Hereditary nonpolyposis colorectal cancer and colonic adenomas: aggressive adenomas?

Upper Gastrointestinal Cancer Surveillance in Lynch Syndrome

Simple Summary

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

Abstract

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

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

Individuals with Lynch syndrome (LS), one of the most common inherited cancer syndromes, are at increased risk of developing malignancies, in particular colorectal cancer (CRC). Regular colonoscopy with polypectomy is recommended to reduce CRC risk in LS individuals. However, recent independent studies demonstrated that a substantial proportion of LS individuals develop CRC despite regular colonoscopy. The reasons for this surprising observation confirmed by large prospective studies are a matter of debate. In this review, we collect existing evidence from clinical, epidemiological and molecular studies and interpret them with regard to the origins and progression of LS-associated CRC. Alongside with hypotheses addressing colonoscopy quality and pace of progression from adenoma to cancer, we discuss the role of alternative precursors and immune system in LS-associated CRC. We also identify gaps in current knowledge and make suggestions for future studies aiming at improved CRC prevention for LS individuals.

Upper Endoscopic Surveillance in Lynch Syndrome Detects Gastric and Duodenal Adenocarcinomas

Lynch syndrome is a prevalent hereditary cancer predisposition syndrome. While colorectal cancer is the most common gastrointestinal (GI) cancer in Lynch syndrome, there is also increased risk of gastric and small intestinal cancers. Recommendations for upper GI cancer surveillance in Lynch syndrome vary widely with limited data supporting effectiveness. Herein, we collected data on individuals with a diagnosis of Lynch syndrome seen at our tertiary care referral center. We identified individuals who underwent upper endoscopy and those with upper GI cancers, and associated demographics, genetic testing results, and endoscopic information. Standard statistical analyses were performed. Among 295 individuals with Lynch syndrome seen at our center, 217 (73.6%) underwent 660 total upper endoscopies. Of these 217, precancerous upper endoscopy findings included Barrett's esophagus (7, 3.2%), gastric intestinal metaplasia (18, 8.3%), and duodenal adenomas (4, 1.8%), and Helicobacter pylori was identified in 6 (2.8%). Upper GI cancers were diagnosed in 11 individuals (3.7%), including esophageal in 1, gastric in 6, and duodenal in 4. Five (1.7%) of these upper GI cancers were identified on surveillance. Individuals with upper GI cancers identified on surveillance were older at first surveillance endoscopy, with median age 63.3 versus 44.9 years (P < 0.001). Of the upper GI cancers detected on surveillance, 80% (4/5) occurred within 2 years of last upper endoscopy and 80% were stage I. In conclusion, upper endoscopy surveillance in Lynch syndrome identifies upper GI cancers. For individuals with Lynch syndrome who undergo upper GI surveillance, a short surveillance interval may be warranted.

Implications of Hereditary Origin on the Immune Phenotype of Mismatch Repair-Deficient Cancers: Systematic Literature Review

Microsatellite instability (MSI) represents one of the major types of genomic instability in human cancers and is most common in colorectal cancer (CRC) and endometrial cancer (EC). MSI develops as a consequence of DNA mismatch repair (MMR) deficiency, which can occur sporadically or in the context of Lynch syndrome (LS), the most common inherited tumor syndrome. MMR deficiency triggers the accumulation of high numbers of somatic mutations in the affected cells, mostly indel mutations at microsatellite sequences. MSI tumors are among the most immunogenic human tumors and are often characterized by pronounced local immune responses. However, so far, little is known about immunological differences between sporadic and hereditary MSI tumors. Therefore, a systematic literature search was conducted to comprehensively collect data on the differences in local T cell infiltration and immune evasion mechanisms between sporadic and LS-associated MSI tumors. The vast majority of collected studies were focusing on CRC and EC. Generally, more pronounced T cell infiltration and a higher frequency of B2M mutations were reported for LS-associated compared to sporadic MSI tumors. In addition, phenotypic features associated with enhanced lymphocyte recruitment were reported to be specifically associated with hereditary MSI CRCs. The quantitative and qualitative differences clearly indicate a distinct biology of sporadic and hereditary MSI tumors. Clinically, these findings underline the need for differentiating sporadic and hereditary tumors in basic science studies and clinical trials, including trials evaluating immune checkpoint blockade therapy in MSI tumors.

Phenotypic and genotypic heterogeneity of Lynch syndrome: a complex diagnostic challenge

Lynch syndrome is the hereditary disorder that most frequently predisposes to colorectal cancer as well as predisposing to a number of extracolonic cancers, most prominently endometrial cancer. It is caused by germline mutations in the mismatch repair genes. Both its phenotype and genotype show marked heterogeneity. This review gives a historical overview of the syndrome, its heterogeneity, its genomic landscape, and its implications for complex diagnosis, genetic counseling and putative implications for immunotherapy.

Impact of an optimized colonoscopic screening program for patients with Lynch syndrome: 6-year results of a specialized French network

BACKGROUND

Despite colonoscopic screening, colorectal cancer (CRC) remains frequent in patients with Lynch syndrome (LS). The objective of this study was to evaluate the impact of an optimized colorectal screening program within a French dedicated network.

METHODS

All LS patients followed at our institution were consecutively included in the Prédisposition au Cancer Colorectal-Ile de France (PRED-IdF) network. Patients were offered an optimized screening program allowing an adjustment of the interval between colonoscopies, depending on bowel preparation, chromoendoscopy achievement and adenoma detection. Colonoscopies were defined as optimal when all the screening criteria were respected. We compared colonoscopy quality and colonoscopy detection rate before and after PRED-IdF inclusion, including polyp detection rate (PDR), adenoma detection rate (ADR) and cancer detection rate (CDR).

RESULTS

Between January 2010 and January 2016, 144 LS patients were consecutively included (male/female = 50/94, mean age = 51 ± 13 years and mutations: MLH1 = 39%, MSH2 = 44%, MSH6 = 15%, PMS2 = 1%). A total of 564 colonoscopies were analyzed, 353 after inclusion and 211 before. After PRED-IdF inclusion, 98/144 (68%) patients had optimal screening colonoscopies versus 33/132 (25%) before (p < 0.0005). The optimal colonoscopy rate was 304/353 (86%) after inclusion versus 87/211 (41%) before, (p < 0.0001). PRED-IdF inclusion was associated with a reduction of CRC occurrence with a CDR of 1/353 (0.3%) after inclusion versus 6/211 (2.8%) before (p = 0.012). ADR and PDR were 99/353 (28%) versus 60/211 (28.8%) (p > 0.05) and 167/353 (48.1%) versus 90/211 (42.2%) (p > 0.05), respectively after and before inclusion.

CONCLUSIONS

An optimized colonoscopic surveillance program in LS patients seems to improve colonoscopic screening quality and might possibly decrease colorectal interval cancer occurrence. Long-term cohort studies are needed to confirm these results.

