Point/Counterpoint: Is It Time for Universal Germline Genetic Testing for all GI Cancers?

Refining the interpretation of variants of uncertain significance in hereditary cancer screening through integrated RNA sequencing

Purpose

Although up to 25% of germline variants are predicted to affect splicing, most are classified as variants of uncertain significance (VUS) because of the limited understanding of their functional consequences. Here, we investigated the impact of RNA sequencing (RNA-seq) data on the ability to resolve splicing-related VUS.

Methods

Patients with VUS predicted to alter splicing identified through commercial hereditary cancer testing between October 2021 to July 2023 were included. RNA-seq was used to compare splicing patterns between patient blood samples and normal controls. VUS reclassification rates were calculated.

Results

In total, 411 VUS in 52 genes predicted to affect splicing were included. RNA-seq results resolved 26.3% (108/411) of the VUS: 28 (6.8%) upgraded to pathogenic/likely pathogenic, and 80 (19.5%) downgraded to not reportable. Among the 28 upgraded, 17 (60.7%) were intronic, 9 (32.1%) were exonic missense variants, and 2 (7.1%) were exonic synonymous variants. Most of the VUS downgraded to not reportable were intronic (64/80, 80%). The remaining 16 (20%) of the downgraded VUS were synonymous variants.

Conclusion

This study underscores the utility of RNA-seq to detect variants that affect splicing and could have an impact on cancer risk assessment management and treatment.

Pilot implementation study of a default genetic referral process for patients with early-onset colorectal cancer

Purpose

Early-onset colorectal cancer (CRC) diagnosed under age 50 is increasing at alarming rates, with >75% of early-onset cases occurring in patients between 40 and 49 years old. Germline genetic risk evaluations are key to delivering high-quality care to these patients.

Methods

We conducted a single-arm pilot implementation study of a default genetic referral process for patients diagnosed with CRC between ages 40 and 49 at 5 hospitals in an academic health system. A research coordinator notified patients and their oncologists of their eligibility for a default genetic referral, after which all patients who did not opt out were referred for genetic counseling, testing, and result disclosure as per usual care. The primary outcome was the genetic referral rate; secondary outcomes included the percentage of eligible patients who were scheduled for a genetic evaluation, completed genetic counseling, and underwent testing within 3 months of the initial referral. We conducted semistructured exit interviews with a subset of patients and oncologists to elicit feedback on the intervention.

Results

We included 53 patients, of whom 49 (92%) were referred to genetics, 38 (72%) were scheduled, 22 (42%) completed genetic counseling, and 13 (25%) underwent testing within 3 months of the initial referral. In exit interviews (n = 10 patients and 10 oncologists), participants reported finding the default genetic referral process acceptable and feasible to implement.

Conclusion

A default genetic referral process is acceptable, feasible, and associated with a high referral rate for patients with early-onset CRC; however, subsequent scheduling, evaluation, and testing rates remain suboptimal.

Poor compliance with germline testing recommendations in colorectal cancer patients undergoing molecular residual disease testing

BACKGROUND

Approximately 15% of colorectal cancers (CRCs) are associated with germline mutations. There is increasing adoption of DNA-based assays for molecular residual disease (MRD) and growing evidence supporting its clinical utility, particularly for CRC by oncologists in the U.S. We assessed the uptake of germline multi-gene panel testing (MGPT) for hereditary cancer in CRC patients receiving MRD analyses in community oncology settings.

METHODS

This retrospective study included 80 patients receiving care for CRC through community oncology practices who were referred for MRD testing at a commercial laboratory (January-March 2022). Clinical data, including test requisition forms, pathology reports, and clinical notes were reviewed. Documentation of tumor microsatellite instability and/or immunohistochemical (IHC) testing for mismatch repair (MMR) deficiency, age of CRC diagnosis, family history of cancer, and any order or recommendation for MGPT were assessed.

RESULTS

Overall, 5/80 (6.3%) patients in the study have documented germline MGPT; 65/80 (81.3%) patients have documented MMR testing of their colorectal tumor. Among the 5 cases with abnormal MMR IHC, 2 have MGPT. Of the 33 patients meeting the 2021 National Comprehensive Cancer Network (NCCN) criteria for genetic/familial high-risk assessment, only 2 have MGPT.

