin

OBJECTIVES

High interindividual variability was reported with capecitabine toxicities among colorectal cancer (CRC) patients. DPYD*9A polymorphism was reported responsible for grade 3 or 4 toxicities. Finding the phenotypic association between DPYD*9A polymorphism and 5-fluorouracil (5-FU) plasma levels will give a better prediction for toxicity susceptibility.

METHODS

A total of 145 CRC patients were included in the final analysis. Each patient received capecitabine of 1,000 mg/m² twice daily for the first 14 days of a 21 day cycle. 5-FU levels were measured at two-time points 2 and 3 h post capecitabine administration across the 1st and 4th cycles of chemotherapy. 5-FU levels were measured using liquid chromatography and tandem mass spectrometry (LC-MS/MS). Genotyping analysis was done by real-time PCR (RT-PCR).

RESULTS

The mean 5-FU drug levels measured during the 1st cycle at time points 2 and 3 h were found to be 267 ng/mL ± (29) and 124 ng/mL ± (22) respectively. Whereas, the observed 5-FU levels in the 4th cycle were 275 ng/mL ± (28) and 130 ng/mL ± (26) respectively. Patients with 5-FU levels in the range of 281-320 and 141-160 ng/mL at 2 and 3 h respectively showed a higher risk for the hand-foot syndrome (HFS) and thrombocytopenia. No association was found between DPYD*9A polymorphism and 5-FU drug levels measured at time point 2 h across both the cycles. However, the drug levels measured at 3 h were found to be significantly different across the DPYD*9A genotypes. Individuals with GG genotype showed significantly higher 5-FU levels when compared to AA genotype.

CONCLUSIONS

DPYD*9A polymorphism had a significant influence on the plasma levels of 5-FU after capecitabine administration. The 5-FU levels measured at 3 h corresponding to elimination t_1/2 was significantly higher in patients with GG genotype compared AA genotype.

Tolerance-based capecitabine dose escalation after DPYD genotype-guided dosing in heterozygote DPYD variant carriers: a single-center observational study

OBJECTIVE

Certain polymorphisms of the DPYD gene encoding for the dihydropyrimidine dehydrogenase (DPD) enzyme are associated with fluoropyrimidine-induced toxicity. Dose reductions of the fluoropyrimidine prodrug capecitabine are recommended for patients carrying these DPYD variants to prevent toxicities. Capecitabine dose escalation after an initial genotype-guided dose reduction is advocated when treatment is well tolerated. However, practical guidelines on how to implement these dose escalations are lacking. We implemented a protocol for tolerance-guided capecitabine dosing in DPYD variant carriers and aimed to explore its effect on toxicity of treatment.

PATIENTS AND METHODS

Patients receiving capecitabine-based chemotherapy for different types of solid tumors were identified retrospectively. Capecitabine doses were reduced in case of a DPYD variant (DPYD*2A, c.2846A>T, DPYD*13, or c.1236G>A) and subsequently adjusted on the basis of tolerance. Outcome was evaluated by clinical chart review and dosing characteristics from the hospital pharmacy. Results were compared with a cohort of capecitabine-treated DPYD wild-type patients.

RESULTS

Of 185 patients eligible for analysis, 11 patients were heterozygous for a DPYD variant. A median dose escalation of 8.5% was achieved using the prespecified protocol. One DPYD variant carrier experienced a grade 3 toxicity after a dose escalation. Overall, DPYD variant carriers did not experience more, or more severe toxicities than DPYD wild-type patients. The total prevalence of severe toxicities in the wild-type group was 43.1% and is comparable with the literature.

CONCLUSION

Tolerance-based capecitabine dose escalation did not lead to more toxicity in DPYD variant carriers compared with wild-type patients. Our results can guide future prospective research.

