The "unnatural" history of colorectal cancer in Lynch syndrome: Lessons from colonoscopy surveillance

[Lynch syndrome]

Patients with Lynch syndrome, one of the most common hereditary tumor predisposition syndromes, harbor an increased risk for a broad spectrum of especially gastrointestinal and gynecological tumors. Causative for the syndrome are variants in DNA mismatch repair genes, which are passed on to the offspring at a 50% chance (autosomal dominant inheritance). The tumor tissue of these patients usually shows microsatellite instability, which is of increasing relevance regarding prognosis and therapeutic decisions. The detection of a causative genetic variant in a patient enables predictive testing of family members to provide relief to noncarriers and provide carriers with intensified risk-adapted surveillance. In addition, chemoprevention with aspirin (acetylsalicylic acid) has been proven useful for chemoprevention in studies. Therefore, the diagnosis of Lynch syndrome is important for patients and their relatives.

Incidences of colorectal adenomas and cancers under colonoscopy surveillance suggest an accelerated "Big Bang" pathway to CRC in three of the four Lynch syndromes

BACKGROUND

Colorectal cancers (CRCs) in the Lynch syndromes have been assumed to emerge through an accelerated adenoma-carcinoma pathway. In this model adenomas with deficient mismatch repair have an increased probability of acquiring additional cancer driver mutation(s) resulting in more rapid progression to malignancy. If this model was accurate, the success of colonoscopy in preventing CRC would be a function of the intervals between colonoscopies and mean sojourn time of detectable adenomas. Contrary to expectations, colonoscopy did not decrease incidence of CRC in the Lynch syndromes and shorter colonoscopy intervals have not been effective in reducing CRC incidence. The prospective Lynch Syndrome Database (PLSD) was designed to examine these issues in carriers of pathogenic variants of the mis-match repair (path_MMR) genes.

MATERIALS AND METHODS

We examined the CRC and colorectal adenoma incidences in 3,574 path_MLH1, path_MSH2, path_MSH6 and path_PMS2 carriers subjected to regular colonoscopy with polypectomy, and considered the results based on sojourn times and stochastic probability paradigms.

RESULTS

Most of the path_MMR carriers in each genetic group had no adenomas. There was no association between incidences of CRC and the presence of adenomas. There was no CRC observed in path_PMS2 carriers.

CONCLUSIONS

Colonoscopy prevented CRC in path_PMS2 carriers but not in the others. Our findings are consistent with colonoscopy surveillance blocking the adenoma-carcinoma pathway by removing identified adenomas which might otherwise become CRCs. However, in the other carriers most CRCs likely arised from dMMR cells in the crypts that have an increased mutation rate with increased stochastic chaotic probabilities for mutations. Therefore, this mechanism, that may be associated with no or only a short sojourn time of MSI tumours as adenomas, could explain the findings in our previous and current reports.

Emerge of colorectal cancer in Lynch syndrome despite colonoscopy surveillance: A challenge of hide and seek

Even with colonoscopy surveillance, Lynch syndromes (LS) carriers still develop colorectal cancer (CRC). The cumulative incidence of CRCs under colonoscopy surveillance varies depending on the affected mismatch repair (MMR) gene. However, the precise mechanisms driving these epidemiological patterns remain incompletely understood. In recent years, several potential mechanisms explaining the occurrence of CRCs during colonoscopy surveillance have been proposed in individuals with and without LS. These encompass biological factors like concealed/accelerated carcinogenesis through a bypassed adenoma stage and accelerated progression from adenomas. Alongside these, various colonoscopy-related factors may contribute to formation of CRCs under colonoscopy surveillance, like missed yet detectable (pre)cancerous lesions, detected yet incompletely removed (pre)cancerous lesions, and colonoscopy-induced carcinogenesis due to tumor cell reimplantation. In this comprehensive literature update, we reviewed these potential factors and evaluated their relevance to each MMR group in an attempt to raise further awareness and stimulate research regarding this conflicting phenomenon.

Mitotic abnormalities precede microsatellite instability in lynch syndrome-associated colorectal tumourigenesis

BACKGROUND

Lynch syndrome (LS) is one of the most common hereditary cancer syndromes worldwide. Dominantly inherited mutation in one of four DNA mismatch repair genes combined with somatic events leads to mismatch repair deficiency and microsatellite instability (MSI) in tumours. Due to a high lifetime risk of cancer, regular surveillance plays a key role in cancer prevention; yet the observation of frequent interval cancers points to insufficient cancer prevention by colonoscopy-based methods alone. This study aimed to identify precancerous functional changes in colonic mucosa that could facilitate the monitoring and prevention of cancer development in LS.

METHODS

The study material comprised colon biopsy specimens (n = 71) collected during colonoscopy examinations from LS carriers (tumour-free, or diagnosed with adenoma, or diagnosed with carcinoma) and a control group, which included sporadic cases without LS or neoplasia. The majority (80%) of LS carriers had an inherited genetic MLH1 mutation. The remaining 20% included MSH2 mutation carriers (13%) and MSH6 mutation carriers (7%). The transcriptomes were first analysed with RNA-sequencing and followed up with Gorilla Ontology analysis and Reactome Knowledgebase and Ingenuity Pathway Analyses to detect functional changes that might be associated with the initiation of the neoplastic process in LS individuals.

FINDINGS

With pathway and gene ontology analyses combined with measurement of mitotic perimeters from colonic mucosa and tumours, we found an increased tendency to chromosomal instability (CIN), already present in macroscopically normal LS mucosa. Our results suggest that CIN is an earlier aberration than MSI and may be the initial cancer driving aberration, whereas MSI accelerates tumour formation. Furthermore, our results suggest that MLH1 deficiency plays a significant role in the development of CIN.

INTERPRETATION

The results validate our previous findings from mice and highlight early mitotic abnormalities as an important contributor and precancerous marker of colorectal tumourigenesis in LS.

FUNDING

This work was supported by grants from the Jane and Aatos Erkko Foundation, the Academy of Finland (330606 and 331284), Cancer Foundation Finland sr, and the Sigrid Jusélius Foundation. Open access is funded by Helsinki University Library.

Screening and surveillance for hereditary colorectal cancer

Hereditary colorectal cancer is a type of cancer that is caused by a genetic mutation. Individuals with a family history of colorectal cancer, or who have a known hereditary syndrome, are at an increased risk of developing the disease. Screening and surveillance are important tools for managing the risk of hereditary colorectal cancer. Screening involves a combination of tests that can detect precancerous or cancerous changes in the colon and rectum. Surveillance involves regular follow-up examinations to monitor disease progression and to identify new developments. The frequency and type of screening and surveillance tests may vary depending on an individual's risk factors, genetic profile, and medical history. However, early detection and treatment of hereditary colorectal cancer can significantly improve patient outcomes and reduce mortality rates. By implementing comprehensive screening and surveillance strategies, healthcare providers can help individuals at risk of hereditary colorectal cancer to receive timely interventions and make informed decisions about their health. Specific examples of screening and surveillance tests for hereditary colorectal cancer include colonoscopy, genetic testing, and imaging tests. In this review article, we will discuss detailed screening and surveillance of hereditary colorectal cancer.

Province-Wide Ascertainment of Lynch Syndrome in Manitoba

BACKGROUND & AIMS

We describe the experience of Lynch syndrome (LS) diagnosis in the province of Manitoba, Canada, over the past 20 years.

METHODS

We performed a retrospective review of charts from the provincial Genetics Clinic from January 1, 2000, to May 31, 2023. We extracted data on individuals identified to carry a germline pathogenic or likely pathogenic LS gene variant, the mode of ascertainment, family history, and cascade genetic testing (CGT). Data were stratified and compared before and after the year of implementation (October 2013) of the provincial LS screening program (LSSP) and ascertainment by the LSSP vs clinic referrals (CRs).

