A DPYD variant (Y186C) specific to individuals of African descent in a patient with life-threatening 5-FU toxic effects: potential for an individualized medicine approach

Electrochemiluminescence immunoassay strategies based on a hexagonal Ru-MOF and MoS2@GO nanosheets: detection of 5-fluorouracil in serum samples

Herein, a competitive-type electrochemiluminescence immunosensor for ultrasensitive detection of 5-fluorouracil (5-FU) was fabricated. Ruthenium(II)-metal-organic framework (Ru-MOF) nanosheets were selected to act a promising ECL luminophore using tris(4,4'-dicarboxylic acid-2,2'-bipyridyl) ruthenium(II) dichloride (Ru(dcbpy)₃²⁺) as the organic ligand. The two-dimensional (2D) Ru-MOF nanosheets achieved an increased loading of Ru(dcbpy)₃²⁺ and effectively prevented leakage of the ECL emitter during application, which exhibited satisfactory ECL performance. Thin two-dimensional MoS₂@GO was used to modify the electrode as the sensing platform for improving the electron transfer rate and loading more 5-FU coating antigens due to its large specific surface area and piezoelectric catalytic efficiency. Under the optimized conditions, the proposed immunosensor presented high sensitivity, a wide detection range (0.0001 ng-100 ng mL^-1), a low limit of detection (0.031 pg mL^-1, S/N = 3), good specificity and stability. Furthermore, the immunosensor was successfully applied for the detection of 5-FU in human serum samples with satisfactory results, proving this strategy has potential applications in bioanalysis and clinical diagnosis.

Implementing Pharmacogenetic Testing in Gastrointestinal Cancers (IMPACT-GI): Study Protocol for a Pragmatic Implementation Trial for Establishing DPYD and UGT1A1 Screening to Guide Chemotherapy Dosing

Background

Fluoropyrimidines (fluorouracil [5-FU], capecitabine) and irinotecan are commonly prescribed chemotherapy agents for gastrointestinal (GI) malignancies. Pharmacogenetic (PGx) testing for germline DPYD and UGT1A1 variants associated with reduced enzyme activity holds the potential to identify patients at high risk for severe chemotherapy-induced toxicity. Slow adoption of PGx testing in routine clinical care is due to implementation barriers, including long test turnaround times, lack of integration in the electronic health record (EHR), and ambiguity in test cost coverage. We sought to establish PGx testing in our health system following the Exploration, Preparation, Implementation, Sustainment (EPIS) framework as a guide. Our implementation study aims to address barriers to PGx testing.

Methods

The Implementing Pharmacogenetic Testing in Gastrointestinal Cancers (IMPACT-GI) study is a non-randomized, pragmatic, open-label implementation study at three sites within a major academic health system. Eligible patients with a GI malignancy indicated for treatment with 5-FU, capecitabine, or irinotecan will undergo PGx testing prior to chemotherapy initiation. Specimens will be sent to an academic clinical laboratory followed by return of results in the EHR with appropriate clinical decision support for the care team. We hypothesize that the availability of a rapid turnaround PGx test with specific dosing recommendations will increase PGx test utilization to guide pharmacotherapy decisions and improve patient safety outcomes. Primary implementation endpoints are feasibility, fidelity, and penetrance. Exploratory analyses for clinical effectiveness of genotyping will include assessing grade ≥3 treatment-related toxicity using available clinical data, patient-reported outcomes, and quality of life measures.

Conclusion

We describe the formative work conducted to prepare our health system for DPYD and UGT1A1 testing. Our prospective implementation study will evaluate the clinical implementation of this testing program and create the infrastructure necessary to ensure sustainability of PGx testing in our health system. The results of this study may help other institutions interested in implementing PGx testing in oncology care.

Clinical Trial Registration

https://clinicaltrials.gov/ct2/show/NCT04736472, identifier [NCT04736472].

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.

