A Focused Clinical Review of Lynch Syndrome

Barriers and Facilitators in Diagnostic Pathways That Align Universal Tumor Screening and Mainstream Genetic Testing for Lynch Syndrome in Colorectal Cancer: Protocol for a Scoping Review With a Narrative Synthesis

BACKGROUND

Approximately 3% of colorectal cancers (CRCs) are due to Lynch syndrome (LS), a hereditary cancer syndrome caused by pathogenic variants (PVs) in the mismatch repair (MMR) genes. Patients with CRC and LS have elevated lifetime risks for a range of cancers and require personalized treatment and targeted surveillance. Relatives of people affected by LS who share the same PV also have elevated cancer risks and can benefit from preventive measures and/or risk-reducing surgeries. Despite this, LS remains vastly underdiagnosed. Universal tumor screening (UTS) for deficient MMR is recommended in diagnosing LS in patients with CRC. This process, when combined with genetic testing (GT) offered within routine cancer care (termed "mainstream GT"), aims to identify individuals at risk efficiently, but integrating UTS and mainstream GT for LS in CRC is a complex endeavor.

OBJECTIVE

The aim of the proposed scoping review will be to comprehensively explore the literature on diagnostic pathways comprising UTS and mainstream GT for LS among patients with CRC and barriers and facilitators in their implementation.

METHODS

The scoping review will follow Arksey and O'Malley's expanded framework. Results will be reported following the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews) guidelines and summarized quantitatively. A narrative synthesis will also be performed using the Theoretical Domains Framework.

RESULTS

The results will be presented in a forthcoming scoping review, which we expect to publish in a peer-reviewed journal by early 2026.

CONCLUSIONS

Aligning UTS with mainstream GT for LS in CRC may boost early diagnosis and prevention while reducing waiting times and other patient burdens. By addressing barriers to and facilitators in diagnostic pathways, health care systems can improve the identification and management of LS, ultimately leading to better outcomes for patients and their families. The insights gained from this scoping review will inform the development of a mixed methods study about implementing diagnostic pathways for LS in CRC that integrate UTS and mainstream GT in Italy.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/70831.

Genomics and integrative clinical data machine learning scoring model to ascertain likely Lynch syndrome patients

BACKGROUND

Lynch syndrome (LS) screening methods include multistep molecular somatic tumor testing to distinguish likely-LS patients from sporadic cases, which can be costly and complex. Also, direct germline testing for LS for every diagnosed solid cancer patient is a challenge in resource limited settings. We developed a unique machine learning scoring model to ascertain likely-LS cases from a cohort of colorectal cancer (CRC) patients.

METHODS

We used CRC patients from the cBioPortal database (TCGA studies) with complete clinicopathologic and somatic genomics data. We determined the rate of pathogenic/likely pathogenic variants in five (5) LS genes (MLH1, MSH2, MSH6, PMS2, EPCAM), and the BRAF mutations using a pre-designed bioinformatic annotation pipeline. Annovar, Intervar, Variant Effect Predictor (VEP), and OncoKB software tools were used to functionally annotate and interpret somatic variants detected. The OncoKB precision oncology knowledge base was used to provide information on the effects of the identified variants. We scored the clinicopathologic and somatic genomics data automatically using a machine learning model to discriminate between likely-LS and sporadic CRC cases. The training and testing datasets comprised of 80% and 20% of the total CRC patients, respectively. Group regularisation methods in combination with 10-fold cross-validation were performed for feature selection on the training data.

RESULTS

Out of 4800 CRC patients frorm the TCGA datasets with clinicopathological and somatic genomics data, we ascertained 524 patients with complete data. The scoring model using both clinicopathological and genetic characteristics for likely-LS showed a sensitivity and specificity of 100%, and both had the maximum accuracy, area under the curve (AUC) and AUC for precision-recall (AUCPR) of 1. In a similar analysis, the training and testing models that only relied on clinical or pathological characteristics had a sensitivity of 0.88 and 0.50, specificity of 0.55 and 0.51, accuracy of 0.58 and 0.51, AUC of 0.74 and 0.61, and AUCPR of 0.21 and 0.19, respectively.

CONCLUSIONS

Simultaneous scoring of LS clinicopathological and somatic genomics data can improve prediction and ascertainment for likely-LS from all CRC cases. This approach can increase accuracy while reducing the reliance on expensive direct germline testing for all CRC patients, making LS screening more accessible and cost-effective, especially in resource-limited settings.

