A cost analysis of upfront DPYD genotype-guided dose individualisation in fluoropyrimidine-based anticancer therapy

Estimating the Effectiveness of DPYD Genotyping in Italian Individuals Suffering from Cancer Based on the Cost of Chemotherapy-Induced Toxicity

Fluoropyrimidines (FLs) have been widely used for more than 60 years against a range of solid tumors and still remains the cornerstone for the treatment of colorectal, gastric, and breast cancer. Here, we performed an economic analysis to estimate the cost of DPYD-guided toxicity management and the clinical benefit expressed as quality adjusted life years (QALYs) in a large group of 571 individuals of Italian origin suffering from cancer and treated with a fluoropyrimidines-based chemotherapy. Individuals suffering from cancer with a histologically confirmed diagnosis of cancer, who received a fluoropyrimidines-based treatment, were retrospectively genotyped in the DPYD gene. Effectiveness was measured as survival of individuals from chemotherapy, while study data on safety and efficacy as well as on resource utilization associated with each adverse drug reaction were used to measure costs to treat these adverse drug reactions. A generalized linear regression model was used to estimate cost differences for both study groups. DPYD extensive metabolizers (528 individuals) had greater effectiveness and lesser cost, representing a cost-saving option over DPYD intermediate and poor metabolizers (43 individuals) with mean QALYs of 4.18 (95%CI: 3.16-5.55) versus 3.02 (95%CI: 1.94-4.25), respectively. Our economic analysis showed that there are some indications for differences in survival between the two groups (p > 0.05), while the cost of DPYD extensive metabolizers was significantly lower (p < 0.01) compared with those belonging to the group of intermediate/poor metabolizers. These findings suggest that DPYD-guided fluoropyrimidines treatment represent a cost-saving choice for individuals suffering from cancer in the Italian healthcare setting.

DPYD and Fluorouracil-Based Chemotherapy: Mini Review and Case Report

5-Fluorouracil remains a foundational component of chemotherapy for solid tumour malignancies. While considered a generally safe and effective chemotherapeutic, 5-fluorouracil has demonstrated severe adverse event rates of up to 30%. Understanding the pharmacokinetics of 5-fluorouracil can improve the precision medicine approaches to this therapy. A single enzyme, dihydropyrimidine dehydrogenase (DPD), mediates 80% of 5-fluorouracil elimination, through hepatic metabolism. Importantly, it has been known for over 30-years that adverse events during 5-fluorouracil therapy are linked to high systemic exposure, and to those patients who exhibit DPD deficiency. To date, pre-treatment screening for DPD deficiency in patients with planned 5-fluorouracil-based therapy is not a standard of care. Here we provide a focused review of 5-fluorouracil metabolism, and the efforts to improve predictive dosing through screening for DPD deficiency. We also outline the history of key discoveries relating to DPD deficiency and include relevant information on the potential benefit of therapeutic drug monitoring of 5-fluorouracil. Finally, we present a brief case report that highlights a limitation of pharmacogenetics, where we carried out therapeutic drug monitoring of 5-fluorouracil in an orthotopic liver transplant recipient. This case supports the development of robust multimodality precision medicine services, capable of accommodating complex clinical dilemmas.

The use of pharmacogenetics to increase the safety of colorectal cancer patients treated with fluoropyrimidines

Fluoropyrimidines (FP) are given in the combination treatment of the advanced disease or as monotherapy in the neo-adjuvant and adjuvant treatment of colorectal cancerand other solid tumors including breast, head and neck and gastric cancer. FP present a narrow therapeutic index with 10 to 26% of patients experiencing acute severe or life-threatening toxicity. With the high number of patients receiving FP-based therapies, and the significant effects of toxicities on their quality of life, the prevention of FP-related adverse events is of major clinical interest. Host genetic variants in the rate limiting enzyme dihydropyrimidine dehydrogenase (DPYD) gene are related to the occurrence of extremely severe, early onset toxicity in FP treated patients. The pre-treatment diagnostic test of 4 DPYD genetic polymorphisms is suggested by the currently available pharmacogenetic guidelines. Several prospective implementation projects are ongoing to support the introduction of up-front genotyping of the patients in clinical practice. Multiple pharmacogenetic studies tried to assess the predictive role of other polymorphisms in genes involved in the FP pharmacokinetics/pharmacodynamic pathways, TYMS and MTHFR, but no additional clinically validated genetic markers of toxicity are available to date. The development of next-generation sequencing platforms opens new possibilities to highlight previously unreported genetic markers. Moreover, the investigation of the genetic variation in the patients immunological system, a pivotal target in cancer treatment, could bring notable advances in the field. This review will describe the most recent literature on the use of pharmacogenetics to increase the safety of a treatment based on FP administration in colorectal cancer patients.

Clinical implementation of pre-treatment DPYD genotyping in capecitabine-treated metastatic breast cancer patients

Purpose

Metastatic breast cancer (mBC) patients with DPYD genetic variants linked to loss of dihydropyrimidine dehydrogenase (DPD) activity are at risk of severe capecitabine-associated toxicities. However, prospective DPYD genotyping has not yet been implemented in routine clinical practice. Following a previous internal review in which two patients underwent lengthy hospitalisations whilst receiving capecitabine, and were subsequently found to be DPD deficient, we initiated routine DPYD genotyping prior to starting capecitabine. This study evaluates the clinical application of routine DPYD screening at a large cancer centre in London.