RESULTS

Between 2014 and 2021, 50 of 101 (49.5%) index cases were identified by the LSSP compared with 51 of 101 (50.5%) from CRs. The proportion of PMS2 variants was 34% (17 of 50) for LSSP index cases compared with 21.6% (11 of 51) for CRs from 2014 to 2021 (P < .001). Among CRs from 2014 to 2021, 24 of 51 (47.1%) families met the Amsterdam criteria, compared with 11 of 50 (22.0%) for the LSSP (P = .01). CGT occurred among 46.8% (95 of 203; average, 1.9 relatives/index) of first-degree relatives of CR index cases vs 36.5% (84 of 230; average, 1.7 relatives/index) of first-degree relatives of LSSP index cases (P = .03). Daughters were most likely to undergo CGT.

CONCLUSIONS

A tumor screening program is more effective at detecting individuals with lower penetrant gene variants and families who do not meet traditional family history-based criteria. Cascade genetic testing is higher among clinic referrals compared with the screening program. These findings suggest a complementary role of these 2 ascertainment methods for Lynch syndrome.

Lynch Syndrome: From Multidisciplinary Management to Precision Prevention

BACKGROUND AND AIMS

Lynch syndrome (LS) is currently one of the most prevalent hereditary cancer conditions, accounting for 3% of all colorectal cancers and for up to 15% of those with DNA mismatch repair (MMR) deficiency, and it was one of the first historically identified. The understanding of the molecular carcinogenesis of LS tumors has progressed significantly in recent years. We aim to review the most recent advances in LS research and explore genotype-based approaches in surveillance, personalized cancer prevention, and treatment strategies.

METHODS

PubMed was searched to identify relevant studies, conducted up to December 2023, investigating molecular carcinogenesis in LS, surveillance strategies, cancer prevention, and treatment in LS tumors.

RESULTS

Multigene panel sequencing is becoming the benchmark in the diagnosis of LS, allowing for the detection of a pathogenic constitutional variant in one of the MMR genes. Emerging data from randomized controlled trials suggest possible preventive roles of resistant starch and/or aspirin in LS. Vaccination with immunogenic frameshift peptides appears to be a promising approach for both the treatment and prevention of LS-associated cancers, as evidenced by pre-clinical and preliminary phase 1/2a studies.

CONCLUSIONS

Although robust diagnostic algorithms, including prompt testing of tumor tissue for MMR defects and referral for genetic counselling, currently exist for suspected LS in CRC patients, the indications for LS screening in cancer-free individuals still need to be refined and standardized. Investigation into additional genetic and non-genetic factors that may explain residual rates of interval cancers, even in properly screened populations, would allow for more tailored preventive strategies.

Detection of (pre)cancerous colorectal lesions in Lynch syndrome patients by microsatellite instability liquid biopsy

Lynch syndrome (LS) is an inherited condition characterized by an increased risk of developing cancer, in particular colorectal cancer (CRC). Microsatellite instability (MSI) is the main feature of (pre)cancerous lesions occurring in LS patients. Close endoscopic surveillance is the only option available to reduce CRC morbidity and mortality. However, it may fail to intercept interval cancers and patients' compliance to such an invasive procedure may decrease over the years. The development of a minimally invasive test able to detect (pre)cancerous colorectal lesions, could thus help tailor surveillance programs in LS patients. Taking advantage of an endoscopic surveillance program, we retrospectively assessed the instability of five microsatellites (BAT26, BAT25, NR24, NR21, and Mono27) in liquid biopsies collected at baseline and possibly at two further endoscopic rounds. For this purpose, we tested a new multiplex drop-off digital polymerase chain reaction (dPCR) assay, reaching mutant allele frequencies (MAFs) as low as 0.01%. Overall, 78 plasma samples at the three time-points from 18 patients with baseline (pre)cancerous lesions and 18 controls were available for molecular analysis. At baseline, the MAFs of BAT26, BAT25 and NR24 were significantly higher in samples of patients with lesions but did not differ with respect to the grade of dysplasia or any other clinico-pathological characteristics. When all markers were combined to determine MSI in blood, this test was able to discriminate lesion-bearing patients with an AUC of 0.80 (95%CI: 0.66; 0.94).

Density clustering-based automatic anatomical section recognition in colonoscopy video using deep learning

Recognizing anatomical sections during colonoscopy is crucial for diagnosing colonic diseases and generating accurate reports. While recent studies have endeavored to identify anatomical regions of the colon using deep learning, the deformable anatomical characteristics of the colon pose challenges for establishing a reliable localization system. This study presents a system utilizing 100 colonoscopy videos, combining density clustering and deep learning. Cascaded CNN models are employed to estimate the appendix orifice (AO), flexures, and "outside of the body," sequentially. Subsequently, DBSCAN algorithm is applied to identify anatomical sections. Clustering-based analysis integrates clinical knowledge and context based on the anatomical section within the model. We address challenges posed by colonoscopy images through non-informative removal preprocessing. The image data is labeled by clinicians, and the system deduces section correspondence stochastically. The model categorizes the colon into three sections: right (cecum and ascending colon), middle (transverse colon), and left (descending colon, sigmoid colon, rectum). We estimated the appearance time of anatomical boundaries with an average error of 6.31 s for AO, 9.79 s for HF, 27.69 s for SF, and 3.26 s for outside of the body. The proposed method can facilitate future advancements towards AI-based automatic reporting, offering time-saving efficacy and standardization.

Liquid biopsy-based early tumor and minimal residual disease detection

Genetic predisposition is one of the major measurable cancer risk factors. Affected patients have an enhanced risk for cancer and require life-long surveillance. However, current screening measures are mostly invasive and only available for certain tumor types. Particularly in hereditary cancer syndromes, liquid biopsy, in addition to monitoring therapy response and assessing minimal residual disease, holds great potential for surveillance at the precancerous stage and potentially even diagnostics. Exploring these options and future clinical translation could help reduce cancer risk and mortality in high-risk individuals and enhance patients' adherence to tailored surveillance protocols.

Dominantly inherited micro-satellite instable cancer - the four Lynch syndromes - an EHTG, PLSD position statement

The recognition of dominantly inherited micro-satellite instable (MSI) cancers caused by pathogenic variants in one of the four mismatch repair (MMR) genes MSH2, MLH1, MSH6 and PMS2 has modified our understanding of carcinogenesis. Inherited loss of function variants in each of these MMR genes cause four dominantly inherited cancer syndromes with different penetrance and expressivities: the four Lynch syndromes. No person has an "average sex "or a pathogenic variant in an "average Lynch syndrome gene" and results that are not stratified by gene and sex will be valid for no one. Carcinogenesis may be a linear process from increased cellular division to localized cancer to metastasis. In addition, in the Lynch syndromes (LS) we now recognize a dynamic balance between two stochastic processes: MSI producing abnormal cells, and the host's adaptive immune system's ability to remove them. The latter may explain why colonoscopy surveillance does not reduce the incidence of colorectal cancer in LS, while it may improve the prognosis. Most early onset colon, endometrial and ovarian cancers in LS are now cured and most cancer related deaths are after subsequent cancers in other organs. Aspirin reduces the incidence of colorectal and other cancers in LS. Immunotherapy increases the host immune system's capability to destroy MSI cancers. Colonoscopy surveillance, aspirin prevention and immunotherapy represent major steps forward in personalized precision medicine to prevent and cure inherited MSI cancer.

Preventive strategies in familial and hereditary colorectal cancer

Colorectal cancer is a leading cause of cancer-related deaths worldwide. While most cases are sporadic, a significant proportion of cases are associated with familial and hereditary syndromes. Individuals with a family history of colorectal cancer have an increased risk of developing the disease, and those with hereditary syndromes such as Lynch syndrome or familial adenomatous polyposis have a significantly higher risk. In these populations, preventive strategies are critical for reducing the incidence and mortality of colorectal cancer. This review provides an overview of current preventive strategies for individuals at increased risk of colorectal cancer due to familial or hereditary factors. The manuscript includes a discussion of risk assessment and genetic testing, highlighting the importance of identifying at-risk individuals and families. This review describes various preventive measures, including surveillance colonoscopy, chemoprevention, and prophylactic surgery, and their respective benefits and limitations. Together, this work highlights the importance of preventive strategies in familial and hereditary colorectal cancer.

