Dihydropyrimidine Dehydrogenase Deficiency and Implementation of Upfront DPYD Genotyping

Implementing DPYD genotyping to predict chemotherapy toxicity in Australia: a feasibility study

BACKGROUND

Implementing pharmacogenomic-guided management in cancer patients equitably and effectively in a large population presents challenges. DPYD genotyping determines clinically significant variants of patients at increased risk of developing grade3-5 fluoropyrimidine (FP) toxicity. FP chemotherapies are prescribed for ~16,000 Australians with a 10%-40% grade3-4 toxicity incidence and 1% mortality. Variant carriers can have FP dosing adjusted to improve treatment tolerance without compromising anticancer effect. This strategy has not been formally adopted within Australia, despite widespread international standardisation.

AIM

This pilot study determined genotyping turnaround-times (TAT) for 4 DPYD variants (c.1905+1G>A, c.1679T>G, c.2846A>T and c.1236G>A/Haplotype B3) in Australian patients. Secondary objectives were identification of FP toxicities of DPYD variant carriers, and analysis of healthcare stakeholder perspectives, including enablers/barriers to implementation.

METHODS

Genotyping was determined by Real-Time Polymerase Chain Reaction. Qualitative data were determined through semi-structured questionnaire.

RESULTS

104 patients recruited over 24 months had a mean TAT of 7.2 days, 5.2 business days (range 1-30). Grade3-4 toxicity occurred in 9/16 DPYD variant carriers, including 2 ICU admissions and 1 death. Themes from 30 questionnaire respondents suggest that clinical environment and resources were fundamental barriers, and motivation to improve patient care was the predominant enabler of change.

CONCLUSION

DPYD genotyping is feasible for improving precision-oncology for patients requiring FP chemotherapies. A TAT of 7 days is acceptable by both stakeholder respondents and national oncology clinician groups. This pilot study, although small, informs a large national project evaluating prospective DPYD genotyping and its impact on FP tolerability, patient safety and cost-effectiveness in Australia.

Total neoadjuvant therapy in early-onset rectal cancer: A multicentre prospective cohort study

AIM

The incidence of early-onset (age <50 years) rectal cancer (EORC) is rising globally, often presenting at an advanced stage. Total neoadjuvant therapy (TNT) is increasingly utilised in the management of advanced rectal cancers due to improved response and survival rates. However, it remains unclear whether EORC in an unscreened population responds similarly to TNT compared to average or late-onset (age ≥50 years) rectal cancer (AORC).

METHOD

This study included consecutive patients treated with curative intent with TNT for rectal cancer at three South Australian hospitals between 2019 and 2024. Patients were divided into EORC and AORC cohorts. The primary outcome was overall complete response (oCR) rate, defined as the proportion of patients who achieved a clinical complete response (cCR) and/or pathological complete response (pCR). Secondary outcomes included compliance and treatment-related toxicity.

RESULTS

Of 202 eligible patients, 48 (23.8%) were in the EORC cohort and 154 (76.2%) in the AORC cohort. No significant difference in oCR rate was observed between EORC and AORC patients (43.8% vs. 37.9%, P = 0.470). cCR, pCR and complete M1 response rates were also similar between the two groups. EORC patients experienced significantly less Grade 3-4 chemotherapy-induced toxicity compared to AORC patients (2.1% vs. 25.3%, P < 0.001), but reported higher rates of patient-reported Grade 3-4 radiotherapy-induced toxicity than AORC patients (31.3% vs. 12.3%, P = 0.004).

CONCLUSION

EORC patients exhibit comparable overall tumour response rates to AORC patients treated with TNT. However, toxicity profiles differ, with EORC patients experiencing less chemotherapy-induced toxicity but more patient-reported radiation-induced toxicity.

