Lynch Syndrome Cases Research Articles

Non-classical phenotypes of mismatch repair deficiency and microsatellite instability in primary and metastatic tumors at different sites in Lynch syndrome.

Lynch syndrome is a genetic disease characterized by abnormal DNA replication caused by germline variation in the mismatch repair (MMR) gene. There are rare non-classical phenotypes with loss of MMR protein expression and inconsistent microsatellite stability (MSS) in Lynch syndrome-related colorectal cancers. However, the difference between microsatellite instability (MSI) of extraintestinal tumors in a patient with Lynch syndrome has been closely studied. Herein, we reported the non-classical phenotypes of mismatch repair deficiency (dMMR) and MSI in four cases of Lynch syndrome in patients with colorectal cancer and other primary and metastatic tumors. A retrospective analysis was conducted on four patients diagnosed with Lynch syndrome between 2018 and 2022 in the Department of Pathology of the Rocket Forces Specialized Medical Center. A one-step immunohistochemical (IHC) assay was employed to detect loss in the expression of Lynch syndrome-associated MMR proteins (MLH1, PMS2, MSH2, and MSH6). MSI detection was performed in both primary and metastatic tumors at different sites in the four patients using NCI 2B3D (BAT25, BAT26, D2S123, D17S250, and D5S346) and single nucleotide site (BAT25, BAT26, NR21, NR24, NR27, and MONO27) methods. In addition, related MMR gene germline variation, somatic mutations, and MLH1 gene promoter methylation were analyzed using next-generation sequencing and TaqMan probe-based methylation-specific polymerase chain reaction (MethyLight). Two of the four patients were heterozygous for MSH6 germline pathogenic variation, and the other two were heterozygous for MSH2 germline pathogenic variation. In all cases, IHC detection of protein expression of the MMR gene with germline variation was negative in all primary and metastatic tumors; non-classical phenotypes of dMMR and MSI were present between primary and metastatic tumors at different sites. dMMR in Lynch colorectal cancer demonstrated high MSI, whereas MSI in primary and metastatic tumors outside the intestine mostly exhibited MSS or low MSI. The non-classical dMMR and MSI phenotype are mostly observed in Lynch syndrome, even in the context of MMR protein expression loss. Extraintestinal tumors infrequently present with a high degree of MSI and often exhibit a stable or low degree of MSI.

Study of Mismatch Repair Protein Expression by Using Immunohistochemistry in Various Carcinomas with Special Reference to Colorectal Adenocarcinomas - At a Tertiary Referral Laboratory in India

Background: DNA mismatch repair (MMR) is an important process during the DNA replication for correcting DNA replication errors. Deficient MMR (dMMR) leads to increased mutational burden and has been associated with several carcinomas and cancer syndromes like Lynch syndrome. The absence of MMR protein by immunohistochemistry is a surrogate marker for microsatellite instability. The aim of the study is to present our datas of MMR deficient tumors and the pattern of MMR protein loss by using immunohistochemistry,also to highlight the technical issues of tissue processing that interfere in result interpretation. Material & Method: 318 cases of various carcinomas were analysed for mismatch repair proteins viz. MLH1, MSH2, MSH6 and PMS2 using immunohistochemistry.Result: Out of total 318 cases,47 cases showed deficient MMR proteins. Among the MMR deficient cases colonic adenocarcinoma cases has the highest percentage with loss of MMR proteins. Regarding pattern of MMR protein loss the simultaneous loss of both MLH1 and PMS2 is the most common pattern. In 5 cases (1.5%) of total cases we could not interpret the result. In compare to MMR proficient colorectal adenocarcinomas, the MMR deficient tumors are predominantly right sided and on histopathology they shows high grade histology,intratumoral lymphocytic infiltration, peritumoral lymphocytic infilatration,,mucinous and signet cell components. Conclusion: Evaluation of MMR proteins using immunohistochemistry is relatively easy to institute in the routine testing as it is a useful predictive and prognostic marker in various carcinomas,also it helps screening the cases of lynch syndrome. This study also highlight the need of using standard protocols for tissue fixation and processing before evaluating for MMR proteins.

