Lower cancer incidence in Amsterdam-I criteria families without mismatch repair deficiency: familial colorectal cancer type X

[DNA methylation defects in sporadic and hereditary colorectal cancer]

DNA methylation is a fundamental epigenetic mechanism in regulating the expression of genes controlling crucial cell functions in cancer development. Methylation defects (both global hypomethylation and hypermethylation of CpG islands) are implicated in colorectal carcinogenesis. Some nutrients have a clear effect on methylation, suggesting that some dietary-associated differences in the incidence of colorectal cancer could be due to the effect of diet on methylation. The presence of methylation defects has clear diagnostic and prognostic implications. Thus, several tests are being used for colorectal cancer screening based on methylated gene analysis, whether in feces or blood. In addition, the reversibility of methylation processes allows the development of chemotherapies that regulate this process through their antineoplastic activity.

Familial colorectal cancer type X syndrome: two distinct molecular entities?

In a fraction of families fulfilling the Amsterdam criteria for hereditary non-polyposis colorectal cancer, colorectal cancers are microsatellite stable and DNA mismatch repair gene (MMR) mutations are not found. These families were designated as familial colorectal cancer type X (FCCTX). We aimed to characterise a group of FCCTX families defined by the Amsterdam criteria and MSS tumours at clinical and molecular level. Twenty-four tumours from 15 FCCTX families were analysed for loss of known tumour suppressor gene (TSG) loci (APC, TP53, SMAD4 and DCC), MGMT and MMR genes promoter methylation, and also APC and KRAS somatic mutations. FCCTX families presented specific clinical features: absence of endometrial tumours, high adenoma/carcinoma ratio (1.91) and prevalence of rectal cancers (13/27, 48%). New molecular features were found: the majority of FCCTX tumours (13/18; 72%) presented TSG loss. TSG loss positive tumours presented frequent APC and KRAS somatic mutations and MGMT methylation [10/13 (77%), 7/13 (54%) and 6/11 (54%), respectively]. In TSG loss negative tumours (5/18; 28%), the same molecular events were found in 2/5 (40%), 2/5 (40%) and 1/3 (33%) tumours, respectively. Transition mutations in KRAS were more frequent among MGMT methylated tumours than in unmethylated [5/8 (63%) vs. 1/10 (10%), P = 0.03]. Although sharing similar clinical features, at least two different molecular entities should exist among FCCTX families, one whose tumours present frequent TSG loss, APC and KRAS somatic mutations, and MGMT promoter methylation, and a second, lesser predominant, with no evidence of TSG loss and rarely presenting promoter methylation.

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.

[Gastrointestinal oncology: the genetics of colorectal cancer]

Colorectal cancer (CRC) is one of the most common malignancies in developed countries, and up to 5% of all cases occur in the context of a hereditary syndrome. These hereditary forms often require a high degree of suspicion for diagnosis, as well as specific and specialized management. In addition, a diagnosis of hereditary CRC has major consequences not only for the patient, for whom there are highly effective prevention measures, but also for relatives, who may be carriers of the same condition. The most significant advances in the field of hereditary CRC have occurred in the characterization of serrated polyposis syndrome and in the diagnosis and management of patients with Lynch syndrome and familial adenomatous polyposis.

Clinical and molecular detection of inherited colorectal cancers in northeast Italy: a first prospective study of incidence of Lynch syndrome and MUTYH-related colorectal cancer in Italy

The reported incidence of hereditary colorectal cancers (CRCs) is widely variable. The principal aim of the study was to prospectively evaluate the incidence of familial CRCs in a region of northern Italy using a standardized method. Consecutive CRC patients were prospectively enrolled from October 2002 to December 2003. Patients underwent a structured family history, the microsatellite instability (MSI) test and a screen for MUTYH mutations. Following family history patients were classified as belonging to high, moderate and mild risk families. Immunohistochemistry for MLH1, MSH2, MSH6 and PMS2 proteins and investigation for MLH1/MSH2 mutations, for MLH1 promoter methylation and for the V600E hotspot BRAF mutation were performed in high MSI (MSI-H) cases. Of the 430 patients enrolled, 17 (4%) were high risk [4 hereditary non-polyposis colorectal cancer (HNPCC), 12 suspected HNPCC and 1 MUTYH-associated adenomatous polyposis coli (MAP)], 53 moderate risk and 360 mild risk cases. The MSI test was performed on 393 tumours, and 46 (12%) of them showed MSI-H. In these patients, one MLH1 pathogenetic mutations and two MSH2 pathogenetic mutations were found. Thirty-two (70%) MSI-H cases demonstrated MLH1 methylation and/or BRAF mutation: None of them showed MLH1/MSH2 mutation. Two biallelic germline MUTYH mutations were found, one with clinical features of MAP. A strong family history of CRC was present in 4% of the enrolled cases; incidence of MLH1/MSH2 or MUTHY mutations was 1.3% and of MSI-H phenotype was 12%. MLH1 methylation and BRAF mutation can exclude 70% of MSI-H cases from gene sequencing.

