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

BackgroundFluoropyrimidines are used in chemotherapy combinations for multiple cancers. Deficient dihydropyrimidine dehydrogenase activity can lead to severe life‐threatening toxicities. DPYD*2A polymorphism is one of the most studied variants. The study objective was to document the impact of implementing this test in routine clinical practice.MethodsWe retrospectively performed chart reviews of all patients who tested positive for a heterozygous or homozygous DPYD*2A mutation in samples obtained from patients throughout the province of Quebec, Canada.ResultsDuring a period of 17 months, 2,617 patients were tested: 25 patients tested positive. All were White. Twenty‐four of the 25 patients were heterozygous (0.92%), and one was homozygous (0.038%). Data were available for 20 patients: 15 were tested upfront, whereas five were identified after severe toxicities. Of the five patients confirmed after toxicities, all had grade 4 cytopenias, 80% grade ≥3 mucositis, 20% grade 3 rash, and 20% grade 3 diarrhea. Eight patients identified with DPYD*2A mutation prior to treatment received fluoropyrimidine‐based chemotherapy at reduced initial doses. The average fluoropyrimidine dose intensity during chemotherapy was 50%. No grade ≥3 toxicities were observed. DPYD*2A test results were available in an average of 6 days, causing no significant delays in treatment initiation.ConclusionUpfront genotyping before fluoropyrimidine‐based treatment is feasible in clinical practice and can prevent severe toxicities and hospitalizations without delaying treatment initiation. The administration of chemotherapy at reduced doses appears to be safe in patients heterozygous for DPYD*2A.Implications for PracticeFluoropyrimidines are part of chemotherapy combinations for multiple cancers. Deficient dihydropyrimidine dehydrogenase activity can lead to severe life‐threatening toxicities. This retrospective analysis demonstrates that upfront genotyping of DPYD before fluoropyrimidine‐based treatment is feasible in clinical practice and can prevent severe toxicities and hospitalizations without delaying treatment initiation. This approach was reported previously, but insufficient data concerning its application in real practice are available. This is likely the first reported experience of systematic DPYD genotyping all over Canada and North America as well.     

The Prevalence of DPYD*9A (c.85T>C) Genotype and the Genotype-Phenotype Correlation in Patients with Gastrointestinal Malignancies Treated With Fluoropyrimidines: Updated Analysis

IntroductionThe dihydropyrimidine dehydrogenase gene (DPYD)*9A (c.85T>C) genotype is relatively common. The correlation between DPYD*9A genotype and dihydropyrimidine dehydrogenase (DPD) deficiency phenotype is controversial. In a cohort of 28 patients, DPYD*9A was the most commonly diagnosed variant (13 patients [46%]) and there was a noticeable genotype-phenotype correlation. In this study we genotyped a larger cohort of a mixed racial background to explore the prevalence of DPYD*9A variant and to confirm the genotype-phenotype correlation.Patients and MethodsBetween 2011 and 2018, in addition to genotyping for high-risk DPYD variants (DPYD*2A, DPYD*13 and DPYD*9B), genotyping for DPYD*9A variant was performed on 113 patients with gastrointestinal malignancies treated with fluoropyrimidines. Fluoropyrimidines-associated toxicity was graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (version 5.0). Fisher exact test was used for statistical analysis.ResultsHeterozygous and homozygous DPYD*9A genotypes were identified in 46 (41%) and 11 (10%) patients, respectively. Among patients with DPYD*9A genotypes (n = 57), men and women represented 30 (53%) and 27 (47%) patients, respectively. Caucasian, African American, and other ethnicities represented 29 (50.9%), 26 (45.6%), and 2 (3.5%) patients, respectively. Grade 3/4 toxicities were experienced in 26 patients with DPYD*9A genotype (3 patients had homozygous status) and in 20 patients with wild type DPYD*9A (P = .4405). In patients who received full-dose fluoropyrimidines (n = 85), Grade 3/4 toxicities were experienced in 22 patients with DPYD*9A genotype (2 patients had homozygous status), and in 17 patients with wild type DPYD (P = .8275).ConclusionIn our updated analysis, the prevalence of heterozygous and homozygous DPYD*9A genotypes were 41% and 10%, respectively. The correlation between DPYD*9A genotype and DPD clinical phenotype was not reproduced. The noticeable correlation that we previously reported is likely because of small sample size and selection bias.     