Pharmacogenomics: DPYD and Prevention of Toxicity

In 2020, the introduction of pre-emptive DPYD genotyping prior to the administration of systemic fluoropyrimidine-based chemotherapy represented one of the first widespread pharmacogenetic testing programmes to be applied nationally in the United Kingdom. Pharmacogenetic variants in the DPYD gene found in between 3 and 6% of the population are a recognised cause of primary DPD enzyme deficiency and associated increased risk of severe fluoropyrimidine toxicity [1]. Yet, the availability of testing globally is heterogeneous. Despite growing evidence that in addition to reducing drug-induced toxicity, DPYD-guided dosing does not negatively affect outcomes, further research on the impact of routine DPYD genotyping in the UK population is required. With mandatory testing in the UK focussed on four well-characterised variants, there is a need to address the applicability of this strategy across diverse ethnic or ancestral populations. We highlight approaches to identify and characterise rare variants in DPYD and in other genes involved in the pyrimidine metabolic pathway to reduce healthcare inequalities. Finally, we discuss the future of pharmacogenomics within cancer care, and the potential to harness innovative digital and genotyping technologies to streamline prescribing and optimise both systemic anti-cancer therapies and supportive care.

Dihydropyrimidine enzyme activity and its effect on chemotherapy toxicity: importance of genetic testing

PURPOSE

Patients with partial or complete DPD deficiency have decreased capacity to degrade fluorouracil and are at risk of developing toxicity, which can be even life-threatening.

CASE

A 43-year-old man with moderately differentiated rectal adenocarcinoma on capecitabine presented to the emergency department with complaints of nausea, vomiting, diarrhea, weakness, and lower abdominal pain for several days. Laboratory findings include grade 4 neutropenia (ANC 10) and thrombocytopenia (platelets 36,000). Capecitabine is used as a component of first-line adjuvant therapy by approximately 2 million patients worldwide each year. Capecitabine is metabolized to fluorouracil via the enzyme dihydropyrimidine dehydrogenase (DPD). With worsening pancytopenia and diarrhea, genetic testing for DPD deficiency was sent. Prompt treatment with uridine triacetate was initiated for presumed DPD deficiency. Unfortunately, he passed away from an infectious complication and was later confirmed to have a heterozygous DPYD*2A mutation.

DISCUSSION

Our case demonstrates uneven testing guidelines for DPD prior to initiating 5-FU chemotherapy, appropriateness of treating with uridine triacetate, and analysis of next-generation sequencing (NGS) on tumor samples and co-incidentally obtaining germline DPD deficiency status. Our case also highlights the severe clinical impact of having DPD deficiency even with early uridine triacetate therapy.

CONCLUSION

It is our recommendation to perform DPD deficiency in curative intent cancer treatment and this information can increasingly be obtained in standard tumor NGS profiling, a growing norm in medical oncology.

DPYD genotype-guided dose personalisation for fluoropyrimidine-based chemotherapy prescribing in solid organ cancer patients in Australia: GeneScreen 5-FU study protocol

BACKGROUND

Fluoropyrimidine (FP) chemotherapies are commonly prescribed for upper and lower gastrointestinal, breast and head and neck malignancies. Over 16,000 people with cancer require FP chemotherapies per annum in Australia. Between 10 and 40% patients experience grade 3-4 (≥ G3) toxicities that require hospital-based management ± intensive care admission. Approximately 1% of patients die secondary to FP toxicities. Prospective screening for DPYD gene variants (encoding the key enzyme for FP catabolism) can identify patients at risk of ≥ G3 toxicity and allow for dose adjustment prior to first FP exposure. Evidence supports this as a cost-effective method of improving patient safety and reducing healthcare burden internationally; however, no Australian data confirms its feasibility on a large scale.

METHOD

This investigator-led, single-arm study will determine large scale feasibility of prospective DPYD genotyping, confirming patient safety and cost-effectiveness within the Australian health care system. 5000 patients aged 18 years and older with solid organ cancers requiring FP chemotherapy will be consented and genotyped prior to commencing treatment, and early toxicity (within 60 days) post-FP exposure will be determined. Toxicity data for DPYD variant carriers who have dose adjustments will be compared to the wild-type cohort and historical cohorts of carriers who did not undergo genotyping prior to FP exposure, and prospective variant carriers who do not undergo dose-adjustment. Prevalence of the four standard DPYD gene variants will be confirmed in an Australian population. Additionally, health economic analysis, implementation research via semi-structured interviews of patients and clinicians, and feasibility of UGT1A1 genotyping will be conducted.

