Population-based detection of Lynch syndrome in young colorectal cancer patients using microsatellite instability as the initial test

The Clinical Outcomes Among Patients Under 60 Years Old with Lynch Syndrome: Variations Based on Different Mutation Patterns

Lynch syndrome (LS)-also known as Hereditary Non-Polyposis Colorectal Cancer (HNPCC)-is caused by pathogenic germline mutations in DNA mismatch repair (MMR) genes such as MLH1, MSH2, MSH6, and PMS2. Although it accounts for only 1-5% of all colorectal cancers (CRCs), LS presents with a particularly high lifetime cancer risk and often occurs at younger ages. Identifying LS in patients under 60 years old is crucial for targeted surveillance and early interventions. Variations in clinical presentation and prognosis may exist based on the specific gene mutated, yet these patterns are not fully elucidated. This review aims to synthesize data on clinical outcomes among LS patients under 60, with an emphasis on how different MMR gene mutation patterns might influence prognosis, survival, and treatment decisions. Five population-based studies examining CRC patients younger than 60 years were included according to predefined eligibility criteria. Two independent reviewers screened and extracted data focusing on MMR deficiency detection methods (microsatellite instability [MSI] and/or immunohistochemistry [IHC]), rates of confirmed germline mutations, frequency of BRAF testing, and clinical endpoints such as stage distribution, survival outcomes, and recurrence. Risk of bias was assessed using standardized tools appropriate to each study design. The synthesis focused on comparing outcomes among individuals with MLH1, MSH2, MSH6, and PMS2 mutations, as well as delineating the proportion of patients with sporadic MSI under 60 years of age. Across the five studies, MSI positivity in CRC patients under 60 years ranged from 7.5% to 13%. The frequency of confirmed germline MMR mutations varied between 0.8% and 5.2% in specific cohorts, aligning with LS prevalence estimates of 1-5%. Different mutation patterns correlated with some variation in clinical presentation. Cases with MSH2 and MLH1 mutations more frequently exhibited synchronous or metachronous tumors, while MSH6 and PMS2 mutations displayed more heterogeneous IHC patterns. Where survival data were provided, LS patients under 60 years had better overall survival compared to MMR-proficient individuals, though some studies also noted a potential lack of benefit from standard 5-fluorouracil adjuvant therapy in MMR-deficient tumors. Screening by MSI or by IHC-supplemented with BRAF mutation testing to exclude sporadic MSI-facilitates early detection of LS in CRC patients under 60 and highlights notable differences between mutation types. Although overall outcomes for LS patients can be favorable, especially for stage II disease, the precise impact of each specific mutated gene on clinical course remains heterogeneous. Future large-scale prospective studies are needed to clarify optimal screening protocols and individualized treatment strategies for LS patients under 60.

Constitutional mismatch repair deficiency mimicking Lynch syndrome is associated with hypomorphic mismatch repair gene variants

Lynch syndrome (LS) and constitutional mismatch repair deficiency (CMMRD) are distinct cancer syndromes caused, respectively, by mono- and bi-allelic germline mismatch repair (MMR) variants. LS predisposes to mainly gastrointestinal and genitourinary cancers in adulthood. CMMRD predisposes to brain, haematological, and LS-spectrum cancers from childhood. Two suspected LS patients with first cancer diagnosis aged 27 or 38 years were found to be homozygous for an MMR (likely) pathogenic variant, MSH6 c.3226C>T (p.(Arg1076Cys)), or variant of uncertain significance (VUS), MLH1 c.306G>A (p.(Glu102=)). MLH1 c.306G>A was shown to cause leaky exon 3 skipping. The apparent genotype-phenotype conflict was resolved by detection of constitutional microsatellite instability in both patients, a hallmark feature of CMMRD. A hypomorphic effect of these and other variants found in additional late onset CMMRD cases, identified by literature review, likely explains a LS-like phenotype. CMMRD testing in carriers of compound heterozygous or homozygous MMR VUS may find similar cases and novel hypomorphic variants. Individualised management of mono- and bi-allelic carriers of hypomorphic MMR variants is needed until we better characterise the associated phenotypes.

Mismatch Repair and Microsatellite Instability Testing for Immune Checkpoint Inhibitor Therapy: Guideline From the College of American Pathologists in Collaboration With the Association for Molecular Pathology and Fight Colorectal Cancer

CONTEXT.—

The US Food and Drug Administration (FDA) approved immune checkpoint inhibitor therapy for patients with advanced solid tumors that have DNA mismatch repair defects or high levels of microsatellite instability; however, the FDA provided no guidance on which specific clinical assays should be used to determine mismatch repair status.

OBJECTIVE.—

To develop an evidence-based guideline to identify the optimal clinical laboratory test to identify defects in DNA mismatch repair in patients with solid tumor malignancies who are being considered for immune checkpoint inhibitor therapy.

DESIGN.—

The College of American Pathologists convened an expert panel to perform a systematic review of the literature and develop recommendations. Using the National Academy of Medicine-endorsed Grading of Recommendations Assessment, Development and Evaluation approach, the recommendations were derived from available evidence, strength of that evidence, open comment feedback, and expert panel consensus. Mismatch repair immunohistochemistry, microsatellite instability derived from both polymerase chain reaction and next-generation sequencing, and tumor mutation burden derived from large panel next-generation sequencing were within scope.

RESULTS.—

Six recommendations and 3 good practice statements were developed. More evidence and evidence of higher quality were identified for colorectal cancer and other cancers of the gastrointestinal (GI) tract than for cancers arising outside the GI tract.

CONCLUSIONS.—

An optimal assay depends on cancer type. For most cancer types outside of the GI tract and the endometrium, there was insufficient published evidence to recommend a specific clinical assay. Absent published evidence, immunohistochemistry is an acceptable approach readily available in most clinical laboratories.

Colorectal Cancer in North-Eastern Iran: a retrospective, comparative study of early-onset and late-onset cases based on data from the Iranian hereditary colorectal cancer registry

BACKGROUND

The incidence rate of colorectal cancer (CRC) is increasing among patients below 50 years of age. The reason for this is unclear, but could have to do with the fact that indicative variables, such as tumour location, gender preference and genetic preponderance have not been followed up in a consistent mann er. The current study was primarily conducted to improve the hereditary CRC screening programme by assessing the demographic and clinicopathological characteristics of early-onset CRC compared to late-onset CRC in northeast Iran.

METHODS

This retrospective study, carried out over a three-year follow-up period (2014-2017), included 562 consecutive CRCs diagnosed in three Mashhad city hospital laboratories in north-eastern Iran. We applied comparative analysis of pathological and hereditary features together with information on the presence of mismatch repair (MMR) gene deficiency with respect to recovery versus mortality. Patients with mutations resulting in absence of the MMR gene MLH1 protein product and normal BRAF status were considered to be at high risk of Lynch syndrome (LS). Analyses using R studio software were performed on early-onset CRC (n = 222) and late-onset CRC (n = 340), corresponding to patients ≤50 years of age and patients > 50 years.

RESULTS

From an age-of-onset point of view, the distribution between the genders differed with females showing a higher proportion of early-onset CRC than men (56% vs. 44%), while the late-onset CRC disparity was less pronounced (48% vs. 52%). The mean age of all participants was 55.6 ± 14.8 years, with 40.3 ± 7.3 years for early-onset CRC and 65.1 ± 9.3 years for late-onset CRC. With respect to anatomical tumour location (distal, rectal and proximal), the frequencies were 61, 28 and 11%, respectively, but the variation did not reach statistical significance. However, there was a dramatic difference with regard to the history of CRC in second-degree relatives between two age categories, with much higher numbers of family-related CRCs in the early-onset group. Expression of the MLH1 and PMS2 genes were significantly different between recovered and deceased, while this finding was not observed with regard to the MSH6 and the MSH2 genes. Mortality was significantly higher in those at high risk of LS.