Prospective DPYD genotyping to reduce the risk of fluoropyrimidine-induced severe toxicity: Ready for prime time

5-Fluorouracil (5-FU) and capecitabine (CAP) are among the most frequently prescribed anticancer drugs. They are inactivated in the liver by the enzyme dihydropyrimidine dehydrogenase (DPD). Up to 5% of the population is DPD deficient and these patients have a significantly increased risk of severe and potentially lethal toxicity when treated with regular doses of 5-FU or CAP. DPD is encoded by the gene DPYD and variants in DPYD can lead to a decreased DPD activity. Although prospective DPYD genotyping is a valuable tool to identify patients with DPD deficiency, and thus those at risk for severe and potential life-threatening toxicity, prospective genotyping has not yet been implemented in daily clinical care. Our goal was to present the available evidence in favour of prospective genotyping, including discussion of unjustified worries on cost-effectiveness, and potential underdosing. We conclude that there is convincing evidence to implement prospective DPYD genotyping with an upfront dose adjustment in DPD deficient patients. Immediate benefit in patient care can be expected through decreasing toxicity, while maintaining efficacy.     

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

The fluoropyrimidine anticancer drugs, especially 5-fluorouracil (5-FU) and capecitabine, are frequently prescribed for several types of cancer, including breast, colorectal, head and neck and gastric cancer. In the current drug labels of 5-FU and capecitabine in the European Union and the United States, no adaptive dosing strategies are incorporated for polymorphic metabolism of 5-FU. Although treatment with fluoropyrimidines is generally well tolerated, a major clinical limitation is that a proportion of the treated population experiences severe, sometimes life-threatening, fluoropyrimidine-related toxicity. This toxicity is strongly affected by interindividual variability in activity of dihydropyrimidine dehydrogenase (DPD), the main metabolic enzyme for inactivation of fluoropyrimidines, with an estimated 3%–8% of the population being partially DPD deficient. A reduced functional or abrogated DPD enzyme is often caused by genetic polymorphisms in DPYD, the gene encoding for DPD, and heterozygous carriers of such DPYD polymorphisms have a partial DPD deficiency. When these partially DPD deficient patients are treated with a full dose of fluoropyrimidines, they are generally exposed to toxic levels of 5-FU and its metabolites, and the risk of developing severe treatment-related toxicity is therefore significantly increased.Currently, functional and clinical validity is well established for four DPYD variants (DPYD*2A, c.2846A>T, c.1679T>G and c.1236G>A), as those variants have retrospectively and in a large population study prospectively been shown to be associated with increased risk of fluoropyrimidine-associated toxicity. Patient safety of fluoropyrimidine treatment can be significantly improved by pre-emptive screening for DPYD genotype variants and dose reductions in heterozygous DPYD variant allele carriers, thereby normalizing 5-FU exposure. Based on the critical appraisal of currently available data, adjusting the labels of capecitabine and 5-FU by including recommendations on pre-emptive screening for DPYD variants and DPYD genotype-guided dose adjustments should be the new standard of care.     

Pharmacogenetic variants in the DPYD,TYMS, CDA and MTHFR genes are clinically significant predictors of fluoropyrimidine toxicity

Background:

Fluoropyrimidine drugs are extensively used for the treatment of solid cancers. However, adverse drug reactions are a major clinical problem, often necessitating treatment discontinuation. The aim of this study was to identify pharmacogenetic markers predicting fluoropyrimidine toxicity.

Methods:

Toxicity in the first four cycles of 5-fluorouracil or capecitabine-based chemotherapy were recorded for a series of 430 patients. The association between demographic variables, DPYD, DPYS, TYMS, MTHFR, CDA genotypes, and toxicity were analysed using logistic regression models.

Results:

Four DPYD sequence variants (c.1905+1G>A, c.2846A>T, c.1601G>A and c.1679T>G) were found in 6% of the cohort and were significantly associated with grade 3–4 toxicity (P<0.0001). The TYMS 3′-untranslated region del/del genotype substantially increased the risk of severe toxicity (P=0.0123, odds ratio (OR)=3.08, 95% confidence interval (CI): 1.38–6.87). For patients treated with capecitabine, a MTHFR c.1298CC homozygous variant genotype predicted hand–foot syndrome (P=4.1 × 10⁻⁶, OR=9.99, 95% CI: 3.84–27.8). The linked CDA c.−92A>G and CDA c.−451C>T variants predicted grade 2–4 diarrhoea (P=0.0055, OR=2.3, 95% CI: 1.3–4.2 and P=0.0082, OR=2.3, 95% CI: 1.3–4.2, respectively).

