Preemptive pharmacogenetic testing to guide chemotherapy dosing in patients with gastrointestinal malignancies: a qualitative study of barriers to implementation

Overcoming Barriers to Discovery and Implementation of Equitable Pharmacogenomic Testing in Oncology

Pharmacogenomics (PGx), the study of inherited genomic variation and drug response or safety, is a vital tool in precision medicine. In oncology, testing to identify PGx variants offers patients the opportunity for customized treatments that can minimize adverse effects and maximize the therapeutic benefits of drugs used for cancer treatment and supportive care. Because individuals of shared ancestry share specific genetic variants, PGx factors may contribute to outcome disparities across racial and ethnic categories when genetic ancestry is not taken into account or mischaracterized in PGx research, discovery, and application. Here, we examine how the current scientific understanding of the role of PGx in differential oncology safety and outcomes may be biased toward a greater understanding and more complete clinical implementation of PGx for individuals of European descent compared with other genetic ancestry groups. We discuss the implications of this bias for PGx discovery, access to care, drug labeling, and patient and provider understanding and use of PGx approaches. Testing for somatic genetic variants is now the standard of care in treatment of many solid tumors, but the integration of PGx into oncology care is still lacking despite demonstrated actionable findings from PGx testing, reduction in avoidable toxicity and death, and return on investment from testing. As the field of oncology is poised to expand and integrate germline genetic variant testing, it is vital that PGx discovery and application are equitable for all populations. Recommendations are introduced to address barriers to facilitate effective and equitable PGx application in cancer care.

Pharmacogenetics testing (DPYD and UGT1A1) for fluoropyrimidine and irinotecan in routine clinical care: Perspectives of medical oncologists and oncology pharmacists

BACKGROUND

Despite robust evidence and international guidelines, to support routine pharmacogenetic (PGx) testing, integration in practice has been limited. This study explored clinicians' views and experiences of pre-treatment DPYD and UGT1A1 gene testing and barriers to and enablers of routine clinical implementation.

METHODS

A study-specific 17-question survey was emailed (01 February-12 April 2022) to clinicians from the Medical Oncology Group of Australia (MOGA), the Clinical Oncology Society of Australia (COSA) and International Society of Oncology Pharmacy Practitioners (ISOPP). Data were analysed and reported using descriptive statistics.

RESULTS

Responses were collected from 156 clinicians (78% medical oncologists, 22% pharmacists). Median response rate of 8% (ranged from 6% to 24%) across all organisations. Only 21% routinely test for DPYD and 1% for UGT1A1. For patients undergoing curative/palliative intent treatments, clinicians reported intent to implement genotype-guided dosing by reducing FP dose for DPYD intermediate metabolisers (79%/94%), avoiding FP for DPYD poor metabolisers (68%/90%), and reducing irinotecan dose for UGT1A1 poor metabolisers (84%, palliative setting only). Barriers to implementation included: lack of financial reimbursements (82%) and perceived lengthy test turnaround time (76%). Most Clinicians identified a dedicated program coordinator, i.e., PGx pharmacist (74%) and availability of resources for education/training (74%) as enablers to implementation.

CONCLUSION

PGx testing is not routinely practised despite robust evidence for its impact on clinical decision making in curative and palliative settings. Research data, education and implementation studies may overcome clinicians' hesitancy to follow guidelines, especially for curative intent treatments, and may overcome other identified barriers to routine clinical implementation.

Patient and healthcare professional acceptability of pharmacogenetic screening for DPYD and UGT1A1: A cross sectional survey

This study explored the acceptability of a novel pharmacist-led pharmacogenetics (PGx) screening program among patients with cancer and healthcare professionals (HCPs) taking part in a multicenter clinical trial of PGx testing (PACIFIC-PGx ANZCTR:12621000251820). Medical oncologists, oncology pharmacists, and patients with cancer from across four sites (metropolitan/regional), took part in an observational, cross-sectional survey. Participants were recruited from the multicenter trial. Two study-specific surveys were developed to inform implementation strategies for scaled and sustainable translation into routine clinical care: one consisting of 21 questions targeting HCPs and one consisting of 17 questions targeting patients. Responses were collected from 24 HCPs and 288 patients. The 5-to-7-day PGx results turnaround time was acceptable to HCP (100%) and patients (69%). Most HCPs (92%) indicated that it was appropriate for the PGx clinical pharmacist to provide results to patients. Patients reported equal preference for receiving PGx results from a doctor/pharmacist. Patients and HCPs highly rated the pharmacist-led PGx service. HCPs were overall accepting of the program, with the majority (96%) willing to offer PGx testing to their patients beyond the trial. HCPs identified that lack of financial reimbursements (62%) and lack of infrastructure (38%) were the main reasons likely to prevent/slow the implementation of PGx screening program into routine clinical care. Survey data have shown overall acceptability from patients and HCPs participating in the PGx Program. Barriers to implementation of PGx testing in routine care have been identified, providing opportunity to develop targeted implementation strategies for scaled translation into routine practice.