Neoplasia risk in patients with Lynch syndrome treated with immune checkpoint blockade

Metastatic and localized mismatch repair-deficient (dMMR) tumors are exquisitely sensitive to immune checkpoint blockade (ICB). The ability of ICB to prevent dMMR malignant or pre-malignant neoplasia development in patients with Lynch syndrome (LS) is unknown. Of 172 cancer-affected patients with LS who had received ≥1 ICB cycles, 21 (12%) developed subsequent malignancies after ICB exposure, 91% (29/32) of which were dMMR, with median time to development of 21 months (interquartile range, 6-38). Twenty-four of 61 (39%) ICB-treated patients who subsequently underwent surveillance colonoscopy had premalignant polyps. Within matched pre-ICB and post-ICB follow-up periods, the overall rate of tumor development was unchanged; however, on subgroup analysis, a decreased incidence of post-ICB visceral tumors was observed. These data suggest that ICB treatment of LS-associated tumors does not eliminate risk of new neoplasia development, and LS-specific surveillance strategies should continue. These data have implications for immunopreventative strategies and provide insight into the immunobiology of dMMR tumors.

Incidence and prevalence of advanced colorectal neoplasia in Lynch syndrome

BACKGROUND AND AIMS

Lynch syndrome (LS) is the most common hereditary cause of colorectal cancer (CRC) and endometrial cancer (EC). Although colonoscopy reduces CRC in LS, the protection is variable. We assessed the prevalence and incidence of neoplasia in LS during surveillance colonoscopy in the United States and factors associated with advanced neoplasia.

METHODS

Patients with LS undergoing ≥1 surveillance colonoscopy and with no personal history of invasive CRC or colorectal surgery were included. Prevalent and incident neoplasia was defined as occurring <6 months before and ≥6 months after germline diagnosis of LS, respectively. We assessed advanced adenoma (AA), CRC, and the impact of mismatch repair pathogenic variant (PV) and typical LS cancer history (personal history of EC and/or family history of EC/CRC) on outcome.

RESULTS

A total of 132 patients (inclusive of 112 undergoing prevalent and incident surveillance) were included. The median examination interval and duration of prevalent and incident surveillance was .88 and 1.06 years and 3.1 and 4.6 years, respectively. Prevalent and incident AA were detected in 10.7% and 6.1% and invasive CRC in 0% and 2.3% of patients. All incident CRC occurred in MSH2 and MLH1 PV carriers and only 1 (.7%) while under surveillance in our center. AAs were detected in both LS cancer history cohorts and represented in all PVs.

CONCLUSIONS

In a U.S. cohort of LS, advanced neoplasia rarely occurred over annual surveillance. CRC was diagnosed only in MSH2/MLH1 PV carriers. AAs occurred regardless of PV or LS cancer history. Prospective studies are warranted to confirm our findings.

Serum matrix metalloproteinase-7: a potential biomarker in patients with Lynch Syndrome

BACKGROUND AND AIMS

The expression of tissue and serum matrix metalloproteinase-7 (MMP-7) was shown to be elevated both in colon cancer and dysplastic lesions. We aimed to evaluate, for the first time, its role as a diagnostic marker in Lynch syndrome (LS) carriers, a hereditary syndrome with predisposition to colon cancer.

METHODS

This was a case control study. Baseline serum MMP-7 levels were determined by ELISA in 40 colon cancer patients, 62 LS-carriers and 60 healthy controls. Retrieved data from medical files included demographics, background diseases, clinical data regarding tumor characteristics and genetic data. We assessed the association of serum MMP-7 levels with different variables in the study cohort using linear regression model adjusted for potential confounders.

RESULTS

In crude analysis, serum MMP-7 levels were significantly higher in colon cancer group compared to LS-carriers and controls [median (IQR) 4.1 ng/ml (2.7-6.0), 2.3 ng/ml (1.7-3.1), 2.5 ng/ml (1.5-3.7), respectively; p value - p < 0.001) while there was no difference between the two last groups (p value = 0.583). However, after adjusting for age and gender, LS-carriers' patients had 18% higher concentrations of serum MMP-7 compared to healthy controls (p value = 0.037), while colon cancer patients had 50% higher serum MMP-7 level in comparison to healthy controls (p value < 0.001). Additionally, age was positively associated with higher serum MMP-7 levels across all study groups (r = 0.67, p value < 0.001). In contrast, no correlation was observed between serum MMP-7 and either tumor staging and gene mutation.

CONCLUSIONS

Age-adjusted serum MMP-7 levels in asymptomatic LS carriers are higher than its levels in healthy population. While in colon cancer, MMP-7 higher level probably reflects the tumor burden and may have a prognostic effect, its significance and clinical applicability as a biomarker for tumorigenesis in LS is less clear and should be elucidated.

Biology of Precancers and Opportunities for Cancer Interception: Lesson from Colorectal Cancer Susceptibility Syndromes

Hereditary gastrointestinal cancer is associated with molecular and neoplastic precursors which have revealed much about sporadic carcinogenesis. Therefore, an appreciation of constitutional and somatic events linked to these syndromes have provided a useful model for the development of risk models and preventative strategies. In this review, we focus of two of the best characterized syndromes, Lynch syndrome (LS) and familial adenomatous polyposis (FAP). Our understanding of the neoplasia-immune interaction in LS has contributed to the development of immune mediated therapies including cancer preventing vaccines and immunotherapy for cancer precursors. Chemoprevention in LS with aspirin and nonsteroidal anti-inflammatory drugs has also translated into clinical cancer, however the efficacy of such agents in FAP remains elusive when cancer is applied as an endpoint in trials rather than the use of 'indirect' endpoints such as polyp burden, and requires further elucidation of biological mechanisms in FAP. Finally, we review controversies in gastrointestinal surveillance for LS and FAP, including limitations and opportunities of upper and lower gastrointestinal endoscopy in the prevention and early detection of cancer.

The Role of Colonoscopy in the Management of Individuals with Lynch Syndrome: A Narrative Review

The history of Lynch syndrome changed definitively in 2000, when a study published in Gastroenterology demonstrated a significant reduction in mortality among individuals with Lynch syndrome who undergo regular endoscopic surveillance. As a consequence of this clinical evidence, all scientific societies developed guidelines, which highlighted the role of colonoscopy in the management of Lynch syndrome, especially for individuals at high risk of colorectal cancer. Over the years, these guidelines were modified and updated. Specialized networks were developed in order to standardize endoscopic surveillance programs and evaluate all the clinical data retrieved by the results of colonoscopies performed for both the screening and the surveillance of individuals with Lynch syndrome. Recent data show that the impact of colonoscopy (with polypectomy) on the prevention of colorectal cancer in individuals with Lynch syndrome is less significant than previously thought. This narrative review summarizes the current discussion, the hypotheses elaborated and the algorithms depicted for the management of individuals with Lynch Syndrome on the basis of the recent data published in the literature.

Evaluating colonoscopy screening intervals in patients with Lynch syndrome from a large Canadian registry

BACKGROUND

Lynch syndrome (LS) screening guidelines originally recommended colonoscopy every 1 to 2 years, beginning between the ages of 20 and 25 years. Recent studies have questioned the benefits of these short screening intervals in preventing colorectal cancer (CRC). Our goal is to determine how colonoscopy screening intervals impact CRC in patients with LS.

METHODS

We analyzed the demographics, screening practices, and outcomes of patients with LS identified through the clinic based Familial Gastrointestinal Cancer Registry at the Zane Cohen Centre, Sinai Health System, Toronto, Canada.

RESULTS

A total of 429 patients with LS were identified with median follow-up of 9.2 years; 44 developed CRC. We found a positive trend between shorter screening intervals and the number of adenomas detected during colonoscopy. Any new adenoma detected at screening decreased 10-year CRC incidence by 11.3%. For MLH1 carriers, a screening interval of 1-2 years vs 2-3 years led to a 20-year cumulative CRC risk reduction of 28% and 14% in females and males, respectively. For MSH2 carriers, this risk reduction was 29% and 17%, respectively, and for male MSH6 carriers 18%. Individuals without any adenomas detected (53.4% of LS carriers) had an increased 20-year CRC risk of 25.7% and 57.2% for women and men, respectively, compared with those diagnosed with adenomas at screening.