Conclusion:

We have identified a panel of clinically useful pharmacogenetic markers predicting toxicity to fluoropyrimidine therapy. Dose reduction should be considered in patients carrying these sequence variants.     

Cost-effectiveness of DPYD Genotyping Prior to Fluoropyrimidine-based Adjuvant Chemotherapy for Colon Cancer

BackgroundAdjuvant fluoropyrimidine-based chemotherapy substantially reduces recurrence and mortality after resection of stage 3 colon cancer. While standard doses of 5-fluorouracil and capecitabine are safe for most patients, the risk of severe toxicity is increased for the approximately 6% of patients with dihydropyimidine dehydrogenase (DPD) deficiency caused by pathogenic DPYD gene variants. Pre-treatment screening for pathogenic DPYD gene variants reduces severe toxicity but has not been widely adopted in the United States.MethodsWe conducted a cost-effectiveness analysis of DPYD genotyping prior to fluoropyrimidine-based adjuvant chemotherapy for stage 3 colon cancer, covering the c.1129-5923C>G (HapB3), c.1679T>G (*13), c.1905+1G>A (*2A), and c.2846A>T gene variants. We used a Markov model with a 5-year horizon, taking a United States healthcare perspective. Simulated patients with pathogenic DPYD gene variants received reduced-dose fluoropyrimidine chemotherapy. The primary outcome was the incremental cost-effectiveness ratio (ICER) for DPYD genotyping.ResultsCompared with no screening for DPD deficiency, DPYD genotyping increased per-patient costs by $78 and improved survival by 0.0038 quality-adjusted life years (QALYs), leading to an ICER of $20,506/QALY. In 1-way sensitivity analyses, The ICER exceeded $50,000 per QALY when the cost of the DPYD genotyping assay was greater than $286. In probabilistic sensitivity analysis using a willingness-to-pay threshold of $50,000/QALY DPYD genotyping was preferred to no screening in 96.2% of iterations.ConclusionAmong patients receiving adjuvant chemotherapy for stage 3 colon cancer, screening for DPD deficiency with DPYD genotyping is a cost-effective strategy for preventing infrequent but severe and sometimes fatal toxicities of fluoropyrimidine chemotherapy.     

Clinical validity of a DPYD‐based pharmacogenetic test to predict severe toxicity to fluoropyrimidines

Pre‐therapeutic DPYD pharmacogenetic test to prevent fluoropyrimidines (FL)‐related toxicities is not yet common practice in medical oncology. We aimed at investigating the clinical validity of DPYD genetic analysis in a large series of oncological patients. Six hundred three cancer patients, treated with FL, have been retrospectively tested for eight DPYD polymorphisms (DPYD‐rs3918290, DPYD‐rs55886062, DPYD‐rs67376798, DPYD‐rs2297595, DPYD‐rs1801160, DPYD‐rs1801158, DPYD‐rs1801159, DPYD‐rs17376848) for association with Grade ≥3 toxicity, developed within the first three cycles of therapy. DPYD‐rs3918290 and DPYD‐rs67376798 were associated to Grade ≥3 toxicity after bootstrap validation and Bonferroni correction (p = 0.003, p = 0.048). DPYD‐rs55886062 was not significant likely due to its low allelic frequency, nonetheless one out of two heterozygous patients (compound heterozygous with DPYD‐rs3918290) died from toxicity after one cycle. Test specificity for the analysis of DPYD‐rs3918290, DPYD‐rs55886062 and DPYD‐rs67376798 was assessed to 99%. Among the seven patients carrying one variant DPYD‐rs3918290, DPYD‐rs55886062 or DPYD‐rs67376798 allele, not developing Grade ≥3 toxicity, 57% needed a FL dose or schedule modification for moderate chronic toxicity. No other DPYD polymorphism was associated with Grade ≥3 toxicity. Our data demonstrate the clinical validity and specificity of the DPYD‐rs3918290, DPYD‐rs55886062, DPYD‐rs67376798 genotyping test to prevent FL‐related Grade ≥3 toxicity and to preserve treatment compliance, and support its introduction in the clinical practice.     