Risk factors for cisplatin-induced acute kidney injury: A pilot study on the usefulness of genetic variants for predicting nephrotoxicity in clinical practice

Several studies have reported risk factors for predicting cisplatin-induced acute kidney injury (AKI), including old age, female sex, smoking, hypoalbuminemia, hypokalemia, hypomagnesemia, a high body surface area, advanced cancer and the total dose of cisplatin administered. Recently, some studies have focused on the associations between genetic alterations in the genes coding for renal drug transporters, such as organic cation transporter 2 (OCT2), and the nephrotoxicity of cisplatin. However, genetic variants have not been fully elucidated for clinical use. Patients who had received cisplatin (≥50 mg/m²)-containing chemotherapy as a first-line treatment were considered as eligible for the present study. The occurrence of AKI and its associations with baseline characteristics, conventional biomarkers and single-nucleotide variants (SNV) were assessed. AKI was defined as an increase in the serum creatinine level of >0.3 mg/dl or to 1.5-2 times the baseline level. Genotyping was conducted using the DMET platform (DMET Plus), which characterizes 1,936 genetic variants (1,931 SNV and 5 copy number variations) in 231 genes. Between April 2014 and June 2016, a total of 28 patients (22 men and 6 women) were enrolled. AKI occurred in 8 of the 28 enrolled patients (28.6%). Univariate analyses demonstrated that the urinary β2-microglobulin level and body surface area were significantly higher in the AKI group (P<0.05). As regards the associations between AKI and SNV, none of the examined SNV were found to be associated with cisplatin-induced AKI. The findings of the present study suggested that certain clinical factors were associated with the onset of AKI, but no associations were identified with genetic factors, including OCT2. Although this was a small pilot study, the findings indicated that genetic factors may not be of value for predicting AKI in clinical practice.

A review on the importance of genotyping and phenotyping in fluoropyrimidine treatment

Fluoropyrimidines, after more than 50 years from their discovery, are still the treatment of many types of cancer, and it is estimated that two million patients receive fluoropyrimidine therapy annually. The toxicity associated with fluoropyrimidines affects 30–40% of patients and some adverse effects can be lethal.

Dihydroypyrimidine dehydrogenase is the main enzyme in the catabolism of 5-FU and DPD activity deficiency can cause important toxicity. This is an important reason to determine DPD activity in order to improve patient safety and to limit potential life-threating toxicity.

At presentmultiple phenotypic and genotypic methods are available for the determination of DPD activity, some of these methods have proven their usefulness in practice, and yet they are not routinely recommended in clinical practice.

This review is another statement of the importance of the determination of DPD status, the phenotypic and genotypic methods that are available and can be used.

New DPYD variants causing DPD deficiency in patients treated with fluoropyrimidine

PURPOSE

Several clinical guidelines recommend genetic screening of DPYD, including coverage of the variants c.1905 + 1G>A(DPYD*2A), c.1679T>G(DPYD*13), c.2846A>T, and c.1129-5923C>G, before initiating treatment with fluoropyrimidines. However, this screening is often inadequate at predicting the occurrence of severe fluoropyrimidine-induced toxicity in patients.

METHODS

Using a complementary approach combining whole DPYD exome sequencing and in silico and structural analysis, as well as phenotyping of DPD by measuring uracilemia (U), dihydrouracilemia (UH₂), and the UH₂/U ratio in plasma, we were able to characterize and interpret DPYD variants in 28 patients with severe fluoropyrimidine-induced toxicity after negative screening.

RESULTS

Twenty-five out of 28 patients (90%) had at least 1 variant in the DPYD coding sequence, and 42% of the variants (6/14) were classified as potentially deleterious by at least 2 of the following algorithms: SIFT, Poly-Phen-2, and DPYD varifier. We identified two very rare deleterious mutations, namely, c.2087G>A (p.R696H) and c.2324T>G (p.L775W). We were able to demonstrate partial DPD deficiency, as measured by the UH₂/U ratio in a patient carrying the variant p.L775W for the first time.

CONCLUSION

Whole exon sequencing of DPYD in patients with suspicion of partial DPD deficiency can help to identify rare or new variants that lead to enzyme inactivation. Combining different techniques can yield abundant information without increasing workload and cost burden, thus making it a useful approach for implementation in patient care.

