Identifying Lynch syndrome: we are all responsible

Racial and Ethnic Disparities in Germline Genetic Testing of Patients With Young-Onset Colorectal Cancer

BACKGROUND & AIMS

Up to 20% of younger patients (age <50 years) diagnosed with colorectal cancer (CRC) have germline mutations in cancer susceptibility genes. Germline genetic testing may guide clinical management and facilitate earlier intervention in affected relatives. Few studies have characterized differences in genetic testing by race/ethnicity.

METHODS

We identified young adults (age 18-49 years) diagnosed with CRC between 2009 and 2017 in 2 health systems in Dallas, TX. We evaluated referral to genetic counseling, attendance at genetic counseling appointments, and receipt of germline genetic testing by race/ethnicity.

RESULTS

Of 385 patients with young-onset CRC (median age at diagnosis 44.4 years), 176 (45.7%) were Hispanic, 98 (25.4%) non-Hispanic Black, and 111 (28.8%) non-Hispanic White. Most patients (76.9%) received immunohistochemistry (IHC) for mismatch repair proteins, and there was no difference in receipt of IHC by race/ethnicity. However, a lower proportion of Black patients were referred to genetic counseling (50.0% vs White patients 54.1% vs Hispanic patients 65.9%; P = .02) and attended genetic counseling appointments (61.2% vs 81.7% White patients vs 86.2% Hispanic patients; P < .01). Of 141 patients receiving genetic testing, 38 (27.0%) had a pathogenic or likely pathogenic variant in a cancer susceptibility gene. An additional 33 patients (23.4%) had variants of uncertain significance, of which 84.8% occurred in racial/ethnic minorities.

CONCLUSIONS

In a diverse population of patients diagnosed with young-onset CRC, we observed racial/ethnic differences in referral to and receipt of germline genetic testing. Our findings underscore the importance of universal genetic testing to address racial/ethnic disparities in young-onset CRC.

Lynch Syndrome: Its Impact on Urothelial Carcinoma

Lynch syndrome, known as hereditary nonpolyposis colorectal cancer (HNPCC), is an autosomal-dominant familial cancer syndrome with an increased risk for urothelial cancer (UC). Mismatch repair (MMR) deficiency, due to pathogenic variants in MLH1, MSH2, MSH6, and PMS2, and microsatellite instability, are known for development of Lynch syndrome (LS) associated carcinogenesis. UC is the third most common cancer type in LS-associated tumors. The diversity of germline variants in the affected MMR genes and their following subsequent function loss might be responsible for the variation in cancer risk, suggesting an increased risk of developing UC in MSH2 mutation carriers. In this review, we will focus on LS-associated UC of the upper urinary tract (UUT) and bladder, their germline profiles, and outcomes compared to sporadic UC, the impact of genetic testing, as well as urological follow-up strategies in LS. In addition, we present a case of metastatic LS-associated UC of the UUT and bladder, achieving complete response during checkpoint inhibition since more than 2 years.

Universal tumor screening for Lynch syndrome: perspectives of Canadian pathologists and genetic counselors

Universal screening of all newly diagnosed colorectal cancer tumors can identify individuals at high risk for Lynch syndrome (LS), a hereditary cancer syndrome predisposing carriers to increased risk of colorectal, endometrial, and other cancers. To inform planning of a universal tumor screening program for LS in our jurisdiction, we undertook online surveys of Canadian pathologists and genetic counselors to describe existing tumor screening programs. Online surveys were hosted on SurveyMonkey between October 2016 and March 2017. Fifty-three pathologists and 66 genetic counselors completed surveys (total n = 119). While attitudes towards tumor screening were positive, considerable variability was observed in the existence of tumor screening, test ordering criteria, and practices. Most respondents indicated consent was not obtained for tumor screening nor were educational materials provided to patients; however, opting out of additional mutation testing in the event of a positive tumor screen was endorsed. Results add to the growing literature on providers' perspectives on population-based tumor screening programs and inform ways to offer these. Findings highlight the need to develop methods of patient education that allow meaningful opt-out decisions. The variability we observed also suggests the need for national standards and guidance on tumor screening for LS.