Uterine serous carcinoma: increased familial risk for lynch-associated malignancies

Serous uterine cancer is not a feature of any known hereditary cancer syndrome. This study evaluated familial risk of cancers for patients with serous uterine carcinoma, focusing on Lynch syndrome malignancies. Fifty serous or mixed serous endometrial carcinoma cases were prospectively enrolled. Pedigrees were developed for 29 probands and tumors were assessed for DNA mismatch repair (MMR) abnormalities. Standardized incidence ratios for cancers in relatives were estimated. A second-stage analysis was undertaken using data from Gynecologic Oncology Group (GOG)-210. Incidence data for cancers reported in relatives of 348 patients with serous and mixed epithelial and 624 patients with endometrioid carcinoma were compared. Nineteen of 29 (65.5%) patients in the single-institution series reported a Lynch-related cancer in relatives. Endometrial and ovarian cancers were significantly overrepresented and a high number of probands (6 of 29, 20.7%) reported pancreatic cancers. None of the probands' tumors had DNA MMR abnormalities. There was no difference in endometrial or ovarian cancer incidence in relatives of serous and endometrioid cancer probands in the case-control study. Pancreatic cancers were, however, significantly more common in relatives of patients with serous cancer [OR, 2.39; 95% confidence interval (CI), 1.06-5.38]. We identified an excess of endometrial, ovarian, and pancreatic cancers in relatives of patients with serous cancer in a single-institution study. Follow-up studies suggest that only pancreatic cancers are overrepresented in relatives. DNA MMR defects in familial clustering of pancreatic and other Lynch-associated malignancies are unlikely. The excess of pancreatic cancers in relatives may reflect an as yet unidentified hereditary syndrome that includes uterine serous cancers.

Familial colorectal cancer: eleven years of data from a registry program in Switzerland

Deleterious germ-line variants involving the DNA mismatch repair (MMR) genes have been identified as the cause of the hereditary nonpolyposis colorectal cancer syndrome known as the Lynch syndrome, but in numerous familial clusters of colon cancer, the cause remains obscure. We analyzed data for 235 German-speaking Swiss families with nonpolyposis forms of colorectal cancer (one of the largest and most ethnically homogeneous cohorts of its kind) to identify the phenotypic features of forms that cannot be explained by MMR deficiency. Based on the results of microsatellite instability analysis and immunostaining of proband tumor samples, the kindreds were classified as MMR-proficient (n = 134, 57%) or MMR-deficient (n = 101, 43%). In 81 of the latter kindreds, deleterious germ-line MMR-gene variants have already been found (62 different variants, including 13 that have not been previously reported), confirming the diagnosis of Lynch syndrome. Compared with MMR-deficient kindreds, the 134 who were MMR proficient were less likely to meet the Amsterdam Criteria II regarding autosomal dominant transmission. They also had primary cancers with later onset and colon-segment distribution patterns resembling those of sporadic colorectal cancers, and they had lower frequencies of metachronous colorectal cancers and extracolonic cancers in general. Although the predisposition to colorectal cancer in these kindreds is probably etiologically heterogeneous, we were unable to identify distinct phenotypic subgroups solely on the basis of the clinical data collected in this study. Further insight, however, is expected to emerge from the molecular characterization of their tumors.

The genetic counselor: an important surgical ally in the optimal care of the cancer patient

Genetic counselors and surgeons both have important roles in the care of patients with hereditary cancer predisposition syndromes. Surgeons have the initial responsibility to identify and refer high-risk patients. Genetic counselors' specialized skill sets are then used in the risk assessment and genetic evaluation of such patients and their at-risk family members, and this may be performed in multiple settings. As discussed in this article, these roles and the processes of genetic counseling and genetic testing may be enhanced through multiple surgeon and genetic counselor collaborations. Continued medical management of patients and families with hereditary cancer predisposition syndromes becomes the responsibility of patients and their multiple health care providers. Box 7 provides a list of resources to assist in finding a local genetic counselor. Because there are various opportunities for surgeons and genetic counselors to collaborate, the authors urge surgeons to recognize the importance of, identify, and work in partnership with a local genetic counselor because that relationship sets the stage for optimal care of the cancer patient.

Identification of individuals at risk for Lynch syndrome using targeted evaluations and genetic testing: National Society of Genetic Counselors and the Collaborative Group of the Americas on Inherited Colorectal Cancer joint practice guideline

Identifying individuals who have Lynch syndrome (LS) involves a complex diagnostic work up that includes taking a detailed family history and a combination of various genetic and immunohistochemical tests. The National Society of Genetic Counselors (NSGC) and the Collaborative Group of the Americas on Inherited Colorectal Cancer (CGA-ICC) have come together to publish this clinical practice testing guideline for the evaluation of LS. The purpose of this practice guideline is to provide guidance and a testing algorithm for LS as well as recommendations on when to offer testing. This guideline does not replace a consultation with a genetics professional. This guideline includes explanations in support of this and a summary of background data. While this guideline is not intended to serve as a review of LS, it includes a discussion of background information on LS, and cites a number of key publications which should be reviewed for a more in-depth understanding of LS. These guidelines are intended for genetic counselors, geneticists, gastroenterologists, surgeons, medical oncologists, obstetricians and gynecologists, nurses and other healthcare providers who evaluate patients for LS.

