Recent regulatory and guideline changes have established pretreatment DPYD genotyping as a critical strategy to prevent severe fluoropyrimidine toxicity. Following earlier European leadership by the European Medicines Agency, the US Food and Drug Administration added boxed warnings to capecitabine and 5-fluorouracil labels recommending genetic testing before therapy. Concurrent updates from the National Comprehensive Cancer Network and ASCO align US with European practice supporting universal testing. Fluoropyrimidines remain foundational treatments across multiple cancers but can cause life-threatening toxicity in patients with dihydropyrimidine dehydrogenase (DPD) deficiency, most commonly because of inherited DPYD variants. DPYD variant carriers receiving standard doses experience markedly increased risk of severe toxicity and treatment-related mortality, emphasizing the clinical importance of DPYD testing and genotype-guided dosing. Evidence demonstrates that dose individualization based on guidance from the Clinical Pharmacogenetics Implementation Consortium reduces toxicity risk while maintaining treatment effectiveness and potentially reducing overall costs. Patient advocacy, particularly efforts led by Advocates for Universal DPD/DPYD Testing, has accelerated policy change, increased clinician awareness, and highlighted ethical implications of preventable harm. Despite growing adoption, implementation challenges persist, including workflow integration, clinician education, and equitable access. Integrated health systems such as the Veterans Health Administration demonstrate how centralized infrastructure and clinical decision support can facilitate uptake. Barriers are more pronounced in resource-constrained settings, where limited infrastructure, reimbursement uncertainty, and insufficient pharmacogenomic education hinder implementation. Regional initiatives illustrate education-focused, context-adapted strategies to expand testing and address population-specific variant knowledge gaps. Collectively, emerging evidence, regulatory alignment, and advocacy efforts position DPYD genotyping as a patient-safety imperative necessary to achieve safer, more equitable fluoropyrimidine therapy worldwide.

Dihydropyrimidine dehydrogenase (DPD) phenotyping through uracil and dihydrouracil determination is a well-established approach to identify (partial) DPD deficiencies prior to fluoropyrimidine chemotherapy. However, preanalytical stability has challenged this test for years. This study therefore investigated whether dried blood spots (DBS) can improve preanalytical stability. Uracil, dihydrouracil, and uridine were determined in 6 mm DBS sub-punch extracts by liquid chromatography-tandem mass spectrometry. Paired venous and capillary DBS were collected from 15 healthy volunteers across three days to evaluate venous-capillary DBS differences. The impact of blood spotting, drying and preanalytical stability for up to two weeks was assessed using venous DBS of the same volunteers. Uracil was elevated in all capillary DBS, with a median of 219 % relative to venous DBS. In addition, the variation between capillary DBS replicates was 29 %, opposed to only 7 % in venous DBS. For dihydrouracil, a small bias of-7 % was observed, while uridine showed no difference, with similar inter-spot variation in venous and capillary DBS. Generation and drying of DBS had statistically significant yet minor effects on all analytes. Venous DBS enhanced preanalytical stability, yielding median uracil levels of 105 % and 107 % after 1 and 2weeks at room temperature, and no differences for dihydrouracil or uridine relative to overnight driedDBS. Capillary DBS are unsuitable for uracil determination in DPD phenotyping owing to poor agreement with venous DBS and substantial variability. Venous DBS, however, demonstrate superior preanalytical stability over liquid samples and may provide a practical solution for managing preanalytical variables.