Chemotherapy-induced necrotising tumour lysis and perforation of a huge gastric cancer simulating emphysematous pancreatitis

A 56-year-old man was diagnosed to have a huge gastric cancer extending from the lesser curvature of the stomach to the pancreas with multiple hepatic and peritoneal metastases. Two days after completing chemotherapy with cisplatin plus high dose leucovorin and fluorouracil, drastic necrotising tumour lysis led to gastric perforation and septic shock most likely due to bacterial peritonitis. The image of tumour lysis looked like an emphysematous pancreatitis. Afterwards, immunohistochemical study of the tumour specimen confirmed moderate positivity of dihydropyrimidine dehydrogenase and absence of Bcl-2 expression. The incomplete expression of dihydropyrimidine dehydrogenase and total deficiency of Bcl-2 are considered to be the main underlying causes of such extraordinary chemosensitivity and so severe a tumour lysis phenomenon. Pre-emptive intensive survey of possible biomarkers of chemosensitivity is thus highly recommended upon treating a massive gastric cancer.

Toxicities associated with chemotherapy regimens containing a fluoropyrimidine: A real-life evaluation in France

AIMS

Despite fluoropyrimidines (FPs) constituting the main component of the chemotherapy combination protocols in 50% of chemotherapies for solid tumour treatments, incidence data for FP-related toxicity are poorly documented in real life. This study evaluated the number of patients receiving FP-based chemotherapies in France, along with the true incidence of FP-related serious adverse effects (SAEs) before the recent mandatory dihydropyrimidine dehydrogenase (DPD)-screening was introduced by French health authorities, DPD being the rate-limiting enzyme of 5-fluorouracil (5-FU) catabolism.

METHODS

Exhaustive data on the number of patients treated with FP-based chemotherapy in 2013-2014 were collected in the Centre-Val de Loire region of France. True incidence of SAEs was extracted from a cohort of 513 patients with incident solid tumours receiving first-line FP-based chemotherapy.

RESULTS

After extrapolation at national level, we estimated that 76,200 patients are currently treated annually with 5FU (53,100 patients, 62% digestive system-related versus 26% breast cancers versus 12% head and neck cancers) or capecitabine (23,100 patients, 45% digestive system-related versus 37% breast cancers versus 18% non-documented). Earlier (in the first two cycles) the SAE incidence rate was 19.3% (95% confidence interval (CI) 16-23%) including one toxic death (0.2%, 95%CI 0-1%). SAE incidence rate was 32.2% (95%CI 28-36%) over the first 6 months of treatment. Incidence of death, life-threatening prognosis or incapacity/disability was 1.4% (95%CI 0.4-2.4%) and 1.6% (95%CI 0.5-2.6%) during first two cycles and first 6 months, respectively.

CONCLUSION

These data highlight the significant public health issue related to FP toxicity, with around 1200 patients developing FP-related life-threatening prognosis or incapacity/disability annually in France, including 150 toxic deaths. It is hoped that DPD-deficiency screening will reduce such iatrogenic events and eradicate toxic deaths.

PCDH17 increases the sensitivity of colorectal cancer to 5-fluorouracil treatment by inducing apoptosis and autophagic cell death

5-Fluorouracil (5-FU) is known as a first-line chemotherapeutic agent against colorectal cancer (CRC), but drug resistance occurs frequently and significantly limits its clinical success. Our previous study showed that the protocadherin 17 (PCDH17) gene was frequently methylated and functioned as a tumor suppressor in CRC. However, the relationship between PCDH17 and 5-FU resistance in CRC remains unclear. Here, we revealed that PCDH17 was more highly expressed in 5-FU-sensitive CRC tissues than in 5-FU-resistant CRC tissues, and high expression of PCDH17 was correlated with high BECN1 expression. Moreover, this expression profile contributed to superior prognosis and increased survival in CRC patients. Restoring PCDH17 expression augmented the 5-FU sensitivity of CRC in vitro and in vivo by promoting apoptosis and autophagic cell death. Furthermore, autophagy played a dominant role in PCDH17-induced cell death, as an autophagy inhibitor blocked cell death to a greater extent than the pancaspase inhibitor Z-VAD-FMK. PCDH17 inhibition by siRNA decreased the autophagy response and 5-FU sensitivity. Mechanistically, we showed that c-Jun NH2-terminal kinase (JNK) activation was a key determinant in PCDH17-induced autophagy. The compound SP600125, an inhibitor of JNK, suppressed autophagy and 5-FU-induced cell death in PCDH17-reexpressing CRC cells. Taken together, our findings suggest for the first time that PCDH17 increases the sensitivity of CRC to 5-FU treatment by inducing apoptosis and JNK-dependent autophagic cell death. PCDH17 may be a potential prognostic marker for predicting 5-FU sensitivity in CRC patients.