Mutations and epimutations in the origin of cancer

Cancer is traditionally viewed as a disease of abnormal cell proliferation controlled by a series of mutations. Mutations typically affect oncogenes or tumor suppressor genes thereby conferring growth advantage. Genomic instability facilitates mutation accumulation. Recent findings demonstrate that activation of oncogenes and inactivation of tumor suppressor genes, as well as genomic instability, can be achieved by epigenetic mechanisms as well. Unlike genetic mutations, epimutations do not change the base sequence of DNA and are potentially reversible. Similar to genetic mutations, epimutations are associated with specific patterns of gene expression that are heritable through cell divisions. Knudson's hypothesis postulates that inactivation of tumor suppressor genes requires two hits, with the first hit occurring either in somatic cells (sporadic cancer) or in the germline (hereditary cancer) and the second one always being somatic. Studies on hereditary and sporadic forms of colorectal carcinoma have made it evident that, apart from genetic mutations, epimutations may serve as either hit or both. Furthermore, recent next-generation sequencing studies show that epigenetic genes, such as those encoding histone modifying enzymes and subunits for chromatin remodeling systems, are themselves frequent targets of somatic mutations in cancer and can act like tumor suppressor genes or oncogenes. This review discusses genetic vs. epigenetic origin of cancer, including cancer susceptibility, in light of recent discoveries. Situations in which mutations and epimutations occur to serve analogous purposes are highlighted.

Meta-analysis of 8q24 for seven cancers reveals a locus between NOV and ENPP2 associated with cancer development

Background

Human chromosomal region 8q24 contains several genes which could be functionally related to cancer, including the proto-oncogene c-MYC. However, the abundance of associations around 128 Mb on chromosome 8 could mask the appearance of a weaker, but important, association elsewhere on 8q24.

Methods

In this study, we completed a meta-analysis of results from nine genome-wide association studies for seven types of solid-tumor cancers (breast, prostate, pancreatic, lung, ovarian, colon, and glioma) to identify additional associations that were not apparent in any individual study.

Results

Fifteen SNPs in the 8q24 region had meta-analysis p-values < 1E-04. In particular, the region consisting of 120,576,000-120,627,000 bp contained 7 SNPs with p-values < 1.0E-4, including rs6993464 (p = 1.25E-07). This association lies in the region between two genes, NOV and ENPP2, which have been shown to play a role in tumor development and motility. An additional region consisting of 5 markers from 128,478,000 bp - 128,524,000 (around gene POU5F1B) had p-values < 1E-04, including rs6983267, which had the smallest p-value (p = 6.34E-08). This result replicates previous reports of association between rs6983267 and prostate and colon cancer.

Conclusions

Further research in this area is warranted as these results demonstrate that the chromosomal region 8q24 may contain a locus that influences general cancer susceptibility between 120,576 and 120,630 kb.

Microsatellite instability and colorectal cancer

CONTEXT

About 15% of colorectal cancers are characterized by genomic microsatellite instability, and of these, about 1 in 5 (2%-4% overall) are due to Lynch syndrome, a dominantly inherited condition predisposing the patient to cancers of multiple organ systems, including the gastrointestinal tract. Identification of individuals with Lynch syndrome allows for increased surveillance of the affected individual and of potentially affected family members.

OBJECTIVE

To review the literature on microsatellite instability in colorectal cancer and current laboratory diagnostic testing strategies for the detection of Lynch syndrome.

DATA SOURCES

This review is based on peer-reviewed literature, published guidelines from professional organizations (Evaluation of Genomic Applications in Practice and Prevention Working Group, National Comprehensive Cancer Network), and information from clinical laboratories performing microsatellite instability testing.

CONCLUSIONS

Universal screening for Lynch syndrome in all individuals affected with colorectal cancer has been recommended by the Evaluation of Genomic Applications in Practice and Prevention Working Group. Preliminary screening tests can identify individuals unlikely to be affected by Lynch syndrome, thereby reducing the need for full gene analysis. Immunohistochemistry and polymerase chain reaction-based tests for microsatellite instability have similar clinical sensitivity and specificity, and each method has advantages and limitations. BRAF and MLH1 methylation testing are useful reflex tests for those with a defect in MLH1 identified by immunohistochemistry. Emerging technologies, such as high-throughput sequencing, may substantially affect diagnostic algorithms in the future.

Patient and tumor characteristics may raise clinicians' awareness of familial colorectal cancer: a Norwegian population-based study

BACKGROUND

The aim of this study was to identify patient and tumor characteristics that may be useful for clinicians in the identification of possible familial colorectal cancer (CRC).

METHODS

Among 562 unselected, consecutively diagnosed colorectal cancer patients, 490 patients were included and divided into familial or sporadic CRC based on family history data collected by standardized patient interviews. Clinical data were collected from the patients' medical records. Patients were classified as familial CRC according to currently accepted family history criteria. Each patient was also classified according to Amsterdam II criteria and the 4th and 5th criteria in the Revised Bethesda Guidelines that address information on family history. Tumors were described by location and histopathology; 316 tumors were examined by molecular analyses.

RESULTS

Right-sided colonic tumors and synchronous CRC tumors were associated with familial CRC, and patients with metachronous CRC or Lynch syndrome-related tumors were more likely to be classified as familial CRC. The patients' age at diagnosis did not differ between the groups. Other patient or tumor characteristics were not associated with familial CRC.

CONCLUSION

CRC patients with right-sided colonic cancers, synchronous cancers and previous CRC and/or LS-related tumors were more likely to have familial CRC, and young age at diagnosis was not associated with familial CRC in these data. A detailed family history of colorectal cancer is essential in the identification of patients and families with familial CRC.

