Current clinical selection strategies for identification of hereditary non-polyposis colorectal cancer families are inadequate: a meta-analysis

A collaborative review of the microsatellite instability/deficient mismatch repair phenotype in patients with upper tract urothelial carcinoma

OBJECTIVE

To perform a collaborative review of the literature exploring the microsatellite instability/deficient mismatch repair (MSI/dMMR) phenotype in patients with upper tract urothelial carcinoma (UTUC).

METHOD

A collaborative review of the literature available on Medline was conducted by the Cancer Committee of the French Association of Urology to report studies describing the genetic mechanisms, investigation, prevalence and impact of the MSI/dMMR phenotype in UTUC patients.

RESULTS

The predominant genetic mechanism leading to the MSI/dMMR phenotype in UTUC patients is related to the constitutional mutation of one allele of the MMR genes MLH1, MSH2, MSH6 and PMS2 within Lynch syndrome. Indications for its investigation currently remain limited to patients with a clinical suspicion for sporadic UTUC to refer only those with a positive testing for germline DNA sequencing to screen for this syndrome. With regard to technical aspects, despite the interest of MSIsensor, only PCR and immunohistochemistry are routinely used to somatically investigate the MSI and dMMR phenotypes, respectively. The prevalence of the MSI/dMMR phenotype in UTUC patients ranges from 1.7% to 57%, depending on the study population, investigation method and definition of a positive test. Younger age and a more balanced male to female ratio at initial diagnosis are the main specific clinical characteristics of UTUC patients with an MSI/dMMR phenotype. Despite the conflicting results available in the literature, these patients may have a better prognosis, potentially related to more favourable pathological features. Finally, they may also have lower sensitivity to chemotherapy but greater sensitivity to immunotherapy.

CONCLUSION

Our collaborative review summarises the available data from published studies exploring the MSI/dMMR phenotype in UTUC patients, the majority of which are limited by a low level of evidence.

Experience of the implementation and outcomes of universal testing for Lynch syndrome in the United Kingdom

AIM

Colorectal cancer (CRC) is diagnosed in approximately 45 000 people annually in the UK, and it is estimated that Lynch syndrome (LS) accounts for 3.1% of these cases. In February 2017, National Institute for Health and Care Excellence (NICE guideline DG27 recommended universal testing of new cases of CRC for mismatch repair (MMR) status. The aim of this study was to implement universal testing for LS in CRC patients in a secondary care setting.

METHOD

We prospectively collected data on consecutive newly diagnosed CRC patients at our centre from November 2016 to August 2018, including evidence of MMR status determined by immunohistochemistry. We recorded clinicopathological data including age at diagnosis, stage, tumour site, reported histological findings and MMR tumour status. Statistical analysis was performed using the chi-square test and the two-tailed t-test for binary and continuous variables, respectively.

RESULTS

A cohort of 203 consecutive patients were diagnosed with CRC during this period. Universal MMR testing was performed for the 198 CRC patients in whom a diagnosis of adenocarcinoma was confirmed, with colonoscopic biopsy used as the source material in 68.6% of cases. Twenty-three CRCs (11.6%) were MMR deficient (dMMR). Most dMMR CRCs (21/23) were early stage tumours (Dukes A or B, P = 0.002). In 39 Dukes B CRCs in patients under 70 years of age, the result of MMR testing influenced decision-making about personalized treatment with 5-fluorouracil based chemotherapy.

CONCLUSION

Our results demonstrate that universal testing of all new cases of CRC for features suggestive of LS is feasible and effective in the UK. Our data also indicate the importance of genetic testing and personalized oncological care.

Diagnostic Accuracy of FOBT and Colorectal Cancer Genetic Testing: A Systematic Review & Meta-Analysis

Introduction:

Colorectal cancer (CRC) is the second leading cause of cancer related death in the world after lung cancer. Early detection of CRC leads to improvement in cancer survival rate. In recent years, efforts have been made to discover a non-invasive screening marker of higher sensitivity and specificity. Fecal occult blood testing (FOBT) and genetic testing become alternative modalities to screen CRC in the population other than colonoscopy. The aim of this systematic review and meta-analysis is to determine the diagnostic accuracy, sensitivity and specificity of FOBT and genetic testing as screening tools in colorectal cancer.

Methods:

A literature search of PubMed, ScienceDirect, and Scopus was carried out. The search strategy was restricted to human subjects and studies are published in English. Data on sensitivity and specificity were extracted and pooled. Heterogeneity was assumed at significance level of p < 0.10 and was tested by chi squared. Degree of heterogeneity was quantified using the I² statistic, and values of less than 25% is considered as homogenous. All analyses were performed using the software Meta-Disc.

Results:

A total of eleven studies were suitable for data synthesis and analysis. Five studies were analyzed for the accuracy of genetic testing, the pooled estimate for sensitivity and specificity were 71% (95% CI: 66, 75%) and 95% (95% CI: 93, 97%) respectively. Another group of studies which had been evaluated for the accuracy of FOBT, the pooled sensitivity was 31% (95% CI: 25, 38%) while the pooled specificity was 87% (95% CI: 86, 89%).

Conclusions:

FOBTs is recommended to use as population-based screening tools for colorectal cancer while genetic testing should be focusing on patients with moderate and high risk individuals.

Mismatch repair deficiency screening via immunohistochemical staining in young Asians with colorectal cancers

BACKGROUND

The incidence of mismatch repair deficiency in colorectal cancer (CRC) in young people remains unknown in Asians. The present study assessed the clinicopathological features and efficacy of immunohistochemistry screening for Lynch syndrome in young Asian CRC patients.

MATERIAL AND METHODS

This was a retrospective review conducted in Singapore General Hospital between January 2006 and December 2010 of 240 unrelated patients under the age of 50. All patients had immunohistochemical (IHC) staining for mismatch repair proteins in resected CRC specimen data retrieved from a prospective computerized database.

RESULTS

A total of 21 % (n = 51) of the patients had abnormal IHC staining. Loss of staining for MLH1, MSH2, MSH6, and PMS2 proteins was observed in 10, 4, 6, and 13 % of tumors, respectively. Of the 22 patients who had abnormal staining of MLH1, 13 had concomitant abnormal staining for PMS2. One tumor specimen had abnormal staining in all four proteins. If the Amsterdam criteria alone were to be used, 86 % (n = 44) of the cohort would have not been detected for mismatch repair gene defects.