The therapeutic efficacy of 5-fluorouracil (5-FU), a cornerstone of gastric cancer chemotherapy, is predominantly limited by its catabolic inactivation in tumors. Dihydropyrimidine dehydrogenase (DPD) is the rate-limiting enzyme responsible for 5-FU inactivation, and its tumor-specific overexpression constitutes a primary mechanism of 5-FU resistance. Here, we report a novel strategy to increase the sensitivity of 5-FU by targeting the post-translational regulation of DPD. We demonstrate that the neural precursor cell expressed, developmentally downregulated 8-activating enzyme (NAE) inhibitor MLN4924 significantly enhances the antitumor activity of 5-FU in both cellular and animal models of gastric cancer without augmenting systemic toxicity. Mechanistically, MLN4924 treatment inhibits the neddylation of DPD, which is dependent on the NAE1/ubiquitin-conjugating enzyme 12 axis. This inhibition triggers the ubiquitination and subsequent proteasomal degradation of DPD, thereby reducing intracellular 5-FU catabolism and augmenting its cytotoxic effects. Our findings identify neddylation as a previously unrecognized regulatory mechanism governing DPD protein stability and activity. This work identifies the neddylation-DPD axis as a novel therapeutic target and provides a strong rationale for combining NAE inhibition with 5-FU-based chemotherapy in gastric cancer. SIGNIFICANCE STATEMENT: This study establishes neddylation as a previously unrecognized regulatory mechanism that stabilizes the drug-metabolizing enzyme dihydropyrimidine dehydrogenase to drive 5-fluorouracil resistance in gastric cancer. It further unveils that inhibiting neddylation with MLN4924 selectively depletes tumor dihydropyrimidine dehydrogenase, enhancing chemotherapy efficacy without increasing toxicity, thereby proposing a targeted strategy to overcome chemoresistance.

5-Fluorouracil (5-FU) is widely used in the treatment of various solid tumors; however, its clinical use is often limited by hepatotoxicity. Boldine, an aporphine alkaloid, has been reported to possess antioxidant, anti-inflammatory, and hepatoprotective properties. The present study evaluated the hepatoprotective potential of boldine against 5-FU-induced liver injury in Wistar rats. Hepatotoxicity was induced by a single intraperitoneal injection of 5-FU (150 mg/kg). Following 5-FU administration, rats were orally treated with boldine (10 or 20 mg/kg body weight) or the standard hepatoprotective agent silymarin (100 mg/kg body weight) once daily for 7 days. At the end of the experimental period, serum transaminases, oxidative stress markers, antioxidant status, and hepatic gene expression related to oxidative stress and inflammation were evaluated using PCR analysis. Administration of 5-FU was associated with increased serum transaminases and oxidative stress markers, consistent with hepatocellular injury. In addition, 5-FU exposure was accompanied by reduced mRNA expression of antioxidant-related genes (Nrf2, NQO1, and HO-1) and increased expression of CUL3 and inflammatory/apoptosis-related markers (ASK1, ERK1, and NF-κB), along with decreased Bcl-2 expression. Boldine treatment significantly attenuated biochemical and molecular alterations, enhanced dihydropyrimidine dehydrogenase expression involved in 5-FU metabolism, and ameliorated histopathological changes. Overall, these findings suggest that boldine may exert hepatoprotective effects against 5-FU-induced liver injury, potentially through modulation of oxidative stress and inflammatory pathways.

Standard adjuvant treatment for stage III colorectal cancer (CRC) combines intravenous oxaliplatin with a fluoropyrimidine, either with intravenous 5-fluorouracil with folinic acid oxaliplatin, capecitabine (CAPOX). This study aims to describe the toxicity of these two regimens in patients with a diverting stoma. We conducted a retrospective, single-center study of patients with stage III CRC who had a diverting stoma and received adjuvant treatment with either FOLFOX or CAPOX between January 2016 and July 2023. Clinical characteristics and treatment details were extracted from electronic health records. The primary end point was the rate of hospitalization during adjuvant chemotherapy. Secondary end points included treatment compliance and toxicity. A total of 87 patients with CRC and a diverting stoma received treatment with either CAPOX (n = 37) or modified FOLFOX regimen: oxaliplatin, 5-fluorouracil, folinic acid (mFOLFOX6) (n = 50). No patient had dihydropyrimidine dehydrogenase deficiency. Baseline clinical characteristics were similar between groups. The hospitalization rate was 35% with CAPOX and 18% with FOLFOX (P = .07). Most hospitalizations occurred during the first cycles of adjuvant treatment and were primarily related to digestive toxicities. Higher hospitalization rates with CAPOX were observed across all subgroups, regardless of sex, age, performance status, or renal function. Patients with a diverting stoma who receive adjuvant chemotherapy with fluoropyrimidines and oxaliplatin are at higher risk of severe digestive toxicities when treated with the CAPOX regimen. The mFOLFOX6 regimen appears to be safer alternative in this population.

