A thirty-year follow-up surveillance study for neoplasia of a dutch ulcerative colitis cohort

BACKGROUND

Patients with ulcerative colitis have an increased risk of developing colorectal cancer (CRC). The aim of this study is to assess the yield of surveillance colonoscopies in a tertiary referral cohort of ulcerative colitis patients and to identify different risk groups for dysplasia.

METHODS

A cohort of 293 patients (148 males, mean age 33.8 years at diagnosis) was built up at our center and started the surveillance program 8-12 years after start of symptoms. They underwent colonoscopies every one to three years. Endpoints were dysplasia or a (sub)total colectomy.

RESULTS

After a follow-up period of 10 years, the cumulative incidence of any dysplasia was 23.5%, and of CRC 4.0%. After 15 years these percentages were 33.3% and 6.8%. Patients with pancolitis (n = 178) had a significantly higher cumulative risk of dysplasia than patients with distal disease, HR 1.9 (95%CI 1.1-3.3). Patients who started surveillance at an older age are at increased risk for any dysplasia, HR 1.03 (95%CI 1.01-1.05).

CONCLUSIONS

This prospective surveillance study shows a high yield of dysplasia in ulcerative colitis patients. We recommend developing separate surveillance programs for different risk groups. In our opinion patients with distal colitis can follow the general population surveillance program.

MSH2 mutation carriers are at higher risk of cancer than MLH1 mutation carriers: a study of hereditary nonpolyposis colorectal cancer families

PURPOSE

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant disease characterized by the clustering of colorectal cancer, endometrial cancer, and various other cancers. The disease is caused by mutations in DNA-mismatch-repair (MMR) genes, most frequently in MLH1, MSH2, and MSH6. The aims of the present study were to compare the risk of developing colorectal, endometrial, and other cancers between families with the various MMR-gene mutations.

PATIENTS AND METHODS

Clinical and pathologic data were collected from 138 families with HNPCC. Mutation analyses were performed for all families. Survival analysis was used to calculate the cumulative risk of developing cancer in the various subsets of relatives.

RESULTS

Mutations were identified in 79 families: 34 in MLH1, 40 in MSH2, and five in MSH6. The lifetime risk of developing cancer at any site was significantly higher for MSH2 mutation carriers than for MLH1 mutation carriers (P < .01). The risk of developing colorectal or endometrial cancer was higher in MSH2 mutation carriers than in MLH1 mutation carriers, but the difference was not significant (P = .13 and P = .057, respectively). MSH2 mutation carriers were found to have a significantly higher risk of developing cancer of the urinary tract (P < .05). The risk of developing cancer of the ovaries, stomach, and brain was also higher in the MSH2 mutation carriers than in the MLH1 mutation carriers, but the difference was not statistically significant.

CONCLUSION

Pending large prospective studies, the extension of the current surveillance program in MSH2 mutation carriers with the inclusion of the urinary tract should be considered.

[Frequency of duodenal adenomas in patients with familial adenomatous polyposis]

OBJECTIVE

To estimate the prevalence of polyps in the stomach and duodenum in patients with familial adenomatous polyposis (FAP), and to examine the relationship between age and severity of duodenal adenomatosis.

DESIGN

Retrospective.

METHOD

Using the FAP-registry of the Netherlands Foundation for the Detection of Hereditary Tumours, data were obtained from patients who had undergone a gastroduodenoscopy before 1 July 1999. The endoscopic and histological findings were used to classify the duodenal adenomas according to the Spigelman classification.

RESULTS

224 patients had undergone at least one gastroduodenoscopy: 117 men and 107 women with a mean age at the time of the first endoscopy of 37 years (range: 13-78). Fundic gland polyposis was detected in 79 patients (35%), stomach adenomas in 6 patients (3%) and duodenal adenomas in 92 patients (41%). A total of 21 patients (9%) had severe duodenal adenomatosis (Spigelman III or IV). Duodenal adenomatosis was often more severe if the patient was older. Ten patients were known to have duodenal cancer; the mean age at diagnosis was 50.3 years (range: 39-67).