CONCLUSIONS

The overall burden of germline mismatch repair deficiency in the Singapore population may be as high as 21 %. The Amsterdam criteria alone are inadequate to detect Lynch syndrome patients. The use of IHC staining of at least four mismatch repair proteins is a useful screening strategy for Lynch syndrome diagnosis. Routine screening of mismatch repair deficiency may be recommended for all young Asian CRC patients.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

INTERPRETATION

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

Familial colorectal cancer type X: polyp burden and cancer risk stratification via a family history score

BACKGROUND

Patients fulfilling Amsterdam-1 criteria without mismatch repair deficiency (termed familial colorectal cancer type X (FCC type X)) were reported to have lower cancer risks than classic Lynch syndrome. This study investigates the polyp and cancer burden of this population and demonstrates relationships with a family history score (FHS).

METHODS

The Jagelman Registry was queried for patients meeting Amsterdam criteria with microsatellite stable/low colorectal cancers. The risk of colorectal neoplasia was ascertained using a published FHS. Polyp distribution, histology and cumulative counts as well as extra-colonic tumours in the pedigree were reviewed.

RESULTS

Twenty-one patients (9 males, 12 females) met study criteria. The median lifetime polyp count was 3 (range 1–36). FHS 8 (80%) was significantly associated with an increased risk of colorectal cancer compared with those with scores <8 who are more likely to develop polyps (P < 0.01). Twelve patients (57%) had predominantly left-sided polyps. Ten colorectal cancers (7 left-sided, 3 right-sided) were diagnosed at a median age of 48 (range 30–74) years. Only three tumours were mucinous or demonstrated tumour-infiltrating lymphocytes, typical of high microsatellite instability tumours. All patients had family history of colorectal cancers (CRCs) and at least 10 patients had a family history of uterine or breast cancer. One patient was found to have hyperplastic polyposis syndrome.

CONCLUSIONS

FCC type X likely represents a heterogenous group of as yet undefined CRC predispositions. The polyp burden and cancer risk are variable and can be somewhat delineated according to an FHS.

Lynch syndrome: clinical, pathological, and genetic insights

INTRODUCTION

Lynch syndrome as the most common hereditary colorectal cancer syndrome and the most common cause of hereditary endometrial cancer is characterized by an autosomal dominant inheritance with a penetrance of 85-90%. The molecular genetic underlying mechanism is a mutation in one of the mismatch repair genes.

METHODS

In order to identify patients with Lynch syndrome, a nuclear family history should be ascertained and matched with the Amsterdam criteria. A different approach for identification is the adherence to Bethesda criteria and subsequent testing for microsatellite instability. In patients with unstable tumors as an indicator for mismatch repair deficiency, genetic counseling and mutation analysis are warranted. For families fulfilling the Amsterdam criteria, intensified screening is recommended, even if a pathogenic mutation is not identified.

RESULTS

Individuals from families with a proven pathogenic mutation that are tested negative are at normal population risk for cancers and may be dismissed from intensified surveillance. Prophylactic surgery in high-risk individuals without neoplasia is not generally recommended. At the time of a colon primary, however, extended surgery should be discussed in the light of a high rate of metachronous cancers. The worries of impairing functional results have now been evaluated in the light of quality of life in a large international cohort. Interestingly, extended (prophylactic) surgery does not lead to inferior quality of life with equal perioperative risks.

CONCLUSIONS

Therefore, taking the risk reduction into account, extended surgery at the time of the first colon primary should at least be discussed, if not recommended. Also, prophylactic hysterectomy and bilateral oophorectomy at the time of a colorectal primary should be recommended if family planning has been completed.

The identification of Lynch syndrome in British Columbia

OBJECTIVE

To determine the prevalence of Lynch syndrome mutations in a Canadian hereditary cancer clinic population, and to determine the effectiveness of the program's referral criteria and testing algorithm.

METHODS

A retrospective chart review of all patients who were referred for and received genetic counselling at the BC Cancer Agency's Hereditary Cancer Program for a family history of colon cancer from August 1, 2004, to September 1, 2006, was performed. Charts were reviewed for referral criteria met, cancer history, whether testing was offered and the outcome of testing.

RESULTS

Lynch syndrome was confirmed or highly suspected in 14.3% of index test patients (eight of 56) by the identification of a deleterious mutation or variant likely to be deleterious in either of the hMLH1 or hMSH2 mismatch repair genes. In the program, the two most effective criteria were a personal diagnosis of two or more primary Lynch syndrome-related cancers (one diagnosed at younger than 50 years of age) or two first-degree relatives with a Lynch syndrome-related cancer (both diagnosed at younger than 50 years of age). The respective positive predictive values of these two criteria were calculated to be 66.7% (95% CI 40% to 93%) and 58.3% (95% CI 30.4% to 86.2%).

CONCLUSIONS

The Hereditary Cancer Program developed and successfully implemented an approach that selected individuals at risk for Lynch syndrome with a significant pretest probability of mutation of 14.3%. Improved ascertainment of families with Lynch syndrome will require greater physician awareness of referral criteria, program advances in the testing algorithm and a population-based approach to screening incident colon cancers.

Prevalence of alterations in DNA mismatch repair genes in patients with young-onset colorectal cancer

BACKGROUND & AIMS

Direct germline analysis could be used to screen high-risk patients for mutations in DNA mismatch repair genes associated with Lynch Syndrome. We examined the prevalence of mutations in MLH1, MSH2, and MSH6 in a population-based sample of patients with young-onset (age <50 years) colorectal cancer (CRC).

METHODS

Young-onset CRC cases were randomly selected from 3 Colon Cancer Family Registry sites. DNA was extracted from peripheral blood leukocytes; MLH1, MSH2, and MSH6 were sequenced, and duplication and deletion analyses was performed for MLH1 and MSH2. Results were reported as deleterious or suspected deleterious, likely neutral, variant of uncertain significance, or no alteration detected. Germline data were compared to Amsterdam II criteria (ACII) and immunohistochemistry results in secondary analyses.