A novel frameshift mutation in the MLH1 gene in a patient with Lynch syndrome

A novel mutation in the MLH1 gene likely to be pathogenic for Lynch syndrome was discovered in a proband with a family history of colon cancer. Immunohistochemistry showed negative expression of PMS2 and MLH1 in the resected tumor sample. The mutation lies at the highly conserved C-terminus of the MLH1 protein, the region through which it dimerizes with PMS2 to carry out its mismatch repair function.

Low Referral Rate for Genetic Testing in Racially and Ethnically Diverse Patients Despite Universal Colorectal Cancer Screening

BACKGROUND & AIMS

Guidelines recommend that all colorectal tumors be assessed for mismatch repair deficiency, which could increase identification of patients with Lynch syndrome. This is of particular importance for minority populations, in whom hereditary syndromes are under diagnosed. We compared rates and outcomes of testing all tumor samples (universal testing) collected from a racially and ethnically diverse population for features of Lynch syndrome.

METHODS

We performed a retrospective analysis of colorectal tumors tested from 2012 through 2016 at 4 academic centers. Tumor samples were collected from 767 patients with colorectal cancer (52% non-Hispanic white [NHW], 26% African American, and 17% Hispanic patients). We assessed rates of tumor testing, recommendations for genetic evaluation, rates of attending a genetic evaluation, and performance of germline testing overall and by race/ethnicity. We performed univariate and multivariate regression analyses.

RESULTS

Overall, 92% of colorectal tumors were analyzed for mismatch repair deficiency without significant differences among races/ethnicities. However, minority patients were significantly less likely to be referred for genetic evaluation (21.2% for NHW patients vs 16.9% for African American patients and 10.9% for Hispanic patients; P = .02). Rates of genetic testing were also lower among minority patients (10.7% for NHW patients vs 6.0% for AA patients and 3.1% for Hispanic patients; P < .01). On multivariate analysis, African American race, older age, and medical center were independently associated with lack of referral for genetic evaluation and genetic testing.

CONCLUSION

In a retrospective analysis, we found that despite similar rates of colorectal tumor analysis, minority patients are less likely to be recommended for genetic evaluation or to undergo germline testing for Lynch syndrome. Improvements in institutional practices in follow up after tumor testing could reduce barriers to diagnosis of Lynch diagnosis in minorities.

Screening for Lynch syndrome among patients with newly diagnosed endometrial cancer: a comprehensive review

Lynch syndrome (LS) is an autosomal dominant condition characterized by an increased risk of hereditary colorectal, endometrial, ovarian, pancreatic, urinary tract, and gastric cancer.It is estimated that around 5% of all endometrial cancer (EC) cases are due to an inherited predisposition, of which LS might be the most frequent. The lifetime risk of developing EC in women with LS ranges between 40% and 71% depending on the type of mutation. In many cases, this risk may even exceed their risk of developing colon cancer. Moreover, in 60% of these women, EC will be the first primary malignancy diagnosed and the sentinel diagnosis of the syndrome. Therefore, it is essential to identify which women with EC have LS in order to allow implementation of individualized screening and preventive strategies.

Current morphologic criteria perform poorly in identifying hereditary leiomyomatosis and renal cell carcinoma syndrome-associated uterine leiomyomas

The contemporary oncologic pathology report conveys diagnostic, prognostic, predictive, and hereditary predisposition information. Each component may be premised on a morphologic feature or a biomarker. Clinical validity and reproducibility are paramount as is standardization of reporting and clinical response to ensure individualization of patient care. Regarding hereditary predisposition, morphology-based genetic referral systems in some instances have eclipsed genealogy-based systems, for example, cell type in ovarian cancer and BRCA screening. In other instances such as Lynch syndrome, morphology-based schemas supplement clinical schemas and there is an emerging standard of care for reflex biomarker testing. Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome predisposes patients to uterine and cutaneous leiomyomas (LMs) and renal cell carcinomas (RCCs). Several authors have emphasized the role pathologists may play in identifying this syndrome by recognizing the morphologic characteristics of syndromic uterine LMs and RCCs. Recently immunohistochemical overexpression of S-(2-succinyl) cysteine (2SC) has been demonstrated as a robust biomarker of mutation status in tumors from HLRCC patients. In this blinded control-cohort study we demonstrate that the proposed morphologic criteria used to identify uterine LMs in HLRCC syndrome are largely irreproducible among pathologists and lack sufficient robustness to serve as a trigger to triage cases for 2SC immunohistochemistry or patients for further family/personal history inquiry. Although refinement of morphologic criteria can be considered, in view of the availability of a clinically robust biomarker, consideration should be given to reflex testing of uterine LMs with an appropriate age cut off or in the setting of a suspicious family history.