Pharmacogenetics of Breast Cancer Treatments: A Sub-Saharan Africa Perspective

Breast cancer is the most frequent cause of cancer death in low- and middle-income countries, in particular among sub-Saharan African women, where response to available anticancer treatment therapy is often limited by the recurrent breast tumours and metastasis, ultimately resulting in decreased overall survival rate. This can also be attributed to African genomes that contain more variation than those from other parts of the world. The purpose of this review is to summarize published evidence on pharmacogenetic and pharmacokinetic aspects related to specific available treatments and the known genetic variabilities associated with metabolism and/or transport of breast cancer drugs, and treatment outcomes when possible. The emphasis is on the African genetic variation and focuses on the genes with the highest strength of evidence, with a close look on CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP3A4/5, CYP19A1, UGT1A4, UGT2B7, UGT2B15, SLC22A16, SLC38A7, FcγR, DPYD, ABCB1, and SULT1A1, which are the genes known to play major roles in the metabolism and/or elimination of the respective anti-breast cancer drugs given to the patients. The genetic variability of their metabolism could be associated with different metabolic phenotypes that may cause reduced patients’ adherence because of toxicity or sub-therapeutic doses. Finally, this knowledge enhances possible personalized treatment approaches, with the possibility of improving survival outcomes in patients with breast cancer.

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.

Impact of total splenectomy on peripheral lymphocytes and their subsets in patients with hypersplenism associated with cirrhotic portal hypertension

To study the impact of total splenectomy (TS) on peripheral lymphocytes and their subsets in patients with hypersplenism associated with cirrhotic portal hypertension (CPH). We studied 102 consecutive patients who received TS from January 2008 to January 2020 due to CPH-related hypersplenism. A similar number of healthy individuals are used as healthy controls (HC). The total lymphocyte counts and their percentages of B lymphocytes, total T lymphocytes (cluster of differentiation (CD)3⁺) and their subsets (CD4⁺, CD8⁺), and natural killer (NK) cells in preoperative peripheral blood samples in hypersplenism patients were significantly lower than that of the HCs (both P < 0.05). The total lymphocyte counts and percentages of B lymphocytes in peripheral blood were significantly increased 1 week and 1 month after TS when compared with the pre-TS values (P < 0.05). There was no significant difference in the percentages of NK cells before or after surgery (P > 0.05). However, the percentages of CD3⁺ cells was significantly higher 1 month after than before surgery (P < 0.001). The percentages of CD4⁺, and CD8⁺ T lymphocytes were significantly lower 1 week after surgery (P < 0.05), but they were significantly higher 1 month after surgery (P < 0.01). The CD4⁺:CD8⁺ ratio was not significantly different from those before surgery, and 1 week or 1 month after surgery (P > 0.05). Patients with hypersplenism associated with CPH were significantly immunosuppressed preoperatively. After TS, the total lymphocyte count and percentages of B lymphocytes, and total T lymphocytes and their subsets increased significantly, resulting in improved immune functions.

Pharmacogenomic-Guided Therapy in Colorectal Cancer

Approximately 20 drugs have been shown to be effective for the treatment of colorectal cancer (CRC). These drugs are from several classes of agents and include cytotoxic drugs, therapeutics that target cell signaling pathways at the extracellular and/or intracellular levels, and combination therapies that contain multiple targeted agents and/or cytotoxic compounds. Targeted therapeutics can include monoclonal antibodies, fusion proteins, and small molecule drugs. The first introduced into clinical use was 5-fluorouracil in the early 1960s and remains the foundation for most CRC treatments in both adjuvant therapy and in advanced (metastatic) treatment regimens. As with other cancers, the consideration of biomarkers has the potential to improve CRC therapy through patient stratification. The biomarkers can include germline genetic markers, tumor-specific genetic markers, immune markers, and other biomarkers that can predict antitumor efficacy or the likelihood of toxicity prior to administration of a specific drug. Consistent with the benefit of considering biomarkers in treatment, many newer targeted therapies are developed and approved simultaneously with a companion diagnostic test to determine efficacy. This review will focus on biomarkers that have demonstrated clinical utility in CRC treatment; however, it is noted that many additional biomarkers have been theorized to contribute to drug response and/or toxicity based on known biological pathways but thus far have not attained widespread use in the clinic. The importance of pretreatment biomarker testing is expected to increase as future drug development will likely continue to focus on the concurrent development of companion diagnostics.