Mismatch repair deficient-crypts in non-neoplastic colonic mucosa in Lynch syndrome: insights from an illustrative case

Mono-allelic germline mutations in DNA mismatch repair (MMR) genes lead to Lynch syndrome (LS). Questions remain as to the timing of the inactivation of the wild-type allele in LS-associated tumorigenesis. Speculation exists that it happens after the neoplasia has been initiated. However, a recent study reported the presence of MMR-deficiency in non-neoplastic colonic crypts in LS; thus the possibility can be raised that these crypts may be tumor precursors, and as such, biallelic loss of MMR may occur prior to neoplasia. Here we report a unique case that showed findings supporting both of the two seemingly conflicting notions. The patient was a 40-year-old female with LS, MSH2 type, who underwent a segmental colectomy for an adenocarcinoma. By immunohistochemistry, the carcinoma lost MSH2/MSH6. Interestingly, there was also complete loss of MSH2/MSH6 in a distinct focus of 20 colonic crypts that were morphologically non-neoplastic, thus supporting the possibility of biallelic loss of MMR before initiation of neoplasia. However, in a separate adenoma, MMR was preserved in neoplastic glands with low grade dysplasia and lost only in glands with high grade dysplasia, i.e., MMR loss after tumor initiation. These are relevant findings with regard to the timing of MMR deficiency in LS tumorigenesis, and bring forth the possibility that varied tumorigenic pathways may exist. Additionally, we observed that the MMR-deficient non-neoplastic crypts harbored increased intraepithelial CD8-positive T-lymphocytes similar to the patient's carcinoma, providing a potential new venue for the study of the natural antitumor immune responses in LS individuals.

Managing young colorectal cancer: a UK and Irish perspective

OBJECTIVE

Young patients with familial syndromes have an increased metachronous cancer rate. Effective management is possible by identifying this high-risk group prior to index colectomy. The study surveys the Association of Coloproctology of Great Britain and Ireland (ACPGBI) membership preoperative evaluation and clinical management in young patients with colorectal cancer (CRC).

METHOD

An electronic survey was sent to the membership of the ACPGBI. The survey polled members on clinical scenarios relating to young-onset CRC patients. We were particularly concerned with preoperative management strategies, the extent of colectomy, and postoperative surveillance. Survey responses were collated and analysed.

RESULTS

A total of 124 members responded to the survey and 74 completed the survey. Of these, 87.8 % would proceed to colectomy without preoperative tumor or genetic testing. Decisions regarding the extent of colectomy depended on family history. A total of 67 (90.6 %) would offer a limited colectomy with no family history, 49 (66.2 %) in a patient with familial CRC type X, 29 (39.2 %) in a young patient with Lynch syndrome. A similar trend was seen with young rectal cancer. Only 16 surgeons (21.6 %) could identify a syndrome of MYH-associated polyposis (MAP).

CONCLUSION

The majority of ACPGBI members will not offer preoperative risk testing based on a young age alone; however, the majority would alter their surgical strategy based on the results of this testing. MAP is poorly recognized by ACPGBI members and therefore an opportunity exists for education among members. WHAT IS NEW IN THIS PAPER?: This study is the first paper to survey the ACPGBI membership on management practices in young-onset CRC. Members are poor in adopting preoperative testing, alter surgical strategy based on a familial syndrome, with a minority recognizing MAP. An opportunity to improve education on young CRC patients exists.

Total proctocolectomy for rectal cancer in Lynch syndrome: indications and considerations

SUMMARY 

Patients with Lynch syndrome and rectal cancer present a unique clinical challenge. Management of the primary rectal cancer and prophylactic removal of the colon should be considered. In patients requiring a mesorectal excision, a combined prophylactic colon removal can be considered. Although surveillance of the colon with frequent colonoscopies is an alternative, concerns of metachronous colon cancer development support prophylactic removal of the colon as an alternative. Since data are not available to confirm superiority of either approach, the final decision is greatly dependent upon a patient's wishes and preferences. Patients interested in pursuing simultaneous prophylactic colon removal can be offered total proctocolectomy with either ileal pouch anal-anastomosis as a sphincter-preserving alternative or a total proctocolectomy with end ileostomy.

Cancer risk and overall survival in mismatch repair proficient hereditary non-polyposis colorectal cancer, Lynch syndrome and sporadic colorectal cancer

Mismatch repair proficient hereditary non-polyposis colorectal cancer (MSS-HNPCC) encloses a heterogeneous group of families consisting of different unknown genetic syndromes and/or aggregations cases. The lack of information about the hereditability of cancer risk in these families makes it difficult to carry out an individualized Genetic Counseling. Therefore, deep description of such families becomes important for a better classification and search for underlying susceptibility causes. The aim of this study is to describe and compare the clinical, morphological features, tumor KRAS status and overall survival in MSS-HNPCC, Lynch and sporadic colorectal cancer. A total of 37 MSS-HNPCC families, 50 Lynch families and 612 sporadic CRC were included. Clinical and morphological data were evaluated by reviewing medical and pathology reports of 55, 69 and 102 tumors respectively. KRAS/BRAF status were detected by allele specific real-time PCR. Standardized incidence ratios (SIR) were calculated among 602 MSS-HNPCC relatives and 668 Lynch relatives. Main features distinguishing MSS-HNPCC were diagnosis age (55.1 ± 12.6), preferential distal location (76%), polyp detection (45%) and familial colorectal cancer incidence (SIR = 6.6). In addition, we found increased incidences rates for kidney, stomach and uterus tumors. KRAS mutation rates were similar in the study populations (48.8 ± 5.8) but higher than those described before by Sanger sequencing. MSS-HNPCC overall survival was similar to Lynch in B Dukes' stage tumors and between Lynch and sporadic in C stage tumors. Anatomical and morphological data of MSS-HNPCC are consistent with other described populations. Our studies disclose an increased HNPCC-extracolonic tumors incidence and improved overall survival in MSS-HNPCC families.

Impact of chromoscopy on adenoma detection in patients with Lynch syndrome: a prospective, multicenter, blinded, tandem colonoscopy study

OBJECTIVES

In Lynch syndrome, flat and diminutive adenomas are particularly prone to malignant transformation, but they can be missed by standard colonoscopy. It is not known whether chromocolonoscopy is able to detect more adenomas than standard colonoscopy in patients with Lynch syndrome.

METHODS

We conducted a prospective, multicenter, randomized trial to compare standard colonoscopy with standard colonoscopy followed by pancolonic chromoscopy with indigo carmine in patients with a proven germline mutation in a mismatch-repair gene related to Lynch syndrome and who were undergoing screening or surveillance colonoscopy. Standard colonoscopy was used first to detect visible lesions. Colonoscopy with chromoscopy was then performed by a second gastroenterologist (blinded to the findings of the first colonoscopy) to detect additional lesions. The primary end point was the number of patients in whom at least one adenoma was detected.

RESULTS

A total of 78 eligible patients (median age, 45 years) were enrolled at 10 centers from July 2008 to August 2009. Significantly more patients with at least one adenoma were identified by chromocolonoscopy (32/78 (41%)) than by standard colonoscopy (18/78 (23%); P<0.001). The percentage of patients in whom at least one additional adenoma was detected during the chromoscopy was 31% (24/78). Overall, chromocolonoscopy plus colonoscopy detected a total of 55 adenomas in 32 patients (mean number of adenomas detected per patient: 0.7 vs. standard colonoscopy alone: 0.3; P<0.001).

