Genomic screening of the general adult population: key concepts for assessing net benefit with systematic evidence reviews

Genetic Basis of Breast and Ovarian Cancer: Approaches and Lessons Learnt from Three Decades of Inherited Predisposition Testing

Germline variants occurring in BRCA1 and BRCA2 give rise to hereditary breast and ovarian cancer (HBOC) syndrome, predisposing to breast, ovarian, fallopian tube, and peritoneal cancers marked by elevated incidences of genomic aberrations that correspond to poor prognoses. These genes are in fact involved in genetic integrity, particularly in the process of homologous recombination (HR) DNA repair, a high-fidelity repair system for mending DNA double-strand breaks. In addition to its implication in HBOC pathogenesis, the impairment of HR has become a prime target for therapeutic intervention utilizing poly (ADP-ribose) polymerase (PARP) inhibitors. In the present review, we introduce the molecular roles of HR orchestrated by BRCA1 and BRCA2 within the framework of sensitivity to PARP inhibitors. We examine the genetic architecture underneath breast and ovarian cancer ranging from high- and mid- to low-penetrant predisposing genes and taking into account both germline and somatic variations. Finally, we consider higher levels of complexity of the genomic landscape such as polygenic risk scores and other approaches aiming to optimize therapeutic and preventive strategies for breast and ovarian cancer.

Does genetic testing offer utility as a supplement to traditional family health history intake for inherited disease risk?

CONTENT

This study examines the potential utility of genetic testing as a supplement to family health history to screen for increased risk of inherited disease. Medical conditions are often misreported or misunderstood, especially those related to different forms of cardiac disease (arrhythmias vs. structural heart disease vs. coronary artery disease), female organ cancers (uterine vs. ovarian vs. cervical), and type of cancer (differentiating primary cancer from metastases to other organs). While these nuances appear subtle, they can dramatically alter medical management. For example, different types of cardiac failure (structural, arrhythmia, and coronary artery disease) have inherited forms that are managed with vastly different approaches.

METHODS

Using a dataset of over 6,200 individuals who underwent genetic screening, we compared the ability of genetic testing and traditional family health history to identify increased risk of inherited disease. A further, in-depth qualitative study of individuals for whom risk identified through each method was discordant, explored whether this discordance could be addressed through changes in family health history intake.

FINDINGS

Of 90 individuals for whom genetic testing indicated significant increased risk for inherited disease, two-thirds (66%) had no corroborating family health history. Specifically, we identify cardiomyopathy, arrhythmia, and malignant hyperthermia as conditions for which discordance between genetic testing and traditional family health history was greatest, and familial hypercholesterolaemia, Lynch syndrome, and hereditary breast and ovarian cancer as conditions for which greater concordance existed.

CONCLUSION

We conclude that genetic testing offers utility as a supplement to traditional family health history intake over certain conditions.

The Challenge of Genetic Variants of Uncertain Clinical Significance : A Narrative Review

Genomic tests expand diagnostic and screening opportunities but also identify genetic variants of uncertain clinical significance (VUSs). Only a minority of VUSs are likely to prove pathogenic when later reassessed, but resolution of the uncertainty is rarely timely. That uncertainty adds complexity to clinical decision making and can result in harms and costs to patients and the health care system, including the time-consuming analysis required to interpret a VUS and the potential for unnecessary treatment and adverse psychological effects. Current efforts to improve variant interpretation will help reduce the scope of the problem, but the high prevalence of rare and novel variants in the human genome points to VUSs as an ongoing challenge. Additional strategies can help mitigate the potential harms of VUSs, including testing protocols that limit identification or reporting of VUSs, subclassification of VUSs according to the likelihood of pathogenicity, routine family-based evaluation of variants, and enhanced counseling efforts. All involve tradeoffs, and the appropriate balance of measures is likely to vary for different test uses and clinical settings. Cross-specialty deliberation and public input could contribute to systematic and broadly supported policies for managing VUSs.

Population Screening for Inherited Predisposition to Breast and Ovarian Cancer

The discovery of genes underlying inherited predisposition to breast and ovarian cancer has revolutionized the ability to identify women at high risk for these diseases before they become affected. Women who are carriers of deleterious variants in these genes can undertake surveillance and prevention measures that have been shown to reduce morbidity and mortality. However, under current strategies, the vast majority of women carriers remain undetected until they become affected. In this review, we show that universal testing, particularly of the BRCA1 and BRCA2 genes, fulfills classical disease screening criteria. This is especially true for BRCA1 and BRCA2 in Ashkenazi Jews but is translatable to all populations and may include additional genes. Utilizing genetic information for large-scale precision prevention requires a paradigmatic shift in health-care delivery. To address this need, we propose a direct-to-patient model, which is increasingly pertinent for fulfilling the promise of utilizing personal genomic information for disease prevention.