CONCLUSIONS

The recommended colonoscopy screening interval of 1-2 years is efficient at detecting adenomas and reducing CRC risk. The observation that 53.4% of LS patients never had an adenoma warrants further investigation about a possible adenoma-free pathway.

Microsatellite Instability and Immune Response: From Microenvironment Features to Therapeutic Actionability-Lessons from Colorectal Cancer

Microsatellite instability (MSI) can be found in 15-20% of all colorectal cancers (CRC) and is the key feature of a defective DNA mismatch repair (MMR) system. Currently, MSI has been established as a unique and pivotal biomarker in the diagnosis, prognosis, and treatment of CRC. MSI tumors display a strong lymphocytic activation and a shift toward a tumoral microenvironment restraining metastatic potential and ensuing in a high responsiveness to immunotherapy of MSI CRC. Indeed, neoplastic cells with an MMR defect overexpress several immune checkpoint proteins, such as programmed death-1 (PD-1) and programmed death-ligand 1(PD-L1), that can be pharmacologically targeted, allowing for the revival the cytotoxic immune response toward the tumor. This review aims to illustrate the role of MSI in the tumor biology of colorectal cancer, focusing on the immune interactions with the microenvironment and their therapeutic implications.

Colorectal Cancer-The "Parent" of Low Bowel Obstruction

Introduction: Despite the improvement of early diagnosis methods for multiple pathological entities belonging to the digestive tract, bowel obstruction determined by multiple etiologies represents an important percentage of surgical emergencies. General data: Although sometimes obstructive episodes are possible in the early stages of colorectal cancer, the most commonly installed intestinal obstruction has the significance of an advanced evolutionary stage of neoplastic disease. Development of Obstructive Mechanism: The spontaneous evolution of colorectal cancer is always burdened by complications. The most common complication is low bowel obstruction, found in approximately 20% of the cases of colorectal cancer, and it can occur either relatively abruptly, or is preceded by initially discrete premonitory symptoms, non-specific (until advanced evolutionary stages) and generally neglected or incorrectly interpreted. Success in the complex treatment of a low neoplastic obstruction is conditioned by a complete diagnosis, adequate pre-operative preparation, a surgical act adapted to the case (in one, two or three successive stages), and dynamic postoperative care. The moment of surgery should be chosen with great care and is the result of the experience of the anesthetic-surgical team. The operative act must be adapted to the case and has as its main objective the resolution of intestinal obstruction and only in a secondary way the resolution of the generating disease. Conclusions: The therapeutic measures adopted (medical-surgical) must have a dynamic character in accordance with the particular situation of the patient. Except for certain or probably benign etiologies, the possibility of colorectal neoplasia should always be considered, in low obstructions, regardless of the patient's age.

Lynch Syndrome Genetics and Clinical Implications

Lynch syndrome (LS) is one of the most prevalent hereditary cancer syndromes in humans and accounts for some 3% of unselected patients with colorectal or endometrial cancer and 10%-15% of those with DNA mismatch repair-deficient tumors. Previous studies have established the genetic basis of LS predisposition, but there have been significant advances recently in the understanding of the molecular pathogenesis of LS tumors, which has important implications in clinical management. At the same time, immunotherapy has revolutionized the treatment of advanced cancers with DNA mismatch repair defects. We aim to review the recent progress in the LS field and discuss how the accumulating epidemiologic, clinical, and molecular information has contributed to a more accurate and complete picture of LS, resulting in genotype- and immunologic subtype-specific strategies for surveillance, cancer prevention, and treatment.

Lynch syndrome: from detection to treatment

Lynch syndrome (LS) is an inherited cancer predisposition syndrome associated with high lifetime risk of developing tumours, most notably colorectal and endometrial. It arises in the context of pathogenic germline variants in one of the mismatch repair genes, that are necessary to maintain genomic stability. LS remains underdiagnosed in the population despite national recommendations for empirical testing in all new colorectal and endometrial cancer cases. There are now well-established colorectal cancer surveillance programmes, but the high rate of interval cancers identified, coupled with a paucity of high-quality evidence for extra-colonic cancer surveillance, means there is still much that can be achieved in diagnosis, risk-stratification and management. The widespread adoption of preventative pharmacological measures is on the horizon and there are exciting advances in the role of immunotherapy and anti-cancer vaccines for treatment of these highly immunogenic LS-associated tumours. In this review, we explore the current landscape and future perspectives for the identification, risk stratification and optimised management of LS with a focus on the gastrointestinal system. We highlight the current guidelines on diagnosis, surveillance, prevention and treatment and link molecular disease mechanisms to clinical practice recommendations.

Lynch syndrome cancer vaccines: A roadmap for the development of precision immunoprevention strategies

Hereditary cancer syndromes (HCS) account for 5~10% of all cancer diagnosis. Lynch syndrome (LS) is one of the most common HCS, caused by germline mutations in the DNA mismatch repair (MMR) genes. Even with prospective cancer surveillance, LS is associated with up to 50% lifetime risk of colorectal, endometrial, and other cancers. While significant progress has been made in the timely identification of germline pathogenic variant carriers and monitoring and early detection of precancerous lesions, cancer-risk reduction strategies are still centered around endoscopic or surgical removal of neoplastic lesions and susceptible organs. Safe and effective cancer prevention strategies are critically needed to improve the life quality and longevity of LS and other HCS carriers. The era of precision oncology driven by recent technological advances in tumor molecular profiling and a better understanding of genetic risk factors has transformed cancer prevention approaches for at-risk individuals, including LS carriers. MMR deficiency leads to the accumulation of insertion and deletion mutations in microsatellites (MS), which are particularly prone to DNA polymerase slippage during DNA replication. Mutations in coding MS give rise to frameshift peptides (FSP) that are recognized by the immune system as neoantigens. Due to clonal evolution, LS tumors share a set of recurrent and predictable FSP neoantigens in the same and in different LS patients. Cancer vaccines composed of commonly recurring FSP neoantigens selected through prediction algorithms have been clinically evaluated in LS carriers and proven safe and immunogenic. Preclinically analogous FSP vaccines have been shown to elicit FSP-directed immune responses and exert tumor-preventive efficacy in murine models of LS. While the immunopreventive efficacy of "off-the-shelf" vaccines consisting of commonly recurring FSP antigens is currently investigated in LS clinical trials, the feasibility and utility of personalized FSP vaccines with individual HLA-restricted epitopes are being explored for more precise targeting. Here, we discuss recent advances in precision cancer immunoprevention approaches, emerging enabling technologies, research gaps, and implementation barriers toward clinical translation of risk-tailored prevention strategies for LS carriers. We will also discuss the feasibility and practicality of next-generation cancer vaccines that are based on personalized immunogenic epitopes for precision cancer immunoprevention.

The Approach to Performance of Quality Upper Endoscopy in Lynch Syndrome (QUELS): An International Expert Statement

Strong evidence demonstrates the protective benefit of frequent colonoscopy surveillance for colorectal cancer prevention in Lynch Syndrome (LS) and is endorsed by many guidelines. Until recently, the evidence supporting the utility of upper endoscopy [esophagogastroduodenoscopy (EGD)] for upper gastrointestinal (UGI) cancer surveillance was limited. Over the last 3 years, multiple studies have demonstrated that EGD surveillance in LS is associated with the detection of both precancerous lesions and early-stage UGI cancers. On the basis of the emerging favorable evidence derived from EGD surveillance programs, the 2022 National Comprehensive Cancer Network (NCCN) Guidelines for LS recommend UGI surveillance with EGD starting between age 30 and 40 years with repeat EGDs every 2 to 4 years, preferably in conjunction with colonoscopy, in all patients with a germline pathogenic variant (PV) in MLH1, MSH2, EPCAM, and MSH6 and, because of the lack of data, consideration in PMS2. Standardization of the approach to performing EGD surveillance in LS and reporting clinically actionable findings is requisite for both improving quality and understanding the cost efficiency and outcomes of patients undergoing EGD as a surveillance tool. Accordingly, the primary objective of this Quality of Upper Endoscopy in Lynch Syndrome (QUELS) statement is to articulate a framework for standardizing the approach to performing and reporting EGD findings in patients with LS by introducing emerging quality metrics. The recommendations presented herein were developed from available evidence and consensus-based expert opinion and provide a practical approach for clinicians applying EGD surveillance in accordance with the most recent and existing LS guidelines.