Select biomarkers for tumors of the gastrointestinal tract: present and future

CONTEXT

Advances in molecular biomarkers of the gastrointestinal tract have contributed to a decline in the incidence of and mortality from diseases of the gastrointestinal tract. The discovery and clinical validation of new biomarkers are important to personalized cancer therapy, and numerous clinical trials are currently ongoing to help identify individualized therapy affecting these biomarkers and molecular mechanisms they represent. Distinct molecular pathways leading to cancers of the colorectum, esophagus, stomach, small bowel, and pancreas have been identified. Using biomarkers in these pathways to direct patient care, including selection of proper molecular testing for identification of actionable mutations and reporting the results of these biomarkers to guide clinicians and genetic counselors, is paramount.

OBJECTIVE

To examine and review select clinically actionable biomarkers of the colon, esophagus, stomach, small bowel, and pancreas, including present and future biomarkers with relevant clinical trials.

DATA SOURCES

Extensive literature review and practical and consultation experience of the authors.

CONCLUSIONS

Although numerous biomarkers have been identified and are currently guiding patient therapy, few have shown evidence of clinical utility in the management of patients with gastrointestinal cancers. Inconsistent results and discordant proposed algorithms for testing were identified throughout the literature; however, the potential for biomarkers to improve outcomes for patients with gastrointestinal cancer remains high. Continued advances through high-quality studies are needed.

Lynch syndrome: an updated review

Lynch syndrome is one of the most common cancer susceptibility syndromes. Individuals with Lynch syndrome have a 50%-70% lifetime risk of colorectal cancer, 40%-60% risk of endometrial cancer, and increased risks of several other malignancies. It is caused by germline mutations in the DNA mismatch repair genes MLH1, MSH2, MSH6 or PMS2. In a subset of patients, Lynch syndrome is caused by 3' end deletions of the EPCAM gene, which can lead to epigenetic silencing of the closely linked MSH2. Relying solely on age and family history based criteria inaccurately identifies eligibility for Lynch syndrome screening or testing in 25%-70% of cases. There has been a steady increase in Lynch syndrome tumor screening programs since 2000 and institutions are rapidly adopting a universal screening approach to identify the patients that would benefit from genetic counseling and germline testing. These include microsatellite instability testing and/or immunohistochemical testing to identify tumor mismatch repair deficiencies. However, universal screening is not standard across institutions. Furthermore, variation exists regarding the optimum method for tracking and disclosing results. In this review, we summarize traditional screening criteria for Lynch syndrome, and discuss universal screening methods. International guidelines are necessary to standardize Lynch syndrome high-risk clinics.

Population-based screening for Lynch syndrome in Western Australia

We showed earlier that routine screening for microsatellite instability (MSI) and loss of mismatch repair (MMR) protein expression in colorectal cancer (CRC) led to the identification of previously unrecognized cases of Lynch syndrome (LS). We report here the results of screening for LS in Western Australia (WA) during 1994-2012. Immunohistochemistry (IHC) for loss of MMR protein expression was performed in routine pathology laboratories, while MSI was detected in a reference molecular pathology laboratory. Information on germline mutations in MMR genes was obtained from the state's single familial cancer registry. Prior to the introduction of routine laboratory-based screening, an average of 2-3 cases of LS were diagnosed each year amongst WA CRC patients. Following the implementation of IHC and/or MSI screening for all younger (<60 years) CRC patients, this has increased to an average of 8 LS cases diagnosed annually. Based on our experience in WA, we propose three key elements for successful population-based screening of LS. First, for all younger CRC patients, reflex IHC testing should be carried out in accredited pathology services with ongoing quality control. Second, a state- or region-wide reference laboratory for MSI testing should be established to confirm abnormal or suspicious IHC test results and to exclude sporadic cases by carrying out BRAF mutation or MLH1 methylation testing. Finally, a state or regional LS coordinator is essential to ensure that all appropriate cases identified by laboratory testing are referred to and attend a Familial Cancer Clinic for follow-up and germline testing.

