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

Preparation of Microsponge Drug Delivery System (MSDDS) Followed by a Scale-Up Approach

In 1987, Won invented the solid-phase porous microsphere (MS), which stores bioactive compounds in many interconnected voids. Spherical particles (5-300 μm), MS, may form clusters of smaller spheres, resulting in many benefits. The current investigation focussed on gel-encased formulation, which can be suitable for dermal usage. First, quasi-emulsion (w/o/w) solvent evaporation was used to prepare 5-fluorouracil (5 FU) MS particles. The final product was characterized (SEM shows porous structure, FTIR and DSC showed drug compatibility with excipients, and gel formulation is shear-thinning) and further scaled up using the 8-fold method. Furthermore, CCD (Central Composite Design) was implemented to obtain the optimized results. After optimizing the conditions, including the polymer (600 mg, ethyl cellulose (EC), eudragit RS 100 (ERS)), stirring speed (1197 rpm), and surfactant concentration (2% w/v), we achieved the following results: optimal yield (63%), mean particle size (152 µm), drug entrapment efficiency (76%), and cumulative drug release (74.24% within 8 h). These findings are promising for industrial applications and align with the objectives outlined in UN Sustainable Development Goals 3, 9, and 17, as well as the goals of the G20 initiative.

Strategies for DPYD testing prior to fluoropyrimidine chemotherapy in the US

PURPOSE

Patients with dihydropyrimidine dehydrogenase (DPD) deficiency are at high risk for severe and fatal toxicity from fluoropyrimidine (FP) chemotherapy. Pre-treatment DPYD testing is standard of care in many countries, but not the United States (US). This survey assessed pre-treatment DPYD testing approaches in the US to identify best practices for broader adoption.

METHODS

From August to October 2023, a 22-item QualtricsXM survey was sent to institutions and clinicians known to conduct pre-treatment DPYD testing and broadly distributed through relevant organizations and social networks. Responses were analyzed using descriptive analysis.

RESULTS

Responses from 24 unique US sites that have implemented pre-treatment DPYD testing or have a detailed implementation plan in place were analyzed. Only 33% of sites ordered DPYD testing for all FP-treated patients; at the remaining sites, patients were tested depending on disease characteristics or clinician preference. Almost 50% of sites depend on individual clinicians to remember to order testing without the assistance of electronic alerts or workflow reminders. DPYD testing was most often conducted by commercial laboratories that tested for at least the four or five DPYD variants considered clinically actionable. Approximately 90% of sites reported receiving results within 10 days of ordering.

CONCLUSION

Implementing DPYD testing into routine clinical practice is feasible and requires a coordinated effort among the healthcare team. These results will be used to develop best practices for the clinical adoption of DPYD testing to prevent severe and fatal toxicity in cancer patients receiving FP chemotherapy.

Capecitabine-associated gastrointestinal ulceration, haemorrhage, and obstruction: a pharmacovigilance analysis based on the FAERS

Background

Capecitabine has been reported to be associated with severe gastrointestinal (GI) adverse drug reactions (gastrointestinal ulceration, haemorrhage, and obstruction). However, statistical correlations have not been demonstrated, and specific GI adverse drug reactions, such as GI obstruction, are not listed on its label.

Aim

We aimed to determine the associations between capecitabine and GI ulceration, haemorrhage, or obstruction among patients with breast cancer by examining data from the United States Food and Drug Administration Adverse Event Reporting System (FAERS).

Methods

We performed disproportionality analysis of GI ulceration, haemorrhage, and obstruction by evaluating the reporting odds ratio (ROR) and the information component (IC) with their 95% confidence intervals (CIs).

Results

We identified 279 patients with capecitabine-associated GI ulceration, haemorrhage, or obstruction reported between 1 January 2004 and 31 December 2020. One-fourth of the cases of GI ulceration, haemorrhage, or obstruction resulted in death. Capecitabine as a drug class had disproportionately high reporting rates for GI ulceration [ROR 1.94 (1.71-2.21); IC 0.80 (0.60-0.99)], haemorrhage [ROR 2.27 (1.86-2.76); IC 0.99 (0.69-1.28)], and obstruction [ROR 2.19 (1.63-2.95); IC 0.96 (0.51-1.40)].

Conclusion

Pharmacovigilance research on the FAERS has revealed a slight increase in reports of GI ulceration, haemorrhage, and obstruction in capecitabine users, which may cause serious or deadly consequences. In addition to the adverse reactions described in the package insert, close attention should be paid to GI obstruction to avoid discontinuation or life-threatening outcomes.

Improving single nucleotide polymorphisms genotyping accuracy for dihydropyrimidine dehydrogenase testing in pharmacogenetics