Influence of DPYD*9A, DPYD*6 and GSTP1 ile105val Genetic Polymorphisms on Capecitabine and Oxaliplatin (CAPOX) Associated Toxicities in Colorectal Cancer (CRC) Patients

AIM

CAPOX treatment in CRC patients was reported to cause several dose-limiting toxicities, and are found responsible for treatment interruption or even discontinuation. Therefore there is a critical need for identifying the predictive biomarkers for such toxicities to prevent them. The aim of our present study is to find the influence of DPYD*9A, DPYD*6 and GSTP1 ile105val gene polymorphisms on CAPOX treatment-associated toxicities in south Indian patients with CRC.

PATIENTS AND METHODS

We have recruited 145 newly diagnosed and treatment naive CRC patients in the study. Each Patient received a standard treatment schedule of oxaliplatin 130 mg/m2 infusion over 2 hours on day 1 and oral capecitabine 1000mg/m2 in divided doses twice daily for the next 14 days of a 21-day cycle. 5 ml of the venous blood was collected from each patient and genomic DNA extraction and genotyping. The genotyping analysis of the selected genetic polymorphisms was carried out by real-time PCR using TaqMan SNP genotyping assays obtained from applied biosystems.

RESULTS

The major dose-limiting toxicities observed with CAPOX treatment were thrombocytopenia, HFS and PN. DPYD*9A carries were found to be at higher risk for HFS, diarrhoea and thrombocytopenia when compared to patients with wild allele. No significant association was found between DPYD*6, GSTP1 ile105val polymorphisms and CAPOX related toxicities except for thrombocytopenia.

CONCLUSION

A significant association was observed between DPYD*9A polymorphism and CAPOX induced dose-limiting toxicities strengthening its role as a predictive biomarker.

Treatment delays during FOLFOX chemotherapy in patients with colorectal cancer: a multicenter retrospective analysis

Background

FOLFOX (folinic acid, 5-fluorouracil and oxaliplatin) is the most commonly used chemotherapy regimen for the treatment of colorectal cancer. FOLFOX is administered in 14-day cycles, though toxicities frequently lead to unplanned delays. We report the incidence of unplanned delays among patients receiving FOLFOX and describe the reasons for delays.

Methods

We conducted a retrospective analysis of patients receiving FOLFOX chemotherapy for colorectal cancer. Patients were treated at one of two tertiary cancer centers between January 2012 and April 2016. Cycles 2-6 were assessed for delays, and treatments were considered delayed when the interval from prior treatment was >18 days. Reasons for unplanned delays were categorized based on review of clinical records.

Results

We identified 214 patients receiving FOLFOX as standard-of-care therapy. The median age was 59 years, and 55% were female. Of 961 evaluable treatment cycles, 124 (13%) had unplanned delays, and 92 of 214 patients (43%) had one or more unplanned delays in cycles 2-6. Cytopenias (neutropenia and/or thrombocytopenia) were the most common cause of unplanned delays, affecting 34% of patients and accounting for 74 of 124 unplanned delays (60%).

Conclusions

Delays are common during FOLFOX chemotherapy, with 43% of patients having at least one unplanned delay prior to completing cycle 6. Neutropenia and thrombocytopenia were the leading causes of unplanned delays. Our findings justify the development of systematic approaches for preventing unplanned delays, such as standardized laboratory treatment criteria and/or proactive dose adjustment strategies.

Tailored therapy in patients treated with fluoropyrimidines: focus on the role of dihydropyrimidine dehydrogenase