CONCLUSION

The results support the proposition that chromocolonoscopy may significantly improve the detection rate of colorectal adenomas in patients undergoing screening or surveillance colonoscopy for Lynch syndrome.

Serrated neoplasia of the colon: what do we really know?

Colonoscopy offers incomplete protection from colorectal cancer, particularly in the right colon. Part of this inadequacy may be related to serrated neoplasia. Serrated polyps of the colorectum are now understood to be a heterogeneous group of polyps, some of which are cancer precursors, such as the sessile serrated adenoma (SSA) and the traditional serrated adenoma (TSA). In contrast to conventional adenomas, there is limited published literature on the epidemiology and natural history of these lesions. Furthermore, existing guidelines regarding screening and surveillance practices for these polyps are based largely on expert opinion without firm evidence. In this review, we describe the current understanding of the molecular biology, histopathology, and endoscopic features of serrated neoplasia of the colorectum, with an emphasis on aspects relevant to the practicing gastroenterologist.

Chemoprevention in Lynch syndrome

CAPP1 tested aspirin 600 mg/day and/or resistant starch 30 g/day in 200 adolescent FAP carriers. Aspirin treatment resulted in a non-significant reduction in polyp number and a significant reduction in polyp size among patients treated with aspirin for more than 1 year. CAPP2 RCT used the same interventions in 937 Lynch syndrome patients, the first RCT to have cancer prevention as the primary endpoint. Aspirin did not reduce the risk of colorectal neoplasia in a mean treatment period of 29 months but double blind post intervention follow-up has revealed 48 participants developed 53 CRCs. Per protocol analysis showed 63% fewer colon cancers with aspirin (p = 0.008) apparent from 4 years, with a similar effect on other LS cancers. Resistant starch was not beneficial at long term followup. CAPP3 will involve a double blind dose non-inferiority trial comparing 100, 300 or 600 mg daily in 3,000 gene carriers. We can now recommend aspirin in people at high risk of colorectal cancer.

Genetics, inheritance and strategies for prevention in populations at high risk of colorectal cancer (CRC)

Hereditary forms of colorectal cancer account for less than 5 % of colorectal cancer but attract disproportionate attention because they offer an opportunity for effective surgical prophylaxis, influence the health of the wider family and give insight into the critical pathways of carcinogenesis. Familial Adenomatous Polyposis (FAP) due to loss of the APC gene and Lynch syndrome or Hereditary Non-Polyposis Colon Cancer (HNPCC) due to breakdown in MisMatch Repair are the principal syndromes of broader interest and both have been the subject of chemoprevention trials. There has been a longstanding interest in non-steroidal anti inflammatories in FAP where trials have shown regression of polyps with the "pro drug"sulindac and the selective COX2 inhibitors though impact on long-term cancer risk is not confirmed. The CAPP1 trial focused on two interventions in a factorial design, aspirin and resistant starch or fermentable fibre. Resistant starch is not absorbed in the small intestine and undergoes colonic fermentation to short-chain fatty acids including butyrate which have anti-cancer effects. Polyposis registry clinicians across Europe recruited adolescents with FAP to receive aspirin (600 mg as 2 tablets/d) and/or 30 g as 2 sachets/d in a 1:1 blend of potato starch and high amylose maize starch [Hylon VII]) with placebo control for at least a year or until surgery before age 21. Fifty-nine percent (133/227) of recruits had a baseline and at least one other endoscopy. After a median of 17 months , the primary endpoint of a risk of an increased polyp number in the rectum and sigmoid colon was not significantly reduced in either treatment group with relative risks of 0.77 (aspirin; 95 % CI, 0.54-1.10;) and 1.05 (RS; 95 % CI, 0.73-1.49. The diameter of the largest polyp detected tended to be smaller in the aspirin arm. The planned subgroup analyses of patients who elected to continue on study for more than one year found a significant reduction in the size of the largest polyp in the aspirin versus non-aspirin group (p = 0.02), Mean crypt length decreased significantly over time on study in the two combined RS groups, compared with the two combined non-RS groups (p < 0.0001 for interaction), in a model of the interaction between intervention and time. In CAPP2, 1009 Lynch syndrome gene carriers were recruited from 43 international centres. 937 commenced intervention: 600 mg enteric coated aspirin and/or 30grams of the resistant starch Novelose in a 2 by 2 factorial placebo controlled design. After a mean of 29 months, intervention, there was no evidence that either agent influenced development of colonic neoplasia. However, the design included double blind follow-up for at least 10 years. After a mean of 55.7 months, and despite regular colonoscopy and polyp removal, 48 recruits developed CRC. Of these, 18 received aspirin and 30 received AP; the HR for CRC for aspirin was 0.63 (CI 0.35-1.13, p = 0.12). Five of the 48 people who developed CRC each had two primary colon cancers. Poisson regression analysis to allow for multiple primary events indicated a protective effect: IRR 0.56 (CI 0.32-0.99, p = 0.05). For those who took aspirin (or AP) for a minimum of 2 years (per protocol) the HR was 0.41 (CI 0.19-0.86 p = 0.02) and the IRR, 0.37 (CI 0.18-0.78 p = 0.008). Combined analysis of all LS cancers including CRC revealed a similar effect. On intention to treat analysis, the HR was 0.65 (CI 0.42-1.00, p = 0.05 and IRR was 0.59 (CI 0.39-0.90 p = 0.01), while the Per Protocol analysis HR was 0.45 (CI 0.26-0.79 p = 0.005,) and IRR was 0.42 (CI 0.25-0.72, p = 0.001). Adverse events in the aspirin and placebo groups were similar with 11 significant gastrointestinal bleeds or ulcers in the aspirin group and 9 in the placebo group. The evidence is now sufficient to recommend aspirin to all Lynch syndrome gene carriers. CAPP3 will recruit 3000 gene carriers into a dose inferiority study to test the relative benefits of 100mg, 300 or 600mg daily doses.

Interval colon cancer in a Lynch syndrome patient under annual colonoscopic surveillance: a case for advanced imaging techniques?

Background

Lynch syndrome confers increased risk for various malignancies, including colorectal cancer. Colonoscopic surveillance programs have led to reduced incidence of colorectal cancer and reduced mortality from colorectal cancer. Colonoscopy every 1–2 years beginning at age 20–25, or 10 years earlier than the first diagnosis of colorectal cancer in a family, with annual colonoscopy after age 40, is the recommended management for mutation carriers. Screening programs have reduced colon cancer mortality, but interval cancers may occur.

Case presentation

We describe a 48-year-old woman with Lynch syndrome who was found to have an adenoma with invasive colorectal cancer within one year after a normal colonoscopy.