RESULTS

Among 195 subjects, 11 had deleterious/suspected deleterious mutations (5.6%; 95% confidence interval [CI], 2.8%-9.9%), 12 had likely neutral alterations (6.2%; 95% CI, 3.2%-10.5%), 14 had variants of uncertain significance (7.2%; 95% CI, 4.0%-11.8%), 2 had a likely neutral alteration and a variant of uncertain significance (1.0%; 95% CI, 0.1%-3.7%), and 156 had no alteration detected (80.0%; 95% CI, 73.7%-85.4%). Sensitivity, specificity, and positive and negative predictive values for detecting deleterious/suspected deleterious mutations, based on ACII, were 36.4% (4/11), 96.7% (178/184), 40.0% (4/10), and 96.2% (178/185), respectively; based on immunohistochemistry these values were 85.7% (6/7), 91.9% (136/148), 33.3% (6/18), and 99.3% (136/137), respectively.

CONCLUSIONS

In a population-based sample of young-onset CRC cases, germline mutations in MLH1, MSH, and/or MSH6 were more prevalent than reported for CRC patients overall. Because only about 5% of young-onset CRC cases had confirmed deleterious or suspected deleterious mutations, further comparative effectiveness research is needed to determine the most appropriate screening strategy for Lynch Syndrome in this high-risk group.

Lower gastrointestinal tract cancer predisposition syndromes

Although inherited predisposition to colorectal cancer (CRC) has been suspected for more than 100 years, definitive proof of Mendelian syndromes had to await maturation of molecular genetic technologies. Since the l980s, the genetics of several clinically distinct entities has been revealed. Five disorders that share a hereditary predisposition to CRC are reviewed in this article.

Lynch syndrome in Tunisia: first description of clinical features and germline mutations

PURPOSE

High rates of early colorectal cancers (CRC) are observed in Tunisia suggesting genetic susceptibility. Nevertheless, up to now, no molecular study has been performed in the Tunisian population. In our research, we evaluated the clinical characteristics of Tunisian families suspected of Lynch syndrome and the contribution of DNA mismatch repair (MMR) genes.

METHODS

Thirty-one unrelated families suspected of Lynch syndrome were studied. Probands were tested for the presence of germline mutations in the MMR genes MLH1, MSH2, MSH6 and in MUTYH. Available tumours were analysed for microsatellite instability and expression of MMR proteins. Detailed family and medical histories were collected.

RESULTS

A total of 134 cancers were noted in the 31 families, the most frequent type of cancer corresponding to CRC (69%), followed by uterine cancer (7.5%). Germline mutations were identified in 11 (35.5%) families (six MSH2, five MLH1, including seven novel mutations), seven of which fulfilled the Amsterdam criteria (sensitivity, 63.6%; positive predictive value, 58.3%). Noteworthy, germline mutations were detected in 52.6% of male patients tested, but in only 8.3% of females (p = 0.02). Moreover, CRC were essentially left sided in families without detected mutation (p = 0.017). Ages of onset of cancers and tumour spectrum were very similar in families with or without MMR germline mutation, contrasting with previous studies performed in other populations.

CONCLUSIONS

MMR genes contribute significantly to CRC susceptibility in the Tunisian population. However, the cause of early CRC susceptibility remains unknown in most cases, especially in women and in patients with early left colon or rectal cancer.

The Genome-based Knowledge Management in Cycles model: a complex adaptive systems framework for implementation of genomic applications

The main mission of the Genomic Applications in Practice and Prevention Network™ is to advance collaborative efforts involving partners from across the public health sector to realize the promise of genomics in healthcare and disease prevention. We introduce a new framework that supports the Genomic Applications in Practice and Prevention Network mission and leverages the characteristics of the complex adaptive systems approach. We call this framework the Genome-based Knowledge Management in Cycles model (G-KNOMIC). G-KNOMIC proposes that the collaborative work of multidisciplinary teams utilizing genome-based applications will enhance translating evidence-based genomic findings by creating ongoing knowledge management cycles. Each cycle consists of knowledge synthesis, knowledge evaluation, knowledge implementation and knowledge utilization. Our framework acknowledges that all the elements in the knowledge translation process are interconnected and continuously changing. It also recognizes the importance of feedback loops, and the ability of teams to self-organize within a dynamic system. We demonstrate how this framework can be used to improve the adoption of genomic technologies into practice using two case studies of genomic uptake.

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.

Germline copy number variation and cancer risk

The human genome is subject to substantial structural variation, including copy number variation (CNV). Constitutional CNVs may either represent benign polymorphic variants or be associated with disease, including cancer predisposition. Rare nonpolymorphic CNVs, that is DNA lesions that result in gene deletions, inversions, and/or fusions, may be responsible for a high cancer risk. In addition, we previously elucidated a mechanism by which CNV-based transcriptional read-through mediates inactivation of a neighboring gene through in cis hypermethylation of its promoter. This novel mechanism explains the etiology of a recurrent and strongly inherited tissue-restricted epimutation. Recently, we obtained supporting evidence for such a CNV-associated scenario, suggesting that it may be more prevalent than previously thought. We expect that copy number profiling in unexplained high-risk families will lead to the discovery of additional cancer-predisposing genes and/or mechanisms.

Preliminary Results of Mismatch Repair Deficiency Screening via Immunohistochemical Staining in Young Asian Colorectal Cancers

Background:

The incidence of mismatch repair (MMR) deficiency in young colorectal cancers (CRC) remains unknown in Asians. This preliminary study assessed the clinicopathological features and efficacy of screening for MMR protein deficiency in young Asian CRC patients.

Methods:

From January 2006 to October 2009, patients under the age of 50 with immunohistochemical (IHC) staining for MMR proteins in resected CRC specimens were retrieved from a prospective computerised database.

Results:

Eighty unrelated patients comprising predominantly 80% Chinese (n = 64), with median age of diagnosis at 41 years (range 22–50 years) had IHC performed. Twenty-three per cent (n=18) of the patients had abnormal IHC staining. Loss of staining for MLH1, MSH2 and MSH6 proteins were observed in 18%, 2% and 6% of tumours respectively. Of the 15 patients who had abnormal staining of MLH1, three had concomitant equivocal staining for MSH6. One tumour specimen had abnormal staining in all 3 proteins. Multivariate analysis revealed that family history was the only significant predictive factor for defective MMR detection (OR 8.06, 95% CI 1.69–38.35, p=0.002). However if Amsterdam criteria alone were to be used, 72% (n=12) of the cohort would have not been detected for MMR gene defects.