CONCLUSIONS

Our real-world data suggest that many CRC patients receiving MRD testing and meeting NCCN (v. 2021) criteria for germline MGPT may not be receiving evaluation beyond routine MMR status. Process and educational improvements are needed in community health settings to increase access and uptake of germline testing among CRC patients regardless of age at diagnosis or MMR status.

Universal screening of colorectal tumors for lynch syndrome: a survey of patient experiences and opinions

BACKGROUND

Lynch syndrome represents the most common hereditary cause of both colorectal and endometrial cancer. It is caused by defects in mismatch repair genes, as well as EPCAM. Universal screening of colon tumors for Lynch syndrome via microsatellite instability (MSI) and/or immunohistochemistry (IHC) can identify patients and families at risk to develop further cancers and potentially impact surveillance and treatment options. The approach to implementation of universal screening, taking ethical considerations into account, is critical to its effectiveness, with patient perspectives providing valuable insight.

METHODS

Patients whose colon tumors underwent universal screening at Penn State Hershey Medical Center over a period of 2.5 years were mailed a survey on universal screening in 2017. Along with the survey, they received a recruitment letter and a summary explanation of research. The survey included both multiple choice and free-response questions that covered topics including respondent knowledge of Lynch syndrome, attitudes toward universal screening and experiences with the screening protocol as implemented.

RESULTS

Sixty-six of 297 possible patients (22.2%) responded to the survey, including 13 whose screening results raised concern for Lynch syndrome. 75.8% of respondents supported universal tumor screening without informed consent. 92.4% preferred receiving screening results regardless of outcome. Respondents described benefits to screening for themselves and their families.

CONCLUSIONS

While broadly supporting universal tumor screening without informed consent, respondents also wanted more information shared about the screening policy, as well as their results. These patient preferences should be one of many factors considered when implementing universal screening and can also inform practices regarding both tumor profiling and universal genetic testing, which is becoming more prevalent.

Outcomes of a universal germline screening program in a community urology practice

The role of germline genetic testing in urologic oncology has expanded in recent years. However, implementation of genetic testing in community practices remains a challenge, often due to limited access to qualified genetics trained providers. In this study, we report outcomes of a universal germline screening program in a community urology practice. Between November 2021 and September 2022, all patients referred for urology clinic visits at Frederick Health (Frederick, MD, USA) were provided an online genetics screening questionnaire prior to the visit. Responses were compared against National Comprehensive Cancer Network (NCCN) criteria for germline testing. Those who met criteria were provided educational materials at the end of the questionnaire, and then counseled by a trained urologic oncologist (HC) in the clinic or referred to a genetic counselor prior to testing. Testing was performed with a 36-gene pan-cancer panel (CancerNext) or a 14-gene targeted prostate cancer panel (ProstateNext), with or without additional RNA analysis (RNAinsight) (Ambry Genetics, CA, USA). Demographic and clinical parameters, as well as genetic testing results, were retrospectively collected under IRB approval. In the study period, 765 patients were seen over 1370 clinic visits. Of these, 505 patients (66.0%) completed the screening questionnaire. The majority were completed via email (54.5%) with the remainder (45.5%) via text message. Of the patients who completed screening, 125/505 (24.7%) met NCCN criteria for germline testing. 58/125 patients (46.4%) who met criteria underwent germline testing, of whom 5/58 (8.6%) had distinct pathogenic mutations identified. These included actionable mutations in BRCA1, BRCA2, and CHEK2, as well as an additional pathogenic mutation in NBN. Variants of unknown significance were identified in 8/58 patients (13.8%) in 11 total genes. Challenges to implementation of this program included meeting institutional requirements for genetic testing consent, facilitating specimen collection in clinic, and integration of results into the electronic health record. Genetic risk assessment for high-risk individuals is feasible as part of a universal screening program in a community urology practice. Approximately 8% of tested patients were found to have pathogenic germline mutations, which is consistent with contemporary tertiary referral cohorts.