Conclusion

Our patient illustrates two current concepts about Lynch syndrome: 1) adenomas are the cancer precursor and 2) such adenomas may be “aggressive,” in the sense that the adenoma progresses more readily and more rapidly to carcinoma in this setting compared to usual colorectal adenomas. Our patient’s resected tumor invaded only into submucosa and all lymph nodes were negative; in that sense, she represents a success for annual colonoscopic surveillance. Still, this case does raise the question of whether advanced imaging techniques are advisable for surveillance colonoscopy in these high-risk patients.

Long-term effect of aspirin on cancer risk in carriers of hereditary colorectal cancer: an analysis from the CAPP2 randomised controlled trial

BACKGROUND

Observational studies report reduced colorectal cancer in regular aspirin consumers. Randomised controlled trials have shown reduced risk of adenomas but none have employed prevention of colorectal cancer as a primary endpoint. The CAPP2 trial aimed to investigate the antineoplastic effects of aspirin and a resistant starch in carriers of Lynch syndrome, the major form of hereditary colorectal cancer; we now report long-term follow-up of participants randomly assigned to aspirin or placebo.

METHODS

In the CAPP2 randomised trial, carriers of Lynch syndrome were randomly assigned in a two-by-two factorial design to 600 mg aspirin or aspirin placebo or 30 g resistant starch or starch placebo, for up to 4 years. Randomisation was in blocks of 16 with provision for optional single-agent randomisation and extended postintervention double-blind follow-up; participants and investigators were masked to treatment allocation. The primary endpoint was development of colorectal cancer. Analysis was by intention to treat and per protocol. This trial is registered, ISRCTN59521990.

RESULTS

861 participants were randomly assigned to aspirin or aspirin placebo. At a mean follow-up of 55·7 months, 48 participants had developed 53 primary colorectal cancers (18 of 427 randomly assigned to aspirin, 30 of 434 to aspirin placebo). Intention-to-treat analysis of time to first colorectal cancer showed a hazard ratio (HR) of 0·63 (95% CI 0·35-1·13, p=0·12). Poisson regression taking account of multiple primary events gave an incidence rate ratio (IRR) of 0·56 (95% CI 0·32-0·99, p=0·05). For participants completing 2 years of intervention (258 aspirin, 250 aspirin placebo), per-protocol analysis yielded an HR of 0·41 (0·19-0·86, p=0·02) and an IRR of 0·37 (0·18-0·78, p=0·008). No data for adverse events were available postintervention; during the intervention, adverse events did not differ between aspirin and placebo groups.

INTERPRETATION

600 mg aspirin per day for a mean of 25 months substantially reduced cancer incidence after 55·7 months in carriers of hereditary colorectal cancer. Further studies are needed to establish the optimum dose and duration of aspirin treatment.

FUNDING

European Union; Cancer Research UK; Bayer Corporation; National Starch and Chemical Co; UK Medical Research Council; Newcastle Hospitals trustees; Cancer Council of Victoria Australia; THRIPP South Africa; The Finnish Cancer Foundation; SIAK Switzerland; Bayer Pharma.

Association between methylation in mismatch repair genes, V600E BRAF mutation and microsatellite instability in colorectal cancer patients

Colorectal cancer (CRC) corresponds to the third most prevalent type of cancer. Its origins can either be sporadic or inherited, being Lynch syndrome the most common form of hereditary CRC. The activation of BRAF oncogene, inactivation of mismatch repair genes by methylation of CpG islands, and microsatellite instability (MSI) have been reported to be involved in CRC development. The goal of the study was to characterize CRC tumors using clinical and molecular criteria through association and cluster analysis. Amsterdam II and Bethesda guidelines and molecular variables were analyzed in 77 patients from Brazil. The replication error (RER) status, based in microsatellite instability, showed association with metachronous tumor, MLH1 gene methylation and inverse association with left-sided and synchronous tumors. The PMS2 gene was considered the best predictor for differentiating levels of methylation and the mononucleotide were considered the best markers to evaluate RER status. The cluster 1 was characterized of individuals over 60 years of age, female, right-sided tumor, high microsatellite instability, and metachronous or synchronous tumors. The individuals in cluster 2 were younger than 45 years of age, male and showed left sided or rectum tumors, and microsatellite stability. Even though it was not observed a significant association, a higher number of individuals with family history of cancer and tumors without promoter methylation were found in cluster 2. The V600E mutation did not show association with clinical or molecular characteristics. Evaluation of MSI and methylation of MLH1 and PMS2 genes should be considered in order to assist with clinical diagnosis.

Genetic polymorphisms of CYP17A1, vitamin D receptor and androgen receptor in Italian heredo-familial and sporadic prostate cancers

BACKGROUND

Searching for genetic and environmental factors predisposing to prostate cancer, common single-nucleotide polymorphisms in CYP17A1, CYP19A1, VDR genes, and the number of CAG repeats from AR were investigated in Italian heredo-familial prostate cancer (HFPC) patients controlled for dietary intake and life style habits.

METHODS

We evaluated differences between HFPC and sporadic cancers, in the pattern of common single-nucleotide polymorphisms in CYP17A1, CYP19A1, VDR genes, and the CAG repeat from AR, controlling for dietary intake and lifestyle habits in a regionwide population. Ninety-five patients with HFPC were identified and 378 sporadic prostate cancers were randomly selected as controls. Dietary intake and lifestyle habits were determined through self-administered questionnaires in all patients. Genotyping of polymorphisms for CYP17A1, CYP19A1, VDR, and the CAG repeat from AR was carried out using pyrosequencing.

RESULTS

HFPC cases were significantly younger than controls, whereas similar proportions of localized tumours, favourable histology, and abnormal prostate serum antigen levels (4-19 ng/ml) were detected in the two groups. A statistically evident gene-gene interaction was found: a 5-fold higher probability [odds ratio (OR)=4.83; 95% confidence interval (CI): 1.37-17.02] of HFPC was observed in the subgroup profiling VDR1 T/T genotypes coupled with VDR2 T/T genotype. Among nutrients, an increase in HFPC risk (OR=3.14; 95% CI: 1.12-8.81) was found only for zinc, when associated with the VDR2 T/T genotype.

CONCLUSIONS

Significant evidence for positive interactions between VDR1 and VDR2 genotypes was demonstrated, suggesting that high-risk multigenic polymorphism profiles could variously sustain HFPC tumorigenesis.

Current hypotheses on how microsatellite instability leads to enhanced survival of Lynch Syndrome patients

High levels of microsatellite instability (MSI-high) are a cardinal feature of colorectal tumors from patients with Lynch Syndrome. Other key characteristics of Lynch Syndrome are that these patients experience fewer metastases and have enhanced survival when compared to patients diagnosed with microsatellite stable (MSS) colorectal cancer. Many of the characteristics associated with Lynch Syndrome including enhanced survival are also observed in patients with sporadic MSI-high colorectal cancer. In this review we will present the current state of knowledge regarding the mechanisms that are utilized by the host to control colorectal cancer in Lynch Syndrome and why these same mechanisms fail in MSS colorectal cancers.