CONCLUSION

Nearly 10% of the patients with FAP had developed severe duodenal adenomatosis. The severity of duodenal adenomatosis was related to the patient's age.

Decision analysis in the surgical treatment of patients with familial adenomatous polyposis: a Dutch-Scandinavian collaborative study including 659 patients

BACKGROUND AND AIMS

The choice of colorectal surgery in patients with familial adenomatous polyposis lies between the morbidity of proctocolectomy and ileum-pouch-anal anastomosis (IPAA) and the mortality from rectal cancer after total colectomy and ileorectal anastomosis (IRA). The aims of the present study were: (1) to assess the risk of dying from rectal cancer after IRA, (2) to compare the life expectancy between patients with an IRA and those with an IPAA, and (3) to investigate whether regular endoscopic examination of the rectum leads to detection of cancer at an earlier stage.

METHODS

Clinical and pathological data on 659 patients who underwent colectomy and ileorectal anastomosis were collected from four national polyposis registries-that is, in Denmark, Finland, Sweden, and the Netherlands. Data were analysed using survival analysis methods. Decision analysis was used to compare the life expectancy between patients with an IRA and those with an IPAA.

RESULTS

A total of 47 patients developed rectal cancer after IRA. The risk of dying from rectal cancer was 12.5% (95% confidence interval 7.1--17.9%) by age 65. Compared with IRA, IPAA would lead to an increase in life expectancy of 1.8 years. Seventy five per cent of patients with rectal cancer had a negative rectoscopy within 12 months before the diagnosis.

CONCLUSION

IRA is associated with substantial mortality due to rectal cancer. Follow up examinations of the rectum does not have sufficient preventive effect on morbidity and mortality of rectal cancer.

The clinical features of ovarian cancer in hereditary nonpolyposis colorectal cancer

OBJECTIVE

Hereditary nonpolyposis colorectal cancer (HNPCC) is a hereditary cancer susceptibility disorder associated with a very high risk for carcinoma of the colon and an elevated risk for certain extracolonic cancers including ovarian cancer. Our aim in this study was to describe the clinicopathologic features of ovarian cancer in HNPCC family members.

METHODS

. Members of the International Collaborative Group on HNPCC collected retrospective data on 80 ovarian cancer patients who were members of HNPCC families, including 31 known mutation carriers, 35 presumptive carriers (by colorectal/endometrial cancer status), and 14 at-risk family members.

RESULTS

Mean age at diagnosis of ovarian cancer was 42.7. Nonepithelial tumors made up only 6.4% of the cancers, and borderline tumors comprised just 4.1% of the epithelial cancers. Among frankly malignant epithelial cases, most cancers were well or moderately differentiated, and 85% were FIGO stage I or II at diagnosis. Synchronous endometrial cancer was reported in 21.5% of cases.

CONCLUSIONS

Ovarian cancer in HNPCC differs from ovarian cancer in the general population in several clinically important respects. It occurs at a markedly earlier age. It is more likely to be epithelial. If it is a frankly invasive epithelial cancer, it is more likely to be well or moderately differentiated. HNPCC patients with ovarian cancer are more likely to have a synchronous endometrial cancer than other ovarian cancer patients and are more likely to be diagnosed at an early stage.

Atypical HNPCC owing to MSH6 germline mutations: analysis of a large Dutch pedigree

Hereditary non-polyposis colorectal cancer (HNPCC) is the most common genetic susceptibility syndrome for colorectal cancer. HNPCC is most frequently caused by germline mutations in the DNA mismatch repair (MMR) genes MSH2 and MLH1. Recently, mutations in another MMR gene, MSH6 (also known as GTBP), have also been shown to result in HNPCC. Preliminary data indicate that the phenotype related to MSH6 mutations may differ from the classical HNPCC caused by defects in MSH2 and MLH1. Here, we describe an extended Dutch HNPCC family not fulfilling the Amsterdam criteria II and resulting from a MSH6 mutation. Overall, the penetrance of colorectal cancer appears to be significantly decreased (p<0.001) among the MSH6 mutation carriers in this family when compared with MSH2 and MLH1 carriers (32% by the age of 80 v >80%). Endometrial cancer is a frequent manifestation among female carriers (six out of 13 malignant tumours). Transitional cell carcinoma of the urinary tract is also relatively common in both male and female carriers (10% of the carriers). Moreover, the mean age of onset of both colorectal cancer (MSH6 v MSH2/MLH1 = 55 years v 44/41 years) and endometrial carcinomas (MSH6 v MSH2/MLH1 = 55 years v 49/48 years) is delayed. As previously reported, we confirm that the pattern of microsatellite instability, in combination with immunohistochemical analysis, can predict the presence of a MSH6 germline defect. The detailed characterisation of the clinical phenotype of this kindred contributes to the establishment of genotype-phenotype correlations in HNPCC owing to mutations in specific mismatch repair genes.