DISCUSSION

This study will determine the prevalence of DPYD gene variant status in Australia and its impact on FP-induced toxicity among Australians with cancer. Feasibility and cost-effectiveness for Australian health care system will be estimated to support national roll-out of prospective DPYD genotyping prior to FP administration. Additionally, feasibility will be confirmed with the intention of including UGT1A1 in future pharmacogenomic panels to aid chemotherapy prescribing.

TRIAL REGISTRATION

This trial was registered with the Australian and New Zealand Cancer Trials Registry on 13th Dec 2023, ACTRN12623001301651.

Identification of diagnostic markers and molecular clusters of cuproptosis-related genes in alcohol-related liver disease based on machine learning and experimental validation

BACKGROUND AND AIMS

Alcohol-related liver disease (ALD) is a worldwide burden. Cuproptosis has been shown to play a key role in the development of several diseases. However, the role and mechanisms of cuproptosis in ALD remain unclear.

METHODS

The RNA-sequencing data of ALD liver samples were downloaded from the Gene Expression Omnibus (GEO) database. Bioinformatical analyses were performed using the R data package. We then identified key genes through multiple machine learning methods. Immunoinfiltration analyses were used to identify different immune cells in ALD patients and controls. The expression levels of key genes were further verified.

RESULTS

We identified three key cuproptosis-related genes (CRGs) (DPYD, SLC31A1, and DBT) through an in-depth analysis of two GEO datasets, including 28 ALD samples and eight control samples. The area under the curve (AUC) value of these three genes combined in determining ALD was 1.0. In the external datasets, the three key genes had AUC values as high as 1.0 and 0.917, respectively. Nomogram, decision curve, and calibration curve analyses also confirmed these genes' ability to predict the diagnosis. These three key genes were found to be involved in multiple pathways associated with ALD progression. We confirmed the mRNA expression of these three key genes in mouse ALD liver samples. Regarding immune cell infiltration, the numbers of B cells, CD8 (+) T cells, NK cells, T-helper cells, and Th1 cells were significantly lower in ALD patient samples than in control liver samples. Single sample gene set enrichment analysis (ssGSEA) was then used to estimate the immune microenvironment of different CRG clusters and CRG-related gene clusters. In addition, we calculated CRG scores through principal component analysis (PCA) and selected Sankey plots to represent the correlation between CRG clusters, gene clusters, and CRG scores. Finally, the three key genes were confirmed in mouse ALD liver samples and liver cells treated with ethanol.

CONCLUSIONS

We first established a prognostic model for ALD based on 3 CRGs and robust prediction efficacy was confirmed. Our investigation contributes to a comprehensive understanding of the role of cuproptosis in ALD, presenting promising avenues for the exploration of therapeutic strategies.

Evaluation of early fluoropyrimidine toxicity in solid organ cancer patients: a retrospective observational study in Australia

BACKGROUND

Despite common global usage, fluoropyrimidine (FP; 5-flurouracil and capecitabine)-related chemotherapy toxicity is poorly reported in the literature, with serious toxicity ranging from 10% to 40% and early toxicity (within 60 days of exposure) quoted at 14%. Data reflecting the incidence of Grades 3-5 FP-related toxicity in Australian cancer patients is scant, despite the significant impact of toxicity on patients (hospitalisations, intensive care unit (ICU) admissions and even death).

AIMS

This retrospective audit evaluated Grades 3-5 toxicities in a contemporaneous cohort of 500 patients receiving FP chemotherapies within the Hunter-New England Local Health District from June 2020 to June 2022. Data were extracted from public hospital records and oncology-specific e-records to determine rates of toxicity and associated hospitalisations, intensive care admissions and deaths that occurred within 60 days of first exposure to FP chemotherapy-containing regimens.