Adenoma-infiltrating lymphocytes (AILs) are a potential marker of hereditary nonpolyposis colorectal cancer

Patients with hereditary nonpolyposis colorectal cancer syndrome (HNPCC) develop microsatellite-unstable colorectal cancers that tend to be more proximally located and are histologically more likely to show high numbers of tumor-infiltrating lymphocytes, a lack of dirty necrosis, mucinous or poor differentiation, and a Crohn-like host immune response, when compared with microsatellite-stable cancers. However, histologic features that are characteristic of and can perhaps distinguish colorectal adenomas in HNPCC patients from those occurring in the general population have not been previously reported. We compared 16 adenomas endoscopically removed from patients with genetically proven HNPCC to 32 control adenomas, group-matched for patient age and sex, along with endoscopic size, shape, anatomic location, and presence of high-grade dysplasia. Adenomas from HNPCC patients were more likely to contain high numbers of adenoma-infiltrating lymphocytes (AILs) with 12 of 16 (75%) adenomas having >or=5 AILs per high-power field (HPF) as opposed to 4 of 32 (12%) adenomas in the control group (P=0.00003). HNPCC adenomas were also less likely to contain increased numbers of apoptotic bodies: 7 of 16 (44%) contained >or=5 apoptoses per HPF, compared with 27 of 36 (84%) control adenomas (P=0.006). The presence of necrosis or serrated architecture, percent villous component, and numbers of mitotic figures per HPF did not differ significantly between the 2 groups. Therefore, increased numbers of AILs and decreased numbers of apoptoses in colorectal adenomas are simple and inexpensive markers that raise the possibility of HNPCC.

Prevalence of adenomas and hyperplastic polyps in mismatch repair mutation carriers among CAPP2 participants: report by the colorectal adenoma/carcinoma prevention programme 2

PURPOSE

To determine the prevalence of adenomatous and hyperplastic polyps in a large cohort of individuals with a germline mutation in a mismatch repair (MMR) gene, the major genetic determinant of hereditary nonpolyposis colorectal cancer (HNPCC). These prevalences have been estimated previously in smaller studies, and the results have been found to be variable.

PATIENTS AND METHODS

Colorectal Adenoma/Carcinoma Prevention Programme 2 trial is a chemoprevention trial in people classified as having HNPCC. The 695 patients with a proven germline MMR mutation and documented screening history before the chemoprevention study were the focus of this study. The number, histology, size, and location of polyps found at the participants' first ever colonoscopy were analyzed in a cross-sectional study.

RESULTS

Seventy-four patients (10.6%) were found to have at least one adenoma at first colonoscopy, whereas 37 (5.3%) had at least one hyperplastic polyp. The frequency of an adenoma at first colonoscopy increased from 5.0% (95% CI, 2.8% to 8.3%) in patients younger than 35 years old to 18.9% (95% CI, 9.4% to 32.0%) in patients age at least 55 years (P = .0001 for trend). No such trend was observed for hyperplastic polyps. No sex differences were found for either type of polyp. A marginal association was found between the co-occurrence of adenomas and hyperplastic polyps. Adenomas tended to be more proximally distributed through the colon, whereas hyperplastic polyps tended to be located in the distal colon.

CONCLUSION

Adenoma prevalence increases with age among MMR mutation carriers, whereas hyperplastic polyp prevalence is consistent. No sex differences were observed for either type of lesion.

Sporadic and syndromic hyperplastic polyps and serrated adenomas of the colon: classification, molecular genetics, natural history, and clinical management

There is now strong evidence for an alternative pathway of colorectal carcinogenesis implicating hyperplastic polyps and serrated adenomas. This article briefly reviews the evidence for this serrated pathway, provides diagnostic criteria for clinically significant hyperplastic polyps and allied serrated polyps, and suggests how this information may be translated into safe, effective guidelines for colonoscopy-based colon cancer prevention. Consideration also is given to the definition and management of hyperplastic polyposis syndrome. The currently proposed management plan for serrated polyps is tentative because of incomplete knowledge of the nature and behavior of these polyps. This article highlights key areas warranting further research.

Utility of computed tomographic colonography in surveillance for hereditary nonpolyposis colorectal cancer syndrome

Computed tomographic colonography (CTC) is suggested to be an alternative to colonoscopy as a surveillance tool in subjects with a high risk for colorectal cancer (CRC). To evaluate the utility of CTC we successively examined 78 subjects, all with a DNA mismatch repair gene mutation, by CTC and colonoscopy. We detected altogether 37 polyps or tumors in 28 subjects (prevalence 35.9%), adenomas in 13 subjects (16.7%), CRC in two (2.6%), and hyperplastic polyps in 13 (16.7%). A great majority of the polyps were diminutive. The per-patient sensitivity for detecting all lesions with CTC was 0.25 and 0.29 by two radiologists and the specificities 0.82 and 0.76. For lesions of 10 mm or larger the sensitivities were 0.6 and 1.0 and the specificities 0.96 by each examiner. Each diagnosed the two cancers correctly. We concluded that CTC has an acceptable accuracy for large lesions in the colon but the detection rate for small polyps is not comparable to that in colonoscopy. Therefore CTC remains a second choice in surveillance for use when colonoscopy for some reason is incomplete or unsuitable.

Prevention of colorectal cancer by colonoscopic surveillance in families with hereditary colorectal cancer

OBJECTIVE

In recent years persons at risk for colorectal cancers (CRC) have been subjected to follow-up with colonoscopy in many centres. There is, however, limited knowledge about the effect of such interventions. The objective of this study was to report the results of our observations during the past 15 years.

MATERIAL AND METHODS

Healthy persons were included in the study according to their family history of CRCs, and prospectively followed with colonoscopies.

RESULTS

Altogether, 1133 individuals were included and observed for a total of 3474 follow-up years from the first to the last colonoscopy initiated by our activity. Mismatch repair (MMR) mutations were detected in 6.5% of cases. A total of 1383 polyps were removed, 72% were less than 5 mm in diameter. Findings were scored as hyperplastic polyps (n=887), adenomas with mild to moderate dysplasia (n=460), adenomas with high-grade dysplasia (n=30) and cancers (n=6). Two cancers were observed after the first colonoscopy, compared with 2.6 expected by chance and more than 20 expected under the hypothesis of predominant inherited diseases in the families. Observed annual incidence rates for adenomas were similar in all groups, while in the mutation carriers there was a higher frequency of progression to severe dysplasia or infiltrating cancer.

CONCLUSIONS

A simple explanation for the combined findings may be that all selected families had a similar tendency to produce adenomas, while mutation carriers more frequently demonstrated dysplasia/cancer in the adenomas. The low annual incidence rates for CRC indicated that the removal of adenomas may have prevented cancers.

Serrated polyps of the large intestine

Serrated polyps of the large intestine comprise a family of lesions bearing some histological similarities, including an overall serrated configuration caused at least in part by inhibition of apoptosis by mutations in one of two genes. Over the past decade, it has become apparent that these lesions can be subdivided by histological criteria into lesions with differing degrees of relationship to the development of carcinoma, including sporadic microsatellite instable (MSI) carcinomas and probably carcinomas demonstrating the CpG island methylator phenotype (CIMP), which includes both MSI and microsatellite stable tumors. These differing histological subtypes can in part predict some of the molecular features of these lesions, and the combination of histological and molecular features is beginning to give us better insight into the potential natural history and therefore management of these lesions. This review will present the histological classification of these lesions, relate that histological classification to molecular aspects of the lesions, and present recommendations for management.