CONCLUSION

The variation of demographic, pathological and genetic characteristics between early-onset and late-onset CRC emphasizes the need for a well-defined algorithm to identify high-risk patients.

Rate of dissemination and prognosis in early and advanced stage colorectal cancer based on microsatellite instability status: systematic review and meta-analysis

INTRODUCTION

For the past two decades, microsatellite instability (MSI) has been reported as a robust clinical biomarker associated with survival advantage attributed to its immunogenicity. However, MSI is also associated with high-risk adverse pathological features (poorly differentiated, mucinous, signet cell, higher grade) and exhibits a double-edged sword phenomenon. We performed a systematic review and meta-analysis to evaluate the rate of dissemination and the prognosis of early and advanced stage colorectal cancer based on MSI status.

METHODS

A systematic literature search of original studies was performed on Ovid searching MEDLINE, Embase, Cochrane Database of Systematic Reviews, American College of Physicians ACP Journal Club, Database of Abstracts of Reviews of Effects DARE, Clinical Trials databases from inception of database to June 2019. Colorectal cancer, microsatellite instability, genomic instability and DNA mismatch repair were used as key words or MeSH terms. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline was followed. Data were pooled using a random-effects model with odds ratio (OR) as the effect size. Statistical analysis was performed using RevMan ver 5.3 Cochrane Collaboration.

RESULTS

From 5288 studies, 136 met the inclusion criteria (n = 92,035; MSI-H 11,746 (13%)). Overall, MSI-H was associated with improved OS (OR, 0.81; 95% CI 0.73-0.90), DFS (OR, 0.73; 95% CI 0.66-0.81) and DSS (OR, 0.69; 95% CI 0.52-0.90). Importantly, MSI-H had a protective effect against dissemination with a significantly lower rate of lymph node and distant metastases. By stage, the protective effect of MSI-H in terms of OS and DFS was observed clearly in stage II and stage III. Survival in stage I CRC was excellent irrespective of MSI status. In stage IV CRC, without immunotherapy, MSI-H was not associated with any survival benefit.

CONCLUSIONS

MSI-H CRC was associated with an overall survival benefit with a lower rate of dissemination. Survival benefit was clearly evident in both stage II and III CRC, but MSI-H was neither a robust prognostic marker in stage I nor stage IV CRC without immunotherapy.

Comparative genomic signatures in young and old Chinese patients with colorectal cancer

BACKGROUND

Occurrence at a young age is known to be associated with unique clinical features in colorectal cancer (CRC). However, the genomic differences between young and old patients with CRC are not well elucidated and, to the best of our knowledge, have never been investigated in a Chinese population.

METHODS

Tumor tissue samples from 29 young (age ≤50 years) and 46 old (age >50 years) patients with CRC were collected. Targeted sequencing of 808 cancer-related genes was conducted to characterize the genomic landscape for Chinese CRC.

RESULTS

Overall, mutational profiles exhibited notable differences between the two groups. In particular, APC and PIK3CA mutations were more frequently observed in old patients (p = 0.009 and p = 0.012, respectively), while SMAD4 mutations tended to occur in young patients (p = 0.054). Mutation loci distributions of KRAS in the young cohort differed from those in the old cohort, and a higher frequency of KRAS codon 12 mutations was potentially associated with a young age (p = 0.076). The frequencies of clinically actionable alterations were analyzed by defined age categories, which unveiled a distinctive targeted genomic profile in the young group. Furthermore, among patients with mismatch repair-proficient (pMMR) CRC, tumor mutation burden (TMB) was positively correlated with age (Pearson's r = 0.306, p = 0.011), and genomic alterations associated with high TMB in young patients differentiated from those in old patients.

CONCLUSIONS

These findings revealed different molecular characterization between young and old Chinese patients with CRC, which may provide novel insights for the personalized treatment of CRC.

Age-dependent performance of BRAF mutation testing in Lynch syndrome diagnostics

BRAF V600E mutations have been reported as a marker of sporadic microsatellite instability (MSI) colorectal cancer (CRC). Current international diagnostic guidelines recommend BRAF mutation testing in MSI CRC patients to predict low risk of Lynch syndrome (LS). We evaluated the age-specific performance of BRAF testing in LS diagnostics. We systematically compared the prevalence of BRAF mutations in LS-associated CRCs and unselected MSI CRCs in different age groups as available from published studies, databases and population-based patient cohorts. Sensitivity/specificity analysis of BRAF testing for exclusion of LS and cost calculations were performed. Among 969 MSI CRCs from LS carriers in the literature and German HNPCC Consortium, 15 (1.6%) harbored BRAF mutations. Six of seven LS patients with BRAF-mutant CRC and reported age were <50 years. Among 339 of 756 (44.8%) of BRAF mutations detected in unselected MSI CRC, only 2 of 339 (0.6%) BRAF mutations were detected in patients <50 years. The inclusion of BRAF testing led to high risk of missing LS patients and increased costs at age <50 years. BRAF testing in patients <50 years carries a high risk of missing a hereditary cancer predisposition and is cost-inefficient. We suggest direct referral of MSI CRC patients <50 years to genetic counseling without BRAF testing.

Current Genetic Service Delivery Models for the Provision of Genetic Testing in Europe: A Systematic Review of the Literature

Background: The provision of genetic services, along with research in the fields of genomics and genetics, has evolved in recent years to meet the increasing demand of consumers interested in prediction of genetic diseases and various inherited traits. The aim of this study is to evaluate genetic services in order to identify and classify delivery models for the provision of genetic testing in European and in extra-European countries. Methods: A systematic review of the literature was conducted using five electronic resources. Inclusion criteria were that studies be published in English or Italian during the period 2000-2015 and carried out in European or extra-European countries (Canada, USA, Australia, or New Zealand). Results: 148 genetic programs were identified in 117 articles and were delivered mostly in the UK (59, 40%), USA (35, 24%) or Australia (16, 11%). The programs were available nationally (66; 45%), regionally (49; 33%) or in urban areas (21, 14%). Ninety-six (64%) of the programs were integrated into healthcare systems, 48 (32.21%) were pilot programs and five (3%) were direct-to-consumer genetic services. The genetic tests offered were mainly for BRCA1/2 (59, 40%), Lynch syndrome (23, 16%), and newborn screening (18, 12%). Healthcare professionals with different backgrounds are increasingly engaged in the provision of genetic services. Based on which healthcare professionals have prominent roles in the respective patient care pathways, genetic programs were classified into five models: (i) the geneticists model; (ii) the primary care model; (iii) the medical specialist model; (iv) the population screening programs model; and (v) the direct-to-consumer model. Conclusions: New models of genetic service delivery are currently under development worldwide to address the increasing demand for accessible and affordable services. These models require the integration of genetics into all medical specialties, collaboration among different healthcare professionals, and the redistribution of professional roles. An appropriate model for genetic service provision in a specific setting should ideally be defined according to the type of healthcare system, the genetic test provided within a genetic program, and the cost-effectiveness of the intervention. Only applications with proven efficacy and cost-effectiveness should be implemented in healthcare systems and made available to all citizens.

Stratification of patients with colorectal cancer without the recorded family history

Colorectal cancer (CRC) is a multifactorial disease and one of the most malignant tumours. In addition to the sporadic form, familial occurrences, particularly hereditary non-polyposis CRC-Lynch syndrome (LS)-are often observed. LS is caused by a germline mutation in mismatch repair (MMR) genes, whose task it is to correct errors in the DNA structure that result from its replication. The aim of the present study was to stratify CRC patients using molecular diagnostics and next generation sequencing, according to the chosen criteria [positive for microsatellite instability (MSI) and negative for a BRAF mutation and MutL homolog 1 (MLH1) methylation], and subsequently to detect pathological germline mutations in MMR genes in Slovak patients. To exclude patients with MSI from further testing, the present study detected the BRAF V600E mutation and examined MLH1 methylation status. From the 300 CRC patients, 37 cases with MSI were identified. In the MSI-positive samples, 13 cases of BRAF V600E mutation were recorded. In 24 BRAF-negative patients, 11 cases of epigenetic methylation of MLH1 and 12 cases without MLH1 methylation suspected for LS were detected, and it was not possible to analyse the methylation phenotype of 1 sample. Thus, the present study reports the novel deletion of four nucleotides, 1627_1630del AAAG (Glu544Lysfs*26) in MSH6, probably associated with LS. A second case with a nonsense mutation in MSH was also detected, namely MMR_c.1030C>T (p.Q344X).