Assessing the implications of positive genomic screening results

Aim:

Before population screening of ‘healthy’ individuals is widely adopted, it is important to consider the harms and benefits of receiving positive results and how harms and benefits may differ by age.

Subjects & methods:

Participants in a preventive genomic screening study were screened for 17 genes associated with 11 conditions. We interviewed 11 participants who received positive results.

Results:

Interviewees expressed little concern about their positive results in light of their older age, the risk condition for which they tested positive, or other pressing health concerns.

Conclusion:

Researchers and clinicians should recognize that returning positive results may not have the impact they presume given the diversity of the conditions screened and those who choose to undergo screening.

Clinical genetic testing in endocrinology: Current concepts and contemporary challenges

Recent advances in DNA sequencing technology have led to an unprecedented period of disease-gene discovery offering many new opportunities for genetic testing in the clinical setting. Endocrinology has seen a rapid expansion in the taxonomy of monogenic disorders, which can be detected by an expanding portfolio of genetic tests in both diagnostic and predictive settings. Successful testing relies on many factors including the ability to identify those at increased risk of genetic disease in the busy clinic as well as a working knowledge of the various testing platforms and their limitations. The clinical utility of a given test is dependent upon many factors, which include the reliability of the genetic testing platform, the accuracy of the test result interpretation and knowledge of disease penetrance and expression. The increasing adoption of "high-content" genetic testing based on next-generation sequencing (NGS) to diagnose hereditary endocrine disorders brings a number of challenges including the potential for uncertain test results and/or genetic findings unrelated to the indication for testing. Therefore, it is increasingly important that the clinician is aware of the current evolution in genetic testing, and understands the different settings in which it may be employed. This review provides an overview of the genetic testing workflow, focusing on each of the major components required for successful testing in adult and paediatric endocrine settings. In addition, the challenges of variant interpretation are highlighted, as are issues related to informed consent, prenatal diagnosis and predictive testing. Finally, the future directions of genetic testing relevant to endocrinology are discussed.

Population genomic screening of all young adults in a health-care system: a cost-effectiveness analysis

Purpose

To consider the impact and cost-effectiveness of offering preventive population genomic screening to all young adults in a single-payer health-care system.

Methods

We modeled screening of 2,688,192 individuals, all adults aged 18–25 years in Australia, for pathogenic variants in BRCA1/BRCA2/MLH1/MSH2 genes, and carrier screening for cystic fibrosis (CF), spinal muscular atrophy (SMA), and fragile X syndrome (FXS), at 71% testing uptake using per-test costs ranging from AUD$200 to $1200 (~USD$140 to $850). Investment costs included genetic counseling, surveillance, and interventions (reimbursed only) for at-risk individuals/couples. Cost-effectiveness was defined below AUD$50,000/DALY (disability-adjusted life year) prevented, using an incremental cost-effectiveness ratio (ICER), compared with current targeted testing. Outcomes were cancer incidence/mortality, disease cases, and treatment costs reduced.

Results

Population screening would reduce variant-attributable cancers by 28.8%, cancer deaths by 31.2%, and CF/SMA/FXS cases by 24.8%, compared with targeted testing. Assuming AUD$400 per test, investment required would be between 4 and 5 times higher than current expenditure. However, screening would lead to substantial savings in medical costs and DALYs prevented, at a highly cost-effective ICER of AUD$4038/DALY. At AUD$200 per test, screening would approach cost-saving for the health system (ICER = AUD$22/DALY).

Conclusion

Preventive genomic screening in early adulthood would be highly cost-effective in a single-payer health-care system, but ethical issues must be considered.

The Ethics of General Population Preventive Genomic Sequencing: Rights and Social Justice

Advances in DNA sequencing technology open new possibilities for public health genomics, especially in the form of general population preventive genomic sequencing (PGS). Such screening programs would sit at the intersection of public health and preventive health care, and thereby at once invite and resist the use of clinical ethics and public health ethics frameworks. Despite their differences, these ethics frameworks traditionally share a central concern for individual rights. We examine two putative individual rights-the right not to know, and the child's right to an open future-frequently invoked in discussions of predictive genetic testing, in order to explore their potential contribution to evaluating this new practice. Ultimately, we conclude that traditional clinical and public health ethics frameworks, and these two rights in particular, should be complemented by a social justice perspective in order adequately to characterize the ethical dimensions of general population PGS programs.