Healthcare professionals' and consumers' knowledge, attitudes, perspectives, and education needs in oncology pharmacogenomics: A systematic review

Clinical implementation of pharmacogenomic (PGx)-guided prescribing in oncology lags behind research evidence generation. We aimed to identify healthcare professionals' (HCPs) and consumers' knowledge, attitudes, perspectives, and education needs to inform strategies for implementation of scalable and sustainable oncology PGx programs. Systematic review of original articles indexed in EMBASE, EMCARE, MEDLINE, and PsycInfo from January 2012 until June 2022, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and using the Mixed Methods Appraisal Tool. PROSPERO registration number CRD42022352348. Of 1442 identified studies; 23 met inclusion criteria with 87% assessed high quality. Of these, 52% reported on HCPs, 35% on consumers, and 13% on both HCPs and consumers. Most were conducted in the United States (70%) and included multiple cancer types (74%). Across studies, HCPs and consumers mostly perceived value in PGx, however, both groups reported barriers to utilization, including cost, lack of consistent recommendations across guidelines, and limited knowledge among HCPs; test accuracy, clear testing benefits, and genomic information confidentiality among consumers. HCPs and consumers value and want to engage in PGx strategies in oncology care, however, are inhibited by unmet needs and practice and knowledge gaps. Implementation strategies aimed at addressing these issues may best support increased PGx uptake in oncology practice.

Pharmacogenomics implementation across multiple clinic settings: a qualitative evaluation

Aim: To advance clinical adoption and implementation of pharmacogenomics (PGx) testing, barriers and facilitators to these efforts must be understood. This study identified and examined barriers and facilitators to active implementation of a PGx program across multiple clinic settings in an academic healthcare system. Materials & methods: 28 contributors to the PGx implementation (e.g., clinical providers, informatics specialists) completed an interview to elicit their perceptions of the implementation. Results: Qualitative analysis identified several barriers and facilitators that spanned different stages of the implementation process. Specifically, unclear test payment mechanisms, decision support tool development, rigid workflows and provider education were noted as barriers to the PGx implementation. A multidisciplinary implementation team and leadership support emerged as key facilitators. Furthermore, participants also suggested strategies to overcome or maintain these factors. Conclusion: Assessing real-world implementation perceptions and suggested strategies from a range of implementation contributors facilitates a more comprehensive framework and best-practice guidelines for PGx implementation.

Response to the FDA Decision Regarding DPYD Testing Prior to Fluoropyrimidine Chemotherapy

Fluoropyrimidine (FP) chemotherapy is associated with severe, life-threatening toxicities, particularly among patients who carry deleterious germline variants in the DPYD gene. Pretreatment DPYD testing is standard of care throughout most of Europe; however, it has not been recommended in clinical practice guidelines in the United States. Due to increased risk of severe toxicity, a Citizen's Petition asked the US Food and Drug Administration (FDA) to update language in FP drug labels to recommend DPYD testing as part of a boxed warning and recommend FP dose reduction in patients carrying deleterious germline variants. In response, the FDA updated the capecitabine package insert to inform patients about the toxicity risk and test availability and consider DPYD testing. However, the FDA did not include a testing recommendation or requirement, or a boxed warning. Additionally, the FDA did not recommend FP dose adjustment in DPYD variant carriers. This review provides a critical assessment of the DPYD-FP pharmacogenetic association using the FDA's previously published Pharmacogenetic Pyramid, demonstrating that the evidence is compelling for recommending DPYD testing prior to FP treatment. Additionally, the FDA's stated concerns about recommending DPYD testing and DPYD-guided FP dose adjustment are addressed and discussed in the context of the FDA's other genetic testing and dose adjustment recommendations. We call on the FDA to follow our European counterparts in recommending DPYD testing and genotype-based dose adjustment to ensure patients with cancer receive safe and effective FP chemotherapy.

Addressing barriers to increased adoption of DPYD genotyping at a large multisite cancer center

PURPOSE

To describe the implementation of an in-house genotyping program to detect genetic variants linked to impaired dihydropyrimidine dehydrogenase (DPD) metabolism at a large multisite cancer center, including barriers to implementation and mechanisms to overcome barriers to facilitate test adoption.