Current mismatch repair deficiency tumor testing practices and capabilities: A survey of Australian pathology providers

AIM & METHODS

An electronic survey of the Royal College of Pathologists of Australasia accredited pathology services was conducted to assess Lynch syndrome tumor screening practices and to identify barriers and capabilities to screen newly diagnosed colorectal and endometrial tumors in Australia.

RESULTS

Australia lacks a national policy for universal mismatch repair-deficient (dMMR) testing of incident colorectal and endometrial tumors cases. Routine Lynch syndrome tumor screening program for colorectal and/or endometrial tumors was applied by 95% (37/39) of laboratories. Tumor dMMR screening methods varied; MMR protein immunohistochemistry (IHC) alone was undertaken by 77% of 39 laboratories, 18% performed both IHC and microsatellite instability testing, 5% did not have the capacity to perform in-house testing. For colorectal tumors, 47% (17/36) reported following a universal approach without age limit, 30% (11/36) tested only "red flag" cases; 6% (3/36) on clinician request only. For endometrial tumors, 37% (12/33) reported clinician request generated testing, 27% (9/33) were screening only "red flag" cases, and 12% (4/33) carried out universal screening without an age criteria. BRAF V600E mutation testing of colorectal tumors demonstrating aberrant MLH1 protein expression by IHC was the most common secondary tumor test, with 53% of laboratories performing the test; 15% of laboratories also applied the BRAF V600E test to endometrial tumors with aberrant MLH1 expression despite no evidence for its utility. Tumor testing for MLH1 promoter methylation was performed by less than 15% laboratories.

CONCLUSION

Although use of tumor screening for evidence of dMMR is widely available, protocols for its use in Australia vary widely. This national survey provides a snapshot of the current availability and practice of tumor dMMR screening and identifies the need for a uniform national testing policy.

Costs and outcomes of Lynch syndrome screening in the Australian colorectal cancer population

BACKGROUND AND AIM

Individuals with Lynch syndrome (LS) are at increased risk of LS-related cancers including colorectal cancer (CRC). CRC tumor screening for mismatch repair (MMR) deficiency is recommended in Australia to identify LS, although its cost-effectiveness has not been assessed. We aim to determine the cost-effectiveness of screening individuals with CRC for LS at different age-at-diagnosis thresholds.

METHODS

We developed a decision analysis model to estimate yield and costs of LS screening. Age-specific probabilities of LS diagnosis were based on Australian data. Two CRC tumor screening pathways were assessed (MMR immunohistochemistry followed by MLH1 methylation (MLH1-Pathway) or BRAF V600E testing (BRAF-Pathway) if MLH1 expression was lost) for four age-at-diagnosis thresholds-screening < 50, screening < 60, screening < 70, and universal screening.

RESULTS

Per 1000 CRC cases, screening < 50 identified 5.2 LS cases and cost $A7041 per case detected in the MLH1-Pathway. Screening < 60 increased detection by 1.5 cases for an incremental cost of $A25 177 per additional case detected. Screening < 70 detected 1.6 additional cases at an incremental cost of $A40 278 per additional case detected. Compared with screening < 70, universal screening detected no additional LS cases but cost $A158 724 extra. The BRAF-Pathway identified the same number of LS cases for higher costs.

CONCLUSIONS

The MLH1-Pathway is more cost-effective than BRAF-Pathway for all age-at-diagnosis thresholds. MMR immunohistochemistry tumor screening in individuals diagnosed with CRC aged < 70 years resulted in higher LS case detection at a reasonable cost. Further research into the yield of LS screening in CRC patients ≥ 70 years is needed to determine if universal screening is justified.

Prevalence and clinicopathological characteristics of mismatch repair-deficient colorectal carcinoma in early onset cases as compared with late-onset cases: a retrospective cross-sectional study in Northeastern Iran

OBJECTIVES

Lynch syndrome (LS), a genetically inherited autosomal disorder, increases the incidence of colorectal carcinoma (CRC). We aimed to perform a universal strategy to assess the prevalence and clinicopathological characteristics of early onset CRCs at high risk of LS versus late-onset ones in the Iranian population.

SETTING

A local population-based study from Northeastern Iran.

PARTICIPANTS

321 consecutive CRCs and pathology specimen screened between 2013 and 2016.

PRIMARY AND SECONDARY OUTCOME MEASURES

Retrospectively, information regarding the clinical criteria was obtained by interviewing the patients with CRC or, their families. Pathologists tested tumours with immunohistochemistry (IHC) staining of four mismatch repair (MMR) proteins (MLH1, MSH2, MSH6 and PMS2). Tumours with absent IHC staining of MLH1 were tested for BRAF mutations to exclude sporadic CRCs. Prevalence of early onset CRCs at high risk of LS and familial CRC type X were assessed as primary and secondary outcome measures, respectively.

RESULTS

Of 321 CRCs (13/123 (10.57%), early onset vs 21/198 (10.6%) late-onset) were detected to be MMR-deficient (dMMR). Nine early onset cases and 14 late-onset ones with a loss of MLH1 underwent testing for the BRAF mutation, none of the early onset and four (2.02%) late-onset were recognised as sporadic. The difference in the outcome of IHC-analysis between early and late-onset CRCs at high risk of LS was not statistically significant (p=0.34). Majority of the suspected LS tumours from early onset patients had arisen in distal part (8/11 (72.72%) vs 8/14 (57.14%)), all of which were occurred in the rectum or sigmoid.

CONCLUSION

Clinically, these findings suggest that in case of limitation for BRAF testing, the practitioner in Iran may consider managing early onset dMMR cases like LS until access to BRAF testing becomes available to them, before germline testing to accurately diagnose LS.

A Systematic Review on the Existing Screening Pathways for Lynch Syndrome Identification

Background

Lynch syndrome (LS) is the most common hereditary colon cancer syndrome, accounting for 3–5% of colorectal cancer (CRC) cases, and it is associated with the development of other cancers. Early detection of individuals with LS is relevant, since they can take advantage of life-saving intensive care surveillance. The debate regarding the best screening policy, however, is far from being concluded. This prompted us to conduct a systematic review of the existing screening pathways for LS.

Methods

We performed a systematic search of MEDLINE, ISI Web of Science, and SCOPUS online databases for the existing screening pathways for LS. The eligibility criteria for inclusion in this review required that the studies evaluated a structured and permanent screening pathway for the identification of LS carriers. The effectiveness of the pathways was analyzed in terms of LS detection rate.

Results

We identified five eligible studies. All the LS screening pathways started from CRC cases, of which three followed a universal screening approach. Concerning the laboratory procedures, the pathways used immunohistochemistry and/or microsatellite instability testing. If the responses of the tests indicated a risk for LS, the genetic counseling, performed by a geneticist or a genetic counselor, was mandatory to undergo DNA genetic testing. The overall LS detection rate ranged from 0 to 5.2%.

Conclusion

This systematic review reported different existing pathways for the identification of LS patients. Although current clinical guidelines suggest to test all the CRC cases to identify LS cases, the actual implementation of pathways for LS identification has not been realized. Large-scale screening programs for LS have the potential to reduce morbidity and mortality for CRC, but coordinated efforts in educating all key stakeholders and addressing public needs are still required.