RESULTS

One hundred and fifty incidents of Grades 3-4 toxicity in the first 60 days led to 87 patients presenting to hospital (87/500, 17.4%). The most common serious toxicities were diarrhoea (39.3%), nausea and vomiting (22.7%) and febrile neutropaenia (10%). Four patients were admitted to the ICU, and four patients died of toxicity. Within the first 60 days, 22.2% of patients required treatment delays, 21.4% required dose reductions, and 7.8% of patients ceased treatment because of toxicities.

DISCUSSION AND CONCLUSION

Our experience reflects international reports and is likely generalisable to the Australian population. These data are a basis to understand the potential benefits of precision medicine strategies such as pharmacogenomic screening to improve patient tolerability and the cost-effectiveness of FP chemotherapy prescribing.

Therapeutic drug monitoring in anticancer agents: perspectives of Australian medical oncologists

BACKGROUND

In the development of anticancer agents for solid tumours, body surface area continues to be used to personalise dosing despite minimal evidence for its use over other dosing strategies. With the development of tyrosine kinase inhibitors and other oral targeted anticancer agents, dosing using therapeutic drug monitoring (TDM) is now utilised in many health systems but has had limited uptake in Australia.

AIM

To determine attitudes and barriers to the implementation of TDM among Australian oncologists.

METHODS

A comprehensive questionnaire was developed by the Dutch Pharmacology Oncology Group from semistructured interviews of stakeholders. Seventy-nine questions across seven domains were developed with three free-text responses. This was rationalised to 17 questions with three free-text responses for Australian medical oncologists who identified limited experience with TDM.

RESULTS

Fifty-seven responses were received, with 49 clinicians (86%) identifying limited experience of performing TDM in daily practice. Clinicians were positive (62-91% agree/strongly agree across seven questions) about the advantages of TDM. There was a mixed response for cost-effectiveness and scientific evidence being a barrier to implementation, but strong agreement that prospective studies were needed (75% agreed or strongly agreed); that national treatment guidelines would enable practice (80%) and that a 'pharmacology of oncolytics' education programme would be useful (96%) to provide knowledge for dose individualisation.

CONCLUSION

Despite the limited experience of TDM in oncology in Australia, medical oncologists appear positive about the potential benefit to their patients. We have identified three barriers to implementation that could be targeted for increased adoption of TDM in oncology in Australia.

Novel Genetic Variants Explaining Severe Adverse Drug Events after Clinical Implementation of DPYD Genotype-Guided Therapy with Fluoropyrimidines: An Observational Study

Fluoropyrimidines (FPs) are commonly prescribed in many cancer streams. The EMA and FDA-approved drug labels for FPs recommend genotyping the DPYD*2A (rs3918290), *13 (rs55886062), *HapB3 (rs56038477), alleles, and DPYD rs67376798 before treatment starts. We implemented the DPYD genotyping in our daily clinical routine, but we still found patients showing severe adverse drug events (ADEs) to FPs. We studied among these patients the DPYD rs1801265, rs17376848, rs1801159, rs1801160, rs1801158, and rs2297595 as explanatory candidates of the interindividual differences for FP-related toxicities, examining the association with the response to FPs . We also studied the impact of DPYD testing for FP dose tailoring in our clinical practice and characterized the DPYD gene in our population. We found a total acceptance among physicians of therapeutic recommendations translated from the DPYD test, and this dose tailoring does not affect the treatment efficacy. We also found that the DPYD*4 (defined by rs1801158) allele is associated with a higher risk of ADEs (severity grade ≥ 3) in both the univariate (O.R. = 5.66; 95% C.I. = 1.35-23.67; p = 0.014) and multivariate analyses (O.R. = 5.73; 95% C.I. = 1.41-28.77; p = 0.019) among FP-treated patients based on the DPYD genotype. This makes it a candidate variant for implementation in clinical practice.