Real-time use of artificial intelligence (CADEYE) in colorectal cancer surveillance of patients with Lynch syndrome-A randomized controlled pilot trial (CADLY)

BACKGROUND

Lynch syndrome (LS), an autosomal dominant disorder caused by pathogenic germline variants in DNA mismatch repair (MMR) genes, represents the most common hereditary colorectal cancer (CRC) syndrome. Lynch syndrome patients are at high risk of CRC despite regular endoscopic surveillance.

OBJECTIVE

Our aim was to investigate the diagnostic performance of artificial intelligence (AI)-assisted colonoscopy in comparison to High-Definition white-light endoscopy (HD-WLE) for the first time.

METHODS

Patients ≥18 years with LS, with a pathogenic germline variant (MLH1, MHS2, MSH6), and at least one previous colonoscopy (interval 10-36 months) were eligible. Patients were stratified by previous CRC and affected MMR gene with a 1:1 allocation ratio (AI-assisted vs. HD white-light endoscopy) in this exploratory pilot trial.

RESULTS

Between Dec-2021 and Dec-2022, 101 LS patients were randomised and 96 patients were finally analyzed after exclusion of 5 patients due to insufficient bowel preparation. In the HD-WLE arm, adenomas were detected in 12/46 patients compared to 18/50 in the AI arm (26.1% [95% CI 14.3-41.1] vs. 36.0% [22.9-50.8]; p = 0.379). The use of AI-assisted colonoscopy especially increased detection of flat adenomas (Paris classification 0-IIb) (examinations with detected flat adenomas: 3/46 [6.5%] vs. 10/50 [20%]; p = 0.07; numbers of detected flat adenomas: 4/20 vs. 17/30, p = 0.018). The median withdrawal time did not differ significantly between HD-WLE and AI (14 vs. 15 min; p = 0.170).

CONCLUSION

We here present first data suggesting that real-time AI-assisted colonoscopy is a promising approach to optimize endoscopic surveillance in LS patients, in particular to improve the detection of flat adenomas.

Strong Hereditary Predispositions to Colorectal Cancer

Cancer is one of the most common causes of death worldwide. A strong predisposition to cancer is generally only observed in colorectal cancer (5% of cases) and breast cancer (2% of cases). Colorectal cancer is the most common cancer with a strong genetic predisposition, but it includes dozens of various syndromes. This group includes familial adenomatous polyposis, attenuated familial adenomatous polyposis, MUTYH-associated polyposis, NTHL1-associated polyposis, Peutz-Jeghers syndrome, juvenile polyposis syndrome, Cowden syndrome, Lynch syndrome, and Muir-Torre syndrome. The common symptom of all these diseases is a very high risk of colorectal cancer, but depending on the condition, their course is different in terms of age and range of cancer occurrence. The rate of cancer development is determined by its conditioning genes, too. Hereditary predispositions to cancer of the intestine are a group of symptoms of heterogeneous diseases, and their proper diagnosis is crucial for the appropriate management of patients and their successful treatment. Mutations of specific genes cause strong colorectal cancer predispositions. Identifying mutations of predisposing genes will support proper diagnosis and application of appropriate screening programs to avoid malignant neoplasm.

Exploring the utility and acceptability of Faecal immunochemical testing (FIT) as a novel intervention for the improvement of colorectal Cancer (CRC) surveillance in individuals with lynch syndrome (FIT for lynch study): a single-arm, prospective, multi-centre, non-randomised study

BACKGROUND

Lynch Syndrome (LS) is an inherited cancer predisposition syndrome defined by pathogenic variants in the mismatch repair (MMR) or EPCAM genes. In the United Kingdom, people with LS are advised to undergo biennial colonoscopy from as early as 25 until 75 years of age to mitigate a high lifetime colorectal cancer (CRC) risk, though the consideration of additional surveillance intervention(s) through the application of non-invasive diagnostic devices has yet to be longitudinally observed in LS patients. In this study, we will examine the role of annual faecal immunochemical testing (FIT) alongside biennial colonoscopy for CRC surveillance in people with LS.

METHODS/DESIGN

In this single-arm, prospective, non-randomised study, 400 LS patients will be recruited across 11 National Health Service (NHS) Trusts throughout the United Kingdom. Study inclusion requires a LS diagnosis, between 25 and 73 years old, and a routine surveillance colonoscopy scheduled during the recruitment period. Eligible patients will receive a baseline OC-Sensor™ FIT kit ahead of their colonoscopy, and annually for 3 years thereafter. A pre-paid envelope addressed to the central lab will be included within all patient mailings for the return of FIT kits and relevant study documents. A questionnaire assessing attitudes and perception of FIT will also be included at baseline. All study samples received by the central lab will be assayed on an OC-Sensor™ PLEDIA Analyser. Patients with FIT results of ≥6 μg of Haemoglobin per gram of faeces (f-Hb) at Years 1 and/or 3 will be referred for colonoscopy via an urgent colonoscopy triage pathway. 16S rRNA gene V4 amplicon sequencing will be carried out on residual faecal DNA of eligible archived FIT samples to characterise the faecal microbiome.

DISCUSSION

FIT may have clinical utility alongside colonoscopic surveillance in people with LS. We have designed a longitudinal study to examine the efficacy of FIT as a non-invasive modality. Potential limitations of this method will be assessed, including false negative or false positive FIT results related to specific morphological features of LS neoplasia or the presence of post-resection anastomotic inflammation. The potential for additional colonoscopies in a subset of participants may also impact on colonoscopic resources and patient acceptability.

TRIAL REGISTRATION

Trial Registration: ISRCTN, ISRCTN15740250 . Registered 13 July 2021.

Pediatric manifestations of Lynch Syndrome: A single center experience

Lynch syndrome is an autosomal dominant condition caused by a heterozygous variation in one of the DNA mismatch repair (MMR) genes that pre-disposes individuals to early onset colorectal cancers and other malignancies. Lynch syndrome is generally considered an adult-onset disorder, with malignancy rarely manifesting in childhood. Colorectal cancer is extremely rare in children, but hereditary syndromes including Lynch syndrome are an important cause. We aimed to assess the frequency and clinical course of children with Lynch syndrome associated pediatric colorectal cancers at our institution over the last 20 years.

In this retrospective study, we describe four cases of children with Lynch syndrome-associated colorectal cancers age 14–17 years at diagnosis. All patients were diagnosed with Lynch syndrome after diagnosis, despite three of them having family histories consistent with Lynch syndrome.

This series highlights a rare but important cause of pediatric malignancy and points to the need for early education on colorectal cancer warning symptoms and open discussion about this condition in affected families. It also illustrates the need for a thorough family history and a high level of suspicion for Lynch syndrome in children based on family background, as early detection may be key to improving cancer outcomes.

Third Asia-Pacific consensus recommendations on colorectal cancer screening and postpolypectomy surveillance

The Asia-Pacific region has the largest number of cases of colorectal cancer (CRC) and one of the highest levels of mortality due to this condition in the world. Since the publishing of two consensus recommendations in 2008 and 2015, significant advancements have been made in our knowledge of epidemiology, pathology and the natural history of the adenoma-carcinoma progression. Based on the most updated epidemiological and clinical studies in this region, considering literature from international studies, and adopting the modified Delphi process, the Asia-Pacific Working Group on Colorectal Cancer Screening has updated and revised their recommendations on (1) screening methods and preferred strategies; (2) age for starting and terminating screening for CRC; (3) screening for individuals with a family history of CRC or advanced adenoma; (4) surveillance for those with adenomas; (5) screening and surveillance for sessile serrated lesions and (6) quality assurance of screening programmes. Thirteen countries/regions in the Asia-Pacific region were represented in this exercise. International advisors from North America and Europe were invited to participate.