Screening for Lynch syndrome in young Saudi colorectal cancer patients using microsatellite instability testing and next generation sequencing

Individuals with Lynch syndrome (LS) have germline variants in DNA mismatch repair (MMR) genes that confer a greatly increased risk of colorectal cancer (CRC), often at a young age. Identification of these individuals has been shown to increase their survival through improved surveillance. We previously identified 33 high risk cases for LS in the Saudi population by screening for microsatellite instability (MSI) in the tumor DNA of 284 young CRC patients. The aim of the present study was to identify MMR gene variants in this cohort of patients. Peripheral blood DNA was obtained from 13 individuals who were at high risk of LS due to positive MSI status and young age (<60 years at diagnosis). Next generation sequencing, Sanger sequencing and Multiplex Ligation-dependent Probe Amplification were used to screen for germline variants in the MLH1, MSH2, MSH6 and PMS2 MMR genes. These were cross-referenced against several variant databases, including the International Society for Gastrointestinal Hereditary Tumors Incorporated database. Variants with pathogenic or likely pathogenic significance were identified in 8 of the 13 high risk cases (62%), comprising 4 in MLH1 and 4 in MSH2. All carriers had a positive family history for CRC or endometrial cancer. Next generation sequencing is an effective strategy for identifying young CRC patients who are at high risk of LS because of positive MSI status. We estimate that 7% of CRC patients aged <60 years in Saudi Arabia are due to LS, potentially involving around 50 new cases per year.

Impact of age and mismatch repair status on survival in colorectal cancer

Previous studies have suggested that deficiencies in mismatch repair genes (dMMR) often occur in patients with colorectal cancer (CRC) and contribute to disease etiology. Here, we looked for a correlation of MMR status to disease outcomes from a large number of Chinese CRC patients stratified by the age of onset of disease. A total of 2233 CRC patients were analyzed and tissue biopsies of surgically removed tumors scored for MMR gene status. The patient distribution after classification consisted of 188 younger aged patients (20-39 years of age), 1024 middle aged patients (40-59 years of age), and 1020 older aged patients (60-85 years of age). In this analysis, the expression of four MMR genes was assessed by immunohistochemistry (IHC). We found that the young group of CRC patients with dMMR had higher overall survival (OS) than the young group of patients with proficient MMR (pMMR) (77% vs. 56%, P = 0.03). Middle-aged patients with dMMR also had higher OS than middle-aged group patients with pMMR (78% vs. 68%, P = 0.012). However, we found no statistical difference in OS between dMMR and pMMR status in the older group of patients (75% vs. 71%, P = 0.224). Finally, the middle- and older-aged group set of patients had higher OS than the young group of patients (69% vs. 71% vs. 59%, P = 0.008). These data demonstrated that the age of disease onset can be an important factor to help evaluate the prognosis of CRC when combined with the analysis of MMR status within tumor biopsied tissue.

Tumor testing to identify lynch syndrome in two Australian colorectal cancer cohorts

BACKGROUND AND AIM

Tumor testing of colorectal cancers (CRC) for mismatch repair (MMR) deficiency is an effective approach to identify carriers of germline MMR gene mutation (Lynch syndrome). The aim of this study was to identify MMR gene mutation carriers in two cohorts of population-based CRC utilizing a combination of tumor and germline testing approaches.

METHODS

Colorectal cancers from 813 patients diagnosed with CRC < 60 years of age from the Australasian Colorectal Cancer Family Registry (ACCFR) and from 826 patients from the Melbourne Collaborative Cohort Study (MCCS) were tested for MMR protein expression using immunohistochemistry, microsatellite instability (MSI), BRAFV600E somatic mutation, and for MLH1 methylation. MMR gene mutation testing (Sanger sequencing and Multiplex Ligation Dependent Probe Amplification) was performed on germline DNA of patients with MMR-deficient tumors and a subset of MMR-proficient CRCs.

RESULTS

Of the 813 ACCFR probands, 90 probands demonstrated tumor MMR deficiency (11.1%), and 42 had a MMR gene germline mutation (5.2%). For the MCCS, MMR deficiency was identified in the tumors of 103 probands (12.5%) and seven had a germline mutation (0.8%). All the mutation carriers were diagnosed prior to 70 years of age. Probands with a MMR-deficient CRC without MLH1 methylation and a gene mutation were considered Lynch-like and comprised 41.1% and 25.2% of the MMR-deficient CRCs for the ACCFR and MCCS, respectively.

CONCLUSIONS

Identification of MMR gene mutation carriers in Australian CRC-affected patients is optimized by immunohistochemistry screening of CRC diagnosed before 70 years of age. A significant proportion of MMR-deficient CRCs will have unknown etiology (Lynch-like) proving problematic for clinical management.

Universal Versus Targeted Screening for Lynch Syndrome: Comparing Ascertainment and Costs Based on Clinical Experience

BACKGROUND

Strategies to screen colorectal cancers (CRCs) for Lynch syndrome are evolving rapidly; the optimal strategy remains uncertain.

AIM

We compared targeted versus universal screening of CRCs for Lynch syndrome.

METHODS

In 2010-2011, we employed targeted screening (age < 60 and/or Bethesda criteria). From 2012 to 2014, we screened all CRCs. Immunohistochemistry for the four mismatch repair proteins was done in all cases, followed by other diagnostic studies as indicated. We modeled the diagnostic costs of detecting Lynch syndrome and estimated the 5-year costs of preventing CRC by colonoscopy screening, using a system dynamics model.

RESULTS

Using targeted screening, 51/175 (29 %) cancers fit criteria and were tested by immunohistochemistry; 15/51 (29 %, or 8.6 % of all CRCs) showed suspicious loss of ≥1 mismatch repair protein. Germline mismatch repair gene mutations were found in 4/4 cases sequenced (11 suspected cases did not have germline testing). Using universal screening, 17/292 (5.8 %) screened cancers had abnormal immunohistochemistry suspicious for Lynch syndrome. Germline mismatch repair mutations were found in only 3/10 cases sequenced (7 suspected cases did not have germline testing). The mean cost to identify Lynch syndrome probands was ~$23,333/case for targeted screening and ~$175,916/case for universal screening at our institution. Estimated costs to identify and screen probands and relatives were: targeted, $9798/case and universal, $38,452/case.

CONCLUSIONS

In real-world Lynch syndrome management, incomplete clinical follow-up was the major barrier to do genetic testing. Targeted screening costs 2- to 7.5-fold less than universal and rarely misses Lynch syndrome cases. Future changes in testing costs will likely change the optimal algorithm.

A Comprehensive Strategy for Accurate Mutation Detection of the Highly Homologous PMS2

Germline mutations in the DNA mismatch repair gene PMS2 underlie the cancer susceptibility syndrome, Lynch syndrome. However, accurate molecular testing of PMS2 is complicated by a large number of highly homologous sequences. To establish a comprehensive approach for mutation detection of PMS2, we have designed a strategy combining targeted capture next-generation sequencing (NGS), multiplex ligation-dependent probe amplification, and long-range PCR followed by NGS to simultaneously detect point mutations and copy number changes of PMS2. Exonic deletions (E2 to E9, E5 to E9, E8, E10, E14, and E1 to E15), duplications (E11 to E12), and a nonsense mutation, p.S22*, were identified. Traditional multiplex ligation-dependent probe amplification and Sanger sequencing approaches cannot differentiate the origin of the exonic deletions in the 3' region when PMS2 and PMS2CL share identical sequences as a result of gene conversion. Our approach allows unambiguous identification of mutations in the active gene with a straightforward long-range-PCR/NGS method. Breakpoint analysis of multiple samples revealed that recurrent exon 14 deletions are mediated by homologous Alu sequences. Our comprehensive approach provides a reliable tool for accurate molecular analysis of genes containing multiple copies of highly homologous sequences and should improve PMS2 molecular analysis for patients with Lynch syndrome.