Lynch syndrome-associated extracolonic tumors are rare in two extended families with the same EPCAM deletion

OBJECTIVES

The Lynch syndrome (LS) is an inherited cancer syndrome showing a preponderance of colorectal cancer (CRC) in context with endometrial cancer and several other extracolonic cancers, which is due to pathogenic mutations in the mismatch repair (MMR) genes, MLH1, MSH2, MSH6, and PMS2. Some families were found to show a LS phenotype without an identified MMR mutation, although there was microsatellite instability and absence of MSH2 expression by immunohistochemistry. Studies of a subset of these families found a deletion at the 3' end of the epithelial cell adhesion molecule (EPCAM) gene, causing transcription read-through resulting in silencing of MSH2 through hypermethylation of its promoter. The tumor spectrum of such families appears to differ from classical LS.

METHODS

Our study of two large families (USA Family R and Dutch Family A) with an EPCAM deletion was carried out using each institution's standard family study protocol. DNA was extracted from peripheral blood and EPCAM deletion analysis was performed.

RESULTS

Both families were found to harbor the same deletion at the 3' end of EPCAM. Analysis showed that the deletion originated from a common ancestor. Family R and Family A members showed segregation of CRC with the presence of this EPCAM mutation. Compared with classic LS, there were almost no extracolonic cancers.

CONCLUSIONS

Members of Family R and Family A, all with the same EPCAM deletion, predominantly presented with CRC but no LS-associated endometrial cancer, confirming findings seen in other, smaller, LS families with EPCAM mutations. In these EPCAM mutation carriers, cancer surveillance should be focused on CRC.

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.

Strategies to identify the Lynch syndrome among patients with colorectal cancer: a cost-effectiveness analysis

BACKGROUND

Testing has been advocated for all persons with newly diagnosed colorectal cancer to identify families with the Lynch syndrome, an autosomal dominant cancer-predisposition syndrome that is a paradigm for personalized medicine.

OBJECTIVE

To estimate the effectiveness and cost-effectiveness of strategies to identify the Lynch syndrome, with attention to sex, age at screening, and differential effects for probands and relatives.

DESIGN

Markov model that incorporated risk for colorectal, endometrial, and ovarian cancers.

DATA SOURCES

Published literature.

TARGET POPULATION

All persons with newly diagnosed colorectal cancer and their relatives.

TIME HORIZON

Lifetime.

PERSPECTIVE

Third-party payer.

INTERVENTION

Strategies based on clinical criteria, prediction algorithms, tumor testing, or up-front germline mutation testing, followed by tailored screening and risk-reducing surgery.

OUTCOME MEASURES

Life-years, cancer cases and deaths, costs, and incremental cost-effectiveness ratios.

RESULTS OF BASE-CASE ANALYSIS

The benefit of all strategies accrued primarily to relatives with a mutation associated with the Lynch syndrome, particularly women, whose life expectancy could increase by approximately 4 years with hysterectomy and salpingo-oophorectomy and adherence to colorectal cancer screening recommendations. At current rates of germline testing, screening, and prophylactic surgery, the strategies reduced deaths from colorectal cancer by 7% to 42% and deaths from endometrial and ovarian cancer by 1% to 6%. Among tumor-testing strategies, immunohistochemistry followed by BRAF mutation testing was preferred, with an incremental cost-effectiveness ratio of $36,200 per life-year gained.

RESULTS OF SENSITIVITY ANALYSIS

The number of relatives tested per proband was a critical determinant of both effectiveness and cost-effectiveness, with testing of 3 to 4 relatives required for most strategies to meet a threshold of $50,000 per life-year gained. Immunohistochemistry followed by BRAF mutation testing was preferred in 59% of iterations in probabilistic sensitivity analysis at a threshold of $100,000 per life-year gained. Screening for the Lynch syndrome with immunohistochemistry followed by BRAF mutation testing only up to age 70 years cost $44,000 per incremental life-year gained compared with screening only up to age 60 years, and screening without an upper age limit cost $88,700 per incremental life-year gained compared with screening only up to age 70 years.

LIMITATION

Other types of cancer, uncertain family pedigrees, and genetic variants of unknown significance were not considered.

CONCLUSION

Widespread colorectal tumor testing to identify families with the Lynch syndrome could yield substantial benefits at acceptable costs, particularly for women with a mutation associated with the Lynch syndrome who begin regular screening and have risk-reducing surgery. The cost-effectiveness of such testing depends on the participation rate among relatives at risk for the Lynch syndrome.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Evidence of linkage to chromosomes 10p15.3-p15.1, 14q24.3-q31.1 and 9q33.3-q34.3 in non-syndromic colorectal cancer families

Up to 25% of colorectal cancer (CRC) may be caused by inherited genetic variants that have yet to be identified. Previous genome-wide linkage studies (GWLSs) have identified a new loci postulated to contain novel CRC risk genes amongst affected families carrying no identifiable mutations in any of the known susceptibility genes for familial CRC syndromes. To undertake a new GWLS, we recruited members from 54 non-syndromic families from Australia and Spain where at least two first-degree relatives were affected by CRC. We used single-nucleotide polymorphism arrays to genotype 98 concordant affected relative pairs that were informative for linkage analyses. We tested for genome-wide significance (GWS) for linkage to CRC using a quantile statistic method, and we found that GWS was achieved at the 5% level. Independently, using the PSEUDO gene-dropping algorithm, we also found that GWS for linkage to CRC was achieved (P=0.02). Merlin non-parametric linkage analysis revealed significant linkage to CRC for chromosomal region 10p15.3-p15.1 and suggestive linkage to CRC for regions on 14q and 9q. The 10p15.3-p15.1 has not been reported to be linked to hereditary CRC in previous linkage studies, but this region does harbour the Kruppel-like factor 6 (KLF6) gene that is known to be altered in common CRC. Further studies aimed at localising the responsible genes, and characterising their function will give insight into the factors responsible for susceptibility in such families, and perhaps shed further light on the mechanisms of CRC development.