Age and perceived risks and benefits of preventive genomic screening

Purpose

As genome sequencing moves from research to clinical practice, sequencing technologies focused on “medically actionable” targets are being promoted for preventive screening despite the dearth of systematic evidence of risks and benefits and criteria for who should be screened. This study investigates researchers’ and research participants’ perceptions of these issues within the context of a preventive genomic screening study, GeneScreen.

Methods

We recorded researcher deliberations regarding age eligibility criteria and the risks and benefits of screening, and conducted interviews with 50 GeneScreen participants about their motivations for joining and perceptions of risks and benefits.

Results

Researchers made assumptions about who would want and benefit from screening based on age. After discussion, researchers opted not to have an upper age limit for enrollment. Participants of all ages perceived similar benefits, including prevention, treatment, and cascade testing, and similar risks such as insurance discrimination and worry.

Conclusion

While clinical benefits of preventive genomic screening for older adults are debatable, our respondents perceived a range of benefits of screening in both clinical and research settings. Researchers and clinicians should carefully consider decisions about excluding older adults and providing information about benefits and risks across age groups.

The Impact of Whole-Genome Sequencing on the Primary Care and Outcomes of Healthy Adult Patients: A Pilot Randomized Trial

Background

Whole-genome sequencing (WGS) in asymptomatic adults might prevent disease but increase health care use without clinical value.

Objective

To describe the effect on clinical care and outcomes of adding WGS to standardized family history assessment in primary care.

Design

Pilot randomized trial. (ClinicalTrials.gov: NCT01736566).

Setting

Academic primary care practices.

Participants

9 primary care physicians (PCPs) and 100 generally healthy patients recruited at ages 40 to 65 years.

Intervention

Patients were randomly assigned to receive a family history report alone (FH group) or in combination with an interpreted WGS report (FH + WGS group), which included monogenic disease risk (MDR) results (associated with Mendelian disorders), carrier variants, pharmacogenomic associations, and polygenic risk estimates for cardiometabolic traits. Each patient met with his or her PCP to discuss the report.

Measurements

Clinical outcomes and health care use through 6 months were obtained from medical records and audio-recorded discussions between PCPs and patients. Patients' health behavior changes were surveyed 6 months after receiving results. A panel of clinician-geneticists rated the appropriateness of how PCPs managed MDR results.

Results

Mean age was 55 years; 58% of patients were female. Eleven FH + WGS patients (22% [95% CI, 12% to 36%]) had new MDR results. Only 2 (4% [CI, 0.01% to 15%]) had evidence of the phenotypes predicted by an MDR result (fundus albipunctatus due to RDH5 and variegate porphyria due to PPOX). Primary care physicians recommended new clinical actions for 16% (CI, 8% to 30%) of FH patients and 34% (CI, 22% to 49%) of FH + WGS patients. Thirty percent (CI, 17% to 45%) and 41% (CI, 27% to 56%) of FH and FH + WGS patients, respectively, reported making a health behavior change after 6 months. Geneticists rated PCP management of 8 MDR results (73% [CI, 39% to 99%]) as appropriate and 2 results (18% [CI, 3% to 52%]) as inappropriate.

Limitation

Limited sample size and ancestral and socioeconomic diversity.

Conclusion

Adding WGS to primary care reveals new molecular findings of uncertain clinical utility. Nongeneticist providers may be able to manage WGS results appropriately, but WGS may prompt additional clinical actions of unclear value.

Primary Funding Source

National Institutes of Health.

Is there evidence that we should screen the general population for Lynch syndrome with genetic testing? A systematic review

BACKGROUND

The emerging dual imperatives of personalized medicine and technologic advances make population screening for preventable conditions resulting from genetic alterations a realistic possibility. Lynch syndrome is a potential screening target due to its prevalence, penetrance, and the availability of well-established, preventive interventions. However, while population screening may lower incidence of preventable conditions, implementation without evidence may lead to unintentional harms. We examined the literature to determine whether evidence exists that screening for Lynch-associated mismatch repair (MMR) gene mutations leads to improved overall survival, cancer-specific survival, or quality of life. Documenting evidence and gaps is critical to implementing genomic approaches in public health and guiding future research.