Fluoropyrimidines, crucial in cancer treatment, often cause toxicity concerns even at standard doses. Toxic accumulation of fluoropyrimidine metabolites, culminating in adverse effects, can stem from impaired dihydropyrimidine dehydrogenase (DPYD) enzymatic function. Emerging evidence underscores the role of single nucleotide polymorphisms (SNPs) in DPYD gene, capable of inducing DPYD activity deficiency. Consequently, DPYD genotyping's importance is on the rise in clinical practice before initiating fluoropyrimidine treatment. Although polymerase chain reaction (PCR) followed by Sanger sequencing (SS; PCR-SS) is a prevalent method for DPYD genotyping, it may encounter limitations. In this context, there is reported a case in which a routine PCR-SS approach for genotyping DPYD SNP rs55886062 failed in a proband of African descent. The Clinical Pharmacogenetics Implementation Consortium (CPIC) categorizes the guanine (G) allele of this SNP as non-functional. The enforcement of whole genome sequencing (WGS) approach led to the identification of two adenine (A) insertions near the PCR primers annealing regions in the proband, responsible for a sequence frameshift and a genotyping error for rs55886062. These SNPs (rs145228578, 1-97981199-T-TA and rs141050810, 1-97981622-G-GA) were extremely rare in non-Finnish Europeans (0.05%) but prevalent in African populations (16%). Although limited evidence was available for these SNPs, they were catalogued as benign variants in public databases. Notably, these two SNPs exhibited a high linkage disequilibrium [LD; squared correlation coefficient (R2) = 0.98]. These findings highlighted the importance to consider the prevalence of genetic variants within diverse ethnic populations when designing primers and probes for SNP genotyping in pharmacogenetic testing. This preventive measure is essential to avoid sequence frameshifts or primer misalignments arising from SNP occurrences in the genome, which can compromise PCR-SS and lead to genotyping failures. Furthermore, this case highlights the significance of exploring alternative genotyping approaches, like WGS, when confronted with challenges associated with conventional techniques.

Phase II study of everolimus and temozolomide as first-line treatment in metastatic high-grade gastroenteropancreatic neuroendocrine neoplasms

BACKGROUND

The optimal treatment for metastatic high-grade gastroenteropancreatic (GEP) neuroendocrine neoplasms when Ki-67 ≤55% is unknown. A prospective multi-centre phase 2 study was performed to evaluate the efficacy and safety of everolimus and temozolomide as first-line treatment for these patients.

METHODS

Patients received everolimus 10 mg daily continuously and temozolomide 150 mg/m2 for 7 days every 2 weeks. Endpoints included response, survival, safety and quality of life (QoL). Histopathological re-evaluation according to the 2019 WHO classification was performed.

RESULTS

For 37 eligible patients, the primary endpoint with 65% disease control rate (DCR) at 6 months (m) was reached. The response rate was 30%, the median progression-free survival (PFS) 10.2 months and the median overall survival (OS) 26.4 months. Considering 26 NET G3 patients, 6 months DCR was 77% vs. 22% among nine NEC patients (p = 0.006). PFS was superior for NET G3 vs. NEC (12.6 months vs. 3.4 months, Log-rank-test: p = 0.133, Breslow-test: p < 0.001). OS was significantly better for NET G3 (31.4 months vs. 7.8 months, p = 0.003). Grade 3 and 4 toxicities were reported in 43% and 38%. QoL remained stable during treatment.

CONCLUSION

Everolimus and temozolomide may be a treatment option for selected GEP-NET G3 patients including careful monitoring. Toxicity did not compromise QoL.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov (NTC02248012).

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.

The Evaluation of Dihydropyrimidine Dehydrogenase Enzyme Level in the Serum of Colorectal Cancer Iraqi Males on Fluoropyrimidine-Based Chemotherapy (Capecitabine)

The cornerstone of systemic chemotherapy for colorectal cancer (CRC) revolves around fluoropyrimidines. This class encompasses 5-fluorouracil (5-FU), which is administered intravenously, along with its oral prodrug counterpart, capecitabine. Central to the metabolism of both 5-FU and capecitabine is the pivotal enzyme dihydropyrimidine dehydrogenase (DPD). Operating at the rate-limiting juncture, DPD assumes a critical role. Notably, a deficiency in DPD significantly elevates the risk quotient for encountering unfavorable outcomes linked to the administration of fluoropyrimidines. This study seeks to assess the significance of DPD enzyme levels in the serum of Iraqi colorectal cancer male patients undergoing fluoropyrimidine-based chemotherapy, specifically with capecitabine. It adopts a case-control design and comprises 80 male participants. Those males are divided into two distinct groups. Group 1 comprises 45 male patients diagnosed with CRC who have experienced relapse subsequent to undergoing chemotherapy based on fluoropyrimidine (capecitabine). Their ages span from 41 to 71 years, and they were treated at the Misan Health Directorate/Misan Center for Tumor Treatment. Group 2 encompasses 35 male patients diagnosed with CRC who underwent fluoropyrimidine-based chemotherapy (capecitabine) without encountering relapse. Their ages range from 40 to 57 years. All participants were provided with comprehensive information regarding the research, and data collection occurred through a structured questionnaire. Subsequent to capecitabine-based treatment, serum samples were collected from CRC patients (stage III). The findings from this research indicate a notable elevation in DPD enzyme activity. Furthermore, a significant reduction in enzyme activity was observed among patients who experienced relapse, in contrast to those who remained non-relapsed. The results indicate that individuals with an insufficiency in DPD are notably more vulnerable to experiencing severe and potentially life-threatening side effects upon exposure to the commonly utilized chemotherapy drug, 5-FU.

Fluoropyrimidine usage in cases with hyperammonemia: real-world data study using the Japanese Adverse Drug Event Report (JADER) database

PURPOSE

Fluoropyrimidines are anticancer drugs and can cause hyperammonemia both intravenously and orally. Renal dysfunction may interact with fluoropyrimidine to cause hyperammonemia. We performed quantitative analyses of hyperammonemia using a spontaneous report database to examine the frequency of intravenously and orally administered fluoropyrimidine, the reported frequency of fluoropyrimidine-related regimens, and fluoropyrimidine's interactions with chronic kidney disease (CKD).

METHODS

This study used data collected between April 2004 and March 2020 from the Japanese Adverse Drug Event Report database. The reporting odds ratio (ROR) of hyperammonemia was calculated for each fluoropyrimidine drug and was adjusted for age and sex. Heatmaps depicting the use of anticancer agents in patients with hyperammonemia were drawn. The interactions between CKD and the fluoropyrimidines were also calculated. These analyses were performed using multiple logistic regression.