Fluoropyrimidines are widely used in the treatment of solid tumors, mainly gastrointestinal, head and neck and breast cancer. Dihydropyrimidine dehydrogenase (DPD) is the rate-limiting enzyme for catabolism of 5-FU and it is encoded by DPYD gene. To date, many known polymorphisms cause DPD deficiency and subsequent increase of 5-FU toxicity. In addition, reduced inactivation of 5-FU could lead to increased 5-FU intracellular concentration and augmented efficacy of this drugs. Therefore DPD expression, particularly intratumoral, has been investigated as predictive and prognostic marker in 5-FU treated patients. There also seems to be a tendency to support the correlation between DPD expression and response/survival in patients treated with fluoropyrimidine even if definitive conclusions cannot be drawn considering that some studies are conflicting. Therefore, the debate on intratumoral DPD expression as a potential predictor and prognostic marker in patients treated with fluoropyrimidines is still open. Four DPD-polymorphisms are the most relevant for their frequency in population and clinical relevance. Many studies demonstrate that treating a carrier of one of these polymorphisms with a full dose of fluoropyrimidine can expose patient to a severe, even life-threatening, toxicity. Severe toxicity is reduced if this kind of patients received a dose-adjustment after being genotyped. CPIC (Clinical Pharmacogenetics Implementation Consortium) is an International Consortium creating guidelines for facilitating use of pharmacogenetic tests for patient care and helps clinicians ensuring a safer drug delivery to the patient. Using predictive DPD deficiency tests in patients receiving 5FU-based chemotherapy, in particular for colorectal cancer, has proven to be a cost-effective strategy.

Colorectal cancer: pharmacogenetics support for the correct drug prescription

Pharmacogenetics (PGx) in clinical practice is a tool that the clinician can use to guide, in a personalized way, the most suitable treatment that will be administered to the patient. The objective of this review is to summarize in a practical and accessible rational way, the advances that currently exist for the application of PGx in colorectal cancer chemotherapy management through the study of the patients' germline polymorphisms. To define the polymorphisms that can be applied, we rely on three fundamental cornerstones: the recommendations of drug regulatory agencies; the implementation guidelines prepared by expert consortia in PGx and information from clinical annotations (the drug/polymorphism relation) according to the scientific level of evidence assigned by PharmGKB experts.

Clinical implementation of pre-treatment DPYD genotyping in capecitabine-treated metastatic breast cancer patients

Purpose

Metastatic breast cancer (mBC) patients with DPYD genetic variants linked to loss of dihydropyrimidine dehydrogenase (DPD) activity are at risk of severe capecitabine-associated toxicities. However, prospective DPYD genotyping has not yet been implemented in routine clinical practice. Following a previous internal review in which two patients underwent lengthy hospitalisations whilst receiving capecitabine, and were subsequently found to be DPD deficient, we initiated routine DPYD genotyping prior to starting capecitabine. This study evaluates the clinical application of routine DPYD screening at a large cancer centre in London.

Methods

We reviewed medical records for consecutive patients with mBC who underwent DPYD genotyping before commencing capecitabine between December 2014 and December 2017. Patients were tested for four DPYD variants associated with reduced DPD activity.

Results

Sixty-six patients underwent DPYD testing. Five (8.4%) patients were found to carry DPYD genetic polymorphisms associated with reduced DPD activity; of these, two received dose-reduced capecitabine. Of the 61 patients with DPYD wild-type, 14 (23%) experienced grade 3 toxicities which involved palmar–plantar erythrodysesthesia (65%), and gastrointestinal toxicities (35%); no patient was hospitalised due to toxicity.

Conclusions

Prospective DPYD genotyping can be successfully implemented in routine clinical practice and can reduce the risk of severe fluoropyrimidine toxicities.

Colorectal Cancer Biomarkers in the Era of Personalized Medicine

The 5-year survival probability for patients with metastatic colorectal cancer has not drastically changed over the last several years, nor has the backbone chemotherapy in first-line disease. Nevertheless, newer targeted therapies and immunotherapies have been approved primarily in the refractory setting, which appears to benefit a small proportion of patients. Until recently, rat sarcoma (RAS) mutations remained the only genomic biomarker to assist with therapy selection in metastatic colorectal cancer. Next generation sequencing has unveiled many more potentially powerful predictive genomic markers of therapy response. Importantly, there are also clinical and physiologic predictive or prognostic biomarkers, such as tumor sidedness. Variations in germline pharmacogenomic biomarkers have demonstrated usefulness in determining response or risk of toxicity, which can be critical in defining dose intensity. This review outlines such biomarkers and summarizes their clinical implications on the treatment of colorectal cancer. It is critical that clinicians understand which biomarkers are clinically validated for use in practice and how to act on such test results.