Fluoropyrimidines are among the most useful drugs in oncology with an established record of efficacy and safety. A minority of oncology patients bear genetic variants with reduced activity of the main enzyme catabolizing these drugs, dihydropyrimidine dehydrogenase (DPYD) and may be prone to severe or even lethal adverse effects. We reviewed the records of gastrointestinal and breast cancer patients treated in our cancer center for the identification of cases that had DPYD genetic testing for variants and received treatment with fluoropyrimidines. The records of patients fulfilling these criteria were retrieved, and the prevalence of the different variants and their clinical implications and outcomes were recorded. The overall prevalence of four common DPYD variants was 7.3% (10 of 137 patients). Most prevalent variant was the haplotype HapB3 (five patients, 3.6%), followed by the DPYD p.D949V variant (3 patients, 2.2%), while one patient each (0.7%) had the two null variants DPYD*2A and DPYD*13. A sizable minority of oncology patients bear variants of DPYD with reduced activity and may be at increased risk of fluoropyrimidine toxicities if treated at full doses. However, variability within the same genotype exists.

Abstract Background: Capecitabine is a valid monotherapy option in multiple metastatic breast cancer (mBC) subtypes. While case reports of capecitabine-related hepatic steatosis have been published, its prevalence remains unknown. Traditional monitoring relies primarily on biochemical tests, which may not fully capture hepatic changes. Our aim was to evaluate the prevalence of capecitabine-related hepatic steatosis and determine whether routinely performed [18F]FDG PET/CT could quantify hepatic changes during capecitabine treatment, including in patients without visually evident steatosis. Methods: We conducted a retrospective analysis of patients with mBC treated with capecitabine between 2014 and 2021 at Gustave Roussy. Clinico-biological variables (age, BMI, metastatic sites, therapy line, dihydropyrimidine dehydrogenase (DPD) testing, biochemical liver tests) at baseline were collected. Baseline PET/CT, first evaluation (<180 days), and last PET/CT scans under capecitabine treatment were analyzed to assess hepatic steatosis prevalence. Hepatic steatosis was defined by visual assessment as a decreased liver attenuation relative to spleen and/or increased hepatic vessel visualization on unenhanced CT. Finally, hepatic changes were quantified using standardized uptake values (SUV) on PET images and Hounsfield units (HU) on CT images. Results: The study cohort included 183 patients with mBC. The median age at capecitabine initiation was 66.3 years (range 51-96), and median BMI was 24.2 (range 14.7-39.1). The most frequent metastatic sites were bone (67%), liver (40%) and lymph nodes (33%), with a median of 2 metastatic sites per patient. 86% of patients received capecitabine as monotherapy. Capecitabine was administered across multiple treatment lines: 1st line (14%), 2nd line (32%), 3rd line (31%) and >= 4th line (23%). When available, DPD testing revealed partial deficit in 16/138 patients (12%). Median treatment duration was 298 days (range 80-2162). Sequential imaging analysis was available for 122 patients with both baseline and first evaluation PET/CT scans, and 77 patients at capecitabine discontinuation. No patients showed hepatic steatosis at baseline. At first evaluation, hepatic steatosis was observed in 3/122 patients (2.5%). All 3 patients with steatosis underwent dose reduction due to other capecitabine toxicities (hand-foot syndrome in 2 patients, general condition deterioration requiring weight-based dose adjustment in 1 patient), resulting in resolution of CT steatosis in 2 patients. At final PET/CT, steatosis was present in 4/77 patients (5.2%) and resolved in 3 patients on follow-up imaging after changing treatment line. All patients who developed visible steatosis received capecitabine monotherapy. Quantitative analysis revealed small magnitude hepatic changes during capecitabine treatment: mean HU liver decreased by -2.3 units (95%CI -4.0 to -0.6, p=0.007) and SUVmean liver increased by +0.2 units (95% CI +0.1 to +0.2, p<0.001). These quantitative changes occurred independently of baseline liver metastases presence (p=0.470 for HU, p=0.881 for SUVmean). Among clinico-biological variables, only baseline bilirubin showed significant correlation with HU changes (p=0.044), while other liver function tests, BMI, and DPD status showed no significant association. Conclusions: This study provides a first estimate of capecitabine-induced hepatic steatosis prevalence, and initial evidence supporting the feasibility of using follow-up [18F]FDG PET/CT to assess its occurrence and reversibility after dose reduction or discontinuation. Further studies are needed to evaluate the potential impact of systematic steatosis evaluation on imaging follow-up, including shorter follow-up intervals and preemptive dose adjustments. Citation Format: A. Daverio, T. Ben Ahmed, J. M Ribeiro, C. Bousrih, E. Rassy, M. Mokdad-Adi, S. Morbelli, B. Pistilli, D. Deandreis, A. Viansone, T. Henry. A retrospective analysis of capecitabine-induced imaging hepatic steatosis in metastatic breast cancer: prevalence and resolution [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS1-06-17.