RESULTS

Hyperammonemia was observed in 861 of the 641,736 adverse events reports. Fluorouracil was the most frequent drug associated with hyperammonemia (389 cases). The ROR of hyperammonemia was 32.5 (95% CI 28.3-37.2) for intravenously administered fluorouracil, 4.7 (95% CI 3.3-6.6) for orally administered capecitabine, 1.9 (95% CI 0.87-4.3) for tegafur/uracil, and 2.2 (95% CI 1.5-3.2) for orally administered tegafur/gimeracil/oteracil. Calcium levofolinate, oxaliplatin, bevacizumab, and irinotecan were the most frequently reported agents in cases of hyperammonemia with intravenously administered fluorouracil. The coefficient of the interaction term between CKD and fluoropyrimidines was 1.12 (95% CI 1.09-1.16).

CONCLUSION

Hyperammonemia cases were more likely to be reported with intravenous fluorouracil than orally administered fluoropyrimidines. Fluoropyrimidines might interact with CKD in hyperammonemia cases.

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.

Ten-year experience with pharmacogenetic testing for DPYD in a national cancer center in Italy: Lessons learned on the path to implementation

Background: Awareness about the importance of implementing DPYD pharmacogenetics in clinical practice to prevent severe side effects related to the use of fluoropyrimidines has been raised over the years. Since 2012 at the National Cancer Institute, CRO-Aviano (Italy), a diagnostic DPYD genotyping service was set up. Purpose: This study aims to describe the evolution of DPYD diagnostic activity at our center over the last 10 years as a case example of a successful introduction of pharmacogenetic testing in clinical practice. Methods: Data related to the diagnostic activity of in-and out-patients referred to our service between January 2012 and December 2022 were retrieved from the hospital database. Results: DPYD diagnostic activity at our center has greatly evolved over the years, shifting gradually from a post-toxicity to a pre-treatment approach. Development of pharmacogenetic guidelines by national and international consortia, genotyping, and IT technology evolution have impacted DPYD testing uptake in the clinics. Our participation in a large prospective implementation study (Ubiquitous Pharmacogenomics) increased health practitioners' and patients' awareness of pharmacogenetic matters and provided additional standardized infrastructures for genotyping and reporting. Nationwide test reimbursement together with recommendations by regulatory agencies in Europe and Italy in 2020 definitely changed the clinical practice guidelines of fluoropyrimidines prescription. A dramatic increase in the number of pre-treatment DPYD genotyping and in the coverage of new fluoropyrimidine prescriptions was noticed by the last year of observation (2022). Conclusion: The long path to a successful DPYD testing implementation in the clinical practice of a National Cancer Center in Italy demonstrated that the development of pharmacogenetic guidelines and genotyping infrastructure standardization as well as capillary training and education activity for all the potential stakeholders are fundamental. However, only national health politics of test reimbursement and clear recommendations by drug regulatory agencies will definitely move the field forward.

Review of genetic and pharmacogenetic differences in cytotoxic and targeted therapies for pancreatic cancer in African Americans

Pancreatic ductal adenocarcinoma (PDAC) is currently the third leading cause of cancer mortality and the incidence is projected to increase by 2030. Despite recent advances in its treatment, African Americans have a 50-60% higher incidence and 30% higher mortality rate when compared to European Americans possibly resulting from differences in socioeconomic status, access to healthcare, and genetics. Genetics plays a role in cancer predisposition, response to cancer therapeutics (pharmacogenetics), and in tumor behavior, making some genes targets for oncologic therapeutics. We hypothesize that the germline genetic differences in predisposition, drug response, and targeted therapies also impact PDAC disparities. To demonstrate the impact of genetics and pharmacogenetics on PDAC disparities, a review of the literature was performed using PubMed with variations of the following keywords: pharmacogenetics, pancreatic cancer, race, ethnicity, African, Black, toxicity, and the FDA-approved drug names: Fluoropyrimidines, Topoisomerase inhibitors, Gemcitabine, Nab-Paclitaxel, Platinum agents, Pembrolizumab, PARP-inhibitors, and NTRK fusion inhibitors. Our findings suggest that the genetic profiles of African Americans may contribute to disparities related to FDA approved chemotherapeutic response for patients with PDAC. We recommend a strong focus on improving genetic testing and participation in biobank sample donations for African Americans. In this way, we can improve our current understanding of genes that influence drug response for patients with PDAC.

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.

Drug monitoring detects under- and overdosing in patients receiving 5-fluorouracil-containing chemotherapy-results of a prospective, multicenter German observational study

INTRODUCTION

Body surface area (BSA)-based dosing of 5-fluorouracil (5-FU) results in marked inter-individual variability in drug levels, whereas determination of plasma 5-FU concentration and area under the curve (AUC) is a more precise dosing method but has not been integrated into clinical routine. We conducted a multicenter, prospective study to study 5-FU AUC distributions and assess clinical factors predicting therapeutic dosing in patients receiving BSA-dosed 5-FU.

METHODS

Between June 2017 and January 2018, a total of 434 patients receiving continuous, infusional BSA-dosed 5-FU from 37 sites in Germany were included. Plasma 5-FU concentration and AUC were measured in venous blood samples at steady state. The primary objective was to determine 5-FU AUC distributions in relation to the target range, which is defined as 20-30 mg × h/l. The second objective was to explore clinical parameters that correlate with achievement of 5-FU AUC target range.