Molecular Features and Methylation Status in Early Onset (≤40 Years) Colorectal Cancer: A Population Based, Case-Control Study

Colorectal cancer is usually considered a disease of the elderly. However, a small fraction of patients develops colorectal cancer earlier. The aim of our study was to define the frequency of known hereditary colorectal syndromes and to characterise genetic and epigenetic features of early nonhereditary tumors. Thirty-three patients ≤40 years with diagnosis of colorectal cancer and 41 patients with disease at >60 years of age were investigated for MSI, Mismatch Repair proteins expression, KRAS and BRAF mutations, hypermethylation, and LINE-1 hypomethylation. Detection of germline mutations was performed in Mismatch Repair, APC and MUTYH genes. Early onset colorectal cancer showed a high incidence of hereditary forms (18%). KRAS mutations were detected in 36% of early nonhereditary tumors. Early onset colorectal cancer disclosed an average number of methylated genes significantly lower when compared to the controls (p = 0.02). Finally both of the two groups were highly methylated in ESR1, GATA5, and WT1 genes and were similar for LINE-1 hypomethylation. The genetic make-up of carcinomas differs from young to elderly patients. Early onset tumors showed more frequently a constitutional defective of Mismatch Repair System and a minor number of methylated genes. Hypermethylation of ESR1, GATA5, and WT1 genes suggests possible markers in the earlier diagnosis of colorectal tumorigenesis.

MSIseq: Software for Assessing Microsatellite Instability from Catalogs of Somatic Mutations

Microsatellite instability (MSI) is a form of hypermutation that occurs in some tumors due to defects in cellular DNA mismatch repair. MSI is characterized by frequent somatic mutations (i.e., cancer-specific mutations) that change the length of simple repeats (e.g., AAAAA…., GATAGATAGATA...). Clinical MSI tests evaluate the lengths of a handful of simple repeat sites, while next-generation sequencing can assay many more sites and offers a much more complete view of their somatic mutation frequencies. Using somatic mutation data from the exomes of a 361-tumor training set, we developed classifiers to determine MSI status based on four machine-learning frameworks. All frameworks had high accuracy, and after choosing one we determined that it had >98% concordance with clinical tests in a separate 163-tumor test set. Furthermore, this classifier retained high concordance even when classifying tumors based on subsets of whole-exome data. We have released a CRAN R package, MSIseq, based on this classifier. MSIseq is faster and simpler to use than software that requires large files of aligned sequenced reads. MSIseq will be useful for genomic studies in which clinical MSI test results are unavailable and for detecting possible misclassifications by clinical tests.

Selective Versus Universal Screening for Lynch Syndrome: A Six-Year Clinical Experience

BACKGROUND

Lynch syndrome is the most common cause of hereditary colorectal cancer (CRC) and confers increased risk of other cancers. Identification of patients improves morbidity and mortality. Screening tumors for absent mismatch repair (MMR) protein expression by immunohistochemistry (IHC) is a recommended approach. Despite guidelines advocating universal screening, significant variation in clinical practice exists.

AIMS/METHODS

A retrospective study of two different IHC-based Lynch syndrome screening protocols at an urban, university hospital was performed. Outcomes from a "selective" screening strategy utilized from August 2007-July 2010 on CRC tumors from patients with high-risk features were compared with a "universal" strategy of screening all CRC tumors from July 2010-August 2013. Positively screened patients were referred for genetic counseling and offered germline testing.

RESULTS

A total of 392 patients with CRC were screened: 107 selectively and 285 universally. The prevalence of Lynch syndrome was 3.1 %, with no difference by strategy. There was a trend (p = 0.06) toward fewer universally screened patients agreeing to genetic counseling compared with those selectively screened. Selective criteria failed to identify one of eight cases of Lynch syndrome from the universal group, though the universal strategy screened 166 additional tumors to find this additional patient.

CONCLUSIONS

Selective screening for Lynch syndrome has similar outcomes as universal screening in terms of identifying Lynch syndrome, despite screening far fewer patients. In addition, fewer eligible patients in our study agreed to undergo genetic counseling and germline testing than in prior studies. These lower rates may better reflect uptake of these services in clinical practice.

DNA Mismatch Repair Status Predicts Need for Future Colorectal Surgery for Metachronous Neoplasms in Young Individuals Undergoing Colorectal Cancer Resection

BACKGROUND

The treatment of colorectal cancer in young patients involves both management of the incident cancer and consideration of the possibility of Lynch syndrome and the development of metachronous colorectal cancers.

OBJECTIVE

This study aims to assess the prognostic role of DNA mismatch repair deficiency and extended colorectal resection for metachronous colorectal neoplasia risk in young patients with colorectal cancer.

DESIGN, SETTING, AND PATIENTS

This is a retrospective review of 285 patients identified in our GI cancer registry with colorectal cancer diagnosed at 35 years or younger in the absence of polyposis.

MAIN OUTCOME MEASURES

Using univariate and multivariate analysis, we assessed the prognostic role of mismatch repair deficiency and standard clinicopathologic characteristics, including the extent of resection, on the rate of developing metachronous colorectal neoplasia requiring resection.

RESULTS

Mismatch repair deficiency was identified in biospecimens from 44% of patients and was significantly associated with an increased risk for metachronous colorectal neoplasia requiring resection (10-year cumulative risk, 13.5% ± 4.2%) compared with 56% of patients with mismatch repair-intact colorectal cancer (10-year cumulative risk, 5.8% ± 3.3%; p = 0.011). In multivariate analysis, mismatch repair deficiency was associated with a HR of 3.65 (95% CI, 1.44-9.21; p = 0.006) for metachronous colorectal neoplasia, whereas extended resection with ileorectal or ileosigmoid anastomosis significantly decreased the risk of metachronous colorectal neoplasia (HR, 0.21; 95% CI, 0.05-0.90; p = 0.036).

LIMITATIONS

This study had a retrospective design, and, therefore, recommendations for colorectal cancer surgery and screening were not fully standardized. Quality of life after colorectal cancer surgery was not assessed.

CONCLUSIONS

Young patients with colorectal cancer with molecular hallmarks of Lynch syndrome were at significantly higher risk for the development of subsequent colorectal neoplasia. This risk was significantly reduced in those who underwent extended resection compared with segmental resection.

Applicability of next generation sequencing technology in microsatellite instability testing

Microsatellite instability (MSI) is a useful marker for risk assessment, prediction of chemotherapy responsiveness and prognosis in patients with colorectal cancer. Here, we describe a next generation sequencing approach for MSI testing using the MiSeq platform. Different from other MSI capturing strategies that are based on targeted gene capture, we utilize “deep resequencing”, where we focus the sequencing on only the microsatellite regions of interest. We sequenced a series of 44 colorectal tumours with normal controls for five MSI loci (BAT25, BAT26, BAT34c4, D18S55, D5S346) and a second series of six colorectal tumours (no control) with two mononucleotide loci (BAT25, BAT26). In the first series, we were able to determine 17 MSI-High, 1 MSI-Low and 26 microsatellite stable (MSS) tumours. In the second series, there were three MSI-High and three MSS tumours. Although there was some variation within individual markers, this NGS method produced the same overall MSI status for each tumour, as obtained with the traditional multiplex PCR-based method.

Association of age with survival in patients with metastatic colorectal cancer: analysis from the ARCAD Clinical Trials Program

PURPOSE

This study addressed whether age is prognostic for overall survival (OS) or progression-free survival (PFS) in patients with metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

A total of 20,023 patients from 24 first-line clinical trials in the ARCAD (Aide et Recherche en Cancérologie Digestive) database were analyzed. Primary age effects and interactions with age,sex, performance status (PS), and metastatic site were modeled using Cox proportional hazards stratified by treatment arm within study.