BRAF V600E mutation analysis simplifies the testing algorithm for Lynch syndrome

OBJECTIVES

To evaluate our experience of adding reflex BRAF mutation analysis following mismatch repair (MMR) protein staining in the test algorithm for Lynch syndrome (LS), the most common inherited predisposition to colorectal cancer (CRC).

METHODS

Since January 1, 2009, BRAF V600E mutation analysis has been performed at our institution for all newly diagnosed CRCs with absent MLH1 and PMS2 proteins.

RESULTS

Ninety (22%) of 412 patients with CRC had at least 1 MMR absent (65 had MLH1 and PMS2 absent and 25 had other stain(s) absent). BRAF mutation was found in 36 (55%) of 65. Fifty-four (13%) of 412 patients required follow-up after addition of BRAF analysis compared with 90 who would have required follow-up without BRAF analysis.

CONCLUSIONS

The addition of reflex BRAF mutation testing in CRCs with absent MLH1 and PMS2 reduced the number of patient contacts by 40% and simplified the genetic testing for LS, leading to cost and time savings.

Era of universal testing of microsatellite instability in colorectal cancer

Colorectal cancer (CRC) incidence and mortality are constantly decreasing, but CRC still remains the third most prevalent cancer and the third most common cause of cancer death in both males and females in the United States. Recent rapid declines in CRC incidence rates have largely been attributed to increases in screening that can detect and remove precancerous polyps, and the decrease in death rates for CRC largely reflects improvements in early detection, treatment and the understanding of molecular/genetic basis of CRC. One of the important molecular/genetic findings is the presence of microsatellite instability (MSI) in CRCs. Many studies have shown the importance of MSI testing in diagnosing Lynch syndrome and predicting prognosis and response to chemotherapeutic agents in CRCs. Increased emphasis has been placed on the importance of MSI testing for all newly diagnosed individuals with CRCs. Both immunohistochemical staining (IHC) and polymerase chain reaction (PCR)-based MSI testing show high sensitivity and specificity in detecting MSI. The current clinical guidelines and histopathology features are indicative of, but not reliable in diagnosing Lynch syndrome and CRCs with MSI. Currently, there are evidences that universal testing for MSI starting with either IHC or PCR-based MSI testing is cost effective, sensitive, specific and is getting widely accepted.

Implementation of universal microsatellite instability and immunohistochemistry screening for diagnosing lynch syndrome in a large academic medical center

PURPOSE

In 2009, the Evaluation of Genomic Applications in Practice and Prevention recommended that all colorectal cancers (CRCs) be screened for Lynch syndrome (LS) through microsatellite instability (MSI) or immunohistochemistry (IHC). No studies report how this process is implemented on a health system-wide basis.

METHODS

Since 2004, Cleveland Clinic has screened CRC specimens with MSI/IHC. Between January 2004 and July 2007, MSI/IHC results went only to the colorectal surgeon (approach 1). Between August 2007 and June 2008, colorectal surgeons and a genetic counselor received the MSI/IHC results, and the counselor e-mailed the colorectal surgeon regarding appropriate patients for genetic counseling (GC) referral (approach 2). After July 2008, the colorectal surgeon and counselor received MSI/IHC results, but the counselor contacted the patient to facilitate referral (approach 3). In approaches 2 and 3, patients were presumed to have sporadic CRC if the tumor lacked MLH1 expression and was also BRAF mutated or if the patient was diagnosed at age greater than 72 years and had no cancer family history.

RESULTS

Abnormal MSI/IHC results occurred in 178 (16%) of 1,108 patients. In approach 1, 21 (55%) of 38 patients with abnormal MSI/IHC were referred for GC, 12 (32%) of 38 underwent GC, and 10 (26%) of 38 underwent genetic testing (GT). In approach 2, nine (82%) of 11 patients were referred for GC, seven (64%) of 11 underwent GC, and five (45%) of 11 underwent GT. In approach 3, 56 (100%) of 56 patients were referred for GC, 40 (71%) of 56 underwent GC, and 37 (66%) of 56 underwent GT. Time from referral to GC was 10-fold quicker in approach 3 than approach 1.

CONCLUSION

Implementation of universal MSI/IHC with GC/GT, along with effective multidisciplinary communication and plans of responsibility for patient contact, resulted in increased identification of patients with LS.