MATERIALS AND METHODS

Our 2014-2015 systematic review identified studies comparing screening with no screening in the general population, and controlled studies assessing analytic validity of targeted next-generation sequencing, and benefits or harms of interventions or screening. We conducted meta-analyses for the association between early or more frequent colonoscopies and health outcomes.

RESULTS

Twelve studies met our eligibility criteria. No adequate evidence directly addressed the main question or the harms of screening in the general population. Meta-analyses found relative reductions of 68% for colorectal cancer incidence (relative risk: 0.32, 95% confidence interval: 0.23-0.43, three cohort studies, 590 participants) and 78% for all-cause mortality (relative risk: 0.22, 95% confidence interval: 0.09-0.56, three cohort studies, 590 participants) for early or more frequent colonoscopies among family members of people with cancer who also had an associated MMR gene mutation.

CONCLUSION

Inadequate evidence exists examining harms and benefits of population-based screening for Lynch syndrome. Lack of evidence highlights the need for data that directly compare benefits and harms.

Which Results to Return: Subjective Judgments in Selecting Medically Actionable Genes

BACKGROUND

Advances in genomics have led to calls for returning information about medically actionable genes (MAGs) to patients, research subjects, biobank participants, and through screening programs, the general adult population. Which MAGs are returned affects the harms and benefits of every genetic testing endeavor. Despite published recommendations of selection criteria for MAGs to return, scant data exist regarding how decision makers actually apply such criteria.

METHODS

The process and criteria used by researchers when selecting MAGs for a preventive genomic sequencing program targeting the general adult population were examined. The authors observed and audio-recorded the gene selection meetings, and analyzed meeting transcripts, gene scoring sheets, and meeting handouts.

RESULTS

To select MAGs, the committee imported, from a preexisting project, "a semiquantitative metric" that scores genes on five criteria. Numerous subjective judgments and conceptual challenges in defining and applying the five criteria complicated the selection process. Criteria-related challenges also included the limited evidence available about facts fundamental to the scoring decisions and the emergence and application of criteria that were not part of the original metric.

CONCLUSIONS

When identifying MAGs appropriate for screening and return, decision makers must expect and prepare to address such issues as the inevitability of subjective judgments, limited evidence about fundamental decision-making elements, the conceptual complexity of defining criteria, and the emergence of unplanned criteria during the gene selection process.

Personal Genome Sequencing in Ostensibly Healthy Individuals and the PeopleSeq Consortium

Thousands of ostensibly healthy individuals have had their exome or genome sequenced, but a much smaller number of these individuals have received any personal genomic results from that sequencing. We term those projects in which ostensibly healthy participants can receive sequencing-derived genetic findings and may also have access to their genomic data as participatory predispositional personal genome sequencing (PPGS). Here we are focused on genome sequencing applied in a pre-symptomatic context and so define PPGS to exclude diagnostic genome sequencing intended to identify the molecular cause of suspected or diagnosed genetic disease. In this report we describe the design of completed and underway PPGS projects, briefly summarize the results reported to date and introduce the PeopleSeq Consortium, a newly formed collaboration of PPGS projects designed to collect much-needed longitudinal outcome data.

The promise and peril of genomic screening in the general population

Purpose

Utilization of sequencing to screen the general population for preventable monogenic conditions is receiving substantial attention due to its potential to decrease morbidity and mortality. However, the selection of which variants to return is a serious implementation challenge. Procedures must be investigated to ensure optimal test characteristics and avoidance of harm from false positive test results.

Methods

We scanned exome sequences from 478 well-phenotyped individuals for potentially pathogenic variants in 17 genes representing 11 conditions that are among the most medically actionable Mendelian disorders in adults. We developed 5 variant selection algorithms with increasing sensitivity and measured their specificity in these 17 genes.

Results

Variant selection algorithms with increasing sensitivity exhibited decreased specificity, and performance was highly dependent on the genes analyzed. The most sensitive algorithm ranged from 88.8% to 99.6% specificity among the 17 genes.

Conclusion

For very low prevalence conditions, small reductions in specificity greatly increase false positives. This inescapable test characteristic governs the predictive value of genomic sequencing in the general population. To address this issue, test performance must be evaluated systematically for each condition so that the false negatives and false positives can be tailored for optimal outcomes, depending on the downstream clinical consequences.