Potential Impact of DPYD Variation on Fluoropyrimidine Drug Response in sub-Saharan African Populations

Cancer is a critical health burden in Africa, and mortality rates are rising rapidly. Treatments are expensive and often cause adverse drug reactions (ADRs). Fluoropyrimidine treatments can lead to severe toxicity events which have been linked to variants within the dihydropyrimidine dehydrogenase (DPYD) gene. There are clinical guidelines to improve safety outcomes of treatment, but these are primarily based on variants assessed in non-African populations. Whole genome sequencing data from the 1000 Genomes Project and the African Genome Variation Project were mined to assess variation in DPYD in eight sub-Saharan African populations. Variant functional annotation was performed with a series of bioinformatics tools to assess potential likelihood of deleterious impact. There were 29 DPYD coding variants identified in the datasets assessed, of which 25 are rare, and some of which are known to be deleterious. One African-specific variant (rs115232898-C), is common in sub-Saharan Africans (1-4%) and known to reduce the function of the dihydropyrimidine dehydrogenase enzyme (DPD), having been linked to cases of severe toxicity. This variant, once validated in clinical trials, should be considered for inclusion in clinical guidelines for use in sub-Saharan African populations. The rs2297595-C variant is less well-characterized in terms of effect, but shows significant allele frequency differences between sub-Saharan African populations (0.5-11.5%; p = 1.5 × 10^-4), and is more common in East African populations. This study highlights the relevance of African-data informed guidelines for fluorouracil drug safety in sub-Saharan Africans, and the need for region-specific data to ensure that Africans may benefit optimally from a precision medicine approach.

Case report: severe toxicity in an African-American patient receiving FOLFOX carrying uncommon allelic variants in DPYD

Cancers of the colon are commonly treated with fluoropyrimidines, which often cause severe toxicities in patients with certain variants in DPYD. Y186C (rs115232898) and a variant in the 3' untranslated region (rs12132152) are uncommon alleles previously observed in African-Americans. An African-American female underwent 5-fluorouracil-based therapy (400 mg/m2 bolus, 1200 mg/m2/day over 46 h). The patient experienced severe pancytopenia after the first cycle. After 5-fluorouracil (5-FU) dose reduction (600 mg/m2/day), the steady-state 5-FU plasma concentration became 474 ng/ml (range 301-619 ng/ml) and increased following a subsequence dose increase (800 mg/m2/day; 1248 ng/ml). After a 1000 mg/m2/day dose resulted in myelosuppression, 5-FU was again de-escalated for the remaining cycles (600 mg/m2). The observed complications are likely a function of uncommon genetic variants that affect DPYD metabolism.

Multi-factorial pharmacokinetic interactions: unraveling complexities in precision drug therapy

Introduction: Precision drug therapy requires accounting for pertinent factors in pharmacokinetic (PK) inter-individual variability (i.e., pharmacogenetics, diseases, polypharmacy, and natural product use) that can cause sub-therapeutic or adverse effects. Although each of these individual factors can alter victim drug PK, multi-factorial interactions can cause additive, synergistic, or opposing effects. Determining the magnitude and direction of these complex multi-factorial effects requires understanding the rate-limiting redundant and/or sequential PK processes for each drug.Areas covered: Perturbations in drug-metabolizing enzymes and/or transporters are integral to single- and multi-factorial PK interactions. Examples of single factor PK interactions presented include gene-drug (pharmacogenetic), disease-drug, drug-drug, and natural product-drug interactions. Examples of multi-factorial PK interactions presented include drug-gene-drug, natural product-gene-drug, gene-gene-drug, disease-natural product-drug, and disease-gene-drug interactions. Clear interpretation of multi-factorial interactions can be complicated by study design, complexity in victim drug PK, and incomplete mechanistic understanding of victim drug PK.Expert opinion: Incorporation of complex multi-factorial PK interactions into precision drug therapy requires advances in clinical decision tools, intentional PK study designs, drug-metabolizing enzyme and transporter fractional contribution determinations, systems and computational approaches (e.g., physiologically-based pharmacokinetic modeling), and PK phenotyping of progressive diseases.