Conclusion:

The overall burden of germline MMR deficiency in the Singapore population may be as high as 23%. Amsterdam criteria alone are insufficient to detect hereditary non-polyposis colorectal cancer (HNPCC) related patients. The use of IHC staining of at least 3 MMR proteins is a useful screening strategy for HNPCC diagnosis and routine screening of mismatch repair deficiency may be recommended for all young Asian CRC patients.

Beyond genome-wide association studies: genetic heterogeneity and individual predisposition to cancer

Genome-wide association studies (GWAS) using population-based designs have identified many genetic loci associated with risk of a range of complex diseases including cancer; however, each locus exerts a very small effect and most heritability remains unexplained. Family-based pedigree studies have also suggested tentative loci linked to increased cancer risk, often characterized by pedigree-specificity. However, comparison between the results of population- and family-based studies shows little concordance. Explanations for this unidentified genetic 'dark matter' of cancer include phenotype ascertainment issues, limited power, gene-gene and gene-environment interactions, population heterogeneity, parent-of-origin-specific effects, and rare and unexplored variants. Many of these reasons converge towards the concept of genetic heterogeneity that might implicate hundreds of genetic variants in regulating cancer risk. Dissecting the dark matter is a challenging task. Further insights can be gained from both population association and pedigree studies.

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

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

Colorectal cancer due to deficiency in DNA mismatch repair function: a review

Lynch syndrome (LS) is an autosomal dominant cancer predisposition syndrome attributable to deleterious germline mutations in mismatch repair (MMR) genes. The syndrome is typified by early-onset, frequently right-sided colorectal cancers (CRCs) with characteristic histologic features and tendency for multiplicity and an increased risk for extracolonic tumors at particular sites; it accounts for 1% to 5% of CRC. Deficient mismatch repair (dMMR) function manifests as immunohistochemically detectable absence of one or more MMR proteins and microsatellite instability (MSI). Approximately 15% of sporadic, noninherited CRC are characterized by high-level MSI, nearly always owing to transcriptional silencing of MLH1; these sporadic and LS cases exhibit considerable phenotypic overlap. Identification of CRC with dMMR is desirable to identify LS and because MSI status is prognostic and potentially predictive. This review will discuss the history of LS, the principles of MMR and MSI, the clinicopathologic features of LS-associated and sporadic high-level MSI CRC, the fundamentals of clinical testing for dMMR CRC, and the results of the Columbus-area Lynch syndrome study. We conclude with our approach to population-based LS screening based on institutional experience with nearly 2000 cases.

Underutilization of microsatellite instability analysis in colorectal cancer patients at high risk for Lynch syndrome

OBJECTIVE

The revised Bethesda Guidelines were published to improve the efficiency of recognizing Lynch syndrome (LS) by identifying LS-related malignancies that should be analyzed for microsatellite instability (MSI). The aim of this study was to evaluate whether MSI analysis was performed in colorectal cancer patients at risk for LS according to the revised Bethesda Guidelines.

MATERIAL AND METHODS

Patients diagnosed with colorectal cancer in 11 Dutch hospitals in 2005 and 2006 were selected from a regional database. The patients were included in the study if they met any of the following criteria; 1) diagnosed with colorectal cancer <50 years, 2) a second LS-associated tumor prior to the diagnosis of colorectal cancer in 2005/2006, and 3) colorectal cancer <60 years with a tumor displaying mucinous or signet-ring differentiation or medullary growth pattern.

RESULTS

Of 1905 colorectal cancer patients, 169 met at least one of the inclusion criteria. MSI analysis had been performed in 23 (14%) of the 169 tumors. MSI status had been determined in 18 of 80 included patients aged <50 years, in 4 of 70 patients with a second LS-related tumor, and in 3 of 41 patients aged <60 years with high-risk pathology features.

CONCLUSIONS

There is marked underutilization of MSI analysis in patients at risk for LS. As a result LS might be underdiagnosed both in patients with colorectal cancer and in their relatives.

Optimizing the detection of hereditary non-polyposis colorectal cancer: An update

Hereditary non-polyposis colorectal cancer (HNPCC) is a dominant inherited disease and accounts for up to 5% of all colorectal cancer (CRC) patients. Despite the optimization of selection criteria and enhancements in molecular techniques for identifying more families with HNPCC, most cases are not recognized. Poor patient recollection of family history and inadequate family history-taking are main causative factors. We propose a new strategy for detecting HNPCC, one in which the pathologist selects patients for microsatellite instability (MSI) testing. Criteria for MSI analysis are: (1) CRC before the age of 50 years, (2) second CRC before 70 years, (3) CRC and HNPCC-associated cancer before 70 years, or (4) adenoma before 40 years. Additionally, patients with a positive MSI test and patients with a positive family history are offered referral for genetic counselling. With this strategy, at least twice the number of HNPCC patients will be identified among a population of CRC patients, and in a cost-effective, efficient and feasible way. The identification of patients with HNPCC is important because intensive surveillance can prevent death from CRC.

Hereditary colorectal cancer syndromes and the role of the surgical oncologist

The expanding understanding of the genetic basis to hereditary colon cancer syndromes is dismantling previously conceived categorizations and shedding light on why those schemes often failed in past. This review highlights evolving concepts regarding the genetic diagnosis and clinical management of the more commonly inherited colorectal cancer syndromes, including a discussion of recently described familial syndromes. This review also addresses clinician responsibilities in recognition of familial syndromes and provision of counseling.

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

Approximately 1-2% of colorectal cancers (CRC) arise because of germline mutations in DNA mismatch repair genes, referred to as Lynch syndrome. These tumours show microsatellite instability (MSI) and loss of expression of mismatch repair proteins. Pre-symptomatic identification of mutation carriers has been demonstrated to improve survival; however, there is concern that many are not being identified using current practices. We evaluated population-based MSI screening of CRC in young patients as a means of ascertaining mutation carriers. CRC diagnosed in patients aged <60 years were identified from pathology records. No prior information was available on family history of cancer. PCR techniques were used to determine MSI in the BAT-26 mononucleotide repeat and mutation in the BRAF oncogene. Loss of MLH1, MSH2, MSH6 and PMS2 protein expression was evaluated in MSI+ tumours by immunohistochemistry. MSI+ tumours were found in 105/1,344 (7.8%) patients, of which 7 were excluded as possible Lynch syndrome because of BRAF mutation. Of the 98 "red flag" cases that were followed up, 25 were already known as mutation carriers or members of mutation carrier families. Germline test results were obtained for 35 patients and revealed that 22 showed no apparent mutation, 11 showed likely pathogenic mutations and 2 had unclassified variants. The proportion of MSI+ cases in different age groups that were estimated to be mutation carriers was 89% (<30 years), 83% (30-39), 68% (40-49) and 17% (50-59). We recommend MSI as the initial test for population-based screening of Lynch syndrome in younger CRC patients, regardless of family history.