RESULTS

The primary tumor was mainly located in the gastrointestinal tract (96.3%), with colorectal cancer being the most common (71.2%) tumor entity. 5-FU was administered as monotherapy (8.1%) or as part of FOLFOX (33.2%), FOLFIRI (26.3%), or other regimens (12.4%). Treatment setting was adjuvant (31.3%) or metastatic (64.5%). The median AUC was 16 mg × h/l. Only 20.3% of patients received 5-FU treatment within the target range, whereas the majority of patients (60.6%) were underdosed and 19.1% of patients were overdosed. In the univariate logistic regression, treatment setting was the only clinical parameter that significantly correlated with achievement of the target range. Patients treated in the metastatic setting had a 2.1 (95% confidence interval 1.186-3.776, P = 0.011) higher odds to reach the target range compared with patients treated in the adjuvant setting.

CONCLUSIONS

The majority of patients received suboptimal doses of 5-FU using BSA dosing. Therapeutic drug monitoring of 5-FU is an option for optimized individualized cancer therapy and should be integrated into the clinical practice.

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.

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.

Clinical Implementation of DPYD Pharmacogenetic Testing to Prevent Early-Onset Fluoropyrimidine-Related Toxicity in Cancer Patients in Switzerland

The implementation of pharmacogenetic testing into clinical practice has been a slow process so far. Here, we review the implementation of pre-treatment testing of dihydropyrimidine dehydrogenase gene (DPYD) risk variants to prevent early-onset fluoropyrimidine (FP)-related toxicity in cancer patients in Switzerland based on data of a large Swiss diagnostic center. In January 2017, the Swiss Federal Office of Public Health introduced the reimbursement of DPYD testing by the compulsory health insurance in Switzerland based on evidence for the clinical relevance of DPYD-risk variants and the cost-effectiveness of pre-treatment testing, and on the availability of international guidelines. However, we did not observe a strong increase in DPYD testing at our diagnostic center from 2017 to 2019. Only a low number of DPYD-testing requests (28-42 per year), concerning mostly retrospective investigations of suspected FP-toxicity, were received. In contrast, we observed a 14-fold increase in DPYD testing together with a strong shift from retrospective to pre-treatment test requests upon the release of recommendations for DPYD testing prior to FP-treatment in April 2020 by the European Medicines Agency. This increase was mainly driven by three geographic regions of Switzerland, where partner institutions of previous research collaborations regarding FP-related toxicity are located and who acted as early-adopting institutions of DPYD testing. Our data suggest the important role of early adopters as accelerators of clinical implementation of pharmacogenetic testing by introducing these policies to their working environment and educating health workers from their own and nearby institutions.

Optimizing the prescription doses and tolerability of systemic therapy in head and neck cancer patients

PURPOSE OF REVIEW

Squamous cell carcinoma of the head and neck accounts for 330 000 deaths and 650 000 cases worldwide annually. Systemic therapy is an essential pillar of multimodal therapy despite being accompanied with substantial toxicity. This article reviews the latest advances in systemic therapy for the treatment of locoregionally advanced and reccurent/metastatic head and neck cancer from a tolerability perspective.

RECENT FINDINGS

Multiple recent attempts have been made to optimize tolerability (and efficacy) of systemic therapy utilizing new regimens, modified prescription doses, drugs such as immunotherapies or genotyping to tailor the systemic therapy to the individual patient.

SUMMARY

Although treatment benefit has to be weighed against potential toxicity, it is reasonable to anticipate potential side effects of systemic therapies. In a vulnerable elderly or Asian patient population upfront dose modifications of cytotoxic chemotherapies might be reasonable. Special attention should be laid on the patient's nutritional status and early intervention recommended. Dihydropyrimidine dehydrogenase genotyping can predict 5-fluorouracil toxicity and identify patients for whom alternative regimens are more suitable. As for immune checkpoint inhibitor therapy, despite being well tolerated, the identification of biomarkers to predict reduced tolerability or severe toxicity would be highly desirable.

Effect of Apatinib Combined with Seggio on the Expression of Serum AFP and CA724 and Long-Term Survival Rate in Patients with Advanced Gastric Cancer Undergoing Comfortable Nursing Intervention

Objective

To study the effect of apatinib combined with seggio on the expression of serum AFP and CA724 and the long-term survival rate in advanced gastric cancer patients undergoing comfort nursing intervention.

Methods

98 advanced gastric cancer patients were divided into single-drug group and joint group. Both groups of patients were given comfort nursing intervention, the single-drug group was treated with seggio, and the joint group was treated with apatinib and seggio. The clinical efficacy, survival rate, relationship between the tumor markers and the survival time, serum tumor markers levels (CA724 and AFP), inflammatory factors (IL-4, IL-10) levels, quality-of-life scores, and immunity function were measured after treatment.

Results

The clinical efficacy in the joint group was better than that in the single-drug group. The three-year survival time in the joint group was upregulated relative to the single-drug group. The patients with high expression of CA724 or AFP had a lower survival time than the patients with low expression of CA724 or AFP. After treatment, IL-10 and IL-4 levels were obviously decreased, and the joint group showed a more obvious decrease compared with the single-drug group. The quality-of-life scores were significantly upregulated after treatment, and compared with the joint group, the scores in the single drug-group were obviously higher. The CD4+/CD8+, CD4+, and CD3+ levels were increased, while CD8+ levels were decreased after treatment, and the changes of each index in the joint group were more significant than those in the single-drug group. The content of CA724 and AFP were significantly decreased after treatment, and the joint group showed a more significant decrease than the single-drug group.