RESULTS

Of total patients, 3,051 (15%) were age < or =50 years. Age was prognostic for both OS (P < .001)and PFS (P < .001), with U-shaped risk (i.e., highest risk was evident in youngest and oldest patients). Relative to patients of middle age, the youngest patients experienced 19% (95% CI, 7% to 33%) increased risk of death and 22% (95% CI, 10% to 35%) increased risk of progression. The oldest patients experienced 42% (95% CI, 31% to 54%) increased risk of death and 15% (95% CI, 7% to 24%) increased risk of progression or death. This relationship was more pronounced in the first year of follow-up. Age remained marginally significant for OS (P = .08) when adjusted forPS, sex, and presence of liver, lung, or peritoneal metastases, and age was significant in an adjusted model for PFS (P = .005). The age effect did not differ by site of metastatic disease, year of enrollment, type of therapy received, or biomarker mutational status.

CONCLUSION

Younger and older age are associated with poorer OS and PFS among treated patients with mCRC. Younger and older patients may represent higher-risk populations, and additional studies are warranted.

Clinical problems of colorectal cancer and endometrial cancer cases with unknown cause of tumor mismatch repair deficiency (suspected Lynch syndrome)

Carriers of a germline mutation in one of the DNA mismatch repair (MMR) genes have a high risk of developing numerous different cancers, predominantly colorectal cancer and endometrial cancer (known as Lynch syndrome). MMR gene mutation carriers develop tumors with MMR deficiency identified by tumor microsatellite instability or immunohistochemical loss of MMR protein expression. Tumor MMR deficiency is used to identify individuals most likely to carry an MMR gene mutation. However, MMR deficiency can also result from somatic inactivation, most commonly methylation of the MLH1 gene promoter. As tumor MMR testing of all incident colorectal and endometrial cancers (universal screening) is becoming increasingly adopted, a growing clinical problem is emerging for individuals who have tumors that show MMR deficiency who are subsequently found not to carry an MMR gene mutation after genetic testing using the current diagnostic approaches (Sanger sequencing and multiplex ligation-dependent probe amplification) and who also show no evidence of MLH1 methylation. The inability to determine the underlying cause of tumor MMR deficiency in these “Lynch-like” or “suspected Lynch syndrome” cases has significant implications on the clinical management of these individuals and their relatives. When the data from published studies are combined, 59% (95% confidence interval [CI]: 55% to 64%) of colorectal cancers and 52% (95% CI: 41% to 62%) of endometrial cancers with MMR deficiency were identified as suspected Lynch syndrome. Recent studies estimated that colorectal cancer risk for relatives of suspected Lynch syndrome cases is lower than for relatives of those with MMR gene mutations, but higher than for relatives of those with tumor MMR deficiency resulting from methylation of the MLH1 gene promoter. The cause of tumor MMR deficiency in suspected Lynch syndrome cases is likely due to either unidentified germline MMR gene mutations, somatic cell mosaicism, or biallelic somatic inactivation. Determining the underlying cause of tumor MMR deficiency in suspected Lynch syndrome cases is likely to reshape the current triaging schemes used to identify germline MMR gene mutations in cancer-affected individuals and their relatives.

Population-based screening for Lynch syndrome in Western Australia

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

Criteria and prediction models for mismatch repair gene mutations: a review

One of the strongest predictors of colorectal cancer risk is carrying a germline mutation in a DNA mismatch repair (MMR) gene. Once identified, mutation carriers can be recommended for intensive screening that will substantially reduce their high colorectal cancer risk. Conversely, the relatives of carriers identified as non-carriers can be relieved of the burden of intensive screening. Criteria and prediction models that identify likely mutation carriers are needed for cost-effective, targeted, germline testing for MMR gene mutation. We reviewed 12 criteria/guidelines and 8 prediction models (Leiden, Amsterdam-plus, Amsterdam-alternative, MMRpro, PREMM1,2,6, MMRpredict, Associazione Italiana per lo studio della Familiarità ed Ereditarietà dei tumori Gastrointestinali (AIFEG) and the Myriad Genetics Prevalence table) for identifying mutation carriers. While criteria are only used to identify individuals with colorectal cancer (yes/no for screening followed by germline testing), all prediction models except MMRpredict and Myriad tables can predict the probability of carrying mutations for individuals with or without colorectal cancer. We conducted a meta-analysis of the discrimination performance of 17 studies that validated the prediction models. The pooled estimate for the area under curve was 0.80 (95% CI 0.72 to 0.88) for MMRpro, 0.81 (95% CI 0.73 to 0.88) for MMRpredict, 0.84 (95% CI 0.81 to 0.88) for PREMM, and 0.85 (95% CI 0.78 to 0.91) for Leiden model. Given the high degree of overlap in the CIs, we cannot state that one model has a higher discrimination than any of the others. Overall, the existing statistical models have been shown to be sensitive and specific (at a 5% cut-off) in predicting MMR gene mutation carriers. Future models may need to: provide prediction of PMS2 mutations, take into account a wider range of Lynch syndrome-associated cancers when assessing family history, and be applicable to all people irrespective of any cancer diagnosis.

CoDP: predicting the impact of unclassified genetic variants in MSH6 by the combination of different properties of the protein

Background

Lynch syndrome is a hereditary cancer predisposition syndrome caused by a mutation in one of the DNA mismatch repair (MMR) genes. About 24% of the mutations identified in Lynch syndrome are missense substitutions and the frequency of missense variants in MSH6 is the highest amongst these MMR genes. Because of this high frequency, the genetic testing was not effectively used in MSH6 so far. We, therefore, developed CoDP (Combination of the Different Properties), a bioinformatics tool to predict the impact of missense variants in MSH6.

Methods

We integrated the prediction results of three methods, namely MAPP, PolyPhen-2 and SIFT. Two other structural properties, namely solvent accessibility and the change in the number of heavy atoms of amino acids in the MSH6 protein, were further combined explicitly. MSH6 germline missense variants classified by their associated clinical and molecular data were used to fit the parameters for the logistic regression model and to assess the prediction. The performance of CoDP was compared with those of other conventional tools, namely MAPP, SIFT, PolyPhen-2 and PON-MMR.

Results

A total of 294 germline missense variants were collected from the variant databases and literature. Of them, 34 variants were available for the parameter training and the prediction performance test. We integrated the prediction results of MAPP, PolyPhen-2 and SIFT, and two other structural properties, namely solvent accessibility and the change in the number of heavy atoms of amino acids in the MSH6 protein, were further combined explicitly. Variants data classified by their associated clinical and molecular data were used to fit the parameters for the logistic regression model and to assess the prediction. The values of the positive predictive value (PPV), the negative predictive value (NPV), sensitivity, specificity and accuracy of the tools were compared on the whole data set. PPV of CoDP was 93.3% (14/15), NPV was 94.7% (18/19), specificity was 94.7% (18/19), sensitivity was 93.3% (14/15) and accuracy was 94.1% (32/34). Area under the curve of CoDP was 0.954, that of MAPP for MSH6 was 0.919, of SIFT was 0.864 and of PolyPhen-2 HumVar was 0.819. The power to distinguish between pathogenic and non-pathogenic variants of these methods was tested by Wilcoxon rank sum test (p < 8.9 × 10^-6 for CoDP, p < 3.3 × 10^-5 for MAPP, p < 3.1 × 10^-4 for SIFT and p < 1.2 × 10^-3 for PolyPhen-2 HumVar), and CoDP was shown to outperform other conventional methods.

Conclusion

In this paper, we provide a human curated data set for MSH6 missense variants, and CoDP, the prediction tool, which achieved better accuracy for predicting the impact of missense variants in MSH6 than any other known tools. CoDP is available at http://cib.cf.ocha.ac.jp/CoDP/.

Diagnosing lynch syndrome in absence of colorectal cancer

There are many ways in which a diagnosis of Lynch syndrome can be made, most prominent of which is family history, presence of cancer, high microsatellite instability, immunohistochemistry, and a mismatch repair germline mutation. There are at least four molecular pathways for colorectal cancer carcinogenesis: 1) adenoma-carcinoma sequence; 2) hereditary microsatellite instability; 3) serrated pathway; 4) epidermal growth factor receptor. The answer to diagnosing Lynch syndrome in the absence of colorectal cancer may be partially based upon the phenotypic characteristics of the colonic polyps should they be identified at colonoscopy, specifically their phenotypic characteristics of location, size, histology, number, and age of polyp onset.