DPYD and UGT1A1 Pharmacogenetic Testing in Patients with Gastrointestinal Malignancies: An Overview of the Evidence and Considerations for Clinical Implementation

Gastrointestinal (GI) malignancies are among the most commonly diagnosed cancers worldwide. Despite the introduction of targeted and immunotherapy agents in the treatment landscape, cytotoxic agents, such as fluoropyrimidines and irinotecan, remain as the cornerstone of chemotherapy for many of these tumors. Pharmacogenetics (PGx) is a rapidly evolving field that accounts for interpatient variability in drug metabolism to predict therapeutic response and toxicity. Given the significant incidence of severe treatment-related adverse events associated with cytotoxic agents, utilizing PGx can allow clinicians to better anticipate drug tolerability while minimizing treatment interruptions or delays. In this review, the PGx profiles of drug-gene pairs with potential impact in GI malignancy therapy - DPYD-5-fluorouracil/capecitabine and UGT1A1-irinotecan - and the available clinical evidence of their roles in reducing severe adverse events are discussed. Considerations for clinical implementation, such as optimal laboratory workflows, electronic health record integration, and stakeholder engagement, as well as provider education, are addressed. Last, exploratory PGx markers in GI malignancy treatment are described. As the PGx knowledge base rapidly evolves, pharmacists will be vital in leveraging their pharmacology knowledge and clinical skills to implement PGx testing in the clinic.

Population-scale predictions of DPD and TPMT phenotypes using a quantitative pharmacogene-specific ensemble classifier

BACKGROUND

Inter-individual differences in dihydropyrimidine dehydrogenase (DPYD encoding DPD) and thiopurine S-methyltransferase (TPMT) activity are important predictors for fluoropyrimidine and thiopurine toxicity. While several variants in these genes are known to decrease enzyme activities, many additional genetic variations with unclear functional consequences have been identified, complicating informed clinical decision-making in the respective carriers.

METHODS

We used a novel pharmacogenetically trained ensemble classifier to analyse DPYD and TPMT genetic variability based on sequencing data from 138,842 individuals across eight populations.

RESULTS

The algorithm accurately predicted in vivo consequences of DPYD and TPMT variants (accuracy 91.4% compared to 95.3% in vitro). Further analysis showed high genetic complexity of DPD deficiency, advocating for sequencing-based DPYD profiling, whereas genotyping of four variants in TPMT was sufficient to explain >95% of phenotypic TPMT variability. Lastly, we provided population-scale profiles of ethnogeographic variability in DPD and TPMT phenotypes, and revealed striking interethnic differences in frequency and genetic constitution of DPD and TPMT deficiency.

CONCLUSION

These results provide the most comprehensive data set of DPYD and TPMT variability published to date with important implications for population-adjusted genetic profiling strategies of fluoropyrimidine and thiopurine risk factors and precision public health.

Identifying a Novel DPYD Polymorphism Associated with Severe Toxicity to 5-FU Chemotherapy in a Saudi Patient

Dihydropyrimidine dehydrogenase (DPD) is the major enzyme in the catabolism of 5-Fluorouracil (5-FU) and its prodrug capecitabine. We report a 65-year-old female with rectal adenocarcinoma who experienced severe toxicities secondary to standard dose 5-FU based chemotherapy. She was found to be heterozygous for rs371313778, c.2434G>A. This finding prompted restarting 5-FU at 50% dose reduction with further titration in subsequent cycles. We herein report the first case of rs371313778, c.2434G>A (p.Val812lle) DPYD polymorphism leading to severe 5-FU toxicities. The patient eventually completed a 6-month course of adjuvant treatment with modification of 5-FU dose.

Predictors of Hand-Foot Syndrome and Pyridoxine for Prevention of Capecitabine-Induced Hand-Foot Syndrome: A Randomized Clinical Trial

Importance

Hand-foot syndrome (HFS) is a common adverse effect of capecitabine treatment.

Objective

To compare the incidence and time to onset of grade 2 or greater HFS in patients receiving pyridoxine vs placebo and to identify biomarkers predictive of HFS.

Design, Setting, and Participants

This single-center, randomized double-blind, placebo-controlled phase 3 trial conducted at National Cancer Centre Singapore assessed whether oral pyridoxine could prevent the onset of grade 2 or higher HFS in 210 patients scheduled to receive single-agent capecitabine chemotherapy for breast, colorectal, and other cancers.