SEOM clinical guidelines for hereditary cancer

Research in genetics has facilitated the identification of highly penetrant genes responsible for a large number of diseases. In the oncology field, genetic counselling and gene testing are focused on the two most common syndromes in familial cancer: hereditary breast and ovarian cancer syndrome (HBOC) and hereditary non-polyposis colorectal cancer or Lynch syndrome (LS). The objective of this guideline in hereditary cancer is to summarise the current state of knowledge and make recommendations in the areas of diagnosis, prevention and treatment of hereditary cancer.

Colorectal cancer screening and prevention in women

Colorectal cancer (CRC) is the third most common cause of cancer in women. Screening for CRC increases early detection of cancer and premalignant polyps and decreases morbidity from this disease. However, adherence to the screening guidelines continues to remain inadequate both at the physician and patient levels. Several factors are of special importance to women. Presence of prior gynecological malignancies may increase the risk of CRC in women. Furthermore, new studies have shown other factors such as obesity and smoking to increase the risk of CRC in women. This article highlights issues unique to women with regards to CRC and outlines special considerations for determining screening intervals in women, identifies factors that make screening more difficult in women, and reviews studies that identify preventative strategies which, together with screening, may reduce the burden of CRC.

Strategies to identify the Lynch syndrome among patients with colorectal cancer: a cost-effectiveness analysis

BACKGROUND

Testing has been advocated for all persons with newly diagnosed colorectal cancer to identify families with the Lynch syndrome, an autosomal dominant cancer-predisposition syndrome that is a paradigm for personalized medicine.

OBJECTIVE

To estimate the effectiveness and cost-effectiveness of strategies to identify the Lynch syndrome, with attention to sex, age at screening, and differential effects for probands and relatives.

DESIGN

Markov model that incorporated risk for colorectal, endometrial, and ovarian cancers.

DATA SOURCES

Published literature.

TARGET POPULATION

All persons with newly diagnosed colorectal cancer and their relatives.

TIME HORIZON

Lifetime.

PERSPECTIVE

Third-party payer.

INTERVENTION

Strategies based on clinical criteria, prediction algorithms, tumor testing, or up-front germline mutation testing, followed by tailored screening and risk-reducing surgery.

OUTCOME MEASURES

Life-years, cancer cases and deaths, costs, and incremental cost-effectiveness ratios.

RESULTS OF BASE-CASE ANALYSIS

The benefit of all strategies accrued primarily to relatives with a mutation associated with the Lynch syndrome, particularly women, whose life expectancy could increase by approximately 4 years with hysterectomy and salpingo-oophorectomy and adherence to colorectal cancer screening recommendations. At current rates of germline testing, screening, and prophylactic surgery, the strategies reduced deaths from colorectal cancer by 7% to 42% and deaths from endometrial and ovarian cancer by 1% to 6%. Among tumor-testing strategies, immunohistochemistry followed by BRAF mutation testing was preferred, with an incremental cost-effectiveness ratio of $36,200 per life-year gained.

RESULTS OF SENSITIVITY ANALYSIS

The number of relatives tested per proband was a critical determinant of both effectiveness and cost-effectiveness, with testing of 3 to 4 relatives required for most strategies to meet a threshold of $50,000 per life-year gained. Immunohistochemistry followed by BRAF mutation testing was preferred in 59% of iterations in probabilistic sensitivity analysis at a threshold of $100,000 per life-year gained. Screening for the Lynch syndrome with immunohistochemistry followed by BRAF mutation testing only up to age 70 years cost $44,000 per incremental life-year gained compared with screening only up to age 60 years, and screening without an upper age limit cost $88,700 per incremental life-year gained compared with screening only up to age 70 years.

LIMITATION

Other types of cancer, uncertain family pedigrees, and genetic variants of unknown significance were not considered.

CONCLUSION

Widespread colorectal tumor testing to identify families with the Lynch syndrome could yield substantial benefits at acceptable costs, particularly for women with a mutation associated with the Lynch syndrome who begin regular screening and have risk-reducing surgery. The cost-effectiveness of such testing depends on the participation rate among relatives at risk for the Lynch syndrome.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Increased frequency of 20q gain and copy-neutral loss of heterozygosity in mismatch repair proficient familial colorectal carcinomas