Key genetic considerations in the management of suspected hereditary colorectal cancer

SUMMARY Hereditary bowel cancer syndromes account for up to 5% of colorectal cancer (CRC) incidence. Presentation of CRC under the age of 50 years should alert clinicians to a possible underlying genetic predisposition. This article focuses on Lynch syndrome (hereditary nonpolyposis CRC). Regular bowel screening is effective in reducing the risk of CRC and improving overall survival in Lynch syndrome families. The issues surrounding the clinical diagnostic criteria and the shortcomings of the referral process are described, and it is questioned whether a universal strategy for diagnosis should be employed. This article summarizes the evidence for the benefit of bowel screening and suggests practical steps to help ensure compliance with screening recommendations. Finally, it is discussed how collaboration between geneticists, gastroenterologists and surgeons can inform surgical decision-making for the benefit of the patient.

Lynch or not Lynch? Is that always a question?

The familial cancer syndrome referred to as Lynch I and II was renamed hereditary nonpolyposis colorectal cancer (HNPCC) only to revert later to Lynch syndrome (LS). LS is the most frequent human predisposition for the development of colorectal cancer (CRC), and probably also for endometrial and gastric cancers, although it has yet to acquire a consensus name. Its estimated prevalence ranges widely from 2% to 7% of all CRCs due to the fact that tumors from patients with LS are difficult to recognize at both the clinical and molecular level. This review is based on two assumptions. First, all LS patients inherit a predisposition to develop CRC (without polyposis) and/or other tumors from the Lynch spectrum. Second, all LS patients have a germline defect in one of the DNA mismatch repair (MMR) genes. When a somatic second hit inactivates the relevant MMR gene, the consequence is instability of DNA repeat sequences such as microsatellites and the tumors are referred to as having the microsatellite instability (MSI) phenotype. However, some of the inherited predisposition to develop CRC without concurrent polyposis, termed HNPCC, is found in non-LS patients, while not all MSI tumors are from LS cases. LS tumors are therefore at the junction of inherited and MSI cases. We describe here the defining characteristics of LS tumors that differentiate them from inherited non-MSI tumors and from non-inherited MSI tumors.

Despite aggressive histopathology survival is not impaired in young patients with colorectal cancer : CRC in patients under 50 years of age

PURPOSE

Colorectal carcinoma (CRC) is generally a disease of persons older than 50 years. Concerning younger patients, controversies still exist regarding features and prognosis of CRC. We performed this study to characterize CRC in young patients (≤50 years) as well as to evaluate outcome in comparison with older patients (>50 years) with CRC.

METHODS

Clinical and histopathological parameters of 244 patients aged 50 years or less were compared with 1,718 patients aged more than 50 years.

RESULTS

Compared with older patients, the younger had less adenocarcinomas (82.8% vs. 89.1%; p = 0.004) and less postoperative complications (18.4% vs. 28.7%; p = 0.001), and less Union Internationale Contre le Cancer stage I colon cancers (22.9% vs. 13.6%, p = 0.046) but elevated overall 5-year survival rates for M0 colon and rectal cancers (p = 0.005; p < 0.001). In young patients, the minority suffered from hereditary cancer syndromes (7.4%) and inflammatory bowel diseases (7.0%). Furthermore, up to 40% of young patients denied any cancers in their families. Cancer-related survival rates were significantly elevated in young patients with M0 rectal carcinoma (p = 0.014), whereas in M0 colon cancers, no differences were detectable (p = 0.542). In case of the presence of distant metastases, overall and cancer-related survival rates were similar in old and young patients.

CONCLUSION

Although young patients present with more aggressive histopathological subtypes and less early stages, cancer-related survival is not less favourable compared with older patients.

Analysis of DNA mismatch repair proteins expression and BRAF V600E mutation in a subset of early- and late-onset colorectal carcinoma patients in Mexico

BACKGROUND AND AIMS

A third of colorectal carcinomas (CRC) affect patients <50 years of age. Fifteen percent of CRC cases with microsatellite instability are due to inherited germ-line mutations in DNA mismatch repair genes. The rest have an epigenetic hypermethylation of the MLH1 promoter in whom the BRAF V600E mutation is a common hallmark. Immunohistochemistry helps to classify colorectal cancers with 100% specificity and 92% sensitivity. We undertook this study to determine if age is a risk factor for defective MMR protein expression and BRAF mutations in our population and to compare these results with the histopathological tumor features.

METHODS

Immunohistochemistry for MLH1 and MSH2 and RT-PCR BRAF V600E mutation was performed on tissue specimens from 57 patients <50 years of age. Data on age, gender, tumor location, histology, depth of infiltration, and the presence of metastatic lymph nodes were collected. Forty eight patients >50 years of age were used as a control group. A statistical analysis using ANOVA, χ(2), and Spearman's rho test were performed.

RESULTS

Absent MMR protein expression was more prevalent in patients <50 years of age. No BRAF V600E mutations were detected in either group. Medullary and mucinous types were more prevalent among young patients, whereas intestinal type was more frequent in older patients (p = 0.0008). No differences were found regarding clinicopathological stages between groups.

CONCLUSIONS

We found an association between young age and defective MMR expression. No V600E BRAF mutations were detected in either group.

Dominantly inherited constitutional epigenetic silencing of MLH1 in a cancer-affected family is linked to a single nucleotide variant within the 5'UTR

Constitutional epimutations of tumor suppressor genes manifest as promoter methylation and transcriptional silencing of a single allele in normal somatic tissues, thereby predisposing to cancer. Constitutional MLH1 epimutations occur in individuals with young-onset cancer and demonstrate non-Mendelian inheritance through their reversal in the germline. We report a cancer-affected family showing dominant transmission of soma-wide highly mosaic MLH1 methylation and transcriptional repression linked to a particular genetic haplotype. The epimutation was erased in spermatozoa but reinstated in the somatic cells of the next generation. The affected haplotype harbored two single nucleotide substitutions in tandem; c.-27C > A located near the transcription initiation site and c.85G > T. The c.-27C > A variant significantly reduced transcriptional activity in reporter assays and is the probable cause of this epimutation.

Pulmonary sclerosing hemangioma in a 21-year-old male with metastatic hereditary non-polyposis colorectal cancer: report of a case

Background

Pulmonary sclerosing hemangioma (SH) is a rare tumor of the lung predominantly affecting Asian women in their fifth decade of life. SH is thought to evolve from primitive respiratory epithelium and mostly shows benign biological behavior; however, cases of lymph node metastases, local recurrence and multiple lesions have been described.

Case Presentation

We report the case of a 21-year-old Caucasian male with a history of locally advanced and metastatic rectal carcinoma (UICC IV; pT4, pN1, M1(hep)) that was eventually identified as having hereditary non-polyposis colorectal cancer (HNPCC, Lynch syndrome). After neoadjuvant chemotherapy followed by low anterior resection, adjuvant chemotherapy and metachronous partial hepatectomy, he was admitted for treatment of newly diagnosed bilateral pulmonary metastases. Thoracic computed tomography showed a homogenous, sharply marked nodule in the left lower lobe. We decided in favor of atypical resection followed by systematic lymphadenectomy. Histopathological analysis revealed the diagnosis of SH.

Conclusions

Cases have been published with familial adenomatous polyposis (FAP) and simultaneous SH. FAP, Gardner syndrome and Li-Fraumeni syndrome, however, had been ruled out in the present case. To the best of our knowledge, this is the first report describing SH associated with Lynch syndrome.