SUMMARY

Fluoropyrimidines, including fluorouracil and capecitabine, are commonly used chemotherapy agents in the treatment of solid tumors, such as gastrointestinal cancers. DPD is encoded by the DPYD gene, and individuals classified as DPYD intermediate and poor metabolizers due to certain genetic variations in DPYD can experience reduced fluoropyrimidine clearance and an increased risk of fluoropyrimidine-related adverse events. Although pharmacogenomic guidelines provide evidence-based recommendations for DPYD genotype-guided dosing, testing has not been widely adopted in the United States for numerous reasons, including limited education/awareness of clinical utility, lack of testing recommendations by oncology professional organizations, testing cost, lack of accessibility to a comprehensive in-house test and service, and prolonged test turnaround time. Based on stakeholder feedback regarding barriers to testing, we developed an in-house DPYD test and workflow to facilitate testing in multiple clinic locations at Levine Cancer Institute. Across 2 gastrointestinal oncology clinics from March 2020 through June 2022, 137 patients were genotyped, and 13 (9.5%) of those patients were heterozygous for a variant and identified as DPYD intermediate metabolizers.

CONCLUSION

Implementation of DPYD genotyping at a multisite cancer center was feasible due to operationalization of workflows to overcome traditional barriers to testing and engagement from all stakeholders, including physicians, pharmacists, nurses, and laboratory personnel. Future directions to scale and sustain testing in all patients receiving a fluoropyrimidine across all Levine Cancer Institute locations include electronic medical record integration (eg, interruptive alerts), establishment of a billing infrastructure, and further refinement of workflows to improve the rate of pretreatment testing.

Upfront DPYD Genotype-Guided Treatment for Fluoropyrimidine-Based Chemotherapy in Advanced and Metastatic Colorectal Cancer: A Cost-Effectiveness Analysis

OBJECTIVES

Fluoropyrimidines are the most widely used chemotherapy drugs for advanced and metastatic colorectal cancer (CRC). Individuals with certain DPYD gene variants are exposed to an increased risk of severe fluoropyrimidine-related toxicities. This study aimed to evaluate the cost-effectiveness of preemptive DPYD genotyping to guide fluoropyrimidine therapy in patients with advanced or metastatic CRC.

METHODS

Overall survival of DPYD wild-type patients who received a standard dose and variant carriers treated with a reduced dose were analyzed by parametric survival models. A decision tree and a partitioned survival analysis model with a lifetime horizon were designed, taking the Iranian healthcare perspective. Input parameters were extracted from the literature or expert opinion. To address parameter uncertainty, scenario and sensitivity analyses were also performed.

RESULTS

Compared with no screening, the genotype-guided treatment strategy was cost-saving ($41.7). Nevertheless, due to a possible reduction in the survival of patients receiving reduced-dose regimens, it was associated with fewer quality-adjusted life-years (9.45 vs 9.28). In sensitivity analyses, the prevalence of DPYD variants had the most significant impact on the incremental cost-effectiveness ratio. The genotyping strategy would remain cost-saving, as long as the genotyping cost is < $49 per test. In a scenario in which we assumed equal efficacy for the 2 strategies, genotyping was the dominant strategy, associated with less costs (∼$1) and more quality-adjusted life-years (0.1292).

CONCLUSIONS

DPYD genotyping to guide fluoropyrimidine treatment in patients with advanced or metastatic CRC is cost-saving from the perspective of the Iranian health system.

Integrating pharmacogenomic testing into paired germline and somatic genomic testing in patients with cancer

Precision medicine has revolutionized clinical care for patients with cancer through the development of targeted therapy, identification of inherited cancer predisposition syndromes and the use of pharmacogenetics to optimize pharmacotherapy for anticancer drugs and supportive care medications. While germline (patient) and somatic (tumor) genomic testing have evolved separately, recent interest in paired germline/somatic testing has led to an increase in integrated genomic testing workflows. However, paired germline/somatic testing has generally lacked the incorporation of germline pharmacogenomics. Integrating pharmacogenomics into paired germline/somatic genomic testing would be an efficient method for increasing access to pharmacogenomic testing. In this perspective, the authors argue for the benefits of implementing a comprehensive approach integrating somatic and germline testing that is inclusive of pharmacogenomics in clinical practice.