Streamlining the diagnostic pathway for Lynch syndrome in colorectal cancer patients: a 10-year experience in a single Italian Cancer Center

BACKGROUND

Universal screening of colorectal cancer (CRC) patients for Lynch syndrome (LS) through MisMatch Repair (MMR) testing is recommended. BRAF V600E mutation and/or MLH1 promoter methylation (Reflex Testing, RefT)generally rule out LS in MLH1-deficient (dMLH1) patients. We estimated the impact of RefTon genetic counseling (GC) and on the diagnostic yield of genetic testing (GT).

METHODS

Overall, 3199 CRC patients were referred to our center between 2011 and 2021. Patients referred until January 2019 (n=2536) underwent universal MMR testing and were termed 'Cohort A'; among patients after February 2019 (n=663), 'Cohort B', RefT was also performed in dMLH1 patients.

RESULTS

Overall, 401/3199 patients (12.5%) were MMR-deficient (dMMR); 312 (77.8%) in cohort A and 89 (22.2%) inB; 346/401 were dMLH1 (86.3%), 262/312 (83.9%) in cohort A and 84/89 (94.3%) in B. In Cohort A, 91/312 (29.1%) dMMR patients were referred to GC, 69/91 (75.8%) were in the dMLH1 group; 57/69 (82.6%) dMLH1 patients underwent GT and 1/57 (1.7%) had LS. In Cohort B, 3/84 dMLH1 patients did not undergo BRAF testing. Three BRAF wt and not hypermethylated of the remaining 81 dMLH1 patients were referred to GC and GT, and one had LS. This diagnostic pathway reduced GC referrals by 96% (78/81) in Cohort B and increased the diagnostic yield of GT by about 20 times.

CONCLUSION

Our findings support RefT in dMLH1 CRC patients within the LS diagnostic pathway, as it reduces the number of GC sessions needed and increases the diagnostic yield of GT.

The Evolution of Genetic Testing from Focused Testing to Panel Testing and from Patient Focused to Population Testing: Are We There Yet?

The field of cancer genetics has evolved significantly over the past 30 years. Genetic testing has become less expensive and more comprehensive which has changed practice patterns. It is no longer necessary to restrict testing to those with the highest likelihood of testing positive. In addition, we have learned that the criteria developed to determine who has the highest likelihood of testing positive are neither sensitive nor specific. As a result, the field is moving from testing only the highest risk patients identified based on testing criteria to testing all cancer patients. This requires new service delivery models where testing can be mainstreamed into oncology clinics and posttest genetic counseling can be provided to individuals who test positive and those with concerning personal or family histories who test negative. The use of videos, testing kiosks, chatbots, and genetic counseling assistants have been employed to help facilitate testing at a larger scale and have good patient uptake and satisfaction. While testing is important for cancer patients as it may impact their treatment, future cancer risks, and family member's cancer risks, it is unfortunate that their cancer could not be prevented in the first place. Population testing for all adults would be a strategy to identify individuals with adult-onset diseases before they develop cancer in an attempt to prevent it entirely. A few research studies (Healthy Nevada and MyCode) have offered population testing for the three Centers for Disease Control and Prevention Tier 1 conditions: hereditary breast and ovarian cancer syndrome, Lynch syndrome, and familial hypercholesterolemia finding a prevalence of 1 in 70 individuals in the general population. We anticipate that testing for all cancer patients and the general population will continue to increase over the next 20 years and the genetics community needs to help lead the way to ensure this happens in a responsible manner.

Feasibility and Clinical Utility of Reporting Hereditary Cancer Predisposition Pathogenic Variants Identified in Research Germline Sequencing: A Prospective Interventional Study

PURPOSE

Patients with cancer frequently undergo research-grade germline sequencing but clinically actionable results are not routinely disclosed. The objective of this study is to evaluate the feasibility of reporting clinically relevant secondary findings (SF) identified in germline research sequencing using the institutional molecular tumor board (MTB) and the treating oncology physician.

METHODS

This prospective, interventional cohort study enrolled Total Cancer Care participants with any cancer diagnosis at a single institution. Patients underwent research-grade germline whole-exome sequencing, with bioinformatic analysis in a Clinical Laboratory Improvement Amendments-certified laboratory to verify pathogenic/likely pathogenic germline variants (PGVs) in any American College of Medical Genomics and Genetics SF v2.0 genes. After a protocol modification in consenting patients, the MTB reported PGVs to treating oncology physicians with recommendations for referral to a licensed genetic counselor and clinical confirmatory testing.