Distinct dysregulated pathways in sporadic and Lynch syndrome-associated colorectal cancer offer insights for targeted treatment

Lynch syndrome (LS) is a hereditary disorder that increases the risk of colorectal cancer (CRC) due to constitutional pathogenic variants in mismatch repair (MMR) genes. When coupled with somatic mutations in the same gene, MMR deficiency occurs. However, the mechanisms driving cancer development remain unclear. This study aimed to identify distinct molecular drivers in LS-associated and sporadic CRC. We found that PI3K-Akt signalling is dysregulated in LS-associated CRC, while Wnt signalling predominates in sporadic CRC. Moreover, our findings highlight the therapeutic potential of PI3K-Akt pathway inhibitors, such as taselisib, for LS-associated CRC patients with high pathway dependency. Similarly, Wnt signalling pathway inhibitors, such as XAV939, offer a promising therapeutic approach for sporadic CRC. These findings underscore the importance of understanding the biological basis of disease for developing targeted therapies tailored to CRC subtype-specific oncogenic pathways.

Implementing recommendations for routine mismatch repair (MMR) immunohistochemistry (IHC) testing of endometrial cancer and subsequent patient management

Lynch syndrome is associated with an increased risk of cancer, including endometrial cancer. We audited the introduction of a nurse-led testing and management pathway for Lynch syndrome. All 191 patients diagnosed with endometrial cancer at Somerset NHS Foundation Trust between January 2022 and December 2023 were tested for mis-match repair (MMR) protein immunohistochemistry; germline testing was offered to all 13 who were eligible. Seven patients were diagnosed with Lynch syndrome; all were referred for bowel screening and Helicobacter pylori testing. Information about prophylactic aspirin recommendations was missing for 3/7 patients. We established an effective, nurse-led Lynch syndrome testing pathway, in line with national guidelines.

Diagnostic Challenges due to a Germline Missense MSH2 Variant in a Patient With Immunotherapy-Responsive Locally Advanced Rectal Adenocarcinoma

BACKGROUND

Rapid and accurate identification of mismatch repair (MMR) deficiency and Lynch syndrome is critical in the prognostication and clinical management of patients with colorectal carcinoma.

CASE DESCRIPTION

We describe here a young woman who developed a locally aggressive rectal adenocarcinoma with intact MMR protein expression by immunohistochemistry and absence of histologic evidence of MMR deficiency-associated increased tumoral immune response. Germline DNA-targeted sequencing identified MSH2 variant p.R711P, initially classified as a variant of undetermined significance. Somatic tumoral DNA analysis revealed the identical MSH2 variant, high tumor mutational burden, and microsatellite instability, in addition to superimposed alterations in β2-microglobulin gene, possibly explaining the altered intratumoral immunity. Consequently, the patient was started on immunotherapy, leading to successful disease control (33 month follow-up).

CONCLUSION

The findings emphasize the utility of an integrative approach in the assessment of MMR status for determining candidacy for immunotherapy, especially in the setting of missense variants in MMR genes.

Mainstreaming cancer genetics: feasibility of an advanced nurse practitioner-led service diagnosing Lynch syndrome from colorectal cancer in Ireland

Colorectal cancer (CRC) is a common cancer in Ireland. Of all CRCs, 2-4% are attributable to Lynch Syndrome (LS), the most common CRC predisposition syndrome. LS is caused by constitutional pathogenic variants (PVs) affecting mismatch repair (MMR) genes with resultant MMR protein deficiency (dMMR). Screening of all CRCs with MMR immunohistochemistry (IHC) testing is advocated to increase the detection of LS. However, successful implementation requires appropriate downstream management. In Ireland the traditional pathway involves referral to cancer genetics services to assess eligibility for genetic testing. Cancer genetics services in Ireland face many challenges in providing uniform access to timely healthcare with current wait times for assessment in excess of 1 year. An increasingly adopted pathway is that of mainstreaming, whereby genetic testing is managed locally by a multidisciplinary team member. Our institution therefore implemented an Advanced Nurse Practitioner (ANP)-led service with responsibility for the LS Diagnostic Pathway and mainstream genetic testing. Data was extracted from a prospectively maintained database of all newly diagnosed CRC patients discussed at our institutions CRC multidisciplinary meeting (MDM) between January 1st, 2023, and May 31st, 2024. MMR IHC testing was performed in 97.9% of the 385 patients diagnosed with CRC. The median time from histological confirmation of CRC to the availability of the MMR IHC report was 6 days. All 51 patients (100%) who required sequential tumor testing underwent BRAF V600 ± MLH1 promoter methylation testing. Additionally, 100% of the 14 patients eligible for mainstream genetic testing were referred to the ANP-led genetics service. The median time from the initial MDM discussion to the initiation of genetic testing was 69 days, while the median time from testing to the availability of results was 19 days. Patients received their results within a median of 21 days. MMR IHC testing increases the detection of LS through identification of dMMR tumours. Successful downstream delivery of clinical services, however, requires appropriate subsequent management, in a resource-limited environment. Our institutional experience demonstrates the feasibility, efficiency, and effectiveness of an ANP-led mainstreaming model of care for hereditary colorectal cancer.