Feasibility of Integrating Panel-Based Pharmacogenomics Testing for Chemotherapy and Supportive Care in Patients With Colorectal Cancer

INTRODUCTION

Pharmacogenomics is about selecting the "right drug in the right amount for the right patient." In metastatic colorectal cancer, germline pharmacogenomics testing presents a unique opportunity to improve outcomes, since the genes dihydropyrimidine dehydrogenase and UDP-glucuronosyltransferase metabolizing the chemotherapy drugs, 5-fluorouracil, and irinotecan are already well known. In a retrospective analysis of the landmark TRIBE clinical trial [(TRIBE - TRIplet plus BEvacizumab multicenter, phase III trial by the Italian Cooperative GONO (Gruppo Oncologico Nord Ovest) group (NCT00719797)], the proportion of patients with serious adverse events was higher in those with dihydropyrimidine dehydrogenase/UDP-glucuronosyltransferase aberrations and was dose dependent. We aimed to report on the feasibility and the results of incorporating pharmacogenomics testing into clinical practice.

METHODS

As a quality improvement initiative and a center of individualized medicine grant, we integrated the use of OneOme RightMed comprehensive test, which reports on 27 genes related to pharmacogenomics and over 300 medications of interest. We limited initial testing to patients with colorectal cancer. Pharmacists provided dosage recommendations based on test results in real-time.

RESULTS

At our cancer center, 155 patients underwent pharmacogenomics testing from November 2017 to January 2019. Results were available within 3 to 5 days of testing for most patients and were integrated into treatment decision-making. Of 155 sampled participants, a total of 89 (57.4%) participants had an UGT1A1 variant genotype, NM_000463.2: c.-53_-52[8] *1/*28, n = 74 (47.7%); *28/*28, n = 15 (9.7%). Additionally, 4 (2.6%) participants were heterozygous for dihydropyrimidine dehydrogenase. Two (1.3%) individuals were heterozygous for both UDP-glucuronosyltransferase and dihydropyrimidine dehydrogenase genes. All (100%) the patients had at least 1 actionable aberration related to supportive care medications (CYP-family) of all the possible medications listed on their pharmacogenomics report.

CONCLUSION

Preemptive comprehensive pharmacogenomics testing can be integrated into clinical practice in real-time for patients with cancer given faster turnaround and low cost. Pharmacist-driven, patient-specific medication management consults add further value given the number of genes/drugs. This sets the stage for a prospective randomized clinical trial to demonstrate the amount of benefit this can result in these patients.

Pharmacogenetic clinical randomised phase II trial to evaluate the efficacy and safety of FOLFIRI with high-dose irinotecan (HD-FOLFIRI) in metastatic colorectal cancer patients according to their UGT1A 1 genotype

Background

Patients harbouring the UGT1A1*28/*28 genotype are at risk of severe toxicity with the standard irinotecan dose. However, this dose is considerably lower than the dose that can be tolerated by UGT1A1*1/*1 and *1/*28 patients. This randomised phase II trial evaluated the efficacy and safety of the FOLFIRI regimen with high-dose irinotecan (HD-FOLFIRI) in metastatic colorectal cancer patients.

Methods

Eighty-two patients with the UGT1A1*1/*1 or the *1/*28 genotype were randomised to receive HD-FOLFIRI versus FOLFIRI. Patients with the UGT1A1*28/*28 genotype were excluded. In the experimental group, the irinotecan dose was 300 mg/m² for UGT1A1*1/*1 and 260 mg/m² for *1/*28 patients. In the control group, the dose was 180 mg/m². We analysed the overall response rate (ORR), toxicity, and survival.

Results

The ORR was significantly higher in the HD-FOLFIRI group (67.5 versus 43.6%; p = 0.001 OR: 1.73 [95% CI:1.03–2.93]). Neutropenia (17.7%), diarrhoea (5.1%), and asthenia (5.1%) were the most common grade 3–4 toxicity. No differences were observed in severe toxicity (22.5% versus 20.5%), dose reduction (22.5% versus 28.2%), or prophylactic G-CSF (17.5% versus 12.8%). No difference in survival was found.

Conclusions

Patients with the UGT1A1*1/*1 and *1/*28 genotypes can receive high doses of irinotecan to achieve a more favourable ORR without significant adverse events.