Rs895819 in MIR27A improves the predictive value of DPYD variants to identify patients at risk of severe fluoropyrimidine‐associated toxicity

The objective of this study was to determine whether genotyping of MIR27A polymorphisms rs895819A>G and rs11671784C>T can be used to improve the predictive value of DPYD variants to identify patients at risk of severe fluoropyrimidine‐associated toxicity (FP‐toxicity). Patients treated previously in a prospective study with fluoropyrimidine‐based chemotherapy were genotyped for rs895819 and rs11671784, and DPYD c.2846A>T, c.1679T>G, c.1129‐5923C>G and c.1601G>A. The predictive value of MIR27A variants for early‐onset grade ≥3 FP‐toxicity, alone or in combination with DPYD variants, was tested in multivariable logistic regression models. Random‐effects meta‐analysis was performed, including previously published data. A total of 1,592 patients were included. Allele frequencies of rs895819 and rs11671784 were 0.331 and 0.020, respectively. In DPYD wild‐type patients, MIR27A variants did not affect risk of FP‐toxicity (OR 1.3 for ≥1 variant MIR27A allele vs. none, 95% CI: 0.87–1.82, p = 0.228). In contrast, in patients carrying DPYD variants, the presence of ≥1 rs895819 variant allele was associated with increased risk of FP‐toxicity (OR 4.9, 95% CI: 1.24–19.7, p = 0.023). Rs11671784 was not associated with FP‐toxicity (OR 2.9, 95% CI: 0.47?18.0, p = 0.253). Patients carrying a DPYD variant and rs895819 were at increased risk of FP‐toxicity compared to patients wild type for rs895819 and DPYD (OR 2.4, 95% CI: 1.27–4.37, p = 0.007), while patients with a DPYD variant but without a MIR27A variant were not (OR 0.3 95% CI: 0.06?1.17, p = 0.081). In meta‐analysis, rs895819 remained significantly associated with FP‐toxicity in DPYD variant allele carriers, OR 5.4 (95% CI: 1.83–15.7, p = 0.002). This study demonstrates the clinical validity of combined MIR27A/DPYD screening to identify patients at risk of severe FP‐toxicity.     

The role of pharmacogenetics in capecitabine efficacy and toxicity

Capecitabine is an oral prodrug of 5-fluorouracil (5-FU) and approved for treatment of various malignancies. Hereditary genetic variants may affect a drug’s pharmacokinetics or pharmacodynamics and account for differences in treatment response and adverse events among patients. In this review we present the current knowledge on genetic variants, commonly single-nucleotide polymorphisms (SNPs), tested in cohorts of cancer patients and possibly useful for prediction of capecitabine efficacy or toxicity. Capecitabine is activated to 5-FU by CES, CDA and TYMP, of which SNPs in CDA and CES2 were found to be associated with efficacy and toxicity. In addition, variants in genes of the 5-FU metabolic pathway, including TYMS, MTHFR and DPYD also influenced capecitabine efficacy and toxicity. In particular, well-known SNPs in TYMS and DPYD as well as putative DPYD SNPs had an association with clinical outcome as well as adverse events. Inconsistent findings may be attributable to factors related to ethnic differences, sample size, study design, study endpoints, dosing schedule and the use of multiple agents. Of the SNPs described in this review, dose reduction of fluoropyrimidines based on the presence of DPYD variants ^*2A (rs3918290), ^*13 (rs55886062), −2846A>T (rs67376798) and −1236G>A/HapB3 (rs56038477) has already been recommended. Other variants merit further validation to establish their definite role in explanation of interindividual differences in the outcome of capecitabine-based therapy.     

Impact of age on sorafenib outcomes in hepatocellular carcinoma: an international cohort study