Tumor characteristics as an analytic tool for classifying genetic variants of uncertain clinical significance

It is important to identify a germline mutation in a patient with an inherited cancer syndrome to allow mutation carriers to be included in cancer surveillance programs, which have been proven to save lives. Many of the mutations identified result in premature termination of translation, and thus in loss-of-function of the encoded mutated protein. However, the significance of a large proportion of the sequence changes reported is unknown. Some of these variants will be associated with a high risk of cancer and have direct clinical consequence. Many criteria can be used to classify variants with unknown significance; most criteria are based on the characteristics of the amino acid change, on segregation data and appearance of the variant, on the presence of the variant in controls, or on functional assays. In inherited cancers, tumor characteristics can also be used to classify variants. It is worthwhile to examine the clinical, morphological and molecular features of a patient, and his or her family, when assessing whether the role of a variant is likely to be neutral or pathogenic. Here we describe the advantages and disadvantages of using the tumor characteristics of patients carrying germline variants of uncertain significance (VUS) in BRCA1, BRCA2, or in one of the mismatch repair (MMR) genes, MLH1, MSH2, or MSH6, to infer pathogenicity.

Hereditary nonpolyposis colorectal cancer (Lynch syndrome): molecular pathogenesis and clinical approaches to diagnosis and management for nurses

Hereditary nonpolyposis colorectal cancer (HNPCC), also referred to as Lynch syndrome, is the most common form of hereditary colorectal cancer and is responsible for 2% to 4% of all colorectal cancers in the Western hemisphere. Generally characterized by early-onset colorectal carcinoma with a mean age of presentation of 40 to 45 years, it can also manifest with extracolonic adenocarcinomas and cancers of the endometrium, ovaries, stomach, pancreas, small intestine, hepatobiliary tract, upper uroepithelial tract, brain, and skin. HNPCC is autosomal dominant and carries an 80% lifetime risk of cancer development. This review addresses the molecular underpinnings of HNPCC while providing a concise approach to clinical detection, diagnosis, and management of patients who may or may not test positive for an HNPCC-causing mutation. Although applicable to any patient-care setting in which cancer may be observed, this review specifically addresses the role of nurses in detecting, diagnosing, and clinically managing HNPCC.

Scoping the family history: assessment of Lynch syndrome (hereditary nonpolyposis colorectal cancer) in primary care settings--a primer for nurse practitioners

PURPOSE

To describe and discuss the characteristic features and red flags of Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer, that warrants referral for genetic cancer risk assessment (GCRA). A focus on the nurse practitioner's (NP) role in familial risk assessment, physical examination, initiation of genetic referrals, and issues related to the genetic counseling process are also discussed.

DATA SOURCES

A review and synopsis of professional guidelines, clinical articles, and research studies on Lynch syndrome and the genetics of inherited cancer syndromes associated with colorectal cancer. Online resources from the American Gastroenterological Association, American Medical Association, the American Nurses Association, the National Comprehensive Cancer Network, the National Cancer Institute, the National Cancer Institute-Physician Data Query, the National Coalition of Health Professional Education in Genetics, the National Human Genome Research Institute, the National Society of Genetic Counselors, International Society of Nurses in Genetics, and the Oncology Nursing Society.

CONCLUSIONS

Approximately 5% of all colon cancers are because of a germ line mutation predisposing individuals and their family members to colorectal and other cancers. Although the efficacy of screening modalities is established, healthcare providers often fail to identify those at greatest risk for disease. The extended family history is the first step in recognition of individuals "suspect" for hereditary colon cancers such as Lynch syndrome. Early-age onset of Lynch syndrome-associated cancers, an autosomal-dominant pattern, multiple primary tumors in an individual or multiple family members with Lynch syndrome-associated cancers, characteristic pathological features of colon cancer, or a known germ line Lynch syndrome mutation in a family member are "red flags" that will aid NPs in identifying individuals who may benefit from GCRA. IMPLICATIONS FOR NURSE PRACTITIONER PRACTICE: The importance of enhanced surveillance for early diagnosis and prevention of disease is a critical part of primary care. Thus, it is imperative that NPs obtain a minimum of a three-generation pedigree, recognize hereditary cancer patterns, and provide referral counseling for consideration of genetic testing of individuals suspect for Lynch syndrome.

Mismatch repair protein expression in Amsterdam II criteria-positive patients in Taiwan

BACKGROUND

Hereditary non-polyposis colorectal cancer (HNPCC) is characterized genetically by germline mutations in DNA mismatch repair (MMR) genes. Immunohistochemistry (IHC) has high sensitivity and specificity for identifying MMR-deficient tumours. This study investigated the clinical presentations and frequency of HNPCC in Taiwan by combined Amsterdam II criteria (AC-II) and IHC.

METHODS

In 1995-2003, 7108 patients with primary colorectal cancer registered in Chang Gung Memorial Hospital's Colorectal Cancer Registry were screened using AC-II. Tumour specimens were analysed for MMR protein expression by IHC, and relevant clinicopathological details were documented.

RESULTS

Some 83 patients fulfilled the AC-II. Clinicopathologically, 43 patients (52 per cent) had proximal tumours, ten (12 per cent) had poorly differentiated cancers, 17 (20 per cent) had mucinous adenocarcinoma and 51 (61 per cent) had stage I-II tumours. Seventeen patients developed second primary colonic and extracolonic cancers over a mean 7.2-year follow-up. Immunohistochemically, 58 patients were MMR protein deficient. They had a significantly earlier age of onset (P < 0.001), more proximal tumour location (P = 0.002), less advanced tumour stage (P = 0.008) and more second primary cancers (P = 0.017) compared with MMR-competent patients.

CONCLUSION

These data show significant differences in clinical features between MMR protein-deficient and MMR competent subgroups.