Interventions

Patients were randomized to receive concurrent pyridoxine (200 mg) or placebo daily for a maximum of 8 cycles of capecitabine, with stratification by sex and use in adjuvant or neoadjuvant vs palliative setting. Patients were withdrawn from the study on development of grade 2 or higher HFS or cessation of capecitabine.

Main Outcomes and Measures

Primary end point was the incidence of grade 2 or higher HFS in patients receiving pyridoxine. Secondary end points included the time to onset (days) of grade 2 or higher HFS and identification of biomarkers predictive of HFS, including baseline folate and vitamin B12 levels, as well as genetic polymorphisms with genome-wide arrays.

Results

In this cohort of 210 patients (median [range] age, 58 [26-82] years; 162 women) grade 2 or higher HFS occurred in 33 patients (31.4%) in the pyridoxine arm vs 39 patients (37.1%) in the placebo arm (P = .38). The median time to onset of grade 2 or higher HFS was not reached in both arms. In univariate analysis, the starting dose of capecitabine (odds ratio [OR], 1.99; 95% CI, 1.32-3.00; P = .001), serum folate levels (OR, 1.27; 95% CI, 1.10-1.47; P = .001), and red blood cell folate levels (OR, 1.25; 95% CI, 1.08-1.44; P = .003) were associated with increased risk of grade 2 or higher HFS. In multivariate analyses, serum folate (OR, 1.30; 95% CI, 1.12-1.52; P < .001) and red blood cell folate (OR, 1.28; 95% CI, 1.10-1.49; P = .001) were the only significant predictors of grade 2 or higher HFS. Grade 2 or higher HFS was associated with 300 DNA variants at genome-wide significance (P < 5 × 10-8), including a novel DPYD variant (rs75267292; P = 1.57 × 10-10), and variants in the MACF1 (rs183324967, P = 4.80 × 10-11; rs148221738, P = 5.73 × 10-10) and SPRY2 (rs117876855, P < 1.01 × 10-8; rs139544515, P = 1.30 × 10-8) genes involved in wound healing.

Conclusions and Relevance

Pyridoxine did not significantly prevent or delay the onset of grade 2 or higher HFS. Serum and red blood cell folate levels are independent predictors of HFS.

Trial Registration

clinicaltrials.gov Identifier: NCT00486213.

Use of exome sequencing to determine the full profile of genetic variants in the fluoropyrimidine pathway in colorectal cancer patients affected by severe toxicity

Aim: To identify genetic variants associated with capecitabine toxicity in fluoropyrimidine pathway genes using exome sequencing. Patients & methods: Exomes from eight capecitabine-treated patients with severe adverse reactions (grade >2), among a population of 319, were sequenced (Ion Proton). SNPs in genes classified as potentially damaging (Sorting Intolerant from Tolerant and Polymorphism Phenotyping v2) were tested for association with toxicity in a validation cohort of 319 capecitabine-treated patients. Results: A total of 17 nonsynonymous genetic variants were identified. Of these, five putative damaging SNPs in DPYD, ABCC4 and MTHFR were genotyped in the validation cohort. DPYD rs1801160 was associated with the risk of toxicity (p = 0.029) and MTHFR rs1801133 with delayed administration of chemotherapy due to toxicity (p = 0.047). Conclusion: Exome sequencing revealed two specific biomarkers of the risk of toxicity to capecitabine.

Causes of peripheral cytopenia in hepatitic cirrhosis and portal hypertensive splenomegaly