Background There is no consensus on the effect of sorafenib dosing on efficacy and toxicity in elderly patients with hepatocellular carcinoma (HCC). Older patients are often empirically started on low-dose therapy with the aim to avoid toxicities while maximising clinical efficacy. We aimed to verify whether age impacts on overall survival (OS) and whether a reduced starting dose impacts on OS or toxicity experienced by the elderly.Methods In an international, multicentre cohort study, outcomes for those aged <75 or ≥75 years were determined while accounting for common prognostic factors and demographic characteristics in univariable and multivariable models.Results Five thousand five hundred and ninety-eight patients were recruited; 792 (14.1%) were aged ≥75 years. The elderly were more likely to have larger tumours (>7 cm) (39 vs 33%, p < 0.01) with preserved liver function (67 vs 57.7%) (p < 0.01). No difference in the median OS of those aged ≥75 years and <75 was noted (7.3 months vs 7.2 months; HR 1.00 (95% CI 0.93–1.08), p = 0.97). There was no relationship between starting dose of sorafenib 800 mg vs 400 mg/200 mg and OS between those <75 and ≥75 years. The elderly experienced a similar overall incidence of grade 2–4 sorafenib-related toxicity compared to <75 years (63.5 vs 56.7%, p = 0.11). However, the elderly were more likely to discontinue sorafenib due to toxicity (27.0 vs 21.6%, p < 0.01). This did not vary between different starting doses of sorafenib.Conclusions Clinical outcomes in the elderly is equivalent to patients aged <75 years, independent of dose of sorafenib prescribed.Subject terms: Targeted therapies, Hepatocellular carcinoma     

Prospective Randomized Phase II Study of Stereotactic Body Radiotherapy (SBRT) vs. Conventional Fractionated Radiotherapy (CFRT) for Chinese Patients with Early-Stage Localized Prostate Cancer

Background: Stereotactic body radiotherapy (SBRT) has potential radiobiologic and economic advantages over conventional fractionated radiotherapy (CFRT) in localized prostate cancer (PC). This study aimed to compare the effects of these two distinct fractionations on patient-reported quality of life (PRQOL) and tolerability. Methods: In this prospective phase II study, patients with low- and intermediate-risk localized PC were randomly assigned in a 1:1 ratio to the SBRT (36.25 Gy/5 fractions/2 weeks) or CFRT (76 Gy/38 fractions/7.5 weeks) treatment groups. The primary endpoint of variation in PRQOL at 1 year was assessed by changes in the Expanded Prostate Cancer Index Composite (EPIC) questionnaire scores and analysed by z-tests and t-tests. Results: Sixty-four eligible Chinese men were treated (SBRT, n = 31; CFRT, n = 33) with a median follow-up of 2.3 years. At 1 year, 40.0%/46.9% of SBRT/CFRT patients had a >5-point decrease in bowel score (p = 0.08/0.28), respectively, and 53.3%/46.9% had a >2-point decrease in urinary score (p = 0.21/0.07). There were no significant differences in EPIC score changes between the arms at 3, 6, 9 and 12 months, but SBRT was associated with significantly fewer grade ≥ 1 acute and 1-year late gastrointestinal toxicities (acute: 35% vs. 87%, p < 0.0001; 1-year late: 64% vs. 84%, p = 0.03), and grade ≥ 2 acute genitourinary toxicities (3% vs. 24%, p = 0.04) compared with CFRT. Conclusion: SBRT offered similar PRQOL and less toxicity compared with CFRT in Chinese men with localized PC.     

Upfront Chemotherapy Followed by Stereotactic Body Radiation Therapy with or without Surgery in Older Patients with Localized Pancreatic Cancer: A Single Institution Experience and Review of the Literature

Objective: To report on clinical outcomes and toxicity in older (age ≥ 70 years) patients with localized pancreatic cancer treated with upfront chemotherapy followed by stereotactic body radiation therapy (SBRT) with or without surgery. Methods: Endpoints included overall survival (OS), local progression-free survival (LPFS), distant metastasis-free survival (DMFS), progression-free survival (PFS), and toxicity. Results: A total of 57 older patients were included in the study. Median OS was 19.6 months, with six-month, one-year, and two-year OS rates of 83.4, 66.5, and 42.4%. On MVA, resection status (HR: 0.30, 95% CI 0.12–0.91, p = 0.031) was associated with OS. Patients with surgically resected tumors had improved median OS (29.1 vs. 7.0 months, p < 0.001). On MVA, resection status (HR: 0.40, 95% CI 0.17–0.93, p = 0.034) was also associated with PFS. Patients with surgically resected tumors had improved median PFS (12.9 vs. 1.6 months, p < 0.001). There were 3/57 cases (5.3%) of late grade 3 radiation toxicity and 2/38 cases (5.3%) of Clavien-Dindo grade 3b toxicity in those who underwent resection. Conclusion: Multimodality therapy involving SBRT is safe and feasible in older patients with localized pancreatic cancer. Surgical resection was associated with improved clinical outcomes. As such, older patients who complete chemotherapy should not be excluded from aggressive local therapy when possible.     