Implementing universal upfront multi-gene panel testing in endometrial cancer: From cost to practical considerations

ObjectivesThe routine use of upfront universal germline genetic testing among patients with newly diagnosed endometrial cancer (EC) has been proposed to improve diagnosis of Lynch syndrome (LS) and discover pathogenic variants (PVs) in other cancer susceptibility genes. We propose an algorithm prioritizing upfront multi-gene panel testing (MGPT) for newly diagnosed EC patients. MethodsA decision analysis compared the cost of the current algorithm of universal mismatch repair (MMR) immunohistochemistry (IHC) for all EC cases to a new MGPT algorithm that employs upfront MGPT for all EC cases and reserves MMR IHC for the recurrent setting. The increase in the number of LS diagnoses using upfront MGPT, and the number of patients with PVs in BRCA1 and BRCA2 are also estimated. ResultsThe MGPT algorithm demonstrated a cost savings of $259 per patient. Assuming 66,950 new cases of EC per year, this would represent $17.1 M of cost savings per year. When applied to all new diagnoses of EC in one year, the MGPT algorithm identified 660 (1%) additional cases of LS that would have been missed with the current algorithm. An additional 660 (1%) EC patients with BRCA1 or BRCA2 PVs would be diagnosed only through implementation of universal MGPT. ConclusionsThe use of universal upfront MGPT is a practical consideration for patients with newly diagnosed EC for cost savings and improved diagnosis of highly penetrant cancer syndromes. Incorporation of germline genetic testing in the upfront setting represents an opportunity to improve access to genetic counseling and testing, and ultimately an avenue to achieve equity and improve the lives of our patients with EC and their families.

A case of strongly suspected Lynch syndrome with colorectal neuroendocrine carcinoma

BackgroundNeuroendocrine cell carcinomas (NEC) of the colon and rectum are uncommon, representing ~ 0.1% of all colorectal carcinomas. They are associated with a much worse prognosis compared to adenocarcinoma of the colon and rectum, as death occurs in approximately half of all patients within 1 year. Lynch syndrome (LS) is the most common cause of inherited colorectal cancer, accounting for 2–4% of newly diagnosed colorectal cancer cases. This case is extremely rare which was strongly suspected LS as the background, and NEC as the histological type of colorectal cancer.Case presentationThe patient was a 44-year-old man presenting with vomiting as the main complaint. He had undergone ileocecal resection for cecal cancer at age 29. The diagnosis was obstructive descending colorectal cancer, and colonoscopy revealed tumors in the rectum and sigmoid colon in addition. Due to multiple occurrences of colorectal cancer and its prevalence in the patient’s family, LS was suspected. The operation which was a subtotal proctocolectomy was performed. Pathological analysis revealed complete curative resection and the descending colon cancer of the obstructed portion was at the most advanced pathological Stage IIIC in UICC TNM classification, and the tissue type was a NEC. The Ki-67 index was 70%. The results of the microsatellite instability (MSI) test showed high-frequency MSI. The BRAF V600E variant was negative. The immunoexpression of MLH1 was positive, MSH2 was negative, PMS2 was positive, and MSH6 was negative.ConclusionsExtended surgery is recommended for incipient colorectal cancer in LS cases in order to reliably reduce the risk of developing metachronous colorectal cancer. The survival outcome of surgery alone on digestive tract NECs, even locoregional lesions that are completely resection, is extremely poor. It is currently unclear if digestive tract NECs develop more readily in patients with LS. The accumulation of additional cases is necessary.