[From gene to disease; from DNA 'mismatch' repair genes to hereditary non-polyposis colorectal carcinoma]

Hereditary non-polyposis colorectal cancer (HNPCC), also known as Lynch syndrome, is the most common autosomal dominant condition associated with early-onset colorectal cancer and the occurrence of cancer at other anatomical sites, i.e. endometrium, stomach, small intestine, urinary tract and ovaries, at an early age. Germline mutations in one of five DNA mismatch repair genes: MSH2, MLH1, PMS1, PMS2, and MSH6, predispose to HNPCC. Tumours of HNPCC patients display a high level of genomic instability, usually observed as changes in repeat numbers of simple repetitive sequences (microsatellite instability), which is a reflection of the malfunction of the DNA mismatch repair machinery.

Prediction of a mismatch repair gene defect by microsatellite instability and immunohistochemical analysis in endometrial tumours from HNPCC patients

Instability of microsatellite repeat sequences has been observed in colorectal carcinomas and in extracolonic malignancies, predominantly endometrial tumours, occurring in the context of hereditary non-polyposis colorectal cancer (HNPCC). Microsatellite instability (MSI) as a feature of human DNA mismatch repair (MMR)-driven tumourigenesis of the uterine mucosa has been studied primarily in sporadic tumours showing predominantly somatic hypermethylation of MLH1. The present study shows that all endometrial carcinomas (n=12) from carriers of MLH1 and MSH2 germline mutations demonstrate an MSI-high phenotype involving all types of repeat markers, while in endometrial carcinomas from MSH6 mutation carriers, only 36% (4 out of 11) demonstrate an MSI-high phenotype. Interestingly, an MSI-high phenotype was found in endometrial hyperplasias from MSH2 mutation carriers, in contrast to hyperplasias from MLH1 mutation carriers, which exhibited an MSI-stable phenotype. Instability of only mononucleotide repeat markers was found in both endometrial carcinomas and hyperplasias from MSH6 mutation carriers. In 29 out of 31 (94%) endometrial tumour foci, combined MSI and immunohistochemical analysis of MLH1, MSH2, and MSH6 could predict the identified germline mutation. The observation of MSI in endometrial hyperplasia and of altered protein staining for the MMR genes supports the idea that inactivation of MMR genes is an early event in endometrial tumourigenesis. A correlation was found between the variation in the extent and level of MSI and the age of onset of carcinoma, suggesting differences in the rate of tumour progression. A high frequency of MSI in hyperplasias, found only in MSH2 mutation carriers, might indicate a more rapid tumour progression, correlating with an earlier age of onset of carcinoma. The present study indicates that assessment of altered protein staining combined with MSI analysis of endometrial tumours might direct the mutational analysis of MMR genes.