DPYD*5 gene mutation contributes to the reduced DPYD enzyme activity and chemotherapeutic toxicity of 5-FU

Background Dihydropyrimidine dehydrogenase (DPYD) plays an important role in the metabolism of 5-FU, which can directly influence the pharmacokinetics and toxicity of 5-FU in patients undergoing chemotherapy. However, little is known of the relationship between DPYD gene polymorphism and metabolism and chemotherapeutic toxicity of 5-FU in gastric carcinoma and colon carcinoma. The present genotyping study demonstrated the relationship between DPYD gene polymorphism among 75 gastric carcinoma and colon carcinoma patients and its impact on 5-FU pharmacokinetic and side effect. Methods We used a chemotherapy scheme based on 5-FU for the treatment of 75 patients with gastrointestinal carcinoma and detected the serum drug concentration and DPYD gene polymorphism (DPYD*2, *3, *4 *5 *9 *12). Results We found that there were no DPYD*2, *3, *4, *12 type mutation, in all patients. Of DPYD*9 gene polymorphism loci in 75 patients, 7 were heterozygote and 68 wild type; of DPYD*5 gene polymorphism loci in 75 patients, 11 were mutation and 23 heterozygote and 41 wild type. The elimination rate constant (Ke) value of DPYD*5 mutation group was statistically lower than the wild type (p=0.022). The incidence of middle-severe nausea and vomiting and white blood cell decreases in DPYD*5 gene type ranging from the highest to lowest can be listed as: mutation, heterozygote, wild type (p<0.05). The incidence of middle-severe nausea and vomiting was significantly higher in DPYD*9 heterozygous genotype than in DPYD*9 wild genotype (p<0.05). Conclusions DPYD*5 gene mutation contribute to reduced DPYD enzyme activity and 5-FU dysmetabolism, which is associated with the accumulation of 5-FU and the chemotherapeutic toxicity in gastric carcinoma and colon carcinoma.     

Effectiveness and safety of reduced-dose fluoropyrimidine therapy in patients carrying the DPYD*2A variant: A matched pair analysis

Carriers of the genetic DPYD*2A variant, resulting in dihydropyrimidine dehydrogenase deficiency, are at significantly increased risk of developing severe fluoropyrimidine-associated toxicity. Upfront DPYD*2A genotype-based dose reductions improve patient safety, but uncertainty exists whether this has a negative impact on treatment effectiveness. Therefore, our study investigated effectiveness and safety of DPYD*2A genotype-guided dosing. A cohort of 40 prospectively identified heterozygous DPYD*2A carriers, treated with a ~50% reduced fluoropyrimidine dose, was identified. For effectiveness analysis, a matched pair-analysis was performed in which for each DPYD*2A carrier a matched DPYD*2A wild-type patient was identified. Overall survival and progression-free survival were compared between the matched groups. The frequency of severe (grade ≥ 3) treatment-related toxicity was compared to 1] a cohort of 1606 wild-type patients treated with full dose and 2] a cohort of historical controls derived from literature, i.e. 86 DPYD*2A variant carriers who received a full fluoropyrimidine dose. For 37 out of 40 DPYD*2A carriers, a matched control could be identified. Compared to matched controls, reduced doses did not negatively affect overall survival (median 27 months versus 24 months, p = 0.47) nor progression-free survival (median 14 months versus 10 months, p = 0.54). Risk of severe fluoropyrimidine-related toxicity in DPYD*2A carriers treated with reduced dose was 18%, comparable to wild-type patients (23%, p = 0.57) and significantly lower than the risk of 77% in DPYD*2A carriers treated with full dose (p < 0.001). Our study is the first to show that DPYD*2A genotype-guided dosing appears to have no negative effect on effectiveness of fluoropyrimidine-based chemotherapy, while resulting in significantly improved patient safety.     

Outcomes of resected pancreatic cancer in patients age ≥70

Objective

To determine outcomes of patients ≥70 years with resected pancreatic cancer.

Methods

A study was conducted to identify pancreatic cancer patients ≥70 years who underwent surgery for pancreatic carcinoma from 2000 to 2012. Patients were excluded if they had neoadjuvant therapy. The primary endpoint was overall survival (OS).