UGT1A1 genotype-guided dosing of irinotecan: time to prioritize patient safety

Tweetable abstract Pretreatment UGT1A1 genotyping and a 70% irinotecan dose intensity in poor metabolizers is safe, feasible, cost-effective and essential for safe irinotecan treatment in cancer patients. It is time to update guidelines to swiftly enable the implementation of UGT1A1 genotype-guided irinotecan dosing in routine oncology care.

The past, present, and future of chemotherapy with a focus on individualization of drug dosing

While there have been rapid advances in developing new and more targeted drugs to treat cancer, much less progress has been made in individualizing dosing. Even though the introduction of immunotherapies such as CAR T-cells and checkpoint inhibitors, as well as personalized therapies that target specific mutations, have transformed clinical treatment of cancers, chemotherapy remains a mainstay in oncology. Chemotherapies are typically dosed on either a body surface area (BSA) or weight basis, which fails to account for pharmacokinetic differences between patients. Drug absorption, distribution, metabolism, and excretion rates can vary between patients, resulting in considerable differences in exposure to the active drugs. These differences result in suboptimal dosing, which can reduce efficacy and increase side-effects. Therapeutic drug monitoring (TDM), genotype guided dosing, and chronomodulation have been developed to address this challenge; however, despite improving clinical outcomes, they are rarely implemented in clinical practice for chemotherapies. Thus, there is a need to develop interventions that allow for individualized drug dosing of chemotherapies, which can help maximize the number of patients that reach the most efficacious level of drug in the blood while mitigating the risks of underdosing or overdosing. In this review, we discuss the history of the development of chemotherapies, their mechanisms of action and how they are dosed. We discuss substantial intraindividual and interindividual variability in chemotherapy pharmacokinetics. We then propose potential engineering solutions that could enable individualized dosing of chemotherapies, such as closed-loop drug delivery systems and bioresponsive biomaterials.

Assessment of the Clinical Utility of Pretreatment DPYD Testing for Patients Receiving Fluoropyrimidine Chemotherapy

PURPOSE

Patients who carry pathogenic variants in DPYD have higher systemic fluoropyrimidine (FP) concentrations and greater risk of severe and fatal FP toxicity. Pretreatment DPYD testing and DPYD-guided FP dosing to reduce toxicity and health care costs is recommended by European clinical oncology guidelines and has been adopted across Europe, but has not been recommended or adopted in the United States. The cochairs of the National Comprehensive Cancer Network Guidelines for colon cancer treatment explained their concerns with recommending pretreatment DPYD testing, particularly the risk that reduced FP doses in DPYD carriers may reduce treatment efficacy.

METHODS

This special article uses previously published frameworks for assessing the clinical utility of cancer biomarker tests, including for germline indicators of toxicity risk, to assess the clinical utility of pretreatment DPYD testing, with a particular focus on the risk of reducing treatment efficacy.

RESULTS

There is no direct evidence of efficacy reduction, and the available indirect evidence demonstrates that DPYD-guided FP dosing results in similar systemic FP exposure and toxicity compared with standard dosing in noncarriers, and is well calibrated to the maximum tolerated dose, strongly suggesting there is minimal risk of efficacy reduction.

CONCLUSION

This article should serve as a call to action for clinicians and clinical guidelines committees in the United States to re-evaluate the clinical utility of pretreatment DPYD testing. If clinical utility has not been demonstrated, further dialogue is needed to clarify what additional evidence is needed and which of the available study designs, also described within this article, would be appropriate. Clinical guideline recommendations for pretreatment DPYD testing would increase clinical adoption and ensure that all patients receive maximally safe and effective FP treatment.

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

Background

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

Methods

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

Conclusion

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

Clinical Trial Registration

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

Opportunities for personalizing colorectal cancer care: an analysis of SEER-medicare data

United States clinical practice guidelines for metastatic colorectal cancer recommend use of medications impacted by genetic variants but do not recommend testing. We analyzed real-world treatment using a cancer registry and claims dataset to explore pharmacogenomic (PGx) medication treatment patterns and characterize exposure. In a cohort of 6957 patients, most (86.9%) were exposed to at least one chemotherapy medication with PGx guidelines. In a cohort of 2223 patients with retail pharmacy claims available, most (79.2%) were treated with at least one non-chemotherapy (79.2%) medication with PGx guidelines. PGx-associated chemotherapy exposure was associated with age, race/ethnicity, educational attainment, and rurality. PGx-associated non-chemotherapy exposure was associated with medication use and comorbidities. The potential impact of PGx testing is large and policies aimed at increasing PGx testing at diagnosis may impact treatment decisions for patients with metastatic colorectal cancer as most patients are exposed to medications with pharmacogenomics implications during treatment.