Colorectal cancer (CRC) is one of the most prevalent malignancies worldwide. Variability in patient response to fluoropyrimidine-based neoadjuvant chemotherapy remains a critical challenge. We aimed to develop a nomogram that integrated dihydropyrimidine dehydrogenase (DPD) and methylenetetrahydrofolate reductase (MTHFR) expression to predict CapeOX (Capecitabine-Oxaliplatin) neoadjuvant chemotherapy outcomes in colorectal cancer. A prospective cohort of 36 advanced-stage CRC patients who received CapeOX neoadjuvant chemotherapy at Wahidin Sudirohusodo Hospital from 2024 to 2025 was analyzed. mRNA expression levels of TS, DPD, and MTHFR were measured in tissue and blood using quantitative RT-PCR. The chemotherapy response was evaluated by RECIST 1.1. Statistical analysis was performed to identify predictors of response, which were incorporated into a nomogram with bootstrap validation. Among the 36 patients with advanced colorectal cancer, response to CapeOX chemotherapy was observed in 50%. Blood-based gene profiling revealed that responders had significantly lower DPD and MTHFR expression compared with non-responders (both p<0.001), while TS showed no predictive relevance. A nomogram that integrated only blood DPD and MTHFR achieved outstanding discrimination (AUC 0.932, C-index 0.78) and demonstrated strong calibration, accurately predicting treatment response across probability ranges. These results established circulating DPD and MTHFR as powerful non-invasive biomarkers and validated the nomogram as a robust tool for individualized response prediction. A predictive nomogram that incorporated DPD and MTHFR has improved individualized estimation of CapeOX neoadjuvant chemotherapy response in CRC, supporting precision oncology strategies.<br />.

Ethyl gallate attenuates 5-fluorouracil induced hepatic injury via MAPK/NF-κB downregulation in rats.

Introduction5-Fluorouracil (5-FU) is a chemotherapeutic agent used in various malignancies. 5-FU-induced leukoencephalopathy is a rare but reversible neurotoxic effect occurring within days of administration. Symptoms include confusion, agitation, and cognitive disturbances, with severe cases potentially causing coma. Diagnosis is supported by magnetic resonance imaging (MRI) showing characteristic brain changes. Treatment involves discontinuing 5-FU and initiating supportive care. Most patients recover within one week, but relapse may occur with repeated exposure, making early recognition critical.Case reportA 42-year-old male with recurrent Stage IV gastric adenocarcinoma and chronic kidney disease developed progressive 5-FU-related leukoencephalopathy after repeated exposure. MRI findings and symptoms of confusion, disorientation, and memory deficits were consistent with 5-FU leukoencephalopathy. Initial work-up was inconclusive, therefore, treatment was continued. Neurologic symptoms worsened after further cycles, leading to chemotherapy discontinuation and surgical resection. Disease recurrence led to reinitiation of modified 5-FU therapy, triggering acute neurotoxicity confirmed by MRI.Management and outcomeThe patient was managed by discontinuing 5-FU, beginning high-dose intravenous thiamine and methylprednisolone, and providing supportive care. Neurologic symptoms including confusion, facial diplegia, and unsteady gait gradually resolved. By Day 9, he returned to baseline mental status without deficits.DiscussionEarly recognition and intervention in 5-FU-induced leukoencephalopathy is crucial, especially in patients with renal dysfunction or repeated exposures. Dihydropyrimidine dehydrogenase (DPD) deficiency has not been directly implicated in this condition. Metabolic disruption and thiamine depletion contribute to pathogenesis. Prompt 5-FU discontinuation and initiation of supportive care can hasten recovery. Clinical vigilance is imperative in patients with known risk factors.