Genetic analysis of a breast-ovarian cancer family, with 7 cases of colorectal cancer linked to BRCA1, fails to support a role for BRCA1 in colorectal tumorigenesis

Mutations in the BRCA1 gene cause strongly elevated risks of breast and ovarian cancers but may also confer a 3-fold increased risk for colorectal cancer. To address the relationship between BRCA1 carriership and colorectal tumorigenesis, we studied the genetics of a breast-ovarian cancer family with 7 cases of colorectal cancer. A germline 3938insG mutation in BRCA1 was found in 5 breast-cancer patients, 1 with ductal carcinoma in situ, ovarian cancer and an adenoma of the colon, and in 4/5 colorectal-cancer patients investigated. However, the youngest patient, diagnosed at age 23, was a non-carrier. Loss of the wild-type BRCA1 allele was observed in 3/3 breast tissues (2 breast carcinomas and 1 ductal carcinoma in situ) but in 0/6 colorectal tissues (5 carcinomas and 1 adenoma), suggesting that BRCA1 loss is not critical for colorectal tumorigenesis. To examine the possibility that an as yet unknown gene linked to BRCA1 was involved in the colorectal cancers, chromosome 17 segregation was studied with 7 polymorphic markers encompassing a 20 cM region including BRCA1. None of these markers showed complete allele sharing among all 5 colorectal-cancer patients studied. Clinical history, mutation analysis and microsatellite instability analysis excluded a role for any of the known colorectal-cancer susceptibility genes. In 4 other Dutch families carrying the same BRCA1 mutation, only 1 colorectal-cancer case was reported, of which the carrier status is unknown.

Prediction of a mismatch repair gene defect by microsatellite instability and immunohistochemical analysis in endometrial tumours from HNPCC patients

Instability of microsatellite repeat sequences has been observed in colorectal carcinomas and in extracolonic malignancies, predominantly endometrial tumours, occurring in the context of hereditary non-polyposis colorectal cancer (HNPCC). Microsatellite instability (MSI) as a feature of human DNA mismatch repair (MMR)-driven tumourigenesis of the uterine mucosa has been studied primarily in sporadic tumours showing predominantly somatic hypermethylation of MLH1. The present study shows that all endometrial carcinomas (n=12) from carriers of MLH1 and MSH2 germline mutations demonstrate an MSI-high phenotype involving all types of repeat markers, while in endometrial carcinomas from MSH6 mutation carriers, only 36% (4 out of 11) demonstrate an MSI-high phenotype. Interestingly, an MSI-high phenotype was found in endometrial hyperplasias from MSH2 mutation carriers, in contrast to hyperplasias from MLH1 mutation carriers, which exhibited an MSI-stable phenotype. Instability of only mononucleotide repeat markers was found in both endometrial carcinomas and hyperplasias from MSH6 mutation carriers. In 29 out of 31 (94%) endometrial tumour foci, combined MSI and immunohistochemical analysis of MLH1, MSH2, and MSH6 could predict the identified germline mutation. The observation of MSI in endometrial hyperplasia and of altered protein staining for the MMR genes supports the idea that inactivation of MMR genes is an early event in endometrial tumourigenesis. A correlation was found between the variation in the extent and level of MSI and the age of onset of carcinoma, suggesting differences in the rate of tumour progression. A high frequency of MSI in hyperplasias, found only in MSH2 mutation carriers, might indicate a more rapid tumour progression, correlating with an earlier age of onset of carcinoma. The present study indicates that assessment of altered protein staining combined with MSI analysis of endometrial tumours might direct the mutational analysis of MMR genes.

[From gene to disease; the APC gene and familial adenomatous polyposis coli]

Familial adenomatous polyposis coli is an autosomal dominant hereditary form of colorectal cancer associated with mutations in the adenomatous polyposis coli (APC) gene on chromosome 5. The APC protein is thought to mediate the stability of beta-catenin in the WNT signaling transduction pathway ('wingless-type mouse mammary tumor virus integration site family member') in normal colonic epithelial cells, thereby indirectly regulating the expression of WNT target genes such as the c-myc-oncogene. APC gene mutations cause the development of multiple adenomatous polyps in the colorectum, which strongly predisposes gene carriers to colorectal cancer. Extracolonic manifestations, including gastric and duodenal polyps, osteomas, desmoids, epidermoid cysts, and retinal lesions, are commonly observed in patients with familial adenomatous polyposis. Detection of mutations in the APC gene allows genetic counselling and reliable identification of at-risk individuals.