Identifying Lynch syndrome in patients with endometrial carcinoma: shortcomings of morphologic and clinical schemas

It has been suggested that reflex testing for Lynch syndrome (LS) using mismatch repair immunohistochemistry and/or microsatellite instability analysis in newly diagnosed colorectal carcinoma (CRC) patients is an emerging standard of care in the United States. The risk of gynecologic malignancy in women with LS approaches and even exceeds that of CRC. Furthermore, gynecologic malignancies are often the sentinel cancers in these patients. There is significant variation in practice, but some groups have similarly recommended deployment of reflex testing strategies in patients presenting with endometrial cancer (EC). The College of American Pathologists has stated that pathologists should recognize the histologic and clinical features that should prompt at least a recommendation for mismatch repair testing. Morphologic and clinical schemas in EC to identify microsatellite unstable/LS tumors are less refined than the colon-centric schemas (Amsterdam, Bethesda, and MsPath). Studies of LS EC are few and interpretation is limited by recruitment strategies and the myriad of definitions and study designs used. Although serous cell type is used to triage ovarian cancer patients for BRCA screening, cell type correlation in LS is less certain but seems to involve a spectrum of cell types. We review the morphologic and clinical features/schemas in LS EC and highlight limitations of restrictive aged-based screening strategies, uncertainty in current clinical schemas and equivocal results of morphologic studies of LS EC. With uncertainty of histologic and clinical schemas, and following developments in CRC, reflex testing of all/vast majority of newly diagnosed EC for LS should be considered.

Use of mismatch repair immunohistochemistry and microsatellite instability testing: exploring Canadian practices

BACKGROUND

The mismatch repair (MMR) status of tumors is being increasingly recognized as a prognostic, predictive, and possible germline predisposition/Lynch syndrome (LS) biomarker in colorectal cancer and other cancer types, particularly in endometrial cancer. Current methods (clinical history and tumor morphology) to predict MMR deficiency (dMMR) are suboptimal, and implementation of reflex laboratory testing of appropriate tumors has been recommended, a strategy requiring test standardization and clinical coordination.

METHODS

Two web-based questionnaires were administered, a general and a specialist laboratory questionnaire, to establish the availability of such tests, requisite clinical/pathology integration, current mode of test initiation, reporting and recommendation practices, and education and attitudes among pathologists. Technical aspects were reviewed on the basis of specialist laboratory practice.

RESULTS

Of 76 respondents, 21.5% were unaware or were uncertain whether they had access to MMR immunohistochemistry. Although 78.9% of respondents had access to such testing, an integrated approach to the identification of patients with LS is lacking, being limited to just 9 centers. The majority (70%) of testing is clinician initiated, with variable implementation of reflex testing and divergent practices in recommendation to test. Standardized reporting is lacking in many centers. Education on MMR in endometrial cancer is poor compared with that in colorectal cancer (P<0.0001).

INTERPRETATION

This multicenter questionnaire highlights heterogenous practices in dMMR testing and LS identification, both in clinical terms and with regard to technical aspects of testing. An integrated multidisciplinary approach is lacking, and there is a need to educate physicians and resolve ethical issues. A Canadian consensus statement and national guidelines on dMMR testing are urgently needed, requiring input from pathologists, clinicians, and genetic counselors.

Immunohistochemistry to detect hereditary nonpolyposis colorectal cancer in young patients: the 7-year Auckland experience

BACKGROUND

In accordance with the Bethesda Guidelines, Auckland's metropolitan hospitals routinely perform immunohistochemistry for mismatch repair proteins on the tumor specimens of all patients with colorectal cancer aged 50 years and younger. When loss of expression is evident, patients are offered genetic counseling and gene mutation analysis.

OBJECTIVES

This study aimed to determine the completeness of young patient capture over the first 7 years of routine testing, to find whether patients were referred for genetic testing, and to determine the proportion of patients found to have a mismatch repair gene mutation.

DESIGN

This study retrospectively reviewed clinical, pathological, and genetic data.

SETTINGS

The study was conducted at 3 public hospitals in Auckland, New Zealand.

PATIENTS

All patients aged 50 years and younger treated for colorectal cancer at Auckland's metropolitan hospitals between January 2001 and December 2007 (n = 243) were included.