Primary vulvar adenocarcinoma of intestinal type: Report of two cases showing molecular similarity with colorectal adenocarcinoma

Primary vulvar adenocarcinoma is a particularly rare tumor with poorly understood histogenesis and unclear clinical characteristics and prognosis. Vulvar adenocarcinoma of intestinal type (VAIt) is a very uncommon subtype of primary vulvar adenocarcinoma and only 27 cases have been described in the literature in the past. Of these cases, two have been described as human papillomavirus (HPV)-associated VAIt. The current report presents two additional cases of primary VAIt showing variants in the KRAS, TP53, and DPYD genes and no evidence of HPV DNA by real-time polymerase chain reaction (RT-PCR). Next-generation sequencing (NGS) revealed TP53 pathogenic variants in both cases, but only one case had aberrant p53 protein immunohistochemical characteristics. KRAS and DPYD mutations were identified separately in the two cases. Due to their capacity to imitate the spread of more prevalent gastrointestinal carcinomas, these tumors may present diagnostic issues. Additional cases can contribute to a better understanding of the pathophysiology and prognosis of VAIt.

Genetic polymorphisms as predictive biomarkers of adverse events during preoperative chemotherapy in esophageal cancer

PURPOSE

This study aimed to explore associations between genetic polymorphisms and adverse effects due to preoperative chemotherapy with docetaxel, cisplatin, and fluorouracil (DCF) for esophageal cancer.

METHODS

Preoperative DCF (docetaxel, 70 mg/m2/day, day 1; cisplatin, 70 mg/m2/day, day 1; fluorouracil, 750 mg/m2/day, days 1-5) was repeated every 3 weeks for up to three cycles. Genotyping of nine candidate genetic polymorphisms was conducted using blood samples from the enrolled patients.

RESULTS

According to a multivariable analysis evaluating 50 patients, grade 3 or worse neutropenia was more likely to occur in those with the ABCC2-24C/T or T/T genotype (rs717620) (OR, 5.30, P = 0.013). Additionally, patients with the TYMS 3'-UTR 0 bp/0 bp genotype (rs151264360) showed a trend toward grade 3 or worse hyponatremia (OR, 0.16, P = 0.005). Grade 2 or worse thrombocytopenia was more likely to occur in patients with the TNF-α-1031C/T or T/T genotype (rs1799964) (OR, 6.30, P = 0.016) and IL-6-634C/C genotype (rs1800796) (OR, 0.18, P = 0.034), and grade 2 or worse anemia was more likely to occur in patients with the MCP-1-2518G/G genotype (rs1024611) (OR, 0.19, P = 0.027).

CONCLUSIONS

ABCC2-24C > T (rs717620), TYMS 3'-UTR 6-bp indel (rs151264360), TNF-α-1031T > C (rs1799964) as well as IL-6-634G > C (rs1800796), and MCP-1-2518A > G (rs1024611) polymorphisms might serve as independent and predictive biomarkers for neutropenia, hyponatremia, thrombocytopenia, and anemia, respectively, during preoperative chemotherapy with docetaxel, cisplatin, and fluorouracil for patients with esophageal cancer.

MIR27A rs895819 TC genotype increases risk of fluoropyrimidine-induced severe toxicity independently of DPYD variations

Aim: MicroRNA 27a (miR-27a) regulates post-transcriptionally DPD activity. We have analyzed the association of MIR27A rs895819T>C variation, that modulates miR-27a expression, with fluropyrimidine-induced toxicity. Materials & methods: MIR27A rs895819T>C genotyping was conducted by TaqMan® allelic discrimination assay in 313 FP-treated cancer patients. Results: In overdominance (TC vs TT + CC), TC genotype was associated with grade 3-4 toxicity (p = 0.002), any grade toxicity (p = 0.052), and delayed drug administration or therapy discontinuation (p = 0.038). Odds of grade 3-4 toxicity were increased by both DPYD deficiency (OR: 8.923; p = 0.006) and MIR27A rs895819 TC genotype (OR: 3.865; p = 0.002). Conclusion: MIR27A rs895819 TC genotype is an independent risk factor for fluoropyrimidine-associated toxicity in the Greek population. Thus, MIR27A rs895819TC patients can be closely monitored for fluoropyrimidine-induced severe toxicity.