Conclusion

Apatinib combined with seggio for advanced gastric cancer patients' treatment based on comfort nursing intervention can improve the clinical efficacy and survival time, reduce inflammatory factors and serum tumor markers levels, enhance patients' immune function, and quality of life.

Capecitabine-Induced Enterocolitis

Capecitabine is an oral fluoropyrimidine carbamate chemotherapy agent approved by the United States Food and Drug Administration (FDA) for the treatment of metastatic colorectal and breast cancer. The common side effects associated with it include gastrointestinal (GI) upset, abdominal pain, palmar-plantar erythrodysesthesia, fatigue, alopecia, leukopenia, neutropenia, thrombocytopenia, anemia, and hyperbilirubinemia. Although GI symptoms are relatively common, enterocolitis is one of the rare side effects of this drug. We present a case of 53-year-old female who developed severe enterocolitis leading to ileus secondary to capecitabine chemotherapy for metastatic breast cancer. She was treated successfully via conservative management.

[Clinical significance of tumor chemosensitivity assay in patients with head and neck cancer]

Objective:To evaluate the clinical significance of OncoDrug-Seq™ tumor gene detection in patients with head and neck malignancies. Methods:A retrospective analysis of 338 patients with locally advanced or unresectable head and neck malignancies admitted to the Department of Otorhinolaryngology Head and Neck Surgery, Chinese PLA General Hospital from April 2011 to February 2021. Among them, 301 patients were pathologically diagnosed as squamous cell carcinoma, 37 cases were non-squamous cell carcinoma. All patients underwent OncoDrug-Seq™ gene detection, combined with the test results and the treatment response after induction chemotherapy to evaluate whether to change the chemotherapy regimen, and to calculate the accuracy of the gene detection and the survival rate of the patient. Results:Among 301 patients with head and neck squamous cell carcinoma, the results of the drug sensitivity test were compared with the actual clinical response, the true positive rate（TP）, true negative rate（TN）, positive predictive value（PPV）, negative predictive value（NPV） and total predictive accuracy rates were 85.37%, 65.45%, 91.70%, 50.00% and 81.73%, respectively. For patients who changed chemotherapy regimen（TN+FP） and did not change（TP+FN）, the 5-year progression-free survival（PFS） was 63.45% and 80.58%（P<0.05）, respectively, the 5-year overall survival（OS） was 54.18% and 84.74%（P<0.05）. Among 37 patients with non-squamous cell carcinoma, the TP, TN, PPV, NPV and total predictive accuracy rates were 88.46%, 72.73%, 88.46%, 72.73%, and 83.78%, respectively. The 5-year PFS of the patients who changed（TN+FP） and did not change the treatment regimen（TP+FN） were 68.57% and 56.00%, and the 5-year OS was 69.26% and 48.72%, the difference was not statistically significant. Conclusion:OncoDrug-Seq™ testing has certain significance in guiding clinicians to formulate personalized chemotherapy regimens. Timely replacement of the treatment plan can enable the patient to obtain a more ideal curative effect. Compared with patients with squamous cell carcinoma, patients with non-squamous cell carcinoma can obtain greater survival benefit from this testing. However, there are still some deviations in the accuracy of the test results compared with the actual clinical situation. Therefore, the decision should be made based on the test results in combination with the clinical reality.

Molecular tests for prediction of tumor sensitivity to cytotoxic drugs

Chemotherapy constitutes the backbone of cancer treatment. Several predictive assays assist personalized administration of cytotoxic drugs and are recommended for use in a clinical setting. The deficiency of DNA repair by homologous recombination (HRD), which is caused by inactivation of BRCA1/2 genes or other genetic events, is associated with high tumor responsiveness to platinum compounds, bifunctional alkylating agents and topoisomerase II poisons. Low activity of MGMT predicts the efficacy of nitrosoureas and tetrazines. Some clinically established pharmacogenetic tests allow for the adjustment of drug dosage, for example, the analysis of DPYD allelic variants for administration of fluoropyrimidines and UGT1A1 genotyping for the use of irinotecan. While there are promising molecular predictors of tumor sensitivity to pemetrexed, gemcitabine and taxanes, they remain in the investigational stage and require additional validation. Comprehensive molecular analysis of tumors obtained from drug responders and non-responders is likely to reveal new clinically useful predictive markers for cytotoxic therapy.

Reproductive and developmental toxicities of 5-fluorouracil in model organisms and humans

Chemotherapy, as an important clinical treatment, has greatly enhanced survival in cancer patients, but the side effects and long-term sequelae bother both patients and clinicians. 5-Fluorouracil (5-FU) has been widely used as a chemotherapeutic agent in the clinical treatment of various cancers, but several studies showed its adverse effects on reproduction. Reproductive toxicity of 5-FU often associates with developmental block, malformation and ovarian damage in the females. In males, 5-FU administration alters the morphology of sexual organs, the levels of reproductive endocrine hormones and the progression of spermatogenesis, ultimately reducing sperm numbers. Mechanistically, 5-FU exerts its effect through incorporating the active metabolites into nucleic acids directly, or inhibiting thymidylate synthase to disrupt the function of DNA and RNA, leading to profound effects on cellular metabolism and viability. However, some studies suggested that the toxicity of 5-FU on reproduction is reversible and certain drugs used in combination with 5-FU during chemotherapy could protect reproductive systems from 5-FU damage both in females and males. Herein, we summarise the recent findings and discuss underlying mechanisms of the 5-FU-induced reproductive toxicity, providing a reference for future research and clinical treatments.