Many hereditary nonpolyposis colorectal cancers (CRCs) cannot be explained by Lynch syndrome. Other high penetrance genetic risk factors are likely to play a role in these mismatch repair (MMR)-proficient CRC families. Because genomic profiles of CRC tend to vary with CRC susceptibility syndromes, our aim is to analyze the genomic profile of MMR-proficient familial CRC to obtain insight into the biological basis of MMR-proficient familial CRC. We studied 30 MMR-proficient familial colorectal carcinomas, from 15 families, for genomic aberrations, including gains, physical losses, and copy-neutral loss of heterozygosity LOH (cnLOH) using SNP array comparative genomic hybridization. In addition, we performed somatic mutation analysis for KRAS, BRAF, PIK3CA and GNAS. The frequency of 20q gain (77%) is remarkably increased when compared with sporadic CRC, suggesting that 20q gain is involved in tumor progression of familial CRC. There is also a significant increase in the frequency of cnLOH and, as a consequence, a reduced frequency of physical loss compared with sporadic CRC. The most frequent aberrations observed included gains of 7p, 7q, 8q, 13q, 20p and 20q as well as physical losses of 17p, 18p and 18q. Most of these changes are also observed in sporadic CRC. Mutations in KRAS were identified in 37% of the MMR-proficient CRCs, and mutations in BRAF were identified in 16%. No mutations were identified in PIK3CA or chromosome 20 candidate gene GNAS. We show that the patterns of chromosomal instability of MMR-proficient familial CRC are clearly distinct from those from sporadic CRC. Both the increased gain on chromosome 20 and the increased levels of cnLOH suggest the presence of yet undiscovered germline defects that can, in part, underlie the cancer risk in these families.

Inherited colorectal cancer syndromes

Colorectal cancer is common in the Western world; ~5% of individuals diagnosed with colorectal cancer have an identifiable inherited genetic predisposition to this malignancy. Genetic testing and rational clinical management recommendations currently exist for the management of individuals with a variety of colorectal cancer syndromes, including hereditary nonpolyposis colorectal cancer (HNPCC, also known as Lynch syndrome), familial adenomatous polyposis (FAP), MYH-associated polyposis (MAP), and the hamartomatous polyposis syndromes (Peutz-Jeghers, juvenile polyposis, and Cowden disease). In addition to colorectal neoplasia, these syndromes frequently predispose carriers to a variety of extracolonic cancers. The elucidation of the genetic basis of several colorectal cancer predisposition syndromes over the past two decades has allowed for better management of individuals who are either affected with, or at-risk for inherited colorectal cancer syndromes. Appropriate multidisciplinary management of these individuals includes genetic counseling, genetic testing, clinical screening, and treatment recommendations.

Genomic instability and carcinogenesis: an update

Cancers arise as a result of stepwise accumulation of mutations which may occur at the nucleotide level and/or the gross chromosomal level. Many cancers particularly those of the colon display a form of genomic instability which may facilitate and speed up tumor initiation and development. In few instances, a "mutator mutation" has been clearly implicated in driving the accumulation of other carcinogenic mutations. For example, the post-replicative DNA mismatch repair deficiency results in dramatic increase in insertion/deletion mutations giving rise to the microsatellite instability (MSI) phenotype and may predispose to a spectrum of tumours when it occurs in the germline. Although many sporadic cancers show multiple mutations suggesting unstable genome, the role of this instability in carcinogenesis, as opposed to the power of natural selection, has been a matter of controversy. This review gives an update of the latest data on these issues particularly recent data from genome-wide, high throughput techniques as well as mathematical modelling. Throughout this review, reference will be made to the relevance of genomic instability to the pathogenesis of colorectal carcinoma particularly its hereditary and familial subsets.

Microsatellite instability in the management of colorectal cancer

Microsatellite instability (MSI) is a form of genetic instability caused by alterations in the DNA mismatch repair system. Approximately 15% of colorectal cancers display MSI due to a germline mutation in one of the mismatch repair genes (MLH1, MSH2, MSH6 and PMS2) or to epigenetic silencing of MLH1. Colorectal cancers with MSI have distinctive features, including a tendency to arise in the proximal colon, poor differentiation, lymphocytic infiltration and mucinous or signet-ring histology. Patients with MSI tumors appear to have a better prognosis than those with microsatellite stable tumors, but curiously the responses to 5-fluorouracil-based chemotherapy regimens are poorer with MSI tumors. Preliminary data suggest possible advantages of irinotecan-based regimens, but these findings need validation in well-designed clinical trials.

Genotype-environment interactions in microsatellite stable/microsatellite instability-low colorectal cancer: results from a genome-wide association study

BACKGROUND

Genome-wide association studies (GWAS) have led to the identification of a number of common susceptibility loci for colorectal cancer (CRC); however, none of these GWAS have considered gene-environment (G × E) interactions. Therefore, it is unclear whether current hits are modified by environmental exposures or whether there are additional hits whose effects are dependent on environmental exposures.

METHODS

We conducted a systematic search for G × E interactions using genome wide data from the Colon Cancer Family Registry that included 1,191 cases of microsatellite stable (MSS) or microsatellite instability-low (MSI-L) CRC and 999 controls genotyped using either the Illumina Human1M or Human1M-Duo BeadChip. We tested for interactions between genotypes and 14 environmental factors using 3 methods: a traditional case-control test, a case-only test, and the recently proposed 2-step method by Murcray and colleagues. All potentially significant findings were replicated in the ARCTIC Study.

RESULTS

No G × E interactions were identified that reached genome-wide significance by any of the 3 methods. When analyzing previously reported susceptibility loci, 7 significant G × E interactions were found at a 5% significance level. We investigated these 7 interactions in an independent sample and none of the interactions were replicated.