Compliance of a Tertiary Centre With Molecular Testing Strategies for Lynch Syndrome in Colorectal Cancer

Introduction Lynch syndrome is one of the most common hereditary cancers associated with germline alterations of DNA mismatch repair genes. Recent advances have shed light on its molecular pathogenesis, leading to the development of various testing strategies. The aim of this study is to evaluate whether all colorectal adenocarcinomas undergo immunohistochemistry (IHC) and microsatellite instability (MSI) testing to identify potential Lynch syndrome patients. Methods This study evaluated the compliance of MSI and IHC testing for Lynch syndrome in a tertiary cancer research centre. All patients undergoing colorectal cancer resection between April 2022 and December 2022 were identified from a prospectively maintained register. The histology, MSI, and IHC testing reports for these patients were recorded to check if they were done and reported. Only patients with colorectal adenocarcinoma were included in this study. Results A total of 314 patients had colorectal cancer resections. A total of 301 were included in the study, with a median age of 65 years (IQR = 35-95). Thirteen (4.14%) patients did not have MSI and IHC testing reported on the system. Of these, eight (61.53%) did not have an MSI/IHC testing request, four (30.76%) did not have sufficient specimens to be sent for further testing, one (7.69%) had MSI and IHC testing but the final report was yet to be authorized. Out of the eight who did not have the testing done, three had early polyp cancer and one had a goblet cell adenocarcinoma. Conclusion According to the data, our hospital has a 97.45% compliance with current guidelines, not considering the insufficient sample for testing and the authorization of the final report. A more comprehensive proforma may be needed to provide a feedback loop for further MSI and IHC testing when entering data into the system. Further auditing is required to check the effectiveness of the proforma in achieving complete compliance.

Asymptomatic endometrial cancer with Lynch syndrome; in a woman with primary infertility-A case report and literature review

Lynch syndrome, also called hereditary non-polyposis colorectal cancer, is an autosomal dominant disorder characterized by germline pathogenic mutations in DNA mismatch repair genes-resulting in increased susceptibility to colorectal, endometrial, and other tumors. This case report presents an incidental finding of endometrial cancer with Lynch syndrome during investigation for primary infertility. A 34-year-old woman presented to the fertility clinic with unexplained primary infertility. Investigations showed possible endometrial polyp, 13 × 11 mm in size. Hysteroscopic polypectomy and endometrial biopsy revealed complex endometrial hyperplasia amounting to endometroid adenocarcinoma. The case was discussed at the West of Scotland Gynecology-Oncology MDT meeting-management options including fertility-sparing treatment or radical surgery were presented to the patient and she opted for the latter. A total laparoscopic hysterectomy with bilateral salpingo-oophorectomy was performed with pathology results consistent with well-differentiated endometroid adenocarcinoma Stage 1A. Peritoneal washings showed no malignant cells. Genetic testing confirmed a diagnosis of Lynch syndrome. On further questioning, it was revealed that the patient had a strong family history of colon cancer but had not previously met the criteria for genetic testing. She was referred to colorectal surgeons and underwent colonoscopy. This showed no abnormality; she was therefore scheduled for 2-yearly colonoscopic surveillance.