Current status and future outlooks on therapeutic drug monitoring of fluorouracil

INTRODUCTION

: Therapeutic drug monitoring (TDM) of the anticancer drug fluorouracil (5FU) as a method to support dose adjustments has been researched and discussed extensively. Despite manifold evidence of the advantages of 5FU-TDM, traditional body surface area (BSA)-guided dosing is still widely applied.

AREAS COVERED

: This review covers the latest evidence on 5FU-TDM based on a literature search in PubMed between June and September 2021. It particularly highlights new approaches of implementing 5FU-TDM into precision medicine by combining TDM with pharmacogenetic testing and/or pharmacometric models. This review further discusses remaining obstacles in order to incorporate 5FU-TDM into clinical routine.

EXPERT OPINION

: New data on 5FU-TDM further strengthen the advantages compared to BSA-guided dosing as it is able to reduce pharmacokinetic variability and thereby improve treatment efficacy and safety. Interprofessional collaboration has the potential to overcome the remaining barriers for its implementation. Pre-emptive pharmacogenetic testing followed by 5FU-TDM can further improve 5FU exposure in a substantial proportion of patients. Developing a model framework integrating pharmacokinetics and pharmacodynamics of 5FU will be crucial to fully advance into the precision medicine era. Model applications can potentially support clinicians in dose finding before starting chemotherapy. Additionally, TDM provides further assistance in continuously improving model predictions.

The Impact of Biomarkers in Pancreatic Ductal Adenocarcinoma on Diagnosis, Surveillance and Therapy

Simple Summary

Pancreatic ductal adenocarcinoma is a leading cause of cancer death worldwide. Due to the frequently late diagnosis, early metastasis and high therapy resistance curation is rare and prognosis remains poor overall. To provide early diagnostic and therapeutic predictors, various molecules from blood, tissue and other origin e.g., saliva, urine and stool, have been identified as biomarkers. This review summarizes current trends in biomarkers for diagnosis and therapy of pancreatic ductal adenocarcinoma.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is still difficult to treat due to insufficient methods for early diagnosis and prediction of therapy response. Furthermore, surveillance after curatively intended surgery lacks adequate methods for timely detection of recurrence. Therefore, several molecules have been analyzed as predictors of recurrence or early detection of PDAC. Enhanced understanding of molecular tumorigenesis and treatment response triggered the identification of novel biomarkers as predictors for response to conventional chemotherapy or targeted therapy. In conclusion, progress has been made especially in the prediction of therapy response with biomarkers. The use of molecules for early detection and recurrence of PDAC is still at an early stage, but there are promising approaches in noninvasive biomarkers, composite panels and scores that can already ameliorate the current clinical practice. The present review summarizes the current state of research on biomarkers for diagnosis and therapy of pancreatic cancer.

Interaction of a conical carbon scaffold with the thio-substituted model of fluorouracil towards approaching the drug delivery purposes

A representative FeN4-doped conical carbon (C) scaffold was investigated for participating in interactions with the thio-substituted fluorouracil (SFU) anticancer drug by performing density functional theory (DFT) calculations. In this regard, all possible relaxation configurations of SFU at the doped tip of C scaffold were examined, in which three models were obtained including one horizontal relaxation configuration (FC1) and two vertical relaxation configurations (FC2 and FC3). The results indicate the highest stability and strength for FC1 model. Examining formations and strengths of interactions showed two medium strength interactions in each of FC1, FC2, and FC3 models. Moreover, the evaluated electronic molecular orbitals features indicated availability of sensor function for the proposed C scaffold towards the interacting SFU substance. As a consequence, the models were determined to work in dual functions of sensor and carrier towards drug delivery purpose of SFU anticancer drug.

Severe ileum bleeding following adjuvant capecitabine chemotherapy for locally advanced colon cancer: a case report and review of the literature

BACKGROUND

Capecitabine is a prodrug that is enzymatically converted to its active form, fluorouracil (also called 5-fluorouracil), which is commonly used as adjuvant chemotherapy in colorectal cancer patients. Severe gastrointestinal bleeding induced by capecitabine is rare. Here, we are presenting the first case report of surgery specimen assisted diagnosis of this uncommon condition.

CASE PRESENTATION

A 63-year-old Chinese male with a history of colon adenocarcinoma and right hemicolectomy presented with severe lower gastrointestinal bleeding 2 days after finishing capecitabine administration during the first cycle of XELOX adjuvant chemotherapy. Because of the negative findings of active bleeding points by digital subtraction angiography (DSA) or colonoscopy, emergency laparotomy and partial enterectomy were performed. The bloody diarrhea had resolved after surgery and a terminal ileitis was diagnosed after pathological examination of the surgical specimen.

CONCLUSIONS

Terminal ileitis induced by capecitabine is likely to be underreported. It should be considered more often as a cause of severe gastrointestinal bleeding during or after treatment with capecitabine agents. Emergency surgery may achieve satisfactory outcomes if endoscopic hemostasis is ineffective.

HIGHLIGHTS OF THIS CASE

1. Gastrointestinal bleeding following capecitabine treatment in colorectal cancer patients might be life-threatening. 2. Terminal ileitis induced by capecitabine should always be considered in the differential diagnosis of severe gastrointestinal bleeding. 3. Awareness of the risk factors such as deficiency of dihydropyrimidine dehydrogenase, advanced age, or right colectomy may aid in reducing capecitabine-related morbidity. 4. When severe bleeding occurs, emergency surgery may achieve satisfactory outcomes if medical and endoscopic interventions are ineffective.