Microsatellite Instability Testing for Lynch Syndrome in Colorectal Adenomas

BackgroundPatients with Lynch Syndrome (LS), a hereditary condition linked to increased risk of colorectal cancer (CRC) and a variety of other cancers, carry at least one germline variant in a DNA mismatch repair protein (MMR) gene, which results in microsatellite instability (MSI). Screening for MMR/MSI status in CRCs helps identify patients with LS, which is imperative for treatment and surveillance. MSI high instability (MSI‐H) status has been detected in some colorectal adenomatous polyps (CRAs). If MSI‐H can be detected in CRAs from LS patients, this could aid in the prevention of cancer development and facilitate early surveillance. Currently, MMR/MSI testing in CRAs is not used to identify cases of LS. Here we analyze a set of CRAs to assess the utility of using MSI testing to identify patients with LS.DesignAfter completing a retrospective review of our pathology database, we selected 54 CRAs (including tubular, villous, and tubulovillous CRAs) from 32 patients with a history of LS, 21 CRAs from 14 patients with history of sporadic CRC with BRAF mutation or MLH1 promotor methylation, and 38 CRAs from 34 patients who underwent screening colonoscopy. Results from previous molecular testing confirmed germline mutations in the LS group and BRAF mutations or MLH1 promotor methylation in the sporadic CRC group. FFPE tissue was analyzed for MSI status using the Idylla MSI assay (Biocartis, Belgium). Patient demographics and clinical characteristics, pathologic features CRAs, and MSI results were analyzed.ResultsFrequency of MSI‐H CRA was significantly higher in the LS group (18.5%, [10/54]) than in the sporadic CRC (4.8%, [1/21]) and screening colonoscopy (0/38) groups. CRAs analyzed included 106 tubular CRAs, 2 villous CRAs and 5 tubulovillous CRAs. The MSI‐H CRAs in the LS group included 9 tubular CRAs and one villous CRA. One MSI‐H tubular CRA was identified in the sporadic CRC group. All CRAs from the screening colonoscopy group were MSI stable. Mean ages in years for patients in each study group were 56.9 in the LS group, 79.2 in the sporadic CRC group, and 60.6 in the screening colonoscopy group.ConclusionMSI‐H status is detectable in CRAs from patients with LS. MSI‐H CRAs are more frequently detected in patients with LS than non‐LS patients. These findings demonstrate the utility of MSI testing in CRAs. This can help to identify LS at a pre‐malignant stage, which prevents cancer development and facilitates early surveillance.

The clinical features and management of Lynch syndrome-associated ovarian cancer.

Lynch syndrome (LS) is one of the most common hereditary cancer syndromes, characterized by mutations in mismatch repair genes and autosomal dominant inheritance. Women with LS have an additional increased risk of gynecologic malignancies, including endometrial cancer (EC) and ovarian cancer (OC). Compared with EC, OC is relatively under investigation. This review thoroughly summarizes the current clinical evidence of surveillance, screening, and prevention strategies, and describes the molecular and clinical characteristics of LS-associated OC. An electronic search from databases of PubMed and Google Scholar was carried out using key words pertaining to Lynch syndrome and ovarian cancer. A review of the literatures including review articles, experimental, and observational studies published between 2000 and 2021 was conducted. The lifetime risk of OC in women with LS of MLH1, MSH2, and MSH6 mutations is approximately 7%, with the median age at onset being 46 years, 10-15 years earlier than that in sporadic cases. Histologically, LS-associated OCs are primarily endometrioid (40%), high-grade (25%), and low-grade (11%) serous, or clear cell (6%) in nature. Eighty-five percent of patients are diagnosed at an early stage, presenting with a good prognosis at 84% 5-year survival. Optimal screening strategies for OC in LS are controversial; combined screening of patients' clinical and family history, immunohistochemical analysis, and microsatellite instability testing for mismatch repair deficiency have been proven efficient. The clinical features were different between ovarian cancer in Lynch syndrome and sporadic cases. More research are needed for a greater understanding of the prevention and medical treatment of LS-associated OC.

Utility of germline multi-gene panel testing in patients with endometrial cancer

ObjectivesPatients with germline mutations in mismatch repair genes (MLH1, MSH2, MSH6, PMS2) associated with Lynch syndrome (LS) have an increased lifetime risk of endometrial cancer (EC). Multi-gene panel testing (MGPT) is a recent hereditary cancer risk tool enabling next-generation sequencing of numerous genes in parallel. We determined the prevalence of actionable cancer predisposition gene mutations identified through MGPT in an EC patient cohort. MethodsA single center retrospective cohort study was conducted of patients with EC who had a clinical indication for genetic testing and who underwent MGPT as part of standard of care treatment between 2012 and 2021. Pathogenic mutations were identified and actionable mutations were defined as those with clinical management implications. Additionally, the number of individuals identified with LS was compared between MGPT and tumor-based screening. ResultsThe study included a total of 224 patients. Thirty-three patients [14.7%, 95% confidence interval (CI) = 10.4–20.1] had actionable mutations. Twenty-one patients (9.4%, 95% CI = 5.9–14.0) had mutations in LS genes (4 MLH1, 5 MSH2, 7 MSH6, 4 PMS2, 1 Epcam-MSH2). MGPT revealed two patients with LS (9.5% of LS cases) not identified through routine tumor-based screening. Thirteen patients (5.8%, 95% CI = 3.1–9.7) had at least one actionable mutation in a non-Lynch syndrome gene (6 CHEK2, 2 BRCA2, 2 ATM, 2 APC, 1 RAD51C, 1 BRCA1). ConclusionsGermline MGPT is both feasible and informative as it identifies LS cases not found on tumor testing as well as additional actionable mutations in patients with EC.