Genetic predisposition to gastrointestinal polyposis: syndromes, tumour features, genetic testing, and clinical management

Gastrointestinal tract polyposis is characterised by the presence of multiple polyps, particularly in the colorectum, and encompasses both cancer predisposition genetic syndromes and non-syndromic clinical manifestations. The sources of the heterogeneity observed in polyposis syndromes relate to genetic cause, mode of inheritance, polyp burden and histological type, and spectrum and frequency of extracolonic manifestations. These features determine the clinical management of carriers, including strategies for cancer prevention and early detection, and oncological treatments. Despite substantial progress in identifying the genetic causes of polyposis, a large proportion of cases remain genetically unexplained. Although some of these cases might be due to lifestyle, environmental factors, or cancer treatments, it is likely that additional polyposis predisposition genes will be identified. This Review provides an overview of the known syndromes and genes, genetic testing, and clinical management of patients with polyposis, and recent advances and challenges in the field of gastrointestinal polyposis.

The English National Lynch Syndrome transformation project: an NHS Genomic Medicine Service Alliance (GMSA) programme

Objective

In England, through the Genomic Medicine Service Alliances (GMSAs), a national transformation project aims to embed robust pathways to deliver universal Lynch syndrome (LS) testing for patients with colorectal and endometrial cancers. Prior to commencement of the project, there was evidence of variation and low testing levels in eligible patients which is consistent with other health systems; however, we believe this is amenable to systematic improvement with responsibility for testing delivery by local cancer teams supported by regional infrastructure.

Methods and analysis

A project team and national oversight group was formed in May 2021 with membership including 21×cancer alliances, 7×GMSAs, charities and other stakeholders who agreed key performance indicators. 'LS champions' within each cancer team were identified and surveyed. Workforce training focused on effective identification of eligible patients, overcoming barriers and mainstreamed constitutional genetic testing. Comprehensive pathway data analysis was performed in conjunction with the National Disease Registration Service.

Results

Survey and baseline testing data illustrated variation, and a disparity between practice and perception, in levels of testing. The main reported barriers related to funding streams and systematic approaches. Multifaceted training programmes were produced to support workforce development. Champions responsible for testing delivery were appointed in >95% of cancer teams. We identified >9000 historically diagnosed LS patients to support ascertainment for a nationally coordinated screening programme.

Conclusion

This ongoing transformational project is strongly supported by stakeholders in England. Significant quality improvement has been implemented, facilitating systematic delivery of universal testing for LS nationally and reduction in variation in care.

From diagnosis of colorectal cancer to diagnosis of Lynch syndrome: The RM Partners quality improvement project

AIM

The UK National Institute for Health and Care Excellence guideline DG27 recommends universal testing for Lynch syndrome (LS) in all newly diagnosed colorectal cancer (CRC) patients. However, DG27 guideline implementation varies significantly by geography. This quality improvement project (QIP) was developed to measure variation and deliver an effective diagnostic pathway from diagnosis of CRC to diagnosis of LS within the RM Partners (RMP) West London cancer alliance.

METHOD

RM Partners includes a population of 4 million people and incorporates nine CRC multidisciplinary teams (MDTs), overseen by a Pathway Group, and three regional genetic services, managing approximately 1500 new CRC cases annually. A responsible LS champion was nominated within each MDT. A regional project manager and nurse practitioner were appointed to support the LS champions, to develop online training packages and patient consultation workshops. MDTs were supported to develop an 'in-house' mainstreaming service to offer genetic testing in their routine oncology clinics. Baseline data were collected through completion of the LS pathway audit of the testing pathway in 30 consecutive CRC patients from each CRC MDT, with measurement of each step of the testing pathway. Areas for improvement in each MDT were identified, delivered by the local champion and supported by the project team.

RESULTS

Overall, QIP measurables improved following the intervention. The Wilcoxon signed rank test revealed significant differences with strong effect sizes on the percentile of CRC cases undergoing mismatch repair (MMR) testing in endoscopic biopsies (p = 0.008), further testing with either methylation or BRAF V600E (p = 0/03) and in effective referral for genetic testing (from 10% to 74%; p = 0.02). During the QIP new mainstreaming services were developed, alongside the implementation of systematic and robust testing pathways. These pathways were tailored to the needs of each CRC team to ensure that patients with a diagnosis of CRC had access to testing for LS. Online training packages were produced which remain freely accessible for CRC teams across the UK.

CONCLUSION

The LS project was completed by April 2022. We have implemented a systematic approach with workforce transformation to facilitate identification and 'mainstreamed' genetic diagnosis of LS. This work has contributed to the development of a National LS Transformation Project in England which recommends local leadership within cancer teams to ensure delivery of diagnosis of LS and integration of genomics into clinical practice.