MAIN OUTCOME MEASURES

The loss of expression of mismatch repair proteins by immunohistochemistry, referral for genetic testing, and proportion with mismatch repair gene mutation were the main outcome measures.

RESULTS

Two hundred fourteen (88%) eligible patients had immunohistochemical analysis of their tumor and 33 (14%) had loss of expression of one or more mismatch repair proteins. Twenty-six patients were referred for genetic counseling, of whom 22 underwent genetic testing. A mismatch repair gene mutation was identified in 10 patients.

LIMITATIONS

Seven patients with loss of expression of mismatch repair proteins by immunohistochemistry were not referred for genetic assessment.

CONCLUSIONS

We have identified a mismatch repair gene mutation diagnostic of hereditary nonpolyposis colorectal cancer in 5% of all patients with colorectal cancer who were aged 50 years and younger. Routine immunohistochemical prescreening has important clinical benefit for these patients and their relatives.

Performance of clinical guidelines compared with molecular tumour screening methods in identifying possible Lynch syndrome among colorectal cancer patients: a Norwegian population-based study

Background:

The aim of this study was to assess the performance of the Revised Bethesda Guidelines (RBG) and the accuracy of the Amsterdam II criteria (AM II) in identifying possible Lynch syndrome (LS) compared with the results of molecular tumour testing.

Methods:

Tumours from 336 unselected colorectal cancer patients were analysed by three molecular tests (namely microsatellite instability (MSI), BRAF mutation and methylation of mismatch-repair genes), and patients were classified according to the RBG and AM II criteria.

Results:

A total of 87 (25.9%) patients fulfilled the RBG for molecular tumour analyses (MSI and/or immunohistochemistry), and the AM II identified 8 (2.4%) patients as having possible LS. Molecular tests identified 12 tumours (3.6%) as probable LS. The RBG identified 6 of the 12 patients (sensitivity 50%), whereas 5 of the 8 patients who fulfilled the AM II criteria were not likely to be LS, based on molecular tests (predictive value of positive test, 38%).

Interpretation:

Assuming a fairly high accuracy of molecular testing, the performance of the RBG in identifying patients with possible LS was poor, and the AM II criteria falsely identified a large proportion as having possible LS. This favours the use of molecular testing in the diagnosis of possible LS.

A review on the molecular diagnostics of Lynch syndrome: a central role for the pathology laboratory

Lynch syndrome (LS) is caused by mutations in mismatch repair genes and is characterized by a high cumulative risk for the development of mainly colorectal carcinoma and endometrial carcinoma. Early detection of LS is important since surveillance can reduce morbidity and mortality. However, the diagnosis of LS is complicated by the absence of a pre-morbid phenotype and germline mutation analysis is expensive and time consuming. Therefore it is standard practice to precede germline mutation analysis by a molecular diagnostic work-up of tumours, guided by clinical and pathological criteria, to select patients for germline mutation analysis. In this review we address these molecular analyses, the central role for the pathologist in the selection of patients for germline diagnostics of LS, as well as the molecular basis of LS.

Review of the Lynch syndrome: history, molecular genetics, screening, differential diagnosis, and medicolegal ramifications

More than one million patients will manifest colorectal cancer (CRC) this year of which, conservatively, approximately 3% (approximately 30,700 cases) will have Lynch syndrome (LS), the most common hereditary CRC predisposing syndrome. Each case belongs to a family with clinical needs that require genetic counseling, DNA testing for mismatch repair genes (most frequently MLH1 or MSH2) and screening for CRC. Colonoscopy is mandated, given CRC's proximal occurrence (70-80% proximal to the splenic flexure). Due to its early age of onset (average 45 years of age), colonoscopy needs to start by age 25, and because of its accelerated carcinogenesis, it should be repeated every 1 to 2 years through age 40 and then annually thereafter. Should CRC occur, subtotal colectomy may be necessary, given the marked frequency of synchronous and metachronous CRC. Because 40-60% of female patients will manifest endometrial cancer, tailored management is essential. Additional extracolonic cancers include ovary, stomach, small bowel, pancreas, hepatobiliary tract, upper uroepithelial tract, brain (Turcot variant) and sebaceous adenomas/carcinomas (Muir-Torre variant). LS explains only 10-25% of familial CRC.