Identification of Germline Mutations in Upper Tract Urothelial Carcinoma With Suspected Lynch Syndrome

ObjectiveWhole-exon sequencing (WES) is a commercially available tool for hereditary disease testing. However, little is known about hereditary upper-tract urothelial carcinoma (UTUC) in the Chinese population. This study aims to investigate the prevalence of Lynch syndrome (LS) in UTUC patients with high-risk features and identify the germline mutations of genetic predisposition gene mutations in those patients.MethodsIn total, 354 consecutive UTUC patients undergoing surgery were universally recruited, of whom 108 patients under 60 years old or with a personal/family history of cancer underwent universal immunohistochemistry staining to detect the expression of mismatch repair (MMR) proteins (MLH1, MSH2, MSH6 and PMS2). Patients with deficient or weak MMR protein staining or meeting the Amsterdam II criterion were defined as suspected LS patients, who further experienced microsatellite instability (MSI) (BAT25, BAT26, BAT40, D2S123, D5S346, D17S250) detection and performed WES analysis to explore germline pathogenic/likely pathogenic (P/LP) alterations.ResultsOf 108 patients, 90 (83.3%) cases were included due to younger than 60 years, and 18 cases due to personal/family history. IHC staining identified 21 patients with deficient MMR protein staining and 15 cases with weak MMR protein staining. Three cases met the Amsterdam II criterion but with proficient MMR protein staining. Finally, WES analysis was performed in 38 suspected LS patients and P/LP germline mutations were identified in 22 individuals. Genetic testing confirmed 5 LS cases, including 3 cases with novel mutations. MSI-harboring tumor was discovered in 4 LS cases, one of whom had weak MMR protein staining. Germline P/LP variants in DNA damage repair genes were found in 11 cases. In addition, we found that 11 patients had high- or moderate- penetrance P/LP mutations other than MMR genes. The common P/LP variants in high- or moderate-penetrance genes were 4 in ATM, 3 in MSH6 and KIT, and 2 in APC, NF1 and DICER.ConclusionsWe identified approximately 11% of UTUC cases as suspected LS and at least 1.4% patients with confirmed LS-associated UTUC. In addition, broader germline genetic testing could be considered to screen for cancer severity in hereditary UTUC patients.

Economic Evaluation of Universal Lynch Syndrome Screening Protocols among Newly Diagnosed Patients with Colorectal Cancer.

We conducted an updated economic evaluation, from a healthcare system perspective, to compare the relative effectiveness and efficiency of eight Lynch syndrome (LS) screening protocols among newly diagnosed colorectal cancer (CRC) patients. We developed decision analytic models for a hypothetical cohort of 1000 patients. Model assumptions and parameter values were based on literature and expert opinion. All costs were in 2018 USD. For identifying LS cases, the direct germline sequencing (DGS) protocol provided the best performance (sensitivity 99.90%, 99.57–99.93%; specificity 99.50%, 97.28–99.85%), followed by the tumor sequencing to germline sequencing (TSGS) protocol (sensitivity, 99.42%, 96.55–99.63%; specificity, 96.58%, 96.46–96.60%). The immunohistochemistry (IHC) protocol was most efficient at $20,082 per LS case identified, compared to microsatellite instability (MSI) ($22,988), DGS ($31,365), and TSGS ($104,394) protocols. Adding double-somatic testing to IHC and MSI protocols did not change sensitivity and specificity, increased costs by 6% and 3.5%, respectively, but reduced unexplained cases by 70% and 50%, respectively. DGS would be as efficient as the IHC protocol when the cost of germline sequencing declines under $368 indicating DGS could be an efficient option in the near future. Until then, IHC and MSI protocols with double-somatic testing would be the optimal choices.

Swiss cost-effectiveness analysis of universal screening for Lynch syndrome of patients with colorectal cancer followed by cascade genetic testing of relatives

BackgroundWe estimated the cost-effectiveness of universal DNA screening for Lynch syndrome (LS) among newly diagnosed patients with colorectal cancer (CRC) followed by cascade screening of relatives from the Swiss healthcare...