RESULTS

Of the 781 enrolled participants, 32 (4.1%) harbored cancer predisposition PGVs, 24 (3.1%) were heterozygous carriers of an autosomal recessive cancer predisposition syndrome, and 14 (1.8%) had other hereditary disease PGVs. Guideline-directed testing would have missed 37.5% (12/32) of the inherited cancer predisposition PGVs, which included BRCA1, BRCA2, MSH6, SDHAF2, SDHB, and TP53 variants. Three hundred fifteen participants consented to reporting results; results for all living patients were reported to the clinical team with half referred to a licensed genetic counselor. There was concordance between all research variants identified in patients (n = 9) who underwent clinical confirmatory sequencing.

CONCLUSION

MTB reporting of research-grade germline sequencing to the clinical oncology team is feasible. Over a third of PGVs identified using a universal testing strategy would have been missed by guideline-based approach, suggesting a role for expanding germline testing.

Genetic insights: High germline variant rate in an indigenous African cohort with early-onset colorectal cancer

Introduction

The increase in incidence of colorectal cancer in young patients of African ancestry coupled with increased aggressiveness has warranted investigation of the heritable nature of these cancers. Only a limited number of published reports of hereditary colorectal cancer in indigenous African populations have been reported and no systematic screening of these groups has been performed previously. We aimed to investigate causative germline variants and to establish the incidence of pathogenic/likely pathogenic germline variants in the known colorectal cancer genes in indigenous African colorectal cancer patients using a next-generation sequencing (NGS) multigene panel.

Materials and methods

Patients were selected from two hospitals in Cape Town and Johannesburg, South Africa. Patients with unresolved molecular diagnosis with an age of onset below or at 60 years were selected. Germline DNA samples were analyzed using a 14-gene NGS panel on the Ion Torrent platform. Variant calling and annotation were performed, and variants were classified according to the American College of Medical Genetics and Genomics guidelines. Observed variants were verified by Sanger sequencing and/or long-range PCR.

Results

Out of 107 patients, 25 (23.4%) presented with a pathogenic/likely pathogenic germline variant (PGV). Fourteen PGVs in at least one mismatch repair (MMR) gene were identified and verified in 12 patients (11.2%). Of these MMR gene variants, five were novel. The remaining 10 PGVs were in the APC, BMPR1A, MUTYH, POLD1, and TP53 genes.

Conclusion

The high incidence of PGVs associated with early-onset colorectal cancer in indigenous African patients has important implications for hereditary colorectal cancer risk management. These findings pave the way for personalized genetic screening programs and cascade testing in South Africa. The next step would involve further screening of the unresolved cases using tools to detect copy number variation, methylation, and whole exome sequencing.

Exploring Stakeholders' Perspectives on Implementing Universal Germline Testing for Colorectal Cancer: Findings From a Clinical Practice Survey

PURPOSE

New guidelines recommend considering germline genetic testing for all patients with colorectal cancer (CRC). However, there is a lack of data on stakeholders' perspectives on the advantages and barriers of implementing universal germline testing (UGT). This study assessed the perspectives of members of the Collaborative Group of the Americas on Inherited Gastrointestinal Cancer (CGA-IGC) regarding the implementation of UGT for patients with CRC, including readiness, logistics, and barriers.

METHODS

A cross-sectional survey was sent to 317 active members of CGA-IGC. The survey included sections on demographics, clinical practice specialty, established institutional practices for testing, and questions pertaining to support of and barriers to implementing UGT for patients with CRC.

RESULTS

Eighty CGA-IGC members (25%) participated, including 42 genetic counselors (53%) and 14 gastroenterologists (18%). Forty-seven (59%) reported an academic medical center as their primary work setting, and most participants (56%) had more than 10 years of clinical practice. Although most participants (73%) supported UGT, 54% indicated that changes in practice would be required before adopting UGT, and 39% indicated that these changes would be challenging to implement. There was support for both genetics and nongenetics providers to order genetic testing, and a majority (57%) supported a standardized multigene panel rather than a customized gene panel. Key barriers to UGT implementation included limited genetics knowledge among nongenetics providers, time-consuming processes for obtaining consent, ordering tests, disclosing results, and lack of insurance coverage.