A Novel DPYD Variant Associated With Severe Toxicity of Fluoropyrimidines: Role of Pre-emptive DPYD Genotype Screening

Background: The fluoropyrimidine anticancer drug, especially 5- fluorouracil (5-FU) and its prodrug capecitabine are still being the backbone of chemotherapeutic regimens for colorectal cancer. Dihydropyrimidine dehydrogenase (DPD) is the crucial enzyme in the catabolism of 5-FU. Over the past 30 years, there is substantial clinical evidence showing that DPD deficiency is strongly associated with severe and fatal fluoropyrimidine-induced toxicity.

Patients and methods: A 49-year-old lady with resected stage III carcinoma of sigmoid colon was scheduled to have a course of 5-FU based adjuvant chemotherapy. She developed unexpected acute severe (grade 4) toxicity after the first cycle of chemotherapy. Genomic DNA was isolated from 3 ml peripheral blood cells for full sequencing of DPYD (the gene encoding DPD).

Results: Exome sequencing confirmed that she is heterozygous for NM_000110.3: c.321+2T>C of the DPYD gene. To the best of our knowledge, this variant is a novel pathogenic splicing variant of the DPYD gene resulting in a non-functional allele. As she has a heterozygous genotype and considered having decreased DPD activity, we followed the international recommendation and restart chemotherapy with at least 50% reduction for 5-FU dose. We then titrated the 5-FU dose, and she tolerated the subsequent cycles of chemotherapy and completed the whole course of adjuvant chemotherapy.

Conclusions: With a pre-emptive test on DPD deficiency before the administration of the fluoropyrimidine drugs, the aforementioned patient's life-threatening event could be avoided. This clinical utility has been confirmed by two recent large-scale studies and called for a drug label update.

Exploring the Use of Molecular Biomarkers for Precision Medicine in Age-Related Macular Degeneration

Precision medicine aims to improve patient care by adjusting medication to each patient's individual needs. Age-related macular degeneration (AMD) is a heterogeneous eye disease in which several pathways are involved, and the risk factors driving the disease differ per patient. As a consequence, precision medicine holds promise for improved management of this disease, which is nowadays a main cause of vision loss in the elderly. In this review, we provide an overview of the studies that have evaluated the use of molecular biomarkers to predict response to treatment in AMD. We predominantly focus on genetic biomarkers, but also include studies that examined circulating or eye fluid biomarkers in treatment response. This involves studies on treatment response to dietary supplements, response to anti-vascular endothelial growth factor, and response to complement inhibitors. In addition, we highlight promising new therapies that have been or are currently being tested in clinical trials and discuss the molecular studies that can help identify the most suitable patients for these upcoming therapeutic approaches.

SNPs in predicting clinical efficacy and toxicity of chemotherapy: walking through the quicksand

In the "precision medicine" era, chemotherapy still remains the backbone for the treatment of many cancers, but no affordable predictors of response to the chemodrugs are available in clinical practice. Single nucleotide polymorphisms (SNPs) are gene sequence variations occurring in more than 1% of the full population, and account for approximately 80% of inter-individual genomic heterogeneity. A number of studies have investigated the predictive role of SNPs of genes enrolled in both pharmacodynamics and pharmacokinetics of chemotherapeutics, but the clinical implementation of related results has been modest so far. Among the examined germline polymorphic variants, several SNPs of dihydropyrimidine dehydrogenase (DPYD) and uridine diphosphate glucuronosyltransferases (UGT) have shown a robust role as predictors of toxicity following fluoropyrimidine- and/or irinotecan-based treatments respectively, and a few guidelines are mandatory in their detection before therapy initiation. Contrasting results, however, have been reported on the capability of variants of other genes as MTHFR, TYMS, ERCC1, XRCC1, GSTP1, CYP3A4/3A5 and ABCB1, in predicting either therapy efficacy or toxicity in patients undergoing treatment with pyrimidine antimetabolites, platinum derivatives, irinotecan and taxanes. While formal recommendations for routine testing of these SNPs cannot be drawn at this moment, therapeutic decisions may indeed benefit of germline genomic information, when available. Here, we summarize the clinical impact of germline genomic variants on the efficacy and toxicity of major chemodrugs, with the aim to facilitate the therapeutic expectance of clinicians in the odiern quicksand field of complex molecular biology concepts and controversial trial data interpretation.