Risk of developing pancreatic cancer in families with familial atypical multiple mole melanoma associated with a specific 19 deletion of p16 (p16-Leiden)

Familial atypical multiple mole melanoma (FAMMM) is an autosomal dominant disease characterized by the familial occurrence of malignant melanoma of the skin and multiple atypical precursor lesions. Germline mutations in the p16 (CDKN2A) gene have been reported in at least a quarter of such families. An association has been reported between p16 mutations and pancreatic cancer. The aim of this study was to assess the risk of developing pancreatic and other cancers in Dutch FAMMM families with a 19 bp deletion in exon 2 of the p16 gene (p16-Leiden). Mutation analysis was performed in 27 families suspected of FAMMM. Clinical and pathological data were collected from all relatives affected with cancer. A p16-Leiden mutation was identified in 19 families. These families included 86 patients with melanoma. The second most frequent cancer was pancreatic cancer, which was observed in 15 patients from 7 families. The mean age at diagnosis of pancreatic cancer was 58 years (range 38-77 years). The estimated cumulative risk of developing pancreatic cancer in putative mutation carriers by age 75 years was 17%. In 8 p16-Leiden-negative families, no cases of pancreatic cancer occurred. p16 mutation carriers have a considerable risk of developing pancreatic cancer. Further studies should evaluate the value of surveillance of the pancreas in these high-risk families.

Three germline mutations in the TP53 gene

Three germline mutations in the TP53 tumor-suppressor gene are reported, two of which are not reported previously. A missense mutation at codon 265 of TP53 was found in three patients of a family that complied with the definition of the Li-Fraumeni syndrome. A nonsense mutation in codon 306 was found in a woman who had had a rhabdomyosarcoma at age 4 and a subsequent breast cancer at age 22. She was part of a Li-Fraumeni-like family, but the parental origin of the mutation could not be traced. Finally, while screening for somatic alterations in TP53 in a series of 141 sporadic breast tumors, we detected a constitutional missense mutation in codon 235 in a woman diagnosed with breast cancer at age 26 and a recurrence 4 years later. The recurrence, but not the primary tumor, showed an additional missense mutation at codon 245 as well as loss of the wild-type allele. This suggests that the 245 mutation was particularly important for tumor progression and that there might exist heterogeneity in terms of cancer predisposition potential among the various germline TP53 mutations.

Familial adenomatous polyposis: from bedside to bench and vice versa. A tribute to the somatic cell geneticist P. Meera Khan

Familial adenomatous polyposis (FAP) is characterized by the presence of numerous adenomatous polyps in the colorectum, as well as an autosomal dominant mode of inheritance. This syndrome will inevitably lead to colorectal cancer when left untreated, and it is estimated that 1% of all colorectal cancer cases are due to it. Over the past 20 years molecular genetic studies on FAP patients have laid down the basis for the elucidation of the genetic phenomena that ultimately result in the development of colorectal cancer. Professor P. Meera Khan was one of the leading authorities in the world of molecular genetics of colorectal cancer in general and of FAP in particular. His scientific contributions from the pre-DNA era up to the recent implementation of molecular genetic research in daily clinical practice have helped revolutionize our approach and management of FAP patients and their relatives.

Quality of life after total colectomy with ileorectal anastomosis or proctocolectomy and ileal pouch-anal anastomosis for familial adenomatous polyposis

BACKGROUND

Knowledge of postoperative health status is important in decision-making about the type of operation necessary in patients with familial adenomatous polyposis (FAP). This study compared the quality of life (QoL) between patients with an ileorectal anastomosis (group 1) and those with an ileal pouch-anal anastomosis (group 2).

METHODS

QoL was assessed with both a generic questionnaire (Short Form-36 Health Survey; SF-36) and a disease-specific questionnaire (European Organization for Research and Treatment of Cancer Colorectal QoL Questionnaire; EORTC QLQ-CR38). The SF-36 consists of 36 items representing eight generic health domains, and the EORTC QLQ-CR38 comprises 38 items representing disease-specific health domains. Both questionnaires were distributed among 323 patients with FAP known at the Dutch Polyposis Registry who had previously undergone either operation. The results of the SF-36 were compared with the scores of age- and sex-matched respondents from the general population.