CONCLUSION

This study demonstrates wide support among hereditary GI cancer experts for implementation of UGT for patients with CRC. However, alternative service delivery models using nongenetics providers should be considered to address the logistical barriers to UGT implementation, particularly the growing demand for genetic testing.

Report from the 24th Annual Western Canadian Gastrointestinal Cancer Consensus Conference on Colorectal Cancer, Richmond, British Columbia, 28-29, October 2022

The 24th annual Western Canadian Gastrointestinal Cancer Consensus Conference (WCGCCC) was held in Richmond, British Columbia, on 28-29 October 2022. The WCGCCC is an interactive multidisciplinary conference attended by healthcare professionals from across Western Canada (British Columbia, Alberta, Saskatchewan, and Manitoba) who are involved in the care of patients with gastrointestinal cancer. Surgical, medical, and radiation oncologists; pathologists; radiologists; and allied health care professionals such as dieticians, nurses and a genetic counsellor participated in presentation and discussion sessions for the purpose of developing the recommendations presented here. This consensus statement addresses current issues in the management of colorectal cancer.

Potential pathogenic germline variant reporting from tumor comprehensive genomic profiling complements classic approaches to germline testing

Existing guidance regarding clinically informed germline testing for patients with cancer is effective for evaluation of classic hereditary cancer syndromes and established gene/cancer type associations. However, current screening methods may miss patients with rare, reduced penetrance, or otherwise occult hereditary risk. Secondary finding of suspected germline variants that may confer inherited cancer risk via tumor comprehensive genomic profiling (CGP) has the potential to help address these limitations. However, reporting practices for secondary finding of germline variants are inconsistent, necessitating solutions for transparent and coherent communication of these potentially important findings. A workflow for improved confidence detection and clear reporting of potential pathogenic germline variants (PPGV) in select cancer susceptibility genes (CSG) was applied to a research dataset from real-world clinical tumor CGP of > 125,000 patients with advanced cancer. The presence and patterns of PPGVs identified across tumor types was assessed with a focus on scenarios in which traditional clinical germline evaluation may have been insufficient to capture genetic risk. PPGVs were identified in 9.7% of tumor CGP cases using tissue- and liquid-based assays across a broad range of cancer types, including in a number of "off-tumor" contexts. Overall, PPGVs were identified in a similar proportion of cancers with National Comprehensive Cancer Network (NCCN) recommendations for germline testing regardless of family history (11%) as in all other cancer types (9%). These findings suggest that tumor CGP can serve as a tool that is complementary to traditional germline genetic evaluation in helping to ascertain inherited susceptibility in patients with advanced cancer.

Germline Variants Incidentally Detected via Tumor-Only Genomic Profiling of Patients With Mesothelioma

IMPORTANCE

Patients with mesothelioma often have next-generation sequencing (NGS) of their tumor performed; tumor-only NGS may incidentally identify germline pathogenic or likely pathogenic (P/LP) variants despite not being designed for this purpose. It is unknown how frequently patients with mesothelioma have germline P/LP variants incidentally detected via tumor-only NGS.

OBJECTIVE

To determine the prevalence of incidental germline P/LP variants detected via tumor-only NGS of mesothelioma.

DESIGN, SETTING, AND PARTICIPANTS

A series of 161 unrelated patients with mesothelioma from a high-volume mesothelioma program had tumor-only and germline NGS performed during April 2016 to October 2021. Follow-up ranged from 18 months to 7 years. Tumor and germline assays were compared to determine which P/LP variants identified via tumor-only NGS were of germline origin. Data were analyzed from January to March 2023.

MAIN OUTCOMES AND MEASURES

The proportion of patients with mesothelioma who had P/LP germline variants incidentally detected via tumor-only NGS.

RESULTS

Of 161 patients with mesothelioma, 105 were male (65%), the mean (SD) age was 64.7 (11.2) years, and 156 patients (97%) self-identified as non-Hispanic White. Most (126 patients [78%]) had at least 1 potentially incidental P/LP germline variant. The positive predictive value of a potentially incidental germline P/LP variant on tumor-only NGS was 20%. Overall, 26 patients (16%) carried a P/LP germline variant. Germline P/LP variants were identified in ATM, ATR, BAP1, CHEK2, DDX41, FANCM, HAX1, MRE11A, MSH6, MUTYH, NF1, SAMD9L, and TMEM127.