Colorectal cancer incidences in Lynch syndrome: a comparison of results from the prospective lynch syndrome database and the international mismatch repair consortium

OBJECTIVE

To compare colorectal cancer (CRC) incidences in carriers of pathogenic variants of the MMR genes in the PLSD and IMRC cohorts, of which only the former included mandatory colonoscopy surveillance for all participants.

METHODS

CRC incidences were calculated in an intervention group comprising a cohort of confirmed carriers of pathogenic or likely pathogenic variants in mismatch repair genes (path_MMR) followed prospectively by the Prospective Lynch Syndrome Database (PLSD). All had colonoscopy surveillance, with polypectomy when polyps were identified. Comparison was made with a retrospective cohort reported by the International Mismatch Repair Consortium (IMRC). This comprised confirmed and inferred path_MMR carriers who were first- or second-degree relatives of Lynch syndrome probands.

RESULTS

In the PLSD, 8,153 subjects had follow-up colonoscopy surveillance for a total of 67,604 years and 578 carriers had CRC diagnosed. Average cumulative incidences of CRC in path_MLH1 carriers at 70 years of age were 52% in males and 41% in females; for path_MSH2 50% and 39%; for path_MSH6 13% and 17% and for path_PMS2 11% and 8%. In contrast, in the IMRC cohort, corresponding cumulative incidences were 40% and 27%; 34% and 23%; 16% and 8% and 7% and 6%. Comparing just the European carriers in the two series gave similar findings. Numbers in the PLSD series did not allow comparisons of carriers from other continents separately. Cumulative incidences at 25 years were < 1% in all retrospective groups.

CONCLUSIONS

Prospectively observed CRC incidences (PLSD) in path_MLH1 and path_MSH2 carriers undergoing colonoscopy surveillance and polypectomy were higher than in the retrospective (IMRC) series, and were not reduced in path_MSH6 carriers. These findings were the opposite to those expected. CRC point incidence before 50 years of age was reduced in path_PMS2 carriers subjected to colonoscopy, but not significantly so.

Characterization of blood-derived exosomal hTERT mRNA as a biomarker for colon cancer and Lynch syndrome

Background

Human telomerase reverse transcriptase (hTERT)- mRNA was shown to be elevated in exosomes derived from the sera of a variety of hematological and solid cancer patients. We aimed to evaluate its role as a diagnostic marker in patients with newly diagnosed colon cancer and in hereditary syndromes with predisposition to colon cancer.

Methods

hTERT -mRNA levels were determined in serum-derived exosomes from 88 patients with colon cancer, 71 Lynch-syndrome carriers with unknown active malignancies and 50 healthy controls. Data, including demographics, background diseases, clinical data regarding tumor characteristics and genetic data, were retrieved data from medical files.

Results

Patients with colon cancer had both higher exosomal hTERT mRNA levels and a higher proportion of patients with positive exosomal hTERT mRNA than controls (29.5% vs. 4%, respectively, P values < 0.001). Within the cancer group, patients with a metastatic disease had higher levels of telomerase mRNA than non-metastatic disease patients, and these levels correlated with CEA levels. Likewise, Lynch syndrome carriers had a higher proportion of positive exosomal hTERT mRNA than controls (21.1% vs. 4%, respectively, P value 0.008) but only a trend towards higher exosomal hTERT mRNA levels. Higher telomerase mRNA levels were not correlated with the mutated gene.

Conclusions

Exosomal serum hTERT –mRNA levels are associated with metastatic colon cancer and were also demonstrated in a subset of Lynch syndrome carriers. Its significance as a biomarker for developing malignancy should be elucidated.

MutL homolog 1 germline mutation c.(453+1_454-1)_(545+1_546-1)del identified in lynch syndrome: A case report and review of literature

BACKGROUND

Lynch syndrome (LS) is an autosomal dominant hereditary disorder because of germline mutations in DNA mismatch repair genes, such as MutL homolog 1 (MLH1), PMS1 homolog 2, MutS homolog 2, and MutS homolog 6. Gene mutations could make individuals and their families more susceptible to experiencing various malignant tumors. In Chinese, MLH1 germline mutation c.(453+1_454-1)_(545+1_546-1)del-related LS has been infrequently reported. Therefore, we report a rare LS patient with colorectal and endometrioid adenocarcinoma and describe her pedigree characteristics.

CASE SUMMARY

A 57-year-old female patient complained of irregular postmenopausal vaginal bleeding for 6 mo. She was diagnosed with LS, colonic malignancy, endometrioid adenocarcinoma, secondary fallopian tube malignancy, and intermyometrial leiomyomas. Then, she was treated by abdominal hysterectomy, bilateral oviduct oophorectomy, and sentinel lymph node resection. Genetic testing was performed using next-generation sequencing technology to detect the causative genetic mutations. Moreover, all her family members were offered a free genetic test, but no one accepted it.

CONCLUSION

No tumor relapse or metastasis was found in the patient during the 30-mo follow-up period. The genetic panel sequencing showed a novel pathogenic germline mutation in MLH1, c.(453+1_454-1)_(545+1_546-1)del, for LS. Moreover, cancer genetic counseling and testing are still in the initial development state in China, and maybe face numerous challenges in the further.

Risk of Metachronous Colorectal Cancer in Lynch Syndrome: Who Needs an Extended Resection?

Lynch syndrome (LS) is the most common genetic condition associated with early-onset colorectal cancer. It is inherited in an autosomal dominant fashion. The increased cancer risk is due to a germline mutation in one of the mismatch repair (MMR) genes (MLH1, MSH2, MSH6, and PMS2) or the EPCAM gene. This leads to a deficient DNA mismatch repair mechanism, resulting in the accumulation of nucleotide changes and microsatellite instability, providing phenotypical evidence that MMR is not functioning normally. LS is associated with a high risk of early-onset colorectal cancer and recurrence. Thus, when undergoing surgery for primary colorectal cancer, extended resection should be discussed with the patient. This review provides an overview of current surgical risk-reducing strategies in LS-associated colorectal cancer. Surgical treatment for LS carriers with colorectal cancer needs to be highly individualized, based on patient and disease characteristics. Strategies are presented to guide decision making in pathologic MMR gene mutation carriers undergoing surgery for colorectal cancer.

Vaccines for immunoprevention of DNA mismatch repair deficient cancers

The development of cancer vaccines to induce tumor-antigen specific immune responses was sparked by the identification of antigens specific to or overexpressed in cancer cells. However, weak immunogenicity and the mutational heterogeneity in many cancers have dampened cancer vaccine successes. With increasing information about mutational landscapes of cancers, mutational neoantigens can be predicted computationally to elicit strong immune responses by CD8 +cytotoxic T cells as major mediators of anticancer immune response. Neoantigens are potentially more robust immunogens and have revived interest in cancer vaccines. Cancers with deficiency in DNA mismatch repair have an exceptionally high mutational burden, including predictable neoantigens. Lynch syndrome is the most common inherited cancer syndrome and is caused by DNA mismatch repair gene mutations. Insertion and deletion mutations in coding microsatellites that occur during DNA replication include tumorigenesis drivers. The induced shift of protein reading frame generates neoantigens that are foreign to the immune system. Mismatch repair-deficient cancers and Lynch syndrome represent a paradigm population for the development of a preventive cancer vaccine, as the mutations induced by mismatch repair deficiency are predictable, resulting in a defined set of frameshift peptide neoantigens. Furthermore, Lynch syndrome mutation carriers constitute an identifiable high-risk population. We discuss the pathogenesis of DNA mismatch repair deficient cancers, in both Lynch syndrome and sporadic microsatellite-unstable cancers. We review evidence for pre-existing immune surveillance, the three mechanisms of immune evasion that occur in cancers and assess the implications of a preventive frameshift peptide neoantigen-based vaccine. We consider both preclinical and clinical experience to date. We discuss the feasibility of a cancer preventive vaccine for Lynch syndrome carriers and review current antigen selection and delivery strategies. Finally, we propose RNA vaccines as having robust potential for immunoprevention of Lynch syndrome cancers.