RESULTS

Some 279 patients (86 per cent), 161 in group 1 and 118 in group 2, completed the questionnaire. Generic and disease-specific QoL was the same for groups 1 and 2. The SF-36 scores of both groups were significantly lower than those of the general population.

CONCLUSION

There were no differences with respect to health status between patients in groups 1 and 2, and preference for either procedure cannot be based on QoL.

Screening for BRCA2 mutations in 81 Dutch breast-ovarian cancer families

We have analysed 81 families with a history of breast and/or ovarian cancer for the presence of germline mutations in BRCA2 with a number of different mutation screening techniques. The protein truncation test (PTT) for exons 10 and 11 detected four different frame-shifting mutations in six of these families. Four of the remaining 75 families had given positive linkage evidence for being due to BRCA2. In these families the entire coding region was analysed by single-strand conformational polymorphism, leading to the detection of a non-sense and a splice-site mutation in two of them. While these studies were in progress, Southern analysis of BRCA1 revealed that in our study-population of 81 families, 15 families were segregating either the exon 13 or exon 22 deletion in BRCA1 (Petrij-Bosch et al (1997) Nat Genet 17: 341-345). This prompted us to examine BRCA2 in the remaining 58 families by Southern analysis, using two different restriction enzymes. No aberrations were found in the restriction patterns. Thus, contrary to BRCA1, large genomic rearrangements within the BRCA2 gene do not represent a major mutation mechanism among Dutch breast cancer families.

Functional outcome after colectomy and ileorectal anastomosis compared with proctocolectomy and ileal pouch-anal anastomosis in familial adenomatous polyposis

OBJECTIVE

To compare the long-term functional results of ileorectal anastomosis (IRA) with those of ileal pouch-anal anastomosis (IPAA) in patients with familial adenomatous polyposis (FAP).

SUMMARY BACKGROUND DATA

In patients with FAP, hundreds of colorectal adenomas develop, and the patient will die of colorectal cancer if left untreated. The surgeon must choose between colectomy with IRA and restorative proctocolectomy with IPAA. One factor crucial to decision making is the functional outcome after either procedure. To date, studies on this issue have reported conflicting results and have been based on small series of patients.

METHODS

To assess various functional variables, a questionnaire was sent to 323 patients with FAP who underwent either IRA or IPAA and who were registered at the Netherlands Foundation for the Detection of Hereditary Tumors. The overall response rate was 86%; the responders comprised 161 patients who underwent IRA and 118 patients who underwent IPAA.

RESULTS

Patients who underwent IRA scored significantly better for daytime and nighttime stool frequency, soiling, occasional passive incontinence, flatus and feces discrimination, stool consistency, and need for antidiarrheal medication. There was no difference with regard to perianal irritation, episodes of bowel discomfort, or dietary restrictions. The functional results according to the aggregate score of the Gastro-Intestinal Functional Outcome Scale, where the items specified above were integrated (0 indicating a poor and 100 a good overall function), were significantly better in patients with an IRA (74.5) than in patients with an IPAA (66.0) (p < 0.01).

CONCLUSION

The functional outcome after IRA is significantly better than after IPAA. On the basis of these results, IRA might still be considered in patients with a mild phenotypic expression of the disease in the rectum.

Treatment of mesenteric desmoid tumours with the anti-oestrogenic agent toremifene: case histories and an overview of the literature

Desmoid tumours are histologically benign but due to their infiltration and compression of surrounding structures potentially life-threatening fibromatous lesions of unknown aetiology. The annual incidence rate is 2-4 per million people. The mesenteric variant constitutes about 10% of all desmoid tumours, although in familial adenomatous polyposis (FAP) patients this may be up to 70%. Due to the small number of patients with mesenteric desmoids the therapy is mainly empirical. This report describes the rationale as well as the value of the short- and long-term treatment (up to 6 years) with the anti-oestrogenic agent toremifene in combination with sulindac in two patients suffering from such a mesenteric desmoid tumour. These patients did not respond to sulindac alone and previous treatment with tamoxifen together with this non-steroidal anti-inflammatory drug had also failed. An overview of the literature on the management of these dismal tumours is presented.