To investigate the relationship between uracilemia (U)and dihydropyrimidine dehydrogenase (DPD) activity in peripheral blood mononuclear cells (PBMC) and whether they are influenced by renal or hepatic impairment. This retrospective study included 176 cancer patients with pre-treatment U (UPLC-MSMS assay) and PBMC-DPD (radioenzymatic assay) analyzed the same day (routine phenotyping). Blood renal (creatinine, BUN) and hepatic (ALT, AST, GGT, ALP, albumin, bilirubin) work-up was performed within 15days before or up to 4days after DPD phenotyping. Biochemical markers were categorized according to CTCAEv5.0 grade (G). Glomerular filtration rate (eGFR) was estimated (CKD-EPI and EKFC). Non-parametric statistical tests wereused. Prevalence of partial deficiency was 3.4 % based on PBMC-DPD (i.e.≤100 pmol/min/mg) and 6.3 % based on U (i.e.≥16 μg/L). No complete deficiency was observed. Fifteen patients out of 176 (8.5 %) exhibited discordant DPD status between PBMC activity and U. The correlation between PBMC-DPD and U was significant but weak (r=-0.309, p<0.001). PBMC-DPD (mean 246, median 235, range 62-926 pmol/min/mg prot) was not influenced by renal or hepatic impairment. U (mean 9.6, median 8.5, range 1.7-57.8 μg/L) was significantly higher in patients with elevated BUN (normal vs. >1-UNL, p=0.009), GGT (G0 vs. G1 vs. G2 vs. G3, p<0.001), AST (G0 vs. G≥1, p=0.015), or with hypoalbuminemia (G0 vs. G≥1, p=0.045). Categorized creatinine or eGFR did not influenceU. It remains unclear whether renal and/or hepatic impairment acts as a confounding factor affecting the accuracy of uracilemia testing, or whether truly impacts DPD activity, suggesting caution in U interpretation.

Ending the Controversy Around Pretreatment Dihydropyrimidine Dehydrogenase (DPD/DPYD) Testing Heightens the Controversy Over Appropriate Fluoropyrimidine Dosing.

112 Background: Fluoropyrimidine (FP) chemotherapy can cause life-threatening toxicity, especially in patients with dihydropyrimidine dehydrogenase (DPD) deficiency. Four DPYD polymorphisms ( DPYD *2A, *13, p.Asp949Val, HapB3) are validated to increase FP toxicity risk but the association for many other DPYD variants has not been demonstrated. This study aims to identify additional DPYD polymorphisms that increase FP-related toxicity. Methods: This retrospective study used genetic data from the Michigan Genomics Initiative institutional biobank, which is linked to the University of Michigan Rogel Cancer Center electronic medical record. Adults treated with standard doses of systemic FP (5-fluorouracil or capecitabine) for any tumor type with available genetic data were included. The primary toxicity endpoint was a composite of CTCAE grade ≥3 toxicity or treatment modification due to toxicity in the first two FP cycles. A literature-curated list of suspected deleterious DPYD variants beyond the four validated variants was classified as uncommon (minor allele frequency &lt;0.01) or common. Uncommon variants were analyzed in aggregate whereas common variants were analyzed individually, excluding patients carrying validated variants. The genetic association with toxicity was analyzed via logistic regression adjusted for demographic and treatment factors. Toxicity prediction was estimated using positive (PPV) and negative (NPV) predictive values for testing the validated variants with and without the uncommon variants. Results: Among 849 eligible patients, the composite toxicity endpoint occurred in 25.1% (16.5% grade ≥3 toxicity, 23.2% treatment modification). Genetic data were available for four uncommon and six common suspected deleterious DPYD variants. In the primary analysis of 799 patients who did not carry a validated variant, carriers of an uncommon variant (1.1% of patients; Table 1) had significantly higher risk of toxicity than non-carriers (66.7% vs. 23.7%; adjusted OR 7.36; 95% CI 1.75–38.2; p=0.009). None of the common variants were associated with toxicity (data not shown). Toxicity prediction in the entire cohort (n=849) was slightly improved by testing the uncommon and validated variants vs. testing only the validated variants (PPV= 44.1% vs. 40.0%, NPV=76.3% vs. 75.8%). Conclusions: Four uncommon DPYD variants that, in combination, increase FP toxicity risk and improve toxicity risk prediction were identified. Inclusion of these variants in DPYD testing would identify more patients with high toxicity risk who should receive adjusted FP doses to prevent severe toxicity. Incidence of toxicity among carriers of each uncommon variant. Uncommon variant Incidence of toxicity among carriers c.1757T&gt;C, p.Val586Ala, rs374527058 0% (0/1) c.557A&gt;G, p.Tyr186Cys, rs115232898 67% (4/6) c.274C&gt;G, p.Pro92Ala, rs143986398 100% (1/1) c.187A&gt;G, p.Lys63Glu, rs367619008 100% (1/1)