The clinical data of 183 patients with hepatitic cirrhosis and portal hypertensive splenomegaly complicated by peripheral cytopenia were retrospectively analyzed to investigate the causes of peripheral cytopenia, as well as the proportion of the causes in these patients. All patients underwent splenectomy. Before operation, these patients had one or more types of peripheral cytopenia (cumulative cytopenia: 390 patient-times). After splenectomy, blood counts in 79.2% (309/390) returned to normal, while in 15.9% (62/390) they increased but failed to reach to normal levels, and in 4.9% (19/390) they became lower than before the operations. For the last group of patients ( n = 19), long-term follow-up showed that blood counts returned to normal in five patients. In other words, in 80.5% [(309 + 5)/390 or 314/390] of patient-times, the peripheral cytopenia was due to hypersplenism, in 15.9% it was due to a combination of factors, and in 3.6% [14/390] it had nothing to do with the hypersplenism. Thus, hypersplenism is a major cause, but not the only cause, of peripheral cytopenia in patients with hepatic cirrhosis and portal hypertensive splenomegaly, and splenectormy is an effective treatment for these patients. Impact statement For a long time, the development of peripheral cytopenias as a complication to cirrhotic portal hypertension has been attributed to hypersplenism; however, this has never been fully demonstrated. Dameshek summarized that hypersplenism should be diagnosed by the presence of four conditions: (a) mono- or multi-lineage peripheral cytopenias; (b) compensatory hyperplasia of bone marrow; (c) splenomegaly; and (d) correction of cytopenias after splenectomy. We retrospectively analyzed the clinical data from 183 surgical patients, and found that 80.5% of peripheral cytopenias was caused by hypersplenism, 16% by a combination of factors, and 3.5% by other factors unrelated to hypersplenism. As the first quantitative findings in this field, our results verify that hypersplenism is a major, but not exclusive, cause of peripheral cytopenias, and provides important clinical evidence for investigating the cause of peripheral cytopenias.

Novel Deleterious Dihydropyrimidine Dehydrogenase Variants May Contribute to 5-Fluorouracil Sensitivity in an East African Population

Clinical studies have identified specific genetic variants in dihydropyrimidine dehydrogenase (DPD; DPYD gene) as predictors of severe adverse toxicity to the commonly used chemotherapeutic 5-fluorouracil (5-FU); however, these studies have focused on European and European-American populations. Our laboratory recently demonstrated that additional variants in non-European haplotypes are predictive of 5-FU toxicity. The objective of this study was to identify potential risk variants in an understudied East African population relevant to our institution's catchment area. The DPYD protein-coding region was sequenced in 588 individuals of Somali or Kenyan ancestry living in central/southeast Minnesota. Twelve novel nonsynonymous variants were identified, seven of which significantly decreased DPD activity in vitro. The commonly reported toxicity-associated variants, *2A, D949V, and I560S, were not detected in any individuals. Overall, this study demonstrates a critical limitation in our knowledge of pharmacogenetic predictors of 5-FU toxicity, which has been based on clinical studies conducted in populations of limited diversity.

The First Case of Severe Takotsubo Cardiomyopathy Associated with 5-Fluorouracil in a Patient with Abnormalities of Both Dihydropyrimidine Dehydrogenase (DPYD) and Thymidylate Synthase (TYMS) Genes

5-Fluorouracil (5-FU) is the backbone of the chemotherapy regimens approved for treatment of many malignancies, especially colorectal cancer (CRC). The incidence of cardiotoxicity associated with 5-FU ranges between 1.5% to 18% and is most commonly manifested as anginal symptoms. Cardiomyopathy is very rarely reported with 5-FU and capecitabine. A 35-year-old Caucasian male with T3, N1, M0 rectal cancer after the initial neoadjuvant chemoradiation with 5FU/LV followed by surgical abdominoperineal resection (APR), began mFOLFOX6 in the adjuvant setting. Following the first treatment, he developed severe cardiomyopathy, with a drop in ejection fraction (EF) to 19% from normal. The cardiac workup showed no ischemic or other etiologies to explain this cardiac event. He was a nonsmoker and only occasionally drank alcohol. He had no previous or family history of heart disease and had normal cholesterol level. He was treated for severe congestive heart failure (CHF). When the patient presented to us for second opinion, we decided to examine him for dihydropyrimidine dehydrogenase (DPD) deficiency and thymidylate synthase (TYMS) polymorphism. The patient was found to be heterozygous for the c.85T>C mutation, resulting in reduced DPYD enzymatic activity and homozygous for TYMS 5’TSER genotype 2R/2R *f. Our group first identified and reported P453L (1358C>T) type DPYD germline mutation in a patient who developed 5-FU induced cardiotoxicity. In this paper, we describe the first case of cardiomyopathy related to DPD deficiency and homozygous polymorphism of TYMS in a patient with colon cancer following 5-FU containing regimen. Fluorouracil-related cardiomyopathy has to be anticipated and treated to prevent the serious consequence of cardiac dysfunction. The prospective testing for DPD deficiency in patients might prevent DPD-deficient patients from severe toxicity or even death, and therefore the development of a unified screening method is warranted.