Systematic review: non-endoscopic surveillance for colorectal neoplasia in individuals with Lynch syndrome

BACKGROUND

Individuals with Lynch syndrome are at high risk for colorectal cancer (CRC). Regular colonoscopies have proven to decrease CRC incidence and mortality. However, colonoscopy is burdensome and interval CRCs still occur. Hence, an accurate, less-invasive screening method that guides the timing of colonoscopy would be of important value.

AIM

To outline the performance of non-endoscopic screening modalities for Lynch-associated CRC and adenomas.

METHODS

Systematic literature search in MEDLINE and EMBASE to identify studies investigating imaging techniques and biomarkers for detection of CRC and adenomas in Lynch syndrome. The QUADAS-2 tool was used for the quality assessment of included studies.

RESULTS

Seven of 1332 screened articles fulfilled the inclusion criteria. Two studies evaluated either CT colonography or MR colonography; both techniques were unable to detect CRC and (advanced) adenomas <10 mm. The other five studies evaluated plasma methylated-SEPTIN9, faecal immunochemical test (FIT), faecal tumour DNA markers (BAT-26, hMLH1, p53, D9S171, APC, D9S162, IFNA and DCC) and faecal microbiome as screening modalities. Sensitivity for CRC varied from 33% (BAT-26) to 70% (methylated-SEPTIN9) to 91% (hMLH1). High specificity (94-100%) for CRC and/or adenomas was observed for methylated-SEPTIN9, FIT and BAT-26. Desulfovibrio was enriched in the stool of patients having adenomas. However, all these studies were characterised by small populations, high/unclear risk of bias and/or low prevalence of adenomas.

CONCLUSIONS

Imaging techniques are unsuitable for colon surveillance in Lynch syndrome, whereas biomarkers are understudied. Having outlined biomarker research in Lynch-associated and sporadic CRC/adenomas, we believe that these non-invasive markers may hold potential (whether or not combined) for this population. As they could be of great value, (pre-)clinical studies in this field should be prioritised.

Review article: Lynch Syndrome-a mechanistic and clinical management update

BACKGROUND

Lynch syndrome (LS) is an autosomal dominant familial condition caused by a pathogenic variant (PV) in a DNA mismatch repair gene, which then predisposes carriers to various cancers.

AIM

To review the pathogenesis, clinical presentation, differential diagnosis and clinical strategies for detection and management of LS.

METHODS

A narrative review synthesising knowledge from published literature, as well as current National Comprehensive Cancer Network guidelines for management of LS was conducted.

RESULTS

LS tumours are characterised by unique pathogenesis, ultimately resulting in hypermutation, microsatellite instability and high immunogenicity that has significant implications for cancer risk, clinical presentation, treatment and surveillance. LS is one of the most common hereditary causes of cancer, and about 1 in 279 individuals carry a PV in an LS gene that predisposes to associated cancers. Individuals with LS have increased risks for colorectal, endometrial and other cancers, with significant variation in lifetime risk by LS-associated gene.

CONCLUSIONS

As genetic testing becomes more widespread, the number of individuals identified with LS is expected to increase in the population. Understanding the pathogenesis of LS informs current strategies for detection and clinical management, and also guides future areas for clinical innovation. Unravelling the mechanisms by which these tumours evolve may help to more precisely tailor management by the gene involved.

Upper Gastrointestinal Cancer Surveillance in Lynch Syndrome

Simple Summary

Lynch syndrome is the most common cause of hereditary colorectal cancer, but is also associated with increased extracolonic cancer risk, including upper gastrointestinal cancers. While there is agreement regarding the benefit of frequent colonoscopic surveillance in Lynch syndrome, there remains a lack of consensus on the use of upper gastrointestinal cancer surveillance. Here, we review the upper gastrointestinal cancer risks in Lynch syndrome, the varying guideline recommendations in this area, and the published outcomes of upper gastrointestinal cancer surveillance in this high-risk population. Finally, we highlight ongoing controversies in upper gastrointestinal cancer surveillance and opine on how upper gastrointestinal cancer surveillance can be incorporated into a Lynch syndrome risk management program. Upper gastrointestinal cancer surveillance is an increasingly studied area of risk management in Lynch syndrome, and continued research will be vital in determining how to best incorporate this surveillance in these high-risk patients.

Abstract

Lynch syndrome is a common hereditary cancer predisposition syndrome associated with increased digestive cancer risk including colorectal, gastric, and duodenal cancers. While colorectal cancer surveillance is widely accepted to be an important part of a comprehensive Lynch syndrome risk management plan, the use of upper gastrointestinal cancer surveillance in Lynch syndrome remains more controversial. Currently, upper gastrointestinal cancer surveillance guidelines for Lynch syndrome vary widely, and there is no consensus on who should undergo upper gastrointestinal cancer surveillance, how surveillance should be performed, the age at which to initiate surveillance, or how often individuals with Lynch syndrome should undergo upper gastrointestinal cancer surveillance. Fortunately, research groups around the world have been focusing on upper gastrointestinal cancer surveillance in Lynch syndrome, and recent evidence in this field has demonstrated that upper gastrointestinal cancer surveillance can be performed with identification of precancerous lesions as well as early-stage upper gastrointestinal cancers. In this manuscript, we review the upper gastrointestinal cancer risks in Lynch syndrome, differing guideline recommendations for surveillance, outcomes of upper gastrointestinal cancer surveillance, and controversies in the field, and we provide a framework based on our collective experience with which to incorporate upper gastrointestinal cancer surveillance into a risk management program for individuals with Lynch syndrome.

Adenoma and colorectal cancer risks in Lynch syndrome, Lynch-like syndrome and familial colorectal cancer type X

Lynch syndrome (LS), Lynch-like syndrome (LLS) and familial colorectal cancer type X (FCCX) are different entities of familial cancer predisposition leading to an increased risk of colorectal cancer (CRC). The aim of this prospective study was to characterise and to compare the risks for adenoma and CRC in these three risk groups. Data was taken from the registry of the German Consortium for Familial Intestinal Cancer. Patients were prospectively followed up in an intensified colonoscopic surveillance programme that included annual examinations. Cumulative risks for adenoma and CRC were calculated separately for LS, LLS and FCCX, and then for males and females. Multivariate Cox regression was used to analyse the independent contributions of risk group, mismatch repair gene (within LS), sex and previous adenoma. The study population comprised 1448 individuals (103 FCCX, 481 LLS and 864 LS). The risks were similar for colorectal adenomas, but different for first and metachronous CRC between the three risk groups. CRC risk was highest in LS, followed by LLS and lowest in FCCX. Male sex and a prevalent adenoma in the index colonoscopy were associated with a higher risk for incident adenoma and CRC. In patients with LS, CRC risks were particularly higher in female MSH2 than MLH1 carriers. Our study may support the development of risk-adapted surveillance policies in LS, LLS and FCCX.

Colorectal Cancer Screening Recommendations and Outcomes in Lynch Syndrome

Screening for colorectal cancer (CRC) in Lynch syndrome enables early detection and likely cancer prevention. CRC screening guidelines have evolved from universal to gene-specific recommendations based on lifetime neoplasia risks. Regular screening for Lynch syndrome reduces CRC-related mortality; however, high CRC incidence during regular colonoscopy screening suggests the possibility of nonpolypoid carcinogenesis. Colonoscopy is the primary modality for screening for Lynch syndrome with mixed and emerging data on quality metrics, chromoendoscopy, artificial intelligence, and nonendoscopic modalities. Screening adherence varies across studies. In this review, we present the current state of CRC screening recommendations, outcomes, and modalities in Lynch syndrome.