TPS250 Background: Fluoropyrimidine (FP) is a common chemotherapy class used across multiple tumor streams, including first line colorectal cancer management. Approximately 30% of patients develop serious toxicities with standard doses, potentially requiring hospitalization, intensive care admission and occasionally death. FP chemotherapy is primarily metabolized by dihydropyrimidine dehydrogenase (DPD, encoded by DPYD ), with DPD deficiency accounting for a significant number of serious toxicities. DPYD genotyping is a valid method of indirect measurement of DPD activity and has been implemented into routine care in some regions, enabling genotype-guided dosing. Despite mounting evidence, uptake of DPYD testing in Australia is currently sporadic and typically self-funded by the patient. This study will be the first to provide nation-wide prospective data on the feasibility and effectiveness of DPYD genotyping to direct FP dosing within the Australian health care system. Methods: This is a prospective, single arm, non-randomized study, aiming to recruit 5000 adult patients across Australia with solid organ malignancies intended to receive FP-based chemotherapy for the first time (trial registered 12/13/2023, Australian and New Zealand Cancer Trials Registry ACTRN12623001301651). DPYD genotyping will be performed for the key variants; c.1905+1G&gt;A, ( DPYD *2A, rs3918290), c.2846A&gt;T (rs67376798), c.1679T&gt;G (DPYD*13, rs55886062.1) and c.1236G&gt;A (rs56038477), with dose adjustments performed in accordance with published Australian guidelines. The primary outcome is incidence of serious (CTCAE v5.0 Grade 3+) FP-associated toxicities in the first 60 days in heterozygote DPYD variant carriers who receive a genotype-guided dose-adjustment, compared to: i) current standard of care (as assessed by a retrospective review of 500 consecutive cases); ii) contemporaneous cases without these variants treated with standard doses; and iii) variant carriers in this study that do not receive genotype-guided dosing. Primary endpoint data is anticipated to be completed by Q4 2027. Secondary outcomes include DPYD variant frequency, health economic and cost effectiveness analysis, and impact of dose adjustment on cancer outcomes. To date, 27 sites have been activated, with over 1200 participants enrolled. Completion of this study will inform a standardised approach for DPYD genotyping to minimise FP complications in Australia. Clinical trial information: ACTRN12623001301651 .

Dihydropyrimidine dehydrogenase (DPD) is a key phase I drug-metabolizing enzyme responsible for catabolizing fluoropyrimidine chemotherapeutics such as 5-fluorouracil, capecitabine and tegafur. Its activity shows marked interindividual variability due to both genetic polymorphisms and environmental factors. Reduced DPD activity results in excessive fluoropyrimidine exposure, potentially causing severe and life-threatening toxicities. Although DPD testing is recommended before initiating fluoropyrimidine therapy, no single analytical strategy has been universally adopted, leading to substantial variability in clinical practice. While genotyping offers high specificity, phenotyping provides greater sensitivity by capturing both genetic and non-genetic influences on enzyme activity. In this study, we developed and validated an HPLC-MS/MS assay for the simultaneous quantification of endogenous uracil and dihydrouracil in human plasma, widely used endogenous biomarkers for DPD phenotyping. Sample preparation involved extraction with lipid removal, followed by chromatographic separation on porous graphitic carbon (100×2.1mm, 5μm; Hypercarb™, Thermo Scientific). Validation was performed according to international guidelines, demonstrating appropriate selectivity, sensitivity, linearity, accuracy, precision, carry-over, and stability. The method was applied to 28 human plasma samples, with uracil concentrations compared against an external laboratory using an independent LC-MS/MS platform. Deming regression showed no significant constant bias at the 95% confidence level, although underestimation occurred at higher concentrations (y=0.63×+4.86). Bland-Altman analysis indicated a small mean difference of -0.02ng/mL but wide limits of agreement (-9.61 to +9.57ng/mL), highlighting the impact of analytical variability near clinical decision thresholds. Further studies are warranted to evaluate the clinical utility of this approach in larger cohorts and to assess its correlation and complementarity with DPD genotyping and clinical outcomes. This method represents a valuable analytical tool to support personalized fluoropyrimidine-based chemotherapy in patients with solid tumors.