Selecting patients with young-onset colorectal cancer for mismatch repair gene analysis

Background

Young patients with colorectal cancer are at increased risk of carrying a germline mutation in mismatch repair (MMR) genes. This study investigated the role of clinical criteria and immunohistochemistry for MMR proteins in selecting young patients for mutation testing.

Methods

A cohort of 56 consecutive patients with colorectal cancer aged less than 45 years were stratified into three groups based on clinical criteria: ‘Amsterdam criteria’, ‘high risk’ and ‘young onset only’. Immunohistochemistry for four MMR proteins was carried out and the rate of compliance with clinical guidelines determined.

Results

Tumours from 11 patients (20 per cent) had abnormal MMR protein expression, of whom eight were referred for genetic assessment. Of 21 patients (38 per cent) in total referred to the genetics unit, six MMR gene mutations were identified, all associated with abnormal immunohistochemistry.

Conclusion

MMR immunohistochemistry should be considered routine in young-onset colorectal cancer.

The Role of Prophylactic Surgery in Cancer Prevention

BACKGROUND

Since the human genome has been sequenced many mysteries of cell biology have been unravelled, thereby clarifying the pathogenesis of several diseases, particularly cancer. In members of kindreds with certain hereditary diseases, it is now possible early in life to predict with great certainty whether or not a family member has inherited the mutated allele causing the disease. In hereditary malignancies this has been particularly important, because in affected family members there is the possibility of removing the organ destined to develop cancer before malignancy develops or while it is in situ. At first consideration, it would appear that "prophylactic surgery" would have a place in many hereditary malignancies; however, the procedure has applicability only if certain criteria are met: (1) the genetic mutation causing the hereditary malignancy must have a very high penetrance and be expressed regardless of environmental factors; (2) there must be a highly reliable test to identify patients who have inherited the mutated gene; (3) the organ must be removed with minimal morbidity and virtually no mortality; (4) there must be a suitable replacement for the function of the removed organ; and (5) there must be a reliable method of determining over time that the patient has been cured by "prophylactic surgery."

CONCLUSIONS

In this monograph we review several hereditary malignancies and consider those where prophylactic surgery might be useful. As we learn, there are various barriers to performing the procedure in many common hereditary cancer syndromes. The archetype disease syndromes, which meet each of the five criteria mentioned above and where prophylactic surgery is most useful, are the type 2 multiple endocrine neoplasia (MEN) syndromes: MEN2A, MEN2B, and the related familial medullary thyroid carcinoma. An additional benefit of the Human Genome Project, has been the development of pharmacologic and biologic compounds that block the metabolic pathway(s) activated by specific genetic mutations. Many of these compounds have shown efficacy in patients with locally advanced or metastatic cancers, and there is the likelihood that they will prove beneficial in preventing the outgrowth of malignant cells in patients destined to develop a hereditary cancer.

Variability and inequity in testing of somatic tissue for hereditary cancer: a survey of UK clinical practice

A growing body of literature demonstrates the benefits of molecular pathological investigations of tumour material in the identification of individuals with hereditary non-polyposis colorectal cancer and debates the best detection strategies. This testing is novel as it is the first widespread use of somatic tissue testing to inform genetic analysis and requires the co-ordination of both histopathology and molecular genetics laboratories. However, the clinical use and experience of microsatellite instability (MSI) testing and immunohistochemical analysis have not been reported. A respondent from every cancer genetics centre in the UK (n= 24, response rate 100%) and laboratory performing MSI testing (n= 5, response rate 100%) was interviewed by telephone to ascertain test availability, testing methods, eligibility criteria and post-test management. Twenty centres (83%) offer eligible clients at least one form of tumour testing, and all use tumour testing to determine who should have access to germ line genetic testing. However, no two laboratories used the same testing methods, seven different testing strategies were applied and there was considerable variation in eligibility criteria. The implications of these variations are considered, and recommendations for the development of a consistent service for testing of somatic tissue offered.

Assessing the Predictive Accuracy of hMLH1 and hMSH2 Mutation Probability Models

Hereditary nonpolyposis colorectal cancer (HNPCC) is characterized by a susceptibility to colorectal and extra-colonic cancers. Several guidelines exist for the identification of families suspected of having HNPCC, however these guidelines lack adequate sensitivity and specificity. In an attempt to improve accuracy for the detection of individuals with HNPCC, the Wijnen pre-test probability model (1998) and Myriad Genetics Laboratory prevalence table (2004) were developed. Here we evaluate the Wijnen model and Myriad table at predicting the presence of a mutation in individuals undergoing genetic testing for HNPCC. Forty-nine patients who had undergone genetic testing for germline mutations in hMLH1 and/or hMSH2 were part of our analysis. Our results revealed that the revised Bethesda guidelines performed with the highest sensitivity for germline mutations (94.4%), however the specificity was low (12.9%). Using a 10.0% mutation probability threshold, the Wijnen model and Myriad table had sensitivities of 55.6 and 60.0%, respectively and specificities of 54.8 and 23.8%, respectively. The Wijnen model and Myriad table were poor predictors of mutation prevalence, which is shown by the areas underneath their corresponding receiver operator characteristic curves (0.616 and 0.400, respectively). The results of this study demonsrate that neither the Wijnen model nor the Myriad table are sensitive or specific enough to be used as the only indication when to offer genetic testing for HNPCC.

Extracolonic cancers associated with hereditary nonpolyposis colorectal cancer in the Utah Population Database

BACKGROUND

The data describing the extracolonic cancers associated with hereditary nonpolyposis colorectal cancer (HNPCC) are variable.

METHODS

We ascertained all Amsterdam I criteria-positive pedigrees (N = 18) in the Utah Population Database (UPDB). We identified the extracolonic cancers in the colorectal cancer cases (N = 65) in these pedigrees, and in their first- (N = 509) and second-degree (N = 1,611) relatives. Standardized morbidity ratios were estimated by comparing the observed rates of extracolonic cancer in defined sets of relatives of probands with population expected rates estimated internally from the UPDB.