Allele-specific loss of heterozygosity in multiple colorectal adenomas: toward an integrated molecular cytogenetic map II

Colorectal cancer (CRC) remains a significant public health challenge despite our increased understanding of the genetic defects underlying the pathogenesis of this common disease. It has been thought that multiple mechanisms lead to the malignant phenotype, with familial predisposition syndromes accounting for only a small proportion of all CRC cases. To identify additional loci likely involved in CRC and to test the hypothesis of allele-specific loss of heterozygosity (LOH) for the localization of CRC susceptibility genes, we initially conducted a genome-wide allelotyping analysis of 48 adenomas from a patient with familial adenomatous polyposis coli (FAP) and 63 adenomas from 7 patients with sporadic CRC using 79 fluorescently tagged oligonucleotide primers amplifying microsatellite loci covering the human genome. Frequent allelic losses were identified at D17S802 (41%), D7S518 (40%), D18S53 (38%), D10S249 (32%), D2S391 (29%), D16S419 (27%), D15S1005 and D15S120 (24%), D9S274 and D11S1318 (23%), D14S65 (20%), D14S274 and D17S953 (19%), D19S424 (18%), D5S346 and D1S397 (15%), and D6S468 (13%) in multiple FAP adenomas. Common LOH was also detected at D4S1584 (42%), D11S968 (31%), D17S953 (28%), D5S394, D9S286 and D10S249 (24%), D8S511 (23%), D13S158 (21%), D7S669 (20%), D18S58 (19%), D2S162 and D16S432 (16%), D2S206 (15%), D7S496 and D17S946 (14%), D6S292 (13%), D4S1586 and D8S283 (11%), and D1S2766 (10%) in multiple CRC adenomas. In addition, allele-specific LOH at D5S346, D15S1005, and D15S120 was observed in multiple FAP adenomas (P < 0.01) and at D2S206 and D16S423 in multiple CRC (P < 0.05). To compare our data to previous reports, we determined the band-specific frequency of chromosomal imbalances in CRC karyotypes reported in the Mitelman database, and from the CGH results of cases accessible through the PROGENETIX website. Furthermore, published genome-wide allelotyping analysis of CRC and other allele-specific LOH studies were compiled and collated with our LOH data. The combined results not only provide a comprehensive view of genetic losses in CRC, indicating the comparability of these different techniques, but they also reveal different novel loci in multiple adenomas from FAP and sporadic CRC patients, suggesting that they represent a distinct subtype of CRC in terms of allelic losses. Allele-specific LOH is an alternative approach for cancer gene mapping.

Use of microsatellite instability and immunohistochemistry testing for the identification of individuals at risk for Lynch syndrome

It is now generally recognized that a specific subset of those patients clinically defined as having hereditary non polyposis colon cancer (HNPCC) have germline mutations in any one of several genes involved in DNA mismatch repair (MMR). This important subset of HNPCC families is now defined as having Lynch syndrome. A considerable amount of data has shown that tumors from patients with Lynch syndrome have characteristic features resulting from the underlying molecular involvement of defective MMR, that is, the presence of microsatellite instability (MSI) and the absence of MMR protein expression by immunohistochemistry (IHC). As a result, identifying patients with Lynch syndrome can now be accomplished by testing tumors for these tumor-related changes. Together, MSI and IHC are powerful tools that help identify individuals at risk for having Lynch syndrome and to distinguish these cases from HNPCC cases with other hereditary gene defects. Furthermore, IHC analysis provides valuable clues as to which MMR gene is mutated, allowing for comprehensive mutational analyses of that gene. Here, we discuss the current and historical perspectives regarding MSI and IHC analyses in tumors from sporadic colon cancer and from patients with Lynch syndrome. Given this background, we also provide a testing strategy for the identification of patients at risk for Lynch syndrome and subsequent gene testing.

Prevention of colorectal cancer by colonoscopic surveillance in individuals with a family history of colorectal cancer: 16 year, prospective, follow-up study

OBJECTIVE

To determine to what extent individuals with various family histories of colorectal cancer (from one to three or more affected first degree relatives) benefit from colonoscopic surveillance.

DESIGN

Prospective, observational study of high risk families, followed up over 16 years.

SETTING

Tertiary referral family cancer clinic in London.

PARTICIPANTS

1678 individuals from families registered with the clinic. Individuals were classified according to the strength of their family history: hereditary non-polyposis colorectal cancer (if they fulfilled the Amsterdam criteria), and one, two, or three affected first degree relatives (moderate risk).

INTERVENTIONS

Colonoscopy was initially offered at five year intervals or three year intervals if an adenoma was detected.

MAIN OUTCOME MEASURES

The incidence of adenomas with high risk pathological features or cancer. This was analysed by age, the extent of the family history, and findings on previous colonoscopies. The cohort was flagged for cancer and death. Incidence of colorectal cancer and mortality during over 15,000 person years of follow-up were compared with those expected in the absence of surveillance.

RESULTS

High risk adenomas and cancer were most common in families with hereditary non-polyposis colorectal cancer (on initial colonoscopy 5.7% and 0.9%, respectively). In the families with moderate risk, these findings were particularly uncommon under age 45 (1.1% and 0%) and on follow-up colonoscopy if advanced neoplasia was absent initially (1.7% and 0.1%). The incidence of colorectal cancer was substantially lower-80% in families with moderate risk (P = 0.00004), and 43% in families with hereditary non-polyposis colorectal cancer (P = 0.06)-than the expected incidence in the absence of surveillance when the family history was taken into account.

CONCLUSIONS

Colonoscopic surveillance reduces the risk of colorectal cancer in people with a strong family history. This study confirms that members of families with hereditary non-polyposis colorectal cancer require surveillance with short intervals. Individuals with a lesser family history may not require surveillance under age 45, and if advanced neoplasia is absent on initial colonoscopy, surveillance intervals may be lengthened. This would reduce the demand for colonoscopic surveillance.

Refining the Amsterdam Criteria and Bethesda Guidelines: testing algorithms for the prediction of mismatch repair mutation status in the familial cancer clinic

PURPOSE

Hereditary nonpolyposis colon cancer (HNPCC) is a Mendelian dominant syndrome of bowel, endometrial, and other cancers and results from germline mutations in mismatch repair (MMR) genes. HNPCC is now best diagnosed on molecular grounds using MMR mutation screening, aided by microsatellite instability (MSI) and immunohistochemistry in tumors. Selection of families for molecular investigation of HNPCC is usually based on suboptimal methods (Amsterdam Criteria or Bethesda Guidelines), but these can be improved using additional clinical data (mean ages of affected persons and presence of endometrial cancer) in a quantitative model.

METHODS

We have verified the performance of the Wijnen model and have shown that it remains valid when HNPCC is diagnosed using mutation screening, MSI, and immunohistochemistry. We have also set up and verified our own models (Amsterdam-plus and Alternative), which perform at least as well as the Wijnen model.