Evaluation of biliary toxicity in patients with hepatic artery infusion pumps

PURPOSE

Identify risk factors for biliary toxicity in patients with colorectal liver metastases who received floxuridine (FUDR) via a surgically implanted hepatic artery infusion pump (HAIP). Describe the incidence of biliary toxicity and evaluate relevant patterns in the biliary toxicity cohort.

METHODS

A single center, retrospective, case-control study included adult colorectal cancer patients with liver metastases who received at least one cycle of FUDR via a surgically implanted HAIP from 1 January 2017, to 1 October 2021. Patients were excluded if they had incomplete records, cholangiocarcinoma diagnosis, or received concurrent mitomycin and FUDR. Biliary toxicity criteria derived from existing HAIP literature were utilized to determine whether patients experienced biliary toxicity. Multiple variables were compared by univariate statistical analysis between the biliary toxicity and non-biliary toxicity cohorts to identify potential risk factors for development of FUDR-induced biliary toxicity.

RESULTS

Out of 50 patients who had a HAIP implanted, 39 met the inclusion criteria. Five of the 39 patients (12.7%) included in the analysis met the pre-specified biliary toxicity criteria. No risk factors for biliary toxicity were identified. All five patients who developed biliary toxicity demonstrated elevations in alkaline phosphatase (ALP) prior to meeting the toxicity criteria.

CONCLUSION

Biliary toxicity remains a significant and therapy-limiting consequence of FUDR administration. Rising ALP may be an early indicator of subsequent biliary toxicity. Future studies with more patients may identify risk factors that can facilitate risk mitigation strategies.

Implementing pharmacogenetic testing in fluoropyrimidine-treated cancer patients: DPYD genotyping to guide chemotherapy dosing in Greece

Introduction: Dihydropyrimidine dehydrogenase (DPD), encoded by DPYD gene, is the rate-limiting enzyme responsible for fluoropyrimidine (FP) catabolism. DPYD gene variants seriously affect DPD activity and are well validated predictors of FP-associated toxicity. DPYD variants rs3918290, rs55886062, rs67376798, and rs75017182 are currently included in FP genetic-based dosing guidelines and are recommended for genotyping by the European Medicines Agency (EMA) before treatment initiation. In Greece, however, no data exist on DPYD genotyping. The aim of the present study was to analyze prevalence of DPYD rs3918290, rs55886062, rs67376798, rs75017182, and, additionally, rs1801160 variants, and assess their association with FP-induced toxicity in Greek cancer patients. Methods: Study group consisted of 313 FP-treated cancer patients. DPYD genotyping was conducted on QuantStudio ™ 12K Flex Real-Time PCR System (ThermoFisher Scientific) using the TaqMan® assays C__30633851_20 (rs3918290), C__11985548_10 (rs55886062), C__27530948_10 (rs67376798), C_104846637_10 (rs75017182) and C__11372171_10 (rs1801160). Results: Any grade toxicity (1-4) was recorded in 208 patients (66.5%). Out of them, 25 patients (12%) experienced grade 3-4 toxicity. DPYD EMA recommended variants were detected in 9 patients (2.9%), all experiencing toxicity (p = 0.031, 100% specificity). This frequency was found increased in grade 3-4 toxicity cases (12%, p = 0.004, 97.9% specificity). DPYD deficiency increased the odds of grade 3-4 toxicity (OR: 6.493, p = 0.014) and of grade 1-4 gastrointestinal (OR: 13.990, p = 0.014), neurological (OR: 4.134, p = 0.040) and nutrition/metabolism (OR: 4.821, p = 0.035) toxicities. FP dose intensity was significantly reduced in DPYD deficient patients (β = -0.060, p <0.001). DPYD rs1801160 variant was not associated with FP-induced toxicity or dose intensity. Triple interaction of DPYD*TYMS*MTHFR was associated with grade 3-4 toxicity (OR: 3.725, p = 0.007). Conclusion: Our findings confirm the clinical validity of DPYD reduced function alleles as risk factors for development of FP-associated toxicity in the Greek population. Pre-treatment DPYD genotyping should be implemented in clinical practice and guide FP dosing. DPYD*gene interactions merit further investigation as to their potential to increase the prognostic value of DPYD genotyping and improve safety of FP-based chemotherapy.