RESULTS

The extracolonic cancers observed in significant excess in the 65 Amsterdam I criteria-positive colorectal cancer (CRC) cases in the UPDB were uterine (N = 3, p = 0.003), lip (N = 2, p = 0.007), stomach (N = 2, p = 0.009), female genitalia (N = 1, p = 0.004) and larynx (N = 1, p = 0.05). Extracolonic cancers observed in significant excess in the 509 first-degree relatives of the 65 colorectal cancer (CRC) cases in these Amsterdam I criteria pedigrees included: thyroid (N = 5, p = 0.0002) and prostate (N = 19, p = 0.002). Thyroid cancer (N = 6, p = 0.003) was found in significant excess in the second-degree relatives of the Amsterdam I criteria-positive CRC cases.

CONCLUSIONS

In this population-based examination of the extracolonic cancers at excess in classic HNPCC pedigrees (selected by Amsterdam I criteria) we not only observed many of the same cancers previously reported to be associated with HNPCC in both CRC probands and their relatives, but also identified several previously unreported associations. Although our sample size is small, this study is population based, lacks ascertainment and recall bias, and benefits from uniform, consistent diagnoses of all cancers in a statewide registry.

Histologic features distinguish microsatellite-high from microsatellite-low and microsatellite-stable colorectal carcinomas, but do not differentiate germline mutations from methylation of the MLH1 promoter

The detection of microsatellite-unstable (microsatellite instability [MSI]) colorectal carcinomas (CRCs) has prognostic value and can help screen for Lynch syndrome. We determined which histologic features are associated with MSI status and presence of germline mutation and/or methylation of MLH1 promoter. Patients diagnosed with CRC were offered participation in the Columbus-area hereditary nonpolyposis colorectal cancer syndrome study regardless of age or family history. Tumors were evaluated for MSI using a modified Bethesda panel of microsatellite markers. Methylation status of the MLH1 promoter was evaluated by methylation-specific polymerase chain reaction and bisulfite PCR followed by restriction digestion of tumor DNA. All patients with microsatellite-unstable tumors underwent mutation analysis of the MLH1, MSH2, and MSH6 genes by full sequencing of genomic DNA and by multiplex ligation probe assay of MLH1 and MSH2. Histologic end points were tumor type, grade, percentage of mucin, border, and lymphoid host response. Of the 482 CRCs, 87 were MSI with 69 MSI high (MSI-H), 18 MSI low (MSI-L), and 395 microsatellite stable (MSS). Of 87 MSI tumors, 12 had germline mutations and 34 had methylation of the MLH1 promoter. Younger age, but not histologic features, was significantly associated with a germline mutation. Percentage of mucin, histologic type, grade, and lymphoid host response differed significantly between MSI-H when compared with MSI-L or MSS. No difference was found between MSI-L versus MSS. Histologic features are associated with MSI-H CRC and are helpful to differentiate MSI-H from MSI-L and MSS. These features are not useful to distinguish MSI-L from MSS carcinomas, and those with a deleterious germline hereditary nonpolyposis colorectal cancer syndrome mutation from those with methylation of the MLH1 promoter region.

A genetic model for determining MSH2 and MLH1 carrier probabilities based on family history and tumor microsatellite instability

Mutation-predicting models can be useful when deciding on the genetic testing of individuals at risk and in determining the cost effectiveness of screening strategies at the population level. The aim of this study was to evaluate the performance of a newly developed genetic model that incorporates tumor microsatellite instability (MSI) information, called the AIFEG model, and in predicting the presence of mutations in MSH2 and MLH1 in probands with suspected hereditary non-polyposis colorectal cancer. The AIFEG model is based on published estimates of mutation frequencies and cancer penetrances in carriers and non-carriers and employs the program MLINK of the FASTLINK package to calculate the proband's carrier probability. Model performance is evaluated in a series of 219 families screened for mutations in both MSH2 and MLH1, in which 68 disease-causing mutations were identified. Predictions are first obtained using family history only and then converted into posterior probabilities using information on MSI. This improves predictions substantially. Using a probability threshold of 10% for mutation analysis, the AIFEG model applied to our series has 100% sensitivity and 71% specificity.

Testing for defective DNA mismatch repair in colorectal carcinoma: a practical guide

CONTEXT

Significant bench and clinical data have been generated during the last decade regarding DNA mismatch repair in colorectal carcinoma.

OBJECTIVES

To review clinically relevant aspects of defective DNA mismatch repair in colorectal carcinoma and to suggest testing algorithms for identification of these tumors in the sporadic and familial settings.

DATA SOURCES

This article is based on literature review and clinical testing experience of more than 2000 patient samples.

CONCLUSIONS

Approximately 15% of colorectal carcinomas arise as a result of defective DNA mismatch repair. Ninety percent of these carcinomas are sporadic, arising as a result of methylation of the MLH1 gene promoter, silencing expression. These sporadic carcinomas have improved stage-specific prognosis and can be identified by demonstrating aberrant loss of expression with an MLH1 immunoperoxidase stain. Familial colorectal carcinomas with defective DNA mismatch repair (Lynch syndrome) are due to a germline defect in one of several DNA mismatch repair genes. The familial carcinomas are best identified with a combination of immunohistochemistry and molecular microsatellite analysis. This testing facilitates subsequent directed genetic testing of the proband and family members.

Surveillance colonoscopy in individuals at risk for hereditary nonpolyposis colorectal cancer: an evidence-based review

PURPOSE

Surveillance colonoscopy plays an important role in the management of asymptomatic patients known to carry and suspected of carrying hereditary nonpolyposis colorectal cancer gene mutations. Although the shortest interval between surveillance examinations may seem to offer the most benefit to patients, excessive use of this procedure may have unwanted consequences. This study was designed to evaluate the evidence and make recommendations regarding the optimal frequency of surveillance colonoscopy and the age at which to initiate surveillance based on the best available evidence.

METHODS

MEDLINE was searched for all articles assessing surveillance colonoscopy from 1966 to 2004 by using the MESH terms "hereditary nonpolyposis colorectal cancer" and "screening." The evidence was systematically reviewed and a critical appraisal of the evidence was performed.

RESULTS

There are no randomized, controlled, clinical trials examining the frequency of surveillance colonoscopy in hereditary nonpolyposis colorectal cancer. Three cohort studies were identified for review. There is one cohort study of good quality that provides evidence that surveillance colonoscopy every three years in patients with hereditary nonpolyposis colorectal cancer reduces the risk of developing colorectal cancer and the risk of death. The two remaining cohort studies provide poor evidence on which to make a recommendation.