CONCLUSIONS AND RELEVANCE

In this case series of 161 patients with mesothelioma, 16% had confirmed germline P/LP variants. Given the implications of a hereditary cancer syndrome diagnosis for preventive care and familial counseling, clinical approaches for addressing incidental P/LP germline variants in tumor-only NGS are needed. Tumor-only sequencing should not replace dedicated germline testing. Universal germline testing is likely needed for patients with mesothelioma.

Family Matters: Germline Testing in Thoracic Cancers

Most thoracic cancers arise via a series of stepwise somatic alterations driven by a well-defined carcinogen (ie, tobacco or asbestos for lung cancer and mesothelioma, respectively). A small proportion can emerge on a background of pathogenic germline variants (PGVs), which have the property of heritability. In general, PGVs may be initially suspected on the basis of the presence of specific clinical features. Such gene × environment interactions significantly increase the risk of developing lung cancer (1.5- to 3.2-fold). PGVs have been discovered involving the actionable driver oncogene, epidermal growth factor receptor (EGFR), with an EGFR T790M PGV rate of 0.3%-0.9% in the nonsquamous non-small-cell lung cancer subtype. Its appearance during routine somatic DNA sequencing in those patients who have not had a previous tyrosine kinase inhibitor should raise suspicion. In patients with sporadic mesothelioma, BAP1 is the most frequently mutated tumor driver, with a PGV rate between 2.8% and 8%, associated with a favorable prognosis. BAP1 PGVs accelerate mesothelioma tumorigenesis after asbestos exposure in preclinical models and may be partly predicted by clinical criteria. At present, routine germline genetic testing for thoracic cancers is not a standard practice. Expert genetic counseling is, therefore, required for patients who carry a PGV. Ongoing studies aim to better understand the natural history of patients harboring PGVs to underpin future cancer prevention, precise counseling, and cancer management with the goal of improving the quality and length of life.

Duty to recontact in genomic cancer care: a tool helping to assess the professional’s responsibility

Tumour DNA and germline testing, based on DNA-wide sequencing analysis, are becoming more and more routine in clinical-oncology practice. A promising step in medicine, but at the same time leading to challenging ethicolegal questions. An important one is under what conditions individuals (patients and their relatives, research participants) should be recontacted with new information, even if many years have passed since the last contact. Based on legal- and ethical study, we developed a tool to help professionals to decide whether or not to recontact an individual in specific cases. It is based on four assessment criteria: (1) professional relationship (2) clinical impact (3) individual's preferences and (4) feasibility. The tool could also serve as a framework for guidelines on the topic.

Does neoadjuvant treatment in resectable pancreatic cancer improve overall survival? A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Neoadjuvant chemotherapy may improve overall survival (OS) in 'borderline' resectable pancreatic cancer (RPC). Whether the results are the same in upfront RPC is unknown.

MATERIALS AND METHODS

To evaluate the association of neoadjuvant treatment and survival outcomes in RPC, a systematic literature review was carried out including prospective randomized trials of neoadjuvant treatment versus upfront surgery. Articles indexed in PubMed, Embase and Scopus were evaluated. Data regarding systemic treatment regimens, R0 resection rates, disease-free survival (DFS) and OS were extracted. The outcomes were compared using a random-effects model. The index I² and the graphs of funnel plot were used for the interpretation of the data.

RESULTS

Of 3229 abstracts, 6 randomized controlled trials were considered eligible with a combined sample size of 805 RPC patients. Among the trials, PACT-15, PREP-02/JSAP-05 and updated long-term results from PREOPANC and NEONAX trials were included. Combining the studies with meta-analysis, we could see that neoadjuvant treatment in RPC does not improve DFS [hazard ratio (HR) 0.71 (0.46-1.09)] or OS [HR 0.76 (0.52-1.11)], without significant heterogeneity. Interestingly, R0 rates improved ∼20% with the neoadjuvant approach [HR 1.2 (1.04-1.37)]. It is important to note that most studies evaluated gemcitabine-based regimens in the neoadjuvant setting.