Determination of test performance of two contemporary screening tests for Lynch syndrome in endometrial cancer: A clinical trial

Background/purposePublished data on the performance of the immunohistochemistry (IHC) test for mismatch repair (MMR) protein expression to detect Lynch syndrome (LS) index cases suggests it is highly variable; its performance in our system was unknown. Moreover, a brief family history questionnaire (bFHQ) developed by Eiriksson and colleagues in Canada demonstrated 100% sensitivity for LS case identification thus was of interest to us, but its performance outside of its original setting was unknown. Determination of the performance of these tests requires complete LS case identification in the testing population. MethodsTwo hundred women were recruited during routine care for endometrial cancer (EC) to administer the bFHQ and perform genetic testing for the LS genes. Independently, the IHC test was performed to screen for presumptive LS cases. We determined the sensitivity, specificity, and positive and negative predictive values of the bFHQ and IHC test as well as simulating outcomes of the complete protocols. ResultsGenetic testing all participants identified 8 cases of LS out of 200 (4% prevalence), the bFHQ identified 5 of 8 of these cases (62.5%, CI: 31.5%–87.6%), and the IHC test identified 6 or 7 of 8 cases (mean of 75% or 87.5%) depending on interpretation of test results. The specificities of the bFHQ and IHC test were 56.8% (CI: 49.8%–63.7%) and 79.8% (CI: 73.6%–85.1%), respectively. ConclusionsThis study is the first, to our knowledge, to test the effectiveness of the bFHQ in an EC population since its original reporting; our results are consistent with many reports of the challenges of collecting family health history. The performance of the IHC test as a screen falls within ranges reported in the literature but do not provide the confidence to drive a decision for or against continued use of this test as a LS screen.

American Gastroenterological Association Institute and College of American Pathologists Quality Measure Development for Detection of Mismatch Repair Deficiency and Lynch Syndrome Management

American Gastroenterological Association Institute and College of American Pathologists Quality Measure Development for Detection of Mismatch Repair Deficiency and Lynch Syndrome Management

S3492 Colon Cancer at 30? What’s Next? A Case of Lynch Syndrome With Negative Screening Colonoscopy After Right Hemicolectomy

S3492 Colon Cancer at 30? What’s Next? A Case of Lynch Syndrome With Negative Screening Colonoscopy After Right Hemicolectomy

Endoscopy to Diagnose and Prevent Digestive Cancers in Lynch Syndrome.

Simple SummaryLynch syndrome is characterized by a higher relative risk of developing certain cancers, especially digestive cancers. Many guidelines from different scientific societies are now available and allow excellent follow-up for these patients, but occasionally propose divergent management approaches. We provide here a synthesis of these guidelines and a focus on prevention, diagnosis, and endoscopic follow-up of these digestive cancers and early neoplasia.Lynch syndrome patients could benefit from various recommendations to prevent digestive cancers. In this review, we summarize the criteria to identify Lynch syndrome in patients with digestive cancers. We detail endoscopic screening procedures in patients with Lynch syndrome for gastric, small bowel, pancreatic, and colorectal cancers. We review the precise modalities of endoscopic follow-up, particularly the discrepancies that exist between the guidelines of the various scientific societies. We discuss the treatment of colorectal cancers in Lynch syndrome cases and patient adherence to endoscopic follow-up programs.

High prevalence of actionable germline variants in unselected endometrial cancer (EC) patients.