CONCLUSIONS

Identifying G × E interactions will present challenges in a GWAS setting. Our power calculations illustrate the need for larger sample sizes; however, as CRC is a heterogeneous disease, a tradeoff between increasing sample size and heterogeneity needs to be considered.

IMPACT

The results from this first genome-wide analysis of G × E in CRC identify several challenges, which may be addressed by large consortium efforts.

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.

Microsatellite instability in colorectal cancer: from molecular oncogenic mechanisms to clinical implications

BACKGROUND

Microsatellite instability (MSI) constitutes an important oncogenic molecular pathway in colorectal cancer (CRC), representing approximately 15% of all colorectal malignant tumours. In roughly one third of the cases, the underlying DNA mismatch repair (MMR) defect is inherited through the transmission of a mutation in one of the genes involved in MMR, predominantly MSH2 and MLH1, or less frequently, MSH6 or PMS2. In the overwhelming number of sporadic cases, MSI results from epigenetic MLH1 silencing through hypermethylation of its promoter. MMR deficiency promotes colorectal oncogenesis through the accumulation of numerous mutations in crucial target genes harbouring mononucleotide repeats, notably in those involved in the control of cell proliferation and differentiation, as well as DNA damage signalling and repair.

DESIGN

In this review, we describe the molecular aspects of the MMR system and the biological consequences of its defect on the oncogenic process, and we discuss the various experimental systems used to evaluate the efficacy of cytotoxic drugs on MSI colorectal cells lines. There is increasing evidence showing that MSI CRCs differ from all CRCs in terms of prognosis and response to the treatment. We report the clinical studies that have evaluated the prognostic and predictive value of MSI status on clinical outcome in patients treated with various chemotherapy regimens used in the adjuvant setting or for advanced CRCs.

CONCLUSION

In view of this, the opportunity of a systematic MSI phenotyping in the clinical management of patients with CRC is further discussed.

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.

Frequency of extracolonic tumors in Brazilian families with Lynch syndrome: analysis of a hereditary colorectal cancer institutional registry

Lynch syndrome (LS) is caused by inherited germline mutations in mismatch repair (MMR) genes. It is one of the commonest forms of inherited predisposition to colorectal cancer (CRC), accounting for 2-5% of all CRC. LS is characterized by early age of onset, with a tendency for multiplicity and an increased risk for extra-colonic tumors at particular sites. In this study we have evaluated the frequency of extra-colonic tumors in 60 unrelated LS families fulfilling the Amsterdam criteria (ACI. ACII) from the Oncotree database of the Hereditary Colorectal Cancer Registry of the AC Camargo Hospital. All families' pedigree was extensively analyzed, varying from 2 to 6 generations with a total of 2,095 individuals evaluated. As expected, colorectal cancer was the most frequent tumor in the families (334 cases). We found 200 extracolonic tumors among all individuals with a higher ratio in women (123 cases) than men (77 cases). By far, breast cancer (32 cases) was the most frequent extracolonic manifestation in women followed by endometrial (20 cases) and uterine cervix cancer (20 cases). For man, prostate (16 cases) and stomach (12 cases) cancer were the most frequent extracolonic tumors. It is well know that establishing the diagnosis is challenging and requires knowledge and surveillance. Thus, recognition of individuals and families with hereditary predisposition to cancer according to clinical and molecular features, combined with intensive surveillance and management programs, can contribute substantially to improve results related to the diagnosis and characterization of LS.

Diagnosing hereditary colorectal cancer

Although progress in the treatment of patients with colorectal cancer (CRC) has resulted in improved median survival, most patients with metastatic CRC still die of their disease, and essentially all patients with early-stage disease must undergo surgical resection and subsequently face the possibility of adjuvant chemotherapy. As effective screening and prevention strategies for CRC have been developed, identification of individuals with a hereditary predisposition to developing CRC is especially important and provides the opportunity to reduce disease burden in this high-risk population. Increased awareness and improved diagnostic techniques for hereditary CRC syndromes have facilitated more frequent diagnosis and management of a small number of highly penetrant syndromes within families. However, known high-penetrance genetic predisposition syndromes account for a minority of all familial CRC, leaving much of the genetic basis of CRC unexplained. Recent advances in high-throughput genotyping have made possible genome-wide association studies, which have identified novel genetic variants associated with modest increases in CRC risk. While these associations have helped to identify potentially important pathways in CRC carcinogenesis, at the current time, the clinical use of such genetic risk variants in colon cancer risk stratification remains limited.

Analysis of the oxidative damage repair genes NUDT1, OGG1, and MUTYH in patients from mismatch repair proficient HNPCC families (MSS-HNPCC)

PURPOSE

Several studies have described molecular differences between microsatellite stable hereditary nonpolyposis colorectal cancer (MSS-HNPCC) and microsatellite unstable Lynch syndrome tumors (MSI-HNPCC). These differences highlight the possibility that other instability forms could explain cancer susceptibility in this group of families. The base excision repair (BER) pathway is the major DNA repair pathway for oxidative DNA damage. A defect in this pathway can result in DNA transversion mutations and a subsequent increased cancer risk. Mutations in MUTYH have been associated with increased colorectal cancer (CRC) risk while no association has been described for OGG1 or NUDT1.

EXPERIMENTAL DESIGN

We performed mutational screening of the three genes involved in defense against oxidative DNA damage in a set of 42 MSS-HNPCC families.