Pharmacogenomic-guided dosing of fluoropyrimidines beyond DPYD: time for a polygenic algorithm?

Fluoropyrimidines are chemotherapeutic agents widely used for the treatment of various solid tumors. Commonly prescribed FPs include 5-fluorouracil (5-FU) and its oral prodrugs capecitabine (CAP) and tegafur. Bioconversion of 5-FU prodrugs to 5-FU and subsequent metabolic activation of 5-FU are required for the formation of fluorodeoxyuridine triphosphate (FdUTP) and fluorouridine triphosphate, the active nucleotides through which 5-FU exerts its antimetabolite actions. A significant proportion of FP-treated patients develop severe or life-threatening, even fatal, toxicity. It is well known that FP-induced toxicity is governed by genetic factors, with dihydropyrimidine dehydrogenase (DPYD), the rate limiting enzyme in 5-FU catabolism, being currently the cornerstone of FP pharmacogenomics. DPYD-based dosing guidelines exist to guide FP chemotherapy suggesting significant dose reductions in DPYD defective patients. Accumulated evidence shows that additional variations in other genes implicated in FP pharmacokinetics and pharmacodynamics increase risk for FP toxicity, therefore taking into account more gene variations in FP dosing guidelines holds promise to improve FP pharmacotherapy. In this review we describe the current knowledge on pharmacogenomics of FP-related genes, beyond DPYD, focusing on FP toxicity risk and genetic effects on FP dose reductions. We propose that in the future, FP dosing guidelines may be expanded to include a broader ethnicity-based genetic panel as well as gene*gene and gender*gene interactions towards safer FP prescription.

Oral Capecitabine Exposures and Use of Uridine Triacetate: A 20-Year Retrospective Analysis

BACKGROUND AND OBJECTIVES

Capecitabine is an oral prodrug of 5-fluorouracil. Toxicity can occur during therapy as well as acutely with overdose and particular genetic susceptibilities. Uridine triacetate is an effective antidote if given within 96 h of exposure. This study seeks to characterize accidental and intentional capecitabine exposures and uridine triacetate use, about which little has been published.

METHODS

A retrospective review of capecitabine exposures from 30 April 2001 to 31 December 2021 reported to a statewide poison control center was performed. All single-substance oral exposures were included.

RESULTS

In total, 81 of 128 reviewed cases were included, with a median age of 63 years. In total, 49 were acute-on-chronic exposures and 32 were acute exposures in capecitabine-naïve patients, 29 of which were accidental. Fifty-six (69%) were managed at home. Of these, none later recontacted the poison control center to report symptoms or were known to have later had healthcare facility evaluations. Of the 25 cases presenting for healthcare facility evaluation, 4 were acutely symptomatic. Thirteen were eligible for uridine triacetate, and six received it; no new or progressive toxicity was reported after. Three developed mild latent toxicity; otherwise, no morbidity or mortality was reported.

CONCLUSIONS

Accidental acute-on-chronic and acute ingestions of capecitabine appear to be well tolerated; most cases were managed at home. Unfortunately, little is known regarding the threshold at which toxicity may present following exposures. The threshold may vary individually given genetic susceptibilities. Management was heterogeneous, likely reflecting inadequate guidelines. Further research is needed to better delineate at-risk populations and treatment strategies.

Implementation of dihydropyrimidine dehydrogenase deficiency testing in Europe

BACKGROUND

The main cause for fluoropyrimidine-related toxicity is deficiency of the metabolizing enzyme dihydropyrimidine dehydrogenase (DPD). In 2020, the European Medicines Agency (EMA) recommended two methods for pre-treatment DPD deficiency testing in clinical practice: phenotyping using endogenous uracil concentration or genotyping for DPYD risk variant alleles. This study assessed the DPD testing implementation status in Europe before (2019) and after (2021) the release of the EMA recommendations.