5577 Background: The use of upfront germline genetic testing for cancer patients to identify hereditary syndromes and to aid in treatment decision making has increased dramatically. Recent evidence suggests that such testing should be considered for all solid tumors. In EC, mismatch repair deficiency (MMRd) has emerged as an important molecular marker for treatment with checkpoint inhibitors. MMRd is the hallmark of Lynch syndrome (LS), the most common hereditary cause of EC. Therefore, identifying LS not only affords opportunities for cancer prevention but also for making treatment decisions for women who already have EC. Although tumor-based screening is highly effective, some LS diagnoses will be missed. Upfront multi-gene panel testing (MGPT) for EC has been evaluated as an alternative approach to identifying LS with the potential to simultaneously find actionable germline variants in other cancer susceptibility genes (CSGs). Our objective was to determine the frequency and types of actionable germline variants in a large, unselected group of women with EC. Methods: Prospective germline MGPT for 47 CSGs was performed for 961 unselected EC cases. Patients diagnosed from 2017-2020 were enrolled at nine different institutions. Clinicopathologic data were abstracted from patients’ records. Results: 101 likely pathogenic (LP) or pathogenic variants (PV) were identified in 98 women (10.2%). LP/PVs in LS genes were most common: 29 LS cases were identified (3.02%, 95% CI 2.1 - 4.3%). MGPT found 9 cases (one-third of LS cases) that were not identified by tumor screening: 6 were from institutions that do not perform tumor screening and 3 had normal immunohistochemistry. There were 72 LP/PVs found in 17 different CSGs. 21 patients (2.1%) had LP/PVs in high penetrance CSGs other than the LS genes, 19 of which were in genes associated with breast and/or ovarian cancer (4 in BRCA1, 6 in BRCA2, 6 in BRIP1, 2 in PALB2, 1 in RAD51C). BRCA1/2 PVs (1.04% of the study population, 95% CI 0.6 - 1.9%) were significantly more frequent in women with type II cancers than the rest of the cohort (P =.005, HR 2.00, 95% CI 1.16 - 4.75). 21 additional LP/PVs were found in moderate risk CSGs ( ATM, CHEK2, NBN, NF1). Conclusions: Upfront MGPT in an unselected EC population improved LS diagnosis and identified an additional 2% of patients with LP/PVs in highly penetrant CSGs. The enrichment of germline BRCA1/2 PVs in type II cancers is consistent with prior reports that non-endometrioid tumors are frequently deficient in homologous recombination. Germline BRCA mutation is a known predictive biomarker in ovarian cancer and an attractive therapeutic target in EC. Knowing germline status at the time of diagnosis facilitates further delineation of germline/phenotype associations, and it defines a genetic syndrome allowing for cancer prevention. Upfront MGPT in EC provides clinically impactful information and should be adopted into routine clinical care. Clinical trial information: NCT03460483.

Improved universal tumor screening program with paired testing: Experience at a large community-based teaching hospital.

e22505 Background: Lynch syndrome (LS) is the most common cause of hereditary predisposition to colon, endometrial, and other cancers. The universal tumor screening program for LS at Beaumont Health (BH) utilizes immunohistochemistry (IHC) of the mismatch repair (MMR) proteins to identify patients for genetics evaluation. We present the 8-year experience of the program at a large community-based teaching hospital. Methods: The MMR IHC results for all colorectal cancer (CRC) resection specimens screened from August 2012 to September 2020 were reviewed. Specimens with absent MLH1 and PMS2 were evaluated for MLH1 promoter hypermethylation with reflex to BRAF V600E mutation analysis. All abnormal results were referred for cancer genetics evaluation. The distribution of abnormal MMR and germline genetic testing results was analyzed. Results: Specimens from 2361 CRC resections were screened, and 511 specimens had abnormal MMR IHC (22%). Most cases of absent MLH1 and PMS2 were explained by hypermethylation or BRAF analysis (n = 338, 66% of all abnormal, 89% of MLH1 and PMS2). Of the remaining cases showing MMR deficiency (n = 173), the most common result was absence of MSH2 and MSH6 (n = 67), followed by absence of MLH1 and PMS2 (n=41, see table). Germline genetic testing of 83 individuals with abnormal MMR IHC revealed 49 cases of Lynch syndrome [MLH1 (n=9), MSH2 (n= 25), MSH6 (n=7), PMS2 (n=7), EPCAM (n=1)]. A significant proportion of cases (n=34, 40%) had negative germline testing, and had unexplained MMR deficiency. Paired germline/tumor testing was implemented in 2017, and 14 patients had this analysis. Using this approach, 5 individuals were identified to have somatic mutations explaining their result, and the proportion of unexplained cases was reduced to 29% (n = 4). Conclusions: Recent advances in cancer screening and therapeutics have underscored the importance of analyzing tumors for mismatch repair deficiency (dMMR), with known challenges to implementation and interpretation of results. The BH cancer genetics program has demonstrated successful growth of a universal tumor screening program over 8 years. This has led to the identification of a large number of dMMR tumors (22% of all CRC resections) and LS cases (2% of all CRC resections), which impacts management for patients and their families. Recent implementation of paired germline/tumor testing has improved the testing algorithm, and resulted in more accurate interpretation of a greater proportion of abnormal IHC results. This combined approach allows for focused high-risk screening for LS patients, access to novel therapeutic interventions including immune therapies for patients with dMMR tumors, and future precision oncology approaches.[Table: see text]

An Update on Immune Checkpoint Therapy for the Treatment of Lynch Syndrome.