Results

We identified 112 patients with a median follow-up of surviving patients of 36 months. The median patient age was 77 years. The median and 5 year OS was 20.5 months and 19%, respectively. Univariate analysis (UVA) showed a significant correlation for increased mortality with N1 (P=0.03) as well as post-op CA19-9 >90 (P<0.001), with a trend towards decreased mortality with adjuvant chemoradiation (P=0.08). Multivariate analysis (MVA) showed a statistically significant increased mortality associated with N1 (P=0.008), post-op CA19-9 >90 (P=0.002), while adjuvant chemoradiation (P=0.04) was associated with decreased mortality.

Conclusions

These data show that in patients ≥70, nodal status, post-op CA19-9, and adjuvant chemoradiation, were associated with OS. The data suggests that outcomes of patients ≥70 years who undergo upfront surgical resection are not inferior to younger patients.     

Clinical importance of risk variants in the dihydropyrimidine dehydrogenase gene for the prediction of early‐onset fluoropyrimidine toxicity

We investigated the clinical relevance of dihydropyrimidine dehydrogenase gene (DPYD) variants to predict severe early‐onset fluoropyrimidine (FP) toxicity, in particular of a recently discovered haplotype hapB3 and a linked deep intronic splice site mutation c.1129–5923C>G. Selected regions of DPYD were sequenced in prospectively collected germline DNA of 500 patients receiving FP‐based chemotherapy. Associations of DPYD variants and haplotypes with hematologic, gastrointestinal, infectious, and dermatologic toxicity in therapy cycles 1–2 and resulting FP‐dose interventions (dose reduction, therapy delay or cessation) were analyzed accounting for clinical and demographic covariates. Fifteen additional cases with toxicity‐related therapy delay or cessation were retrospectively examined for risk variants. The association of c.1129–5923C>G/hapB3 (4.6% carrier frequency) with severe toxicity was replicated in an independent prospective cohort. Overall, c.1129–5923G/hapB3 carriers showed a relative risk of 3.74 (RR, 95% CI = 2.30–6.09, p = 2 × 10^?5) for severe toxicity (grades 3–5). Of 31 risk variant carriers (c.1129–5923C>G/hapB3, c.1679T>G, c.1905+1G>A or c.2846A>T), 11 (all with c.1129–5923C>G/hapB3) experienced severe toxicity (15% of 72 cases, RR = 2.73, 95% CI = 1.61–4.63, p = 5 × 10^?6), and 16 carriers (55%) required FP‐dose interventions. Seven of the 15 (47%) retrospective cases carried a risk variant. The c.1129–5923C>G/hapB3 variant is a major contributor to severe early‐onset FP toxicity in Caucasian patients. This variant may substantially improve the identification of patients at risk of FP toxicity compared to established DPYD risk variants (c.1905+1G>A, c.1679T>G and c.2846A>T). Pre‐therapeutic DPYD testing may prevent 20–30% of life‐threatening or lethal episodes of FP toxicity in Caucasian patients.     

Gender-specific elimination of continuous-infusional 5-fluorouracil in patients with gastrointestinal malignancies: results from a prospective population pharmacokinetic study

Background

This study was initiated to assess the quantitative impact of patient anthropometrics and dihydropyrimidine dehydrogenase (DPYD) mutations on the pharmacokinetics (PK) of 5-fluorouracil (5FU) and to explore limited sampling strategies of 5FU.

Patients and methods

We included 32 patients with gastrointestinal malignancies, receiving 46-h continuous-infusional 5FU and performed PK-sampling at baseline, 15, 30, 45 min, 1 and 2 h after the start of infusion and at the end of infusion, for 2 subsequent cycles. Plasma concentrations of 5FU, 5-fluorodihydrouracil (5FUH2), uracil (U) and 5,6-dihydrouracil (UH2) were determined using LC–MS/MS and submitted to population PK analysis using nonlinear mixed-effects modeling. Broad genotyping of DPYD was performed, and the potential impact of the DPYD genotype on the elimination of 5FU was assessed. Limited sampling strategies were evaluated for their accuracy to predict steady-state concentrations of 5FU (CSS_5FU), using data simulations based on the final PK-model.