The purpose of this study was to determine long-term outcomes and prognostic factors in patients with locally advanced rectal cancer who received preoperative chemoradiotherapy with oral dihydropyrimidine dehydrogenase (DPD)-inhibiting fluoropyrimidines. Fifty-seven locally advanced rectal cancer patients who underwent preoperative chemoradiotherapy (CRT) with oral DPD-inhibitory fluoropyrimidines from 2006 to 2013 were retrospectively enrolled in this study. Patients with T3-T4 lower rectal cancer were irradiated once daily (2 Gy) with a total dose of 40 Gy, and chemotherapy was administered with tegafur-uracil (300 mg / m2 / day) or S-1 (80 mg / m2 / day) on radiation days. Five-year overall survival was 77.8% and 5-year disease-free survival was 65.1%. Recurrence was observed in 20 patients (35.1%) and local recurrence in 9 patients (15.8%). Multivariate analysis of prognostic factors for overall survival identified pre-CRT lateral lymph node metastasis and circumferential resection margin as independent prognostic factors, and ypStage as an independent prognostic factor for disease-free survival. Evaluation of lateral lymph node before CRT is useful in predicting prognosis in patients with locally advanced lower rectal cancer treated with preoperative chemoradiotherapy with oral DPD-inhibiting fluoropyrimidines, and surgical planning to ensure a 1-mm circumferential resection margin is important for improving prognosis. J. Med. Invest. 73 : 62-67, February, 2026.

Fluoropyrimidine anticancer agents, exemplified by 5-fluorouracil (5-FU), induce severe adverse effects-such as myelosuppression, emesis, diarrhea, and hand-foot syndrome-in approximately 10-30% of patients. As such toxicities can result in delays or discontinuation of therapy, accurate prediction of drug response prior to treatment initiation is of critical importance. The metabolic degradation of 5-FU is primarily mediated by the drug-metabolizing enzymes dihydropyrimidine dehydrogenase (DPD) and dihydropyrimidinase (DHPase). These enzymes are encoded by the DPYD and DPYS genes, respectively; polymorphisms in these genes that reduce or abolish enzymatic activity lead to elevated systemic concentrations of 5-FU, thereby increasing the risk of severe toxicity. In Caucasian populations, four DPYD polymorphisms have been identified as predictive markers of adverse drug reactions. However, these variants are rarely observed in Japanese individuals, and reliable pharmacogenomic biomarkers remain largely unreported in this population. To address this gap, we conducted a comprehensive in vitro functional analysis of DPD and DHPase activity of DPYD and DPYS variants identified through large-scale whole-genome sequencing databases. This review summarizes our findings and elucidates the underlying mechanisms affecting the function of 5-FU-metabolizing enzymes, as revealed by our prior research.