RESULTS

Eight rare variants and 5 frequent variants were found in MSS-HNPCC patients. All variants were previously described by other authors except variant c.285C>T in OGG1. Segregation studies were done and in silico programs were used to estimate the level of amino acid conservation, protein damage prediction, and possible splicing alterations. Variants OGG1 c.137G>A; MUTYH c.1187G>A were detected in Amsterdam I families and cosegregate with cancer. Analysis of OGG1 c.137G>A transcripts showed an inactivation of the splicing donor of exon 1.

CONCLUSIONS

Two rare variants (OGG1 c.137G>A; MUTYH c.1187G>A) and one common polymorphism (NUDT1 c.426C>T) were associated with CRC risk. We show that the BER pathway can play a significant role in a number of MSS-HNPCC colorectal cancers. More studies could be of interest in order to gain further understanding of yet unexplained CRC susceptibility cases.

Identification of patients at-risk for Lynch syndrome in a hospital-based colorectal surgery clinic

AIM: To determine the prevalence of a family history suggestive of Lynch syndrome (LS) among patients with colorectal cancer (CRC) followed in a coloproctology outpatient clinic in Southern Brazil.

METHODS: A consecutive sample of patients with CRC were interviewed regarding personal and family histories of cancer. Clinical data and pathology features of the tumor were obtained from chart review.

RESULTS: Of the 212 CRC patients recruited, 61 (29%) reported a family history of CRC, 45 (21.2%) were diagnosed under age 50 years and 11 (5.2%) had more than one primary CRC. Family histories consistent with Amsterdam and revised Bethesda criteria for LS were identified in 22 (10.4%) and 100 (47.2%) patients, respectively. Twenty percent of the colorectal tumors had features of the high microsatellite instability phenotype, which was associated with younger age at CRC diagnosis and with Bethesda criteria (P < 0.001). Only 5.3% of the patients above age 50 years had been previously submitted for CRC screening and only 4% of patients with suspected LS were referred for genetic risk assessment.

CONCLUSION: A significant proportion of patients with CRC were at high risk for LS. Education and training of health care professionals are essential to ensure proper management.

How to manage a patient with multiple adenomatous polyps

Adenomatous polyps are found on screening colonoscopy in 22.5% to 58.2% of the adult population and therefore represent a common problem. Patients with multiple adenomatous polyps are of unique interest because a proportion of these patients have an inheritable form of colorectal cancer. This article discusses the history and clinical features, genetic testing, surveillance, and treatments for the condition.

Clinical genetics of hereditary colorectal cancer

Colorectal cancer (CRC) is a common disease, and approximately 25% of patients have a familial component. High-penetrance singlegene germline mutations conferring a true hereditary susceptibility account for around 5% to 6% of all cases. Lynch syndrome is the most common hereditary form of colorectal cancer. Much of the hereditary component in the remaining familial cases of CRC is likely polygenic, and many of the genetic changes involved are as yet unidentified. This article addresses the most clinically important CRC genetic syndromes.

The search for unaffected individuals with Lynch syndrome: do the ends justify the means?

Lynch syndrome is the most common cause of inherited colorectal and endometrial cancers yet it is underrecognized in clinical practice. The relative merits of screening for Lynch syndrome among healthy adults without cancer versus among adults with colorectal or endometrial cancer are discussed in this Perspective article. Newly diagnosed colorectal cancer patients are a much easier target population for screening and this approach leads to more informative genetic test results, at a lower cost in most cases.

Surgical management of hereditary nonpolyposis colorectal cancer

HNPCC is a diverse disease with significant colorectal and extracolonic malignancy risk. A high index of suspicion is necessary to identify patients and families who potentially have this disease. Patients suspected with Lynch syndrome should be referred for genetic counseling and testing for accurate diagnosis. Timely surveillance and intervention are essential to reduce the incidence and mortality from colorectal cancer. Once cancer is diagnosed, aggressive surgical management is warranted because there is significant metachronous colorectal neoplasia risk for all remaining colorectal mucosa. In medically fit patients, consideration should be given to colectomy for the treatment of colon cancer and proctocolectomy for the treatment of rectal cancer. For patients treated with anything less than total proctocolectomy, annual endoscopic surveillance of the remaining colorectum is mandatory.

[Lynch syndrome: genetics and surgery]

Hereditary nonpolyposis colorectal cancer or Lynch Syndrome, caused by germinal mutations in mismatch deoxyribonucleic acid (DNA) repair genes, is the most common form of hereditary colorectal cancer. The identification of these individuals is not easy and is based on clinical and molecular criteria. A review is presented on the genetics and diagnosis in Lynch Syndrome, as well as on its surgical management and prevention.

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.

Genetic counseling considerations in the evaluation of families for Lynch syndrome--a review

Lynch syndrome is the most common hereditary colorectal cancer syndrome and the most common cause of hereditary endometrial cancer. Identifying and evaluating families for Lynch syndrome is increasing in complexity due to the recognition that: family history-based clinical criteria lack sensitivity and specificity; genetic testing for Lynch syndrome continues to evolve as understanding of the molecular mechanisms underlying it evolves; and the Lynch syndrome phenotype encompasses multiple organ systems and demonstrates overlap with other hereditary cancer syndromes. This document is a summary of considerations when evaluating individuals and families for Lynch syndrome, including information on cancer risks, diagnostic criteria, tumor and genetic testing strategies, and the management of individuals with this condition.