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

BACKGROUND

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

OBJECTIVES

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

DESIGN

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

SETTINGS

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

PATIENTS

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

MAIN OUTCOME MEASURES

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

RESULTS

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

LIMITATIONS

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

CONCLUSIONS

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

De novo constitutional MLH1 epimutations confer early-onset colorectal cancer in two new sporadic Lynch syndrome cases, with derivation of the epimutation on the paternal allele in one

Lynch syndrome is an autosomal dominant cancer predisposition syndrome classically caused by germline mutations of the mismatch repair genes, MLH1, MSH2, MSH6 and PMS2. Constitutional epimutations of the MLH1 gene, characterized by soma-wide methylation of a single allele of the promoter and allelic transcriptional silencing, have been identified in a subset of Lynch syndrome cases lacking a sequence mutation in MLH1. We report two individuals with no family history of colorectal cancer who developed that disease at age 18 and 20 years. In both cases, cancer had arisen because of the de novo occurrence of a constitutional MLH1 epimutation and somatic loss-of-heterozygosity of the functional allele in the tumors. We show for the first time that the epimutation in one case arose on the paternally inherited allele. Analysis of 13 tumors from seven individuals with constitutional MLH1 epimutations showed eight tumors had lost the second MLH1 allele, two tumors had a novel pathogenic missense mutation and three had retained heterozygosity. Only 1 of 12 tumors demonstrated the BRAF V600E mutation and 3 of 11 tumors harbored a mutation in KRAS. The finding that epimutations can originate on the paternal allele provides important new insights into the mechanism of origin of epimutations. It is clear that the second hit in MLH1 epimutation-associated tumors typically has a genetic not epigenetic basis. Individuals with mismatch repair-deficient cancers without the BRAF V600E mutation are candidates for germline screening for sequence or methylation changes in MLH1.

The revised Bethesda guidelines: extent of utilization in a university hospital medical center with a cancer genetics program

BACKGROUND

In 1996, the National Cancer Institute hosted an international workshop to develop criteria to identify patients with colorectal cancer who should be offered microsatellite instability (MSI) testing due to an increased risk for Hereditary Nonpolyposis Colorectal Cancer (HNPCC). These criteria were further modified in 2004 and became known as the revised Bethesda Guidelines. Our study aimed to retrospectively evaluate the percentage of patients diagnosed with HNPCC tumors in 2004 who met revised Bethesda criteria for MSI testing, who were referred for genetic counseling within our institution.

METHODS

All HNPCC tumors diagnosed in 2004 were identified by accessing CoPath, an internal database. Both the Tumor Registry and patients' electronic medical records were accessed to collect all relevant family history information. The list of patients who met at least one of the revised Bethesda criteria, who were candidates for MSI testing, was then cross-referenced with the database of patients referred for genetic counseling within our institution.

RESULTS

A total of 380 HNPCC-associated tumors were diagnosed at our institution during 2004 of which 41 (10.7%) met at least one of the revised Bethesda criteria. Eight (19.5%) of these patients were referred for cancer genetic counseling of which 2 (25%) were seen by a genetics professional. Ultimately, only 4.9% of patients eligible for MSI testing in 2004 were seen for genetic counseling.

CONCLUSION

This retrospective study identified a number of barriers, both internal and external, which hindered the identification of individuals with HNPCC, thus limiting the ability to appropriately manage these high risk families.

MSH6 and MUTYH deficiency is a frequent event in early-onset colorectal cancer

PURPOSE

Early-onset colorectal cancer (CRC) is suggestive of a hereditary predisposition. Lynch syndrome is the most frequent CRC hereditary cause. The MUTYH gene has also been related to hereditary CRC. A systematic characterization of these two diseases has not been reported previously in this population.

EXPERIMENTAL DESIGN

We studied a retrospectively collected series of 140 patients ≤50 years old diagnosed with nonpolyposis CRC. Demographic, clinical, and familial features were obtained. Mismatch repair (MMR) deficiency was determined by microsatellite instability (MSI) analysis, and immunostaining for MLH1, MSH2, MSH6, and PMS2 proteins. Germline MMR mutations were evaluated in all MMR-deficient cases. Tumor samples with loss of MLH1 or MSH2 protein expression were analyzed for somatic methylation. Germline MUTYH mutations were evaluated in all cases. BRAF V600E and KRAS somatic mutational status was also determined.

RESULTS

Fifteen tumors (11.4%) were MSI, and 20 (14.3%) showed loss of protein expression (7 for MLH1/PMS2, 2 for isolated MLH1, 3 for MSH2/MSH6, 7 for isolated MSH6, and 1 for MSH6/PMS2). We identified 11 (7.8%) germline MMR mutations, 4 in MLH1, 1 in MSH2, and 6 in MSH6. Methylation analysis revealed one case with somatic MLH1 methylation. Biallelic MUTYH mutations were detected in four (2.8%) cases. KRAS and BRAF V600E mutations were present in 39 (27.9%) and 5 (3.6%) cases, respectively.

CONCLUSIONS

Loss of MSH6 expression is the predominant cause of MMR deficiency in early-onset CRC. Our findings prompt the inclusion of MSH6 and MUTYH screening as part of the genetic counseling of these patients and their relatives.

Microsatellite instability in colorectal cancer

Approximately 20 percent of right-sided colon cancers and 5 percent of left-sided colon and rectal cancers have a deficient DNA mismatch repair system. This results in the widespread accumulation of mutations to nucleotide repeats, some of which occur within the coding regions of cancer-related genes such as TGFβRII and BAX. A standardized definition for microsatellite instability (MSI) based on the presence of deletions to mononucleotide repeats is gaining widespread acceptance in both research and the clinic. Colorectal cancer (CRC) with MSI are characterized histologically by an abundance of tumor-infiltrating lymphocytes, poor differentiation and a signet ring or mucinous phenotype. In younger patients these tumors usually develop along the chromosomal instability pathway, in which case the mismatch repair genes are inactivated by germline mutation, somatic mutation and loss of heterozygosity. In older patients MSI CRC usually develops against a background of widespread hypermethylation that includes methylation-induced silencing of the mismatch repair gene MLH1. The overall biological and clinical phenotype of MSI CRC that arise in these two pathways is likely to be different and may account for some of the discordant results reported in the literature relating to the clinical properties of these tumors. The available evidence indicates that MSI is unlikely to be a clinically useful marker for the prognostic stratification of early-stage CRC. The predictive value of MSI for response to 5-fluorouracil-based chemotherapy remains controversial, while for other agents the predictive value is difficult to assess because they are used in combination regimens. The MSI phenotype is being actively investigated for novel therapeutic approaches based on the principle of synthetic lethality. Finally, the MSI status of CRC is an extremely useful marker for population-based screening programs that aim to identify individuals and families with the hereditary cancer condition known as Lynch syndrome.

Cancer survivors: familial risk perception and management advice given to their relatives

The aim of this study was to describe 2 years cancer survivors' perception of the cancer risk running in their family, and to describe how frequently these survivors recommended cancer screening to their relatives. A national cross-sectional survey was launched by the French Ministry of Health to investigate the living conditions of adult cancer patients 2 years after cancer diagnosis. Among the 13,923 patients identified, 6,957 were eligible to participate in this study and 4460 (64.1%) answered the questionnaire administered by telephone. One participant out of every two (50.8%) reported that they thought their relatives' risk of cancer was greater than that of the relatives of unaffected persons. Higher percentages were recorded among breast and colorectal cancer patients (65 and 65.1%, respectively), and lower percentages among those with lung and hematological cancer (34.9 and 28.4%, respectively). Overall, 61.1% of the participants had already advised relatives to undergo cancer screening and 10.4% planned to do so. Eighty-one percent of the participants with breast cancer and 76.3% of those with colorectal cancer said they had advised relatives to undergo screening. Lower percentages were obtained among patients with urinary tract (41.7%) and hematological malignancies (27.1%). Although patients' perceptions tend to fit the latest data on the frequency of cancer germline mutations, physicians should help their patients to convey more accurate advice to their families. If survivors were better informed, they could play a critical role by conveying relevant and sound risk reduction messages to their relatives.