METHODS

The survey was conducted from 16 March 2022 to 31 July 2022. An electronic form with seven closed and three open questions was e-mailed to 251 professionals with DPD testing expertise of 34 European countries. A descriptive analysis was conducted.

RESULTS

We received 79 responses (31%) from 23 countries. Following publication of the EMA recommendations, 87% and 75% of the countries reported an increase in the amount of genotype and phenotype testing, respectively. Implementation of novel local guidelines was reported by 21 responders (27%). Countries reporting reimbursement of both tests increased in 2021, and only four (18%) countries reported no coverage for any testing type. In 2019, major implementation drivers were 'retrospective assessment of fluoropyrimidine-related toxicity' (39%), and in 2021, testing was driven by 'publication of guidelines' (40%). Although the major hurdles remained the same after EMA recommendations-'lack of reimbursement' (26%; 2019 versus 15%; 2021) and 'lack of recognizing the clinical relevance by medical oncologists' (25%; 2019 versus 8%; 2021)-the percentage of specialists citing these decreased. Following EMA recommendations, 25% of responders reported no hurdles at all in the adoption of the new testing practice in the clinics.

CONCLUSIONS

The EMA recommendations have supported the implementation of DPD deficiency testing in Europe. Key factors for successful implementation were test reimbursement and clear clinical guidelines. Further efforts to improve the oncologists' awareness of the clinical relevance of DPD testing in clinical practice are needed.

DPYD genotyping and predicting fluoropyrimidine toxicity: where do we stand?

Fluoropyrimidines (FPs) are antineoplastic drugs widely used in the treatment of various solid tumors. Nearly 30% of patients treated with FP chemotherapy experience severe FP-related toxicity, and in some cases, toxicity can be fatal. Patients with reduced activity of DPD, the main enzyme responsible for the breakdown of FP, are at an increased risk of experiencing severe FP-related toxicity. While European regulatory agencies and clinical societies recommend pre-treatment DPD deficiency screening for patients starting treatment with FPs, this is not the case with American ones. Pharmacogenomic guidelines issued by several pharmacogenetic organizations worldwide recommend testing four DPD gene (DPYD) risk variants, but these can predict only a proportion of toxicity cases. New evidence on additional common DPYD polymorphisms, as well as identification and functional characterization of rare DPYD variants, could partially address the missing heritability of DPD deficiency and FP-related toxicity.

Predicting Dihydropyrimidine Dehydrogenase Deficiency and Related 5-Fluorouracil Toxicity: Opportunities and Challenges of DPYD Exon Sequencing and the Role of Phenotyping Assays

Deficiency of dihydropyrimidine dehydrogenase (DPD), encoded by the DPYD gene, is associated with severe toxicity induced by the anti-cancer drug 5-Fluorouracil (5-FU). DPYD genotyping of four recommended polymorphisms is widely used to predict toxicity, yet their prediction power is limited. Increasing availability of next generation sequencing (NGS) will allow us to screen rare variants, predicting a larger fraction of DPD deficiencies. Genotype−phenotype correlations were investigated by performing DPYD exon sequencing in 94 patients assessed for DPD deficiency by the 5-FU degradation rate (5-FUDR) assay. Association of common variants with 5-FUDR was analyzed with the SNPStats software. Functional interpretation of rare variants was performed by in-silico analysis (using the HSF system and PredictSNP) and literature review. A total of 23 rare variants and 8 common variants were detected. Among common variants, a significant association was found between homozygosity for the rs72728438 (c.1974+75A>G) and decreased 5-FUDR. Haplotype analysis did not detect significant associations with 5-FUDR. Overall, in our sample cohort, NGS exon sequencing allowed us to explain 42.5% of the total DPD deficiencies. NGS sharply improves prediction of DPD deficiencies, yet a broader collection of genotype−phenotype association data is needed to enable the clinical use of sequencing data.