5-fluorouracil-based regimen FOLFOX (5-fluorouracil, folinic acid, oxaliplatin) is the first-line chemotherapeutic for metastatic colorectal cancer patients. On the other hand, the medicinal herb Patrinia villosa (Thunb.) Dufr. [Caprifoliaceae] is commonly prescribed by Chinese medicine practitioners to colorectal cancer patients in recent years. Thus, the possibility of concurrent use of P. villosa with FOLFOX occurs. The present study aimed to investigate whether P. villosa water extract would interfere with the metabolism and anti-tumor efficacy of chemotherapy regimen FOLFOX in preclinical colon cancer models. Human HCT-116 xenograft-bearing and murine Colon-26 orthotopic tumor-bearing mouse models were established and received FOLFOX and/or PV water extract treatments for 3weeks. FOLFOX was administered intravenously once a week and PV water extract was administered daily by oral gavage except on the FOLFOX administration day. The levels of metabolising enzymes dihydropyrimidine dehydrogenase (for 5-fluorouracil), serine hydroxymethyltransferase (for folinic acid), as well as molecules, cysteine, methionine and reduced glutathione, involved in oxaliplatin biotransformation, were determined in plasma of xenograft-bearing mice receiving FOLFOX and/or PV water extract treatment. The tumor progression, metastasis and tumor microenvironment in mice were also assessed. The PV water extract treatment did not affect the plasma levels of metabolising enzymes of 5-fluorouracil and folinic acid, nor the plasma levels of cysteine, methionine and reduced glutathione in HCT-116 xenograft-bearing mice. On the other hand, the combined treatment of FOLFOX and PV water extract inhibited both HCT-116 and Colon-26 tumor growth, with HCT-116 tumor weight of FOLFOX plus PV water extract group being the lowest among all treated groups. PV water extract treatment could further potentiate the anti-angiogenesis, apoptosis and immunomodulatory effect of FOLFOX in colon tumors. This is the first report to demonstrate that no observable interference induced by PV water extract on the plasma levels of selected metabolism enzymes and precursor molecules of FOLFOX component drugs in colon tumor-bearing mice. The combined use of FOLFOX plus PV water extract resulted in better anti-tumor efficacy in colon cancer mouse models than single treatment alone. The beneficial potentials of combined use of FOLFOX and PV water extract has been scientifically verified, which supports the clinical use in colon cancer management.

Introduction: Deficiency of the dihydropyrimidine dehydrogenase enzyme can result in capecitabine-related toxicity due to genetic alterations in the DPYD gene, leading to complete or partial DPD deficiency and poor or intermediate metabolizer phenotypes. The distribution of DPYD variants varies across populations. While routine DPYD genotyping is recommended in Western populations, data from India, particularly from next-generation sequencing (NGS)-based studies, remain limited. Methods: This exploratory analysis was conducted within the D-TORCH trial, a randomized, double-blind, placebo-controlled study evaluating topical diclofenac for prevention of capecitabine-induced hand-foot syndrome. Germline whole-exome sequencing was performed in consenting patients prior to capecitabine initiation. DPYD variants were identified using an NGS pipeline, annotated via ANNOVAR and PharmGKB, and classified according to CPIC guidelines. Results: Seventy-six patients underwent DPYD sequencing; 54 (71%) carried at least one variant and 22 (29%) were wild-type. Thirteen coding or splice-site variants were identified, including three (3.9%) associated with an intermediate metabolizer phenotype; no poor metabolizers were detected. The most common variants were classified as normal metabolizers. Grade 2 toxicity occurred in 63.6% of variant carriers and 55.6% of wild-type patients, with diarrhea and mucositis being most frequent. No significant association was observed between DPYD variant status and toxicity. Discussion: This first NGS-based DPYD report from India highlights the low prevalence of clinically actionable variants. Larger studies are required to validate these findings and guide population-specific fluoropyrimidine dosing strategies.

Fluoropyrimidines are a vital component of chemotherapy regimens. Deleterious DPYD variants reduce activity of dihydropyrimidine dehydrogenase, the rate-limiting enzyme of fluoropyrimidine catabolism, resulting in reduced fluoropyrimidine clearance and elevated risk of life-threatening toxicities. DPYD genotype-guided fluoropyrimidine therapy can mitigate the risk of severe life-threatening toxicities, but adoption of testing globally has been limited. We developed a 91-item survey investigating global DPYD implementation strategies to gain insight into common practices and successful strategies. The survey was disseminated to Pharmacogenomics Global Research Network Implementation Working Group members consisting of 54 health care sites across 15 countries. Survey responses were received from 28 sites (52%) across 9 countries. Over 80% of sites implemented, or planned to implement, a preemptive testing strategy (i.e., before a fluoropyrimidine is administered) leveraging the electronic health record (EHR) to disseminate DPYD results to providers. All sites created infrastructure to support DPYD testing (e.g., order sets, EHR decision support), but 70% of sites indicated reliance on clinicians to remember test ordering. Only 2 sites reported high DPYD testing rates (> 75%) among patients planned to receive a fluoropyrimidine. Most sites (57%) used in-house clinical laboratories that tested for the majority of DPYD Tier 1 variants. Among sites that had implemented DPYD testing, the median turnaround time was 10 days. Few sites indicated that a high percentage (> 75%) of DPYD results were returned before fluoropyrimidine administration. Our results suggest that additional implementation strategies are needed, addressing barriers and facilitators of DPYD testing.