CONCLUSIONS

The best available evidence supports surveillance with complete colonoscopy to the cecum every three years in patients with hereditary nonpolyposis colorectal cancer (B recommendation). There is no evidence to support or refute more frequent screening. Further research is required to examine the potential harms and benefits of more frequent screening. However, given the potential for rapid progression from adenoma to carcinoma and missing lesions at colonoscopy, there is consensus that screening more frequently than every three years is required.

Genetic counseling outcomes: perceived risk and distress after counseling for hereditary colorectal cancer

Genetic counseling may turn risk information into cancer prevention behavior by modifying health beliefs and cancer-related distress. We assessed the effect of genetic counseling on these factors in 101 adult first-degree-relatives of colorectal cancer patients from families with known or suspected hereditary nonpolyposis colorectal cancer. Before counseling and once afterward, subjects completed self-report measures of perceived lifetime risk and cancer-distress. Most persons overestimated their cancer risk, and higher perceived risk was associated with believing that colorectal cancer cannot be prevented. Individual perceived risk changed after counseling, although mean perceived risk was unchanged. After adjusting for baseline risk, older persons and those with higher estimated objective cancer risk had larger postcounseling decreases. Distress after counseling was positively correlated with baseline distress and anxiety symptoms, and inversely correlated with tolerance for ambiguity. The findings suggest counseling interventions that should increase the likelihood of screening and offer hypotheses for future research.

Use of molecular tumor characteristics to prioritize mismatch repair gene testing in early-onset colorectal cancer

PURPOSE

The relationships between mismatch repair (MMR) protein expression, microsatellite instability (MSI), family history, and germline MMR gene mutation status have not been studied on a population basis.

METHODS

We studied 131 unselected patients with colorectal cancer diagnosed younger than age 45 years. For the 105 available tumors, MLH1, MSH2, MSH6, and PMS2 protein expression using immunohistochemistry (IHC) and MSI were measured. Germline DNA was screened for hMLH1, hMSH2, hMSH6, and hPMS2 mutations for the following patients: all from families fulfilling the Amsterdam Criteria for hereditary nonpolyposis colorectal cancer (HNPCC); all with tumors that were high MSI, low MSI, or that lacked expression of any MMR protein; and a random sample of 23 with MS-stable tumors expressing all MMR proteins.

RESULTS

Germline mutations were found in 18 patients (nine hMLH1, four hMSH2, four hMSH6, and one hPMS2); all tumors exhibited loss of MMR protein expression, all but one were high MSI or low MSI, and nine were from a family fulfilling Amsterdam Criteria. Sensitivities of IHC testing, MSI (high or low), and Amsterdam Criteria for MMR gene mutation were 100%, 94%, and 50%, respectively. Corresponding positive predictive values were 69%, 50%, and 75%.

CONCLUSIONS

Tumor IHC analysis of four MMR proteins and MSI testing provide a highly sensitive strategy for identifying MMR gene mutation-carrying, early-onset colorectal cancer patients, half of whom would have been missed using Amsterdam Criteria alone. Tumor-based approaches for triaging early-onset colorectal cancer patients for MMR gene mutation testing, irrespective of family history, appear to be an efficient screening strategy for HNPCC.

TGFBR1*6A may contribute to hereditary colorectal cancer

PURPOSE

TGFBR16A is a tumor susceptibility gene that increases breast, colon, and ovarian cancer risk. Fourteen percent of the general population carries TGFBR16A, and TGFBR16A homozygotes have a greater than 100% increased colon cancer risk compared with noncarriers. Low-penetrance genes such as TGFBR16A may account for a sizable proportion of familial colorectal cancer occurrences. To test this hypothesis, we determined whether TGFBR16A contributes to a proportion of mismatch repair (MMR) gene mutation-negative hereditary nonpolyposis colorectal cancer (HNPCC) patients.

PATIENTS AND METHODS

A case-case study was performed of 208 index patients with HNPCC meeting the Amsterdam criteria. Patients were examined for mutations and genomic rearrangements in the MLH1, MSH2, and MSH6 genes and genotyped for TGFBR16A. Tumor microsatellite instability status was available for 95 patients.

RESULTS

A total of 144 patients (69.2%) carried a deleterious mutation and were classified as positive for MMR gene mutation; 64 patients (30.8%) had no evidence of mutations and were classified as MMR negative. TGFBR16A allelic frequency was significantly higher among MMR-negative patients (0.195) than among MMR-positive patients (0.104; P = .011). The proportion of TGFBR16A homozygotes was nine-fold higher among MMR-negative (6.3%) than among MMR-positive patients (0.7%; P = .032). The highest TGFBR16A allelic frequency was found among MMR-negative patients with tumors exhibiting no microsatellite instability (0.211), and the lowest frequency was found among MMR-positive patients with tumors exhibiting microsatellite instability (0.121); the difference was not statistically significant (P = .17).

CONCLUSION

TGFBR16A may be causally responsible for a proportion of HNPCC occurrences.

Genetic testing for inherited colon cancer

The genes associated with each of the inherited syndromes of colon cancer have now been identified, and genetic testing is available for diagnosis. These syndromes include familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer, Peutz-Jeghers syndrome, juvenile polyposis syndrome, and, possibly, Cowden's syndrome. Clinical genetic testing approaches have been developed for each of these syndromes and are now a part of accepted clinical care. Disease-causing mutations can be found in the majority of families affected with one of the inherited syndromes, and, most importantly, once a mutation is found in an index case of the family, relatives can be tested for the presence or absence of that mutation with near 100% accuracy. Cancer screening and management in syndrome families is then based on the results of genetic testing. For the physician to order and properly interpret genetic tests, a basic understanding of the types of mutations that lead to inherited disease and the methods for detecting them is vital. These issues will be presented. Additional clinical issues somewhat unique to genetic testing include genetic counseling and informed consent for genetic testing, both of which will also be reviewed. Often the most difficult aspect of genetic testing is deciding which patients and families should undergo the testing. Furthermore, this issue is quite specific for each of the syndromes. Thus, following presentation of general principles of selection for genetic testing, a detailed approach for identifying persons who should undergo testing for each of the individual syndromes will be given, together with relevant descriptions of the syndromes. Finally, the ongoing work to discover new and possibly more common but less penetrant colon cancer susceptibility genes that cause common familial colon cancer will be presented.