CONCLUSIONS

Neoadjuvant chemotherapy or chemoradiation does not improve DFS or OS in RPC compared to upfront surgery followed by adjuvant treatment. Neoadjuvant treatment improves R0 rates by ∼20%. Randomized ongoing trials are eagerly awaited with more active combined regimens including modified FOLFIRINOX.

Saturation-scale functional evidence supports clinical variant interpretation in Lynch syndrome

BACKGROUND

Lynch syndrome (LS) is a cancer predisposition syndrome affecting more than 1 in every 300 individuals worldwide. Clinical genetic testing for LS can be life-saving but is complicated by the heavy burden of variants of uncertain significance (VUS), especially missense changes.

RESULT

To address this challenge, we leverage a multiplexed analysis of variant effect (MAVE) map covering >94% of the 17,746 possible missense variants in the key LS gene MSH2. To establish this map's utility in large-scale variant reclassification, we overlay it on clinical databases of >15,000 individuals with LS gene variants uncovered during clinical genetic testing. We validate these functional measurements in a cohort of individuals with paired tumor-normal test results and find that MAVE-based function scores agree with the clinical interpretation for every one of the MSH2 missense variants with an available classification. We use these scores to attempt reclassification for 682 unique missense VUS, among which 34 scored as deleterious by our function map, in line with previously published rates for other cancer predisposition genes. Combining functional data and other evidence, ten missense VUS are reclassified as pathogenic/likely pathogenic, and another 497 could be moved to benign/likely benign. Finally, we apply these functional scores to paired tumor-normal genetic tests and identify a subset of patients with biallelic somatic loss of function, reflecting a sporadic Lynch-like Syndrome with distinct implications for treatment and relatives' risk.

CONCLUSION

This study demonstrates how high-throughput functional assays can empower scalable VUS resolution and prospectively generate strong evidence for variant classification.

Comparison of Germline Genetic Testing Before and After a Medical Policy Covering Universal Testing Among Patients With Colorectal Cancer

IMPORTANCE

In 2020, some health insurance plans updated their medical policy to cover germline genetic testing for all patients diagnosed with colorectal cancer (CRC). Guidelines for universal tumor screening via microsatellite instability and/or immunohistochemistry (MSI/IHC) for mismatch repair protein expression for patients with CRC have been in place since 2009.

OBJECTIVES

To examine whether uptake of MSI/IHC screening and germline genetic testing in patients with CRC has improved under these policies and to identify actionable findings and management implications for patients referred for germline genetic testing.

DESIGN, SETTING, AND PARTICIPANTS

The multicenter, retrospective cohort study comprised 2 analyses of patients 18 years or older who were diagnosed with CRC between January 1, 2017, and December 31, 2020. The first analysis used an insurance claims data set to examine use of MSI/IHC screening and germline genetic testing for patients diagnosed with CRC between 2017 and 2020 and treated with systemic therapy. The second comprised patients with CRC who had germline genetic testing performed in 2020 that was billed under a universal testing policy.

MAIN OUTCOMES AND MEASURES

Patient demographic characteristics, clinical information, and use of MSI/IHC screening and germline genetic testing were analyzed.

RESULTS

For 9066 patients with newly diagnosed CRC (mean [SD] age, 64.2 [12.7] years; 4964 [54.8%] male), administrative claims data indicated that MSI/IHC was performed in 6645 eligible patients (73.3%) during the study period, with 2288 (25.2%) not receiving MSI/IHC despite being eligible for coverage. Analysis of a second cohort of 55 595 patients with CRC diagnosed in 2020 and covered by insurance found that only 1675 (3.0%) received germline genetic testing. In a subset of patients for whom germline genetic testing results were available, 1 in 6 patients had pathogenic or likely pathogenic variants, with most of these patients having variants with established clinical actionability.

CONCLUSIONS AND RELEVANCE

This nationwide cohort study found suboptimal rates of MSI/IHC screening and germline genetic testing uptake, resulting in clinically actionable genetic data being unavailable to patients diagnosed with CRC, despite universal eligibility. Effective strategies are required to address barriers to implementation of evidence-based universal testing policies that support precision treatment and optimal care management for patients with CRC.