Consensus of experts from the Spanish Pharmacogenetics and Pharmacogenomics Society and the Spanish Society of Medical Oncology for the genotyping of DPYD in cancer patients who are candidates for treatment with fluoropyrimidines

5-Fluorouracil (5-FU) and oral fluoropyrimidines, such as capecitabine, are widely used in the treatment of cancer, especially gastrointestinal tumors and breast cancer, but their administration can produce serious and even lethal toxicity. This toxicity is often related to the partial or complete deficiency of the dihydropyrimidine dehydrogenase (DPD) enzyme, which causes a reduction in clearance and a longer half-life of 5-FU. It is advisable to determine if a DPD deficiency exists before administering these drugs by genotyping DPYD gene polymorphisms. The objective of this consensus of experts, in which representatives from the Spanish Pharmacogenetics and Pharmacogenomics Society and the Spanish Society of Medical Oncology participated, is to establish clear recommendations for the implementation of genotype and/or phenotype testing for DPD deficiency in patients who are candidates to receive fluoropyrimidines. The genotyping of DPYD previous to treatment classifies individuals as normal, intermediate, or poor metabolizers. Normal metabolizers do not require changes in the initial dose, intermediate metabolizers should start treatment with fluoropyrimidines at doses reduced to 50%, and poor metabolizers are contraindicated for fluoropyrimidines.

A case-control study of a combination of single nucleotide polymorphisms and clinical parameters to predict clinically relevant toxicity associated with fluoropyrimidine and platinum-based chemotherapy in gastric cancer

Background

Fluoropyrimidine plus platinum chemotherapy remains the standard first line treatment for gastric cancer (GC). Guidelines exist for the clinical interpretation of four DPYD genotypes related to severe fluoropyrimidine toxicity within European populations. However, the frequency of these single nucleotide polymorphisms (SNPs) in the Latin American population is low (< 0.7%). No guidelines have been development for platinum. Herein, we present association between clinical factors and common SNPs in the development of grade 3–4 toxicity.

Methods

Retrospectively, 224 clinical records of GC patient were screened, of which 93 patients were incorporated into the study. Eleven SNPs with minor allelic frequency above 5% in GSTP1, ERCC2, ERCC1, TP53, UMPS, SHMT1, MTHFR, ABCC2 and DPYD were assessed. Association between patient clinical characteristics and toxicity was estimated using logistic regression models and classification algorithms.

Results

Reported grade ≤ 2 and 3–4 toxicities were 64.6% (61/93) and 34.4% (32/93) respectively. Selected DPYD SNPs were associated with higher toxicity (rs1801265; OR = 4.20; 95% CI = 1.70–10.95, p = 0.002), while others displayed a trend towards lower toxicity (rs1801159; OR = 0.45; 95% CI = 0.19–1.08; p = 0.071). Combination of paired SNPs demonstrated significant associations in DPYD (rs1801265), UMPS (rs1801019), ABCC2 (rs717620) and SHMT1 (rs1979277). Using multivariate logistic regression that combined age, sex, peri-operative chemotherapy, 5-FU regimen, the binary combination of the SNPs DPYD (rs1801265) + ABCC2 (rs717620), and DPYD (rs1801159) displayed the best predictive performance. A nomogram was constructed to assess the risk of developing overall toxicity.

Conclusion

Pending further validation, this model could predict chemotherapy associated toxicity and improve GC patient quality of life.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08745-0.

The CIRCULATE Trial: Circulating Tumor DNA Based Decision for Adjuvant Treatment in Colon Cancer Stage II Evaluation (AIO-KRK-0217)

BACKGROUND

Guidance regarding adjuvant treatment decisions in stage II colorectal cancer (CRC) remains uncertain due to lack of predictive clinical or molecular markers. Recently, postoperative circulating tumour (ct)DNA has been demonstrated to be a strong prognostic marker in early colon cancer.

PATIENTS AND METHODS

CIRCULATE enrols patients with stage II microsatellite stable CRC in Germany (AIO) and Austria (ABCSG). Within the AIO, screening is supported by ColoPredict Plus 2.0, a molecular registry, and screening platform for interventional trials. Patient-specific mutations are centrally analysed by next generation sequencing in the resected primary tumour. A postoperative plasma sample is subsequently screened for the specific mutation(s). ctDNA positive (ctDNApos) patients are randomised (2:1) chemotherapy (capecitabine, oxaliplatin added an investigator's choice) or to follow-up (control group). ctDNA negative (ctDNAneg) patients are randomised (1:4) to be followed-up within CIRCULATE (control group) or outside the trial. Patients in the control group remain blinded to the ctDNA results. The primary objective is to compare disease free survival (DFS) of ctDNApos patients with chemotherapy or control. To demonstrate a treatment effect with a hazard ratio of 0.617 (3-year DFS rates 42.5% vs. 25%), 231 ctDNApos and estimated 2079 ctDNAneg patients are randomised. Secondary aims include to compare overall survival and DFS in the ctDNApos and ctDNAneg patient cohorts and ctDNA kinetics.

CONCLUSION

The CIRCULATE trial may establish ctDNA for adjuvant treatment decision in stage II colon cancer - and with the secondary objectives - support a ctDNA guided follow up in colon cancer stage II and beyond.

Choosing the Right Treatment Option for the Right R/M HNSCC Patient: Should We Adhere to PFE for First-Line Therapy?

Background

The landmark EXTREME trial established cisplatin, 5-fluorouracil and cetuximab (PFE) as first-line chemotherapy (1L-ChT) for recurrent/metastatic head and neck squamous cell carcinoma (R/M HNSCC). We were interested in outcome differences of R/M HNSCC in 1L-ChT and factors influencing outcome in certain subgroups, especially patients receiving PFE, and the value of PFE compared to other 1L-ChT regimens to provide real world evidence (RWE).