No Difference in Penetrance between Truncating and Missense/Aberrant Splicing Pathogenic Variants in MLH1 and MSH2: A Prospective Lynch Syndrome Database Study

Background. Lynch syndrome is the most common genetic predisposition for hereditary cancer. Carriers of pathogenic changes in mismatch repair (MMR) genes have an increased risk of developing colorectal (CRC), endometrial, ovarian, urinary tract, prostate, and other cancers, depending on which gene is malfunctioning. In Lynch syndrome, differences in cancer incidence (penetrance) according to the gene involved have led to the stratification of cancer surveillance. By contrast, any differences in penetrance determined by the type of pathogenic variant remain unknown. Objective. To determine cumulative incidences of cancer in carriers of truncating and missense or aberrant splicing pathogenic variants of the MLH1 and MSH2 genes. Methods. Carriers of pathogenic variants of MLH1 (path_MLH1) and MSH2 (path_MSH2) genes filed in the Prospective Lynch Syndrome Database (PLSD) were categorized as truncating or missense/aberrant splicing according to the InSiGHT criteria for pathogenicity. Results. Among 5199 carriers, 1045 had missense or aberrant splicing variants, and 3930 had truncating variants. Prospective observation years for the two groups were 8205 and 34,141 years, respectively, after which there were no significant differences in incidences for cancer overall or for colorectal cancer or endometrial cancers separately. Conclusion. Truncating and missense or aberrant splicing pathogenic variants were associated with similar average cumulative incidences of cancer in carriers of path MLH1 and path_MSH2.

From Genetics to Histomolecular Characterization: An Insight into Colorectal Carcinogenesis in Lynch Syndrome

Lynch syndrome is a hereditary cancer-predisposing syndrome caused by germline defects in DNA mismatch repair (MMR) genes such as MLH1, MSH2, MSH6, and PMS2. Carriers of pathogenic mutations in these genes have an increased lifetime risk of developing colorectal cancer (CRC) and other malignancies. Despite intensive surveillance, Lynch patients typically develop CRC after 10 years of follow-up, regardless of the screening interval. Recently, three different molecular models of colorectal carcinogenesis were identified in Lynch patients based on when MMR deficiency is acquired. In the first pathway, adenoma formation occurs in an MMR-proficient background, and carcinogenesis is characterized by APC and/or KRAS mutation and IGF2, NEUROG1, CDK2A, and/or CRABP1 hypermethylation. In the second pathway, deficiency in the MMR pathway is an early event arising in macroscopically normal gut surface before adenoma formation. In the third pathway, which is associated with mutations in CTNNB1 and/or TP53, the adenoma step is skipped, with fast and invasive tumor growth occurring in an MMR-deficient context. Here, we describe the association between molecular and histological features in these three routes of colorectal carcinogenesis in Lynch patients. The findings summarized in this review may guide the use of individualized surveillance guidelines based on a patient’s carcinogenesis subtype.

Distinct Mutational Profile of Lynch Syndrome Colorectal Cancers Diagnosed under Regular Colonoscopy Surveillance

Regular colonoscopy even with short intervals does not prevent all colorectal cancers (CRC) in Lynch syndrome (LS). In the present study, we asked whether cancers detected under regular colonoscopy surveillance (incident cancers) are phenotypically different from cancers detected at first colonoscopy (prevalent cancers). We analyzed clinical, histological, immunological and mutational characteristics, including panel sequencing and high-throughput coding microsatellite (cMS) analysis, in 28 incident and 67 prevalent LS CRCs (n total = 95). Incident cancers presented with lower UICC and T stage compared to prevalent cancers (p < 0.0005). The majority of incident cancers (21/28) were detected after previous colonoscopy without any pathological findings. On the molecular level, incident cancers presented with a significantly lower KRAS codon 12/13 (1/23, 4.3% vs. 11/21, 52%; p = 0.0005) and pathogenic TP53 mutation frequency (0/17, 0% vs. 7/21, 33.3%; p = 0.0108,) compared to prevalent cancers; 10/17 (58.8%) incident cancers harbored one or more truncating APC mutations, all showing mutational signatures of mismatch repair (MMR) deficiency. The proportion of MMR deficiency-related mutational events was significantly higher in incident compared to prevalent CRC (p = 0.018). In conclusion, our study identifies a set of features indicative of biological differences between incident and prevalent cancers in LS, which should further be monitored in prospective LS screening studies to guide towards optimized prevention protocols.

Mathematical modeling of multiple pathways in colorectal carcinogenesis using dynamical systems with Kronecker structure

Like many other types of cancer, colorectal cancer (CRC) develops through multiple pathways of carcinogenesis. This is also true for colorectal carcinogenesis in Lynch syndrome (LS), the most common inherited CRC syndrome. However, a comprehensive understanding of the distribution of these pathways of carcinogenesis, which allows for tailored clinical treatment and even prevention, is still lacking. We suggest a linear dynamical system modeling the evolution of different pathways of colorectal carcinogenesis based on the involved driver mutations. The model consists of different components accounting for independent and dependent mutational processes. We define the driver gene mutation graphs and combine them using the Cartesian graph product. This leads to matrix components built by the Kronecker sum and product of the adjacency matrices of the gene mutation graphs enabling a thorough mathematical analysis and medical interpretation. Using the Kronecker structure, we developed a mathematical model which we applied exemplarily to the three pathways of colorectal carcinogenesis in LS. Beside a pathogenic germline variant in one of the DNA mismatch repair (MMR) genes, driver mutations in APC, CTNNB1, KRAS and TP53 are considered. We exemplarily incorporate mutational dependencies, such as increased point mutation rates after MMR deficiency, and based on recent experimental data, biallelic somatic CTNNB1 mutations as common drivers of LS-associated CRCs. With the model and parameter choice, we obtained simulation results that are in concordance with clinical observations. These include the evolution of MMR-deficient crypts as early precursors in LS carcinogenesis and the influence of variants in MMR genes thereon. The proportions of MMR-deficient and MMR-proficient APC-inactivated crypts as first measure for the distribution among the pathways in LS-associated colorectal carcinogenesis are compatible with clinical observations. The approach provides a modular framework for modeling multiple pathways of carcinogenesis yielding promising results in concordance with clinical observations in LS CRCs.

Discovering the Mutational Profile of Early Colorectal Lesions: A Translational Impact

Simple Summary

Colorectal cancer (CRC) is one of the most common malignancies worldwide. Next-generation sequencing technologies have identified new candidate genes and deepened the knowledge of the molecular mechanisms underlying the progression of colonic adenomas towards CRC. The main genetic, epigenetic, and molecular alterations driving the onset and progression of CRC in both hereditary and sporadic settings have also been investigated. The evaluation of the CRC risk based on the molecular characterization of early pre-cancerous lesions may contribute to the development of targeted preventive strategies development, help define specific risk profiles, and identify patients who will benefit from targeted endoscopic surveillance.

Abstract

Colorectal cancer (CRC) develops through a multi-step process characterized by the acquisition of multiple somatic mutations in oncogenes and tumor-suppressor genes, epigenetic alterations and genomic instability. These events lead to the progression from precancerous lesions to advanced carcinomas. This process requires several years in a sporadic setting, while occurring at an early age and or faster in patients affected by hereditary CRC-predisposing syndromes. Since advanced CRC is largely untreatable or unresponsive to standard or targeted therapies, the endoscopic treatment of colonic lesions remains the most efficient CRC-preventive strategy. In this review, we discuss recent studies that have assessed the genetic alterations in early colorectal lesions in both hereditary and sporadic settings. Establishing the genetic profile of early colorectal lesions is a critical goal in the development of risk-based preventive strategies.

Progress Report: New insights into the prevention of CRC by colonoscopic surveillance in Lynch syndrome

Lynch syndrome is the most frequent hereditary colorectal cancer (CRC) syndrome, affecting approximately 1 in 300 in the Western population. It is caused by pathogenic variants in the mismatch repair (MMR) genes including MLH1, MSH2 (EPCAM), MSH6 and PMS2, and is associated with high risks of CRC, endometrial cancer and other cancers. In view of these risks, carriers of such variants are encouraged to participate in colonoscopic surveillance programs that are known to substantially improve their prognosis. In the last decade several important studies have been published that provide detailed cancer risk estimates and prognoses based on large numbers of patients. These studies also provided new insights regarding the pathways of carcinogenesis in CRC, which appear to differ depending on the specific MMR gene defect. In this report, we will discuss the implications of these new findings for the development of new surveillance protocols.