During the recent years, immune checkpoint-based therapy has proven highly effective in microsatellite instable (MSI) solid tumors irrespective of organ site. MSI tumors are associated with a defective mismatch repair (MMR) system and a highly immune-infiltrative tumor microenvironment—both characteristics of Lynch syndrome. Lynch syndrome is a multi-tumor syndrome that not only confers a high risk of colorectal and endometrial cancer but also cancer in, eg the upper urinary tract, ovaries, and small bowel. Since the genetic predisposition for Lynch syndrome are pathogenic variants in one of the four MMR genes, MLH1, MSH2, MSH6 or PMS2, most of the Lynch syndrome cancers show MMR deficiency, MSI, and activation of the immune response system. Hence, Lynch syndrome cancer patients may be optimal candidates for immune checkpoint-based therapies. However, molecular differences have been described between sporadic MSI tumors (developed due to MLH1 promoter hypermethylation) and Lynch syndrome tumors, which may result in different treatment responses. Furthermore, the response profile of the rare Lynch syndrome cases may be masked by the more frequent cases of sporadic MSI tumors in large clinical trials. With this review, we systematically collected response data on Lynch syndrome patients treated with FDA- and EMA-approved immune checkpoint-based drugs (pembrolizumab, atezolizumab, durvalumab, avelumab, ipilimumab, and nivolumab) to elucidate the objective response rate and progression-free survival of cancer in Lynch syndrome patients. Herein, we report Lynch syndrome-related objective response rates between 46 and 71% for colorectal cancer and 14–100% for noncolorectal cancer in unselected cohorts as well as an overview of the Lynch syndrome case reports. To date, no difference in the response rates has been reported between Lynch syndrome and sporadic MSI cancer patients.

Model-Based Re-Examination of the Effectiveness of Tumor/Immunohistochemistry and Direct-to-Sequencing Protocols for Lynch Syndrome Case Finding in Endometrial Cancer.

Despite widespread provision of Lynch syndrome (LS) screening programs, questions remain about the most effective and efficient protocol for LS case finding. The purpose of this study was to explore the performance of the two protocols widely shown to be the most efficient and effective, respectively: immunohistochemical (IHC) staining of tumor and direct-to-sequencing (DtS) in endometrial cancer populations. Simulation models were developed to explore performance of the IHC and DtS protocols, updated to reflect current evidence. Analyses explicitly account for protocol complexity and failure points, as well as decreased sequencing costs. Key outcomes are percent of LS cases identified, total protocol costs and efficiency, and break-even analyses of sequencing costs. All costs are in 2020 US dollars (USD). Under plausible conditions, the IHC protocol is expected to identify 40%-78% of LS cases and DtS protocol from 49% to 97%. When the key variable success in proceeding to sequencing is fixed for both protocols at 50%, 75%, and 100%, the DtS protocol is 9%, 12%, and 16% better at case finding, respectively, than the IHC protocol. The break-even cost of sequencing is about $488 USD when the outcome is total direct testing protocol costs; it is about $670 USD when the outcome is cost per LS case detected. This study quantifies the plausible differences in the clinical effectiveness and cost-effectiveness of the two LS case-finding protocols. We demonstrate the large influence of success in proceeding to sequencing and potential impact of decreasing sequencing prices.

Lynch syndrome associated endometrial carcinomas in Western Australia: an analysis of universal screening by mismatch repair protein immunohistochemistry

BackgroundIn 2016 universal screening with mismatch repair protein immunohistochemistry in all newly diagnosed endometrial carcinomas was introduced in Western Australia.ObjectiveTo compare the prevalence of Lynch syndrome associated endometrial carcinomas between...

Universal testing for MSI/MMR status in colorectal and endometrial cancers to identify Lynch syndrome cases: state of the art in Italy and consensus recommendations from the Italian Association for the Study of Familial Gastrointestinal Tumors (A.I.F.E.G.).

Universal testing for MSI/MMR status in colorectal and endometrial cancers to identify Lynch syndrome cases: state of the art in Italy and consensus recommendations from the Italian Association for the Study of Familial Gastrointestinal Tumors (A.I.F.E.G.).