RESULTS

The Amsterdam-plus model improves on the Amsterdam Criteria by using five extra variables (numbers of colorectal and endometrial cancers in the family, number of patients with five or more adenomas, number with more than one primary cancer of the colorectum or endometrium, and mean age of presentation) and performs better than the Wijnen model. The Alternative model avoids the need to evaluate the Amsterdam Criteria and performs nearly as well as the other models.

CONCLUSION

We believe that a quantitative model, such as the Amsterdam-plus model, should be the first choice for selecting families or patients for evaluation of HNPCC using molecular tests. We present an algorithm for this process.

Genetic predisposition to cancer - insights from population genetics

Individuals differ in their inherited tendency to develop cancer. Major single-gene defects that cause early cancer onset have been known for many years from their inheritance patterns, and inherited defects that have weaker effects on predisposition were also suspected to exist. Recent progress in cancer genetics has identified specific loci that are involved in cancer progression, many of which have key roles in DNA repair, cell-cycle control and cell-death pathways. Those loci, which are often mutated somatically during cancer progression, sometimes also contain inherited mutations. Recent genetic studies and quantitative population-genetic analyses provide a framework for understanding the frequency of inherited mutations and the consequences of these mutations for increased predisposition to cancer.

Multiple colorectal adenomas, classic adenomatous polyposis, and germ-line mutations in MYH

BACKGROUND

Germ-line mutations in the base-excision-repair gene MYH have been associated with recessive inheritance of multiple colorectal adenomas. Tumors from affected persons displayed excess somatic transversions of a guanine-cytosine pair to a thymine-adenine pair (G:C-->T:A) in the APC gene.

METHODS

We screened for germ-line MYH mutations in 152 patients with multiple (3 to 100) colorectal adenomas and 107 APC-mutation-negative probands with classic familial adenomatous polyposis (>100 adenomas). Subgroups were analyzed for changes in the related genes MTH1 and OGG1. Adenomas were tested for somatic APC mutations.

RESULTS

Six patients with multiple adenomas and eight patients with polyposis had biallelic germline MYH variants. Missense and protein-truncating mutations were found, and the spectrums of mutations were very similar in the two groups of patients. In the tumors of carriers of biallelic mutations, all somatic APC mutations were G:C-->T:A transversions. In the group with multiple adenomas, about one third of patients with more than 15 adenomas had biallelic MYH mutations. In the polyposis group, no patient with biallelic MYH mutations had severe disease (>1000 adenomas), but three had extracolonic disease. No clearly pathogenic MTH1 or OGG1 mutations were identified.

CONCLUSIONS

Germ-line MYH mutations predispose persons to a recessive phenotype, multiple adenomas, or polyposis coli. For patients with about 15 or more colorectal adenomas--especially if no germ-line APC mutation has been identified and the family history is compatible with recessive inheritance--genetic testing of MYH is indicated for diagnosis and calculation of the level of risk in relatives. Clinical care of patients with biallelic MYH mutations should be similar to that of patients with classic or attenuated familial adenomatous polyposis.

Pathogenesis and clinical management of hereditary non-polyposis colorectal cancer

BACKGROUND

Hereditary non-polyposis colorectal cancer (HNPCC) is an inherited genetic condition associated with microsatellite instability; it accounts for around 5 per cent of all cases of colorectal cancer. This review examines recent data on management strategies for this condition.

METHODS

A Medline-based literature search was performed using the keywords 'HNPCC' and 'microsatellite instability'. Additional original papers were obtained from citations in articles identified by the initial search.

RESULTS AND CONCLUSION

The Amsterdam criteria identify patients in whom the presence of an inherited mutation should be investigated. Those with a mutation should be offered counselling and screening. The role of prophylactic surgery has been superseded by regular colonoscopy, which dramatically reduces the risk of colorectal cancer. Screening for extracolonic malignancy is also advocated, but the benefits are uncertain. Chemoprevention may be of value in lowering the incidence of bowel cancer in affected patients, but further studies are required.

Emerging concepts in colorectal neoplasia

An understanding of the mechanisms that explain the initiation and early evolution of colorectal cancer should facilitate the development of new approaches to effective prevention and intervention. This review highlights deficiencies in the current model for colorectal neoplasia in which APC mutation is placed at the point of initiation. Other genes implicated in the regulation of apoptosis and DNA repair may underlie the early development of colorectal cancer. Inactivation of these genes may occur not by mutation or loss but through silencing mediated by methylation of the gene's promoter region. hMLH1 and MGMT are examples of DNA repair genes that are silenced by methylation. Loss of expression of hMLH1 and MGMT protein has been demonstrated immunohistochemically in serrated polyps. Multiple lines of evidence point to a "serrated" pathway of neoplasia that is driven by inhibition of apoptosis and the subsequent inactivation of DNA repair genes by promoter methylation. The earliest lesions in this pathway are aberrant crypt foci (ACF). These may develop into hyperplastic polyps or transform while still of microscopic size into admixed polyps, serrated adenomas, or traditional adenomas. Cancers developing from these lesions may show high- or low-level microsatellite instability (MSI-H and MSI-L, respectively) or may be microsatellite stable (MSS). The suggested clinical model for this alternative pathway is the condition hyperplastic polyposis. If colorectal cancer is a heterogeneous disease comprising discrete subsets that evolve through different pathways, it is evident that these subsets will need to be studied individually in the future.

Molecular and cellular biology of pre-malignancy in the gastrointestinal tract

Important pathogenic alterations within established cancers are acquired during the pre-malignant stage. These genetic alterations can be grouped into specific neoplastic pathways that differ within and between anatomical sites. By understanding the mechanisms that determine the initiation and progression of each pathway, it will be possible to develop novel approaches to the diagnosis, prevention and treatment of cancer. This chapter outlines the principles underlying the molecular characterization of pre-malignant lesions, taking colorectal neoplasia as the main model.

Serrated route to colorectal cancer: back street or super highway?

Morphological and molecular studies are beginning to distinguish separate evolutionary pathways for colorectal cancer. The serrated pathway encompassing hyperplastic aberrant crypt foci, hyperplastic polyps, mixed polyps, and serrated adenoma is increasingly being linked with genetic alterations, including DNA methylation, DNA microsatellite instability, K-ras mutation, and loss of chromosome 1p. The importance of the serrated pathway has been underestimated in terms of its frequency and potential for rapid progression.

Microsatellite instability in adenomas as a marker for hereditary nonpolyposis colorectal cancer

Hereditary nonpolyposis colorectal cancer (HNPCC) is the most common of the well-defined colorectal cancer syndromes, accounting for at least 2% of the total colorectal cancer burden and carrying a greater than 80% lifetime risk of cancer. Significant reduction in cancer morbidity and mortality can be accomplished by appropriate clinical cancer screening of HNPCC patients with mutations in mismatch repair (MMR) genes. Thus, it is desirable to identify individuals who are mutation-positive. In individuals with cancer, mutation detection can be accomplished relatively efficiently by germline mutation analysis of individuals whose cancers show microsatellite instability (MSI). This study was designed to assess the feasibility of screening colorectal adenoma patients for HNPCC in the same manner. Among 378 adenoma patients, six (1.6%) had at least one MSI adenoma. Five out of the six patients (83%) had a germline MMR gene mutation. We conclude that MSI analysis is a useful method of prescreening colorectal adenoma patients for HNPCC.