Methods

We reviewed medical records for consecutive patients with mBC who underwent DPYD genotyping before commencing capecitabine between December 2014 and December 2017. Patients were tested for four DPYD variants associated with reduced DPD activity.

Results

Sixty-six patients underwent DPYD testing. Five (8.4%) patients were found to carry DPYD genetic polymorphisms associated with reduced DPD activity; of these, two received dose-reduced capecitabine. Of the 61 patients with DPYD wild-type, 14 (23%) experienced grade 3 toxicities which involved palmar–plantar erythrodysesthesia (65%), and gastrointestinal toxicities (35%); no patient was hospitalised due to toxicity.

Conclusions

Prospective DPYD genotyping can be successfully implemented in routine clinical practice and can reduce the risk of severe fluoropyrimidine toxicities.

DPYD*6 plays an important role in fluoropyrimidine toxicity in addition to DPYD*2A and c.2846A>T: a comprehensive analysis in 1254 patients

Dihydropyrimidine dehydrogenase (DPYD) is a highly polymorphic gene and classic deficient variants (i.e., c.1236G>A/HapB3, c.1679T>G, c.1905+1G>A and c.2846A>T) are characterized by impaired enzyme activity and risk of severe adverse drug reactions (ADRs) in patients treated with fluoropyrimidines. The identification of poor metabolizers by pre-emptive DPYD screening may reduce the rate of ADRs but many patients with wild-type genotype for classic variants may still display ADRs. Therefore, the search for additional DPYD polymorphisms associated with ADRs may improve the safety of treatment with fluoropyrimidines. This study included 1254 patients treated with fluoropyrimidine-containing regimens and divided into cohort 1, which included 982 subjects suffering from gastrointestinal G≥2 and/or hematological G≥3 ADRs, and cohort 2 (control group), which comprised 272 subjects not requiring dose reduction, delay or discontinuation of treatment. Both groups were screened for DPYD variants c.496A>G, c.1236G>A/HapB3, c.1601G>A (DPYD*4), c.1627A>G (DPYD*5), c.1679T>G (DPYD*13), c.1896T>C, c.1905 + 1G>A (DPYD*2A), c.2194G>A (DPYD*6), and c.2846A>T to assess their association with toxicity. Genetic analysis in the two cohorts were done by Real-Time PCR of DNA extracted from 3 ml of whole blood. DPYD c.496A>G, c.1601G>A, c.1627A>G, c.1896T>C, and c.2194G>A variants were found in both cohort 1 and 2, while c.1905+1G>A and c.2846A>T were present only in cohort 1. DPYD c.1679T>G and c.1236G>A/HapB3 were not found. Univariate analysis allowed the selection of c.1905+1G>A, c.2194G>A and c.2846A>T alleles as significantly associated with gastrointestinal and hematological ADRs (p < 0.05), while the c.496A>G variant showed a positive trend of association with neutropenia (p = 0.06). In conclusion, c.2194G>A is associated with clinically-relevant ADRs in addition to the already known c.1905+1G>A and c.2846A>T variants and should be evaluated pre-emptively to reduce the risk of fluoropyrimidine-associated ADRs.

Feasibility of Integrating Panel-Based Pharmacogenomics Testing for Chemotherapy and Supportive Care in Patients With Colorectal Cancer

INTRODUCTION

Pharmacogenomics is about selecting the "right drug in the right amount for the right patient." In metastatic colorectal cancer, germline pharmacogenomics testing presents a unique opportunity to improve outcomes, since the genes dihydropyrimidine dehydrogenase and UDP-glucuronosyltransferase metabolizing the chemotherapy drugs, 5-fluorouracil, and irinotecan are already well known. In a retrospective analysis of the landmark TRIBE clinical trial [(TRIBE - TRIplet plus BEvacizumab multicenter, phase III trial by the Italian Cooperative GONO (Gruppo Oncologico Nord Ovest) group (NCT00719797)], the proportion of patients with serious adverse events was higher in those with dihydropyrimidine dehydrogenase/UDP-glucuronosyltransferase aberrations and was dose dependent. We aimed to report on the feasibility and the results of incorporating pharmacogenomics testing into clinical practice.

METHODS

As a quality improvement initiative and a center of individualized medicine grant, we integrated the use of OneOme RightMed comprehensive test, which reports on 27 genes related to pharmacogenomics and over 300 medications of interest. We limited initial testing to patients with colorectal cancer. Pharmacists provided dosage recommendations based on test results in real-time.

RESULTS

At our cancer center, 155 patients underwent pharmacogenomics testing from November 2017 to January 2019. Results were available within 3 to 5 days of testing for most patients and were integrated into treatment decision-making. Of 155 sampled participants, a total of 89 (57.4%) participants had an UGT1A1 variant genotype, NM_000463.2: c.-53_-52[8] *1/*28, n = 74 (47.7%); *28/*28, n = 15 (9.7%). Additionally, 4 (2.6%) participants were heterozygous for dihydropyrimidine dehydrogenase. Two (1.3%) individuals were heterozygous for both UDP-glucuronosyltransferase and dihydropyrimidine dehydrogenase genes. All (100%) the patients had at least 1 actionable aberration related to supportive care medications (CYP-family) of all the possible medications listed on their pharmacogenomics report.

CONCLUSION

Preemptive comprehensive pharmacogenomics testing can be integrated into clinical practice in real-time for patients with cancer given faster turnaround and low cost. Pharmacist-driven, patient-specific medication management consults add further value given the number of genes/drugs. This sets the stage for a prospective randomized clinical trial to demonstrate the amount of benefit this can result in these patients.