Results

The area-under-the concentration–time curve of 5FU (AUC_5FU) was found to be <20 mg h/L in 33 occasions (58 %), between 20 and 30 mg h/L in 17 occasions (30 %) and >30 mg h/L in 7 occasions (12 %). Men had a 26 % higher elimination of 5FU and a 18 % higher apparent elimination of 5FUH2. Accordingly, women had a higher AUC_5FU compared to men (22 vs. 18 mg h/L, p = 0.04). No DPYD risk variants were found, and the DPYD variants detected (c.496A>G, c.1601G>A, c.1627A>G) were not significantly associated with the elimination of 5FU. Individual baseline UH₂/U ratio was significantly associated with AUC_5FU (R = ?0.49, p < 0.001). Limited sampling strategies with time-points <3 h after the start of infusion were not adequate to predict CSS_5FU. Female gender was the only predictor of nausea/emesis in the multivariate model.

Conclusions

Gender-specific elimination of 5FU is supported by the present data and may partly explain the gender-specific association between DPYD risk variants and 5FU-specific toxicity.     

DPYD*2A mutation: the most common mutation associated with DPD deficiency

Background Dihydropyrimidine dehydrogenase (DPD) enzyme is responsible for the elimination of approximately 80% of administered dose of 5-FU. DPD deficiency has been associated with severe 5-FU toxicity. Syndrome of DPD deficiency manifests as diarrhea, stomatitis, mucositis, and neurotoxicity and in some cases death. This is a true pharmacogenetic syndrome, with symptoms being unrecognizable until exposure to the drug. Patients and methods A 75-year-old patient with metastatic pancreatic adenocarcinoma developed grade 4 thrombocytopenia, grade 3 coagulopathy, and grade 3 neurologic toxicity with a fatal outcome following administration of 5-FU. Due to pancytopenia, DPD activity could not be determined in peripheral blood mononuclear cells (PBMC) using a previously described radioassay. Therefore, screening and genotypic analysis of homozygous and heterozygous, known and unknown sequence variants, in the DPYD gene were performed using DHPLC as previously described. All DPYD sequence variants identified by DHPLC were confirmed by DNA sequencing using a dideoxynucleotide chain termination method and capillary electrophoresis on an ABI 310 Automated DNA Sequencer. Results Genotyping analysis of the DPYD gene revealed the presence of the heterozygous mutation, IVS14 + 1 G > A, DPYD*2A. Conclusion Genotypic analysis using DHPLC can be employed to screen DPD deficiency in a patient with severe neutropenia. The mutation IVS14 + 1 G > A, DPYD*2A, is the most common mutation associated with DPD deficiency. A G > A base change at the splice recognition sequence of intron 14, leads to exon skipping and results in a 165-bp deletion in the DPD mRNA. We have previously demonstrated that a homozygote DPYD*2A genotype results in complete deficiency while the heterozygous DPYD*2A genotype results in partial deficiency of DPD. This work was supported in part by NIH grant CA 62164.     

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.     

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

Aim: CAPOX treatment in CRC patients was reported to cause several dose-limiting toxicities, and are found responsible for treatment interruption or even discontinuation. Therefore there is a critical need for identifying the predictive biomarkers for such toxicities to prevent them. The aim of our present study is to find the influence of DPYD*9A, DPYD*6 and GSTP1 ile105val gene polymorphisms on CAPOX treatment-associated toxicities in south Indian patients with CRC. Patients and Methods: We have recruited 145 newly diagnosed and treatment naive CRC patients in the study. Each Patient received a standard treatment schedule of oxaliplatin 130 mg/m2 infusion over 2 hours on day 1 and oral capecitabine 1000mg/m2 in divided doses twice daily for the next 14 days of a 21-day cycle. 5 ml of the venous blood was collected from each patient and genomic DNA extraction and genotyping. The genotyping analysis of the selected genetic polymorphisms was carried out by real-time PCR using TaqMan SNP genotyping assays obtained from applied biosystems. Results: The major dose-limiting toxicities observed with CAPOX treatment were thrombocytopenia, HFS and PN. DPYD*9A carries were found to be at higher risk for HFS, diarrhoea and thrombocytopenia when compared to patients with wild allele. No significant association was found between DPYD*6, GSTP1 ile105val polymorphisms and CAPOX related toxicities except for thrombocytopenia. Conclusion: A significant association was observed between DPYD*9A polymorphism and CAPOX induced dose-limiting toxicities strengthening its role as a predictive biomarker.