Broadsheet number 52: Molecular genetics of colorectal cancer

The molecular genetics of colorectal cancer is presented in an order that ascends from the basic to the applied: molecular mechanisms, morphogenesis, classification and diagnosis. Major consideration is given to the nature of genetic instability and the role of this mechanism in driving neoplastic progression. It is shown how the fundamental principle of genetic instability cuts across applied research, tissue diagnosis and clinical management with respect to both sporadic and inherited forms of colorectal cancer.

Inherited susceptibility to colorectal adenomas and carcinomas: evidence for a new predisposition gene on 15q14-q22

BACKGROUND & AIMS

The aim of this study was to evaluate the role of known colorectal adenoma and carcinoma susceptibility genes and to locate a novel susceptibility gene in an Ashkenazi family (SM1311) with dominantly inherited predisposition to colorectal adenomas and carcinomas.

METHODS

Clinicopathologic and family history data were collected. Genetic linkage and mutational analyses were used to investigate the genetic basis of the family's disease.

RESULTS

Affected members of SM1311 develop multiple tubular, villous, tubulovillous, and/or serrated colorectal adenomas throughout the large bowel, and some develop colon carcinoma. There are no extracolonic features clearly associated with disease in SM1311. We have shown that the family's phenotype does not result from APC mutations (including the I1307K variant) or from genetic changes in the other known genes that predispose to colon cancer. Using genetic linkage analysis, supplemented by allele loss in tumors, we have provided evidence for a new colorectal cancer susceptibility gene, CRAC1 (colorectal adenoma and carcinoma), mapping to chromosome 15q14-q22.

CONCLUSIONS

We provide evidence for a novel colorectal adenoma and carcinoma susceptibility gene on chromosome 15q14-q22. Further studies are needed to confirm this localization and to evaluate the contribution of CRAC1 to this disease.

Rectal cancer after sulindac therapy for a sporadic adenomatous colonic polyp

Like adenomatous polyps in familial adenomatous polyposis, some sporadic colorectal polyps have been reported to regress in response to sulindac administration. However, a rapidly growing invasive rectal cancer developed in one of 15 patients with sulindac-treated sporadic adenomatous colorectal polyps 16 months after sulindac treatment. In this patient, both the adenomatous polyp that responded partially to sulindac and the rectal cancer developing after sulindac therapy showed immunostaining for cyclooxygenase-2. Although short term sulindac therapy seems to be able to cause some adenomatous colorectal polyps to regress, 4 months of sulindac therapy may not reliably prevent colorectal cancer development in these patients.

Diagnosis of hereditary non-polyposis colorectal cancer

The term hereditary non-polyposis colorectal cancer (HNPCC) was introduced initially to encompass autosomal dominant syndromes predisposing to colorectal cancer other than the polyposes. The term is a poor descriptor and is often applied to families on the basis of inadequate information. It is suggested that 'hereditary mismatch repair deficiency syndrome' (HMRDS) should replace the term HNPCC for describing the specific autosomal dominant condition which predisposes to cancer displaying the mutator phenotype. Population-based studies have shown that HMRDS probably accounts for no more than 2% of bowel cancer. A working diagnosis of HMRDS can be made on the basis of clinical, pathological and molecular characteristics. The histopathologist has an important role to play in the recognition and diagnosis of HMRDS. The characteristic morphology of colorectal cancer in HMRDS is reviewed and the diagnostic utility of 'field changes' and adenomas is discussed critically.

Colon polyps

Colon polyps may be single or multiple, noninherited or inherited, histologically may vary from inflammatory, hamartomatous, neurogenic, or adenomatous, and may be benign or malignant. The various recognized syndromes are discussed including their clinical presentation, malignant potential, and associated tumors. Recognition of these clinical syndromes will allow the clinician to categorize the patient and the relative risk. The discussion goes into the genetic studies identifying the adenomatous polyposis coli gene on chromosome 5 q21 and the identification of mutations arising in the DNA repair genes (MSA2, MLH1, PMSI, and M52) in the HNPCC syndrome. This identified two divergent pathologies, both involving "multiple hits" with mucosal cells going from normal to adenoma-dysplasia-carcinoma. The understanding of the multiple hit concept with the adenoma-dysplasia-carcinoma progression will aid in the further understanding of the broad neoplastic process.

Hereditary nonpolyposis colorectal cancer (Lynch syndrome). An updated review

BACKGROUND

Hereditary nonpolyposis colorectal cancer (HNPCC) dates to Aldred Warthin's description of Family G a century ago. The phenotype features an excess of early onset colorectal carcinoma (CRC) with a propensity to involve the proximal colon, and a variety of extracolonic cancers, particularly carcinoma of the endometrium, ovary, stomach, small bowel, ureter, and renal pelvis. The recent discovery that HNPCC patients carry germline mutations in DNA mismatch repair genes has engendered great interest in the syndrome.

METHODS

This is a description of HNPCC based on the authors' experience with more than 170 families and a review of the world literature.

RESULTS

This review describes the genotypic and phenotypic features of HNPCC. The distinctive natural history of the syndrome is discussed in light of the recent discovery that ineffective DNA mismatch repair is the principal abnormality in affected individuals.

CONCLUSIONS

Clinical and molecular genetic knowledge about HNPCC is now available to physicians, and should enable them to provide highly targeted surveillance and management for patients with a high cancer risk. Genetic counseling can prove lifesaving. The study of HNPCC will likely contribute to knowledge about the causes and control of common forms of cancer in the general population.

Colorectal neoplasms detected colonoscopically in at-risk members of colorectal cancer families stratified by the demonstration of DNA microsatellite instability

This study compared colonoscopic findings in families meeting the Amsterdam criteria (A) for hereditary non-polyposis colorectal cancer (HNPCC) but stratified according to whether the familial cancers showed DNA microsatellite instability. DNA was extracted from paired samples of normal and cancer, and microsatellite instability was analysed at up to six loci. Families were termed replication error positive (RER+) when at least 50% of tumours tested per family were positive. Of 26 families studied 17 were RER+ and 9 were RER-. Cancers in the A/RER- families showed no right-sided predilection (P < 0.001). Colonoscopies have been performed on 182 at-risk members of A/RER+ families and 60 members of A/RER- families. More of the at-risk members of A/RER-families were found to have adenomas at colonoscopy (P = 0.095), but these were smaller than those of A/RER+ families (P = 0.19). The adenoma:carcinoma ratio was twice as high in A/RER- families (13:1) as in A/RER+ families (7:1). One of the A/RER- families had hyperplastic polyposis. The others do not appear to have attenuated familial adenomatous polyposis and are similar to the adenoma families or late-onset colorectal cancer families described by others. This study illustrates the importance of molecular technology in separating HNPCC from syndromes with overlapping phenotypes.