Methods

For this retrospective monocentric study, 124 R/M HNSCC patients without curative surgical or radiotherapy options receiving at least one cycle of 1L-ChT were eligible. We analyzed their outcome using Kaplan-Meier plot and Cox regression to identify predictors for prolonged survival.

Results

Subgroups benefiting significantly from PFE were patients suffering from an index HNSCC outside the oropharynx. The PFE regimen proved to be superior to all other 1L-ChT regimens in clinical routine. Significant outcome differences between PFE treatment within or outside controlled trials were not seen.

Conclusion

This retrospective analysis provides RWE for factors linked to improved outcome. Subgroup analyses highlight the lasting value of PFE among the growing spectrum of 1L-ChT. Importantly, fit smokers with high level alcohol consumption benefit from PFE; considering the patient's lifestyle factors, PFE should not be ignored in decision-making.

Metastatic colorectal cancer: Advances in the folate-fluoropyrimidine chemotherapy backbone

Notwithstanding recent treatment advances in metastatic colorectal cancer (mCRC), chemotherapy with a combination of a fluoropyrimidine and a folate agent, often 5-fluorouracil (5-FU) and leucovorin, remains the backbone of treatment regimens for the majority of patients with mCRC. This is despite a recent focus on molecular-targeted treatments and patient stratification according to mutational status or expression levels of specific genes. Intracellular folate concentration was discovered to be pivotal in the cytotoxic efficacy of 5-FU, paving the way to the current standard combination therapy approach. Subsequent discovery that systemic chemotherapy agents, such as irinotecan and oxaliplatin, can further increase the efficacy of 5-FU-based treatments led to the development of several combination chemotherapy regimens, including FOLFOX, FOLFIRI and FOLFOXIRI. Subsequent efforts to optimise 5-FU-based treatments have focused on 5-FU analogues, initially capecitabine and the combination drug tegafur/gimeracil/oteracil (S-1) and then TAS-102, which has recently been evaluated in phase 3 clinical trials for refractory colorectal cancer. Further approaches taken to improve the efficacy of 5-FU chemotherapy regimens have focused on optimising the route and dosing schedules and regulating folate metabolism. Pharmacokinetic variability caused by the requirement for metabolic conversion of leucovorin has been central to recent research, and the development of agents such as arfolitixorin which bypass the need for metabolic conversion remains promising for future therapeutic candidates. In this review, we summarise the evidence leading to the current treatment regimens employing 5-FU and leucovorin, focusing on recent approaches taken to optimise and refine treatments to improve clinical outcomes in patients with mCRC.

Capecitabine-Induced Terminal Ileitis: Case Report and Literature Review

Capecitabine is a well-established agent for adjuvant chemotherapy in breast and colorectal cancers. However, one of the limiting adverse events of this therapy is severe diarrhea, which is reported with increasing frequency as of late. Capecitabine-induced ileitis should be suspected in cases with severe, treatment-refractory diarrhea. We present a case of capecitabine-induced terminal ileitis in a patient who received the medication as adjuvant therapy for previously resected colon adenocarcinoma. Capecitabine-induced diarrhea secondary to ileitis is a severe adverse drug event, which occurs during adjuvant chemotherapy and does not respond to conservative treatment with antidiarrheals, often necessitating permanent drug withdrawal. A high index of suspicion is critical as the complications, such as dehydration and the associated electrolyte derangements, may be life-threatening if diagnosis and cause-specific treatment are delayed.

Overcoming barriers to implementing precision dosing with 5-fluorouracil and capecitabine

Despite advances in targeted cancer therapy, the fluoropyrimidines 5-fluorouracil (5FU) and capecitabine continue to play an important role in oncology. Historically, dosing of these drugs has been based on body surface area. This approach has been demonstrated to be an imprecise way to determine the optimal dose for a patient. Evidence in the literature has demonstrated that precision dosing approaches, such as DPD enzyme activity testing and, in the case of intravenous 5FU, pharmacokinetic-guided dosing, can reduce toxicity and yield better patient outcomes. However, despite the evidence, there has not been uniform adoption of these approaches in the clinical setting. When a drug such as 5FU has been used clinically for many decades, it may be difficult to change clinical practice. With the aim of facilitating change of practice, issues and barriers to implementing precision dosing approaches for 5FU and capecitabine are identified and discussed with possible solutions proposed.

Near Miss or Standard of Care? DPYD Screening for Cancer Patients Receiving Fluorouracil

5-fluorouracil (5-FU) and its pro-drug capecitabine are widely used anticancer agents. Most 5-FU catabolism is dependent on dihydropyrimidine dehydrogenase (DPD) encoded by the DPYD gene, and DPYD variants that reduce DPD function increase 5-FU toxicity. Most DPD deficient patients are heterozygous and can be treated with reduced 5-FU dosing. We describe a patient with a genotype associated with near complete absence of DPD function, and severe and likely fatal toxicity with 5-FU treatment. The patient was treated effectively with alternative systemic therapy. Routine pretreatment DPYD genotyping is recommended by the European Medicines Agency, and guidelines for use of 5-FU in DPD deficient patients are available. However, outside the province of Quebec, routine pretreatment screening for DPD deficiency remains unavailable in Canada. It is likely our patient would have died from 5-FU toxicity under the current standard of care, but instead provides an example of the potential benefit of DPYD screening on patient outcomes.