Gene-environment interaction in hereditary nonpolyposis colorectal cancer with implications for diagnosis and genetic testing

Hereditary nonpolyposis colorectal cancer (Lynch syndrome) is an autosomal dominant disease caused by mutations in the mismatch repair genes in particular in MLH1, MSH2 and MSH6. The disease is characterized by the development of colorectal, endometrial cancer and several other cancers. There is evidence that the clinical expression of the disease varies from one country to another. This variation might affect not only the application of criteria proposed to identify families but also clinical risk factors reported to predict the outcome of genetic testing. Data on site of the cancer, age at diagnosis and pathology were collected from 155 families with suspected HNPCC known at the Korean and Dutch HNPCC registries. DGGE, SSCP and DNA-sequencing were performed to identify MSH2, MLH1 and MSH6 mutations. A total of 33 Korean and 42 Dutch families met the clinical criteria for HNPCC. Germline mutations in the MMR-genes were found in 23 Korean and 24 Dutch families. In families that met the Amsterdam criteria, and also in those associated with MLH1 mutations, more cancers of the stomach and pancreas were observed in the Korean families than in the Dutch HNPCC families; in relative terms, the incidence of cancers of the endometrium in the Korean families was lower. Multivariate analysis showed that an early age at diagnosis, and the occurrence of pancreatic cancer were independent predictive factors of germline mutations in MLH1, MSH2 and MSH6 in the Korean subset of families.

Gene-environment interaction in hereditary nonpolyposis colorectal cancer with implications for diagnosis and genetic testing

Hereditary nonpolyposis colorectal cancer (Lynch syndrome) is an autosomal dominant disease caused by mutations in the mismatch repair genes in particular in MLH1, MSH2 and MSH6. The disease is characterized by the development of colorectal, endometrial cancer and several other cancers. There is evidence that the clinical expression of the disease varies from one country to another. This variation might affect not only the application of criteria proposed to identify families but also clinical risk factors reported to predict the outcome of genetic testing. Data on site of the cancer, age at diagnosis and pathology were collected from 155 families with suspected HNPCC known at the Korean and Dutch HNPCC registries. DGGE, SSCP and DNA-sequencing were performed to identify MSH2, MLH1 and MSH6 mutations. A total of 33 Korean and 42 Dutch families met the clinical criteria for HNPCC. Germline mutations in the MMR-genes were found in 23 Korean and 24 Dutch families. In families that met the Amsterdam criteria, and also in those associated with MLH1 mutations, more cancers of the stomach and pancreas were observed in the Korean families than in the Dutch HNPCC families; in relative terms, the incidence of cancers of the endometrium in the Korean families was lower. Multivariate analysis showed that an early age at diagnosis, and the occurrence of pancreatic cancer were independent predictive factors of germline mutations in MLH1, MSH2 and MSH6 in the Korean subset of families.

[Genetics of colorectal cancer. II. Hereditary background of sporadic and familial colorectal cancer]

About 15% of patients with colorectal cancer have a positive family history: 5% have hereditary colorectal cancer (hereditary non-polyposis colorectal carcinoma (HNPCC), familial adenomatous polyposis (FAP) or some other hereditary syndrome), while in 10% no clear hereditary pattern can be recognized ('familial colorectal cancer'). In sporadic and in familial intestinal cancer, a demonstrable hereditary predisposition may undoubtedly exist. HNPCC is often characterized by microsatellite instability, i.e. an increased number of short DNA sequences in the DNA indicating a disorder in DNA repair and a mutation in a DNA 'mismatch repair' (MMR) gene. Indicative of hereditary bowel cancer on the basis of such an MMR gene mutation are: (a) presence of bowel cancer in > or = 3 relatives, (b) early age at the time of the diagnosis of 'bowel cancer', (c) multiple primary bowel tumours, (d) uterine cancer in the family and (e) bowel and uterine cancer in a woman. Recent data demand a new subdivision of hereditary bowel cancer, based upon both the clinical picture and the results of DNA-tests. The genetic alterations in colonic adenomas and carcinomas are known to a large extent. In future these insights may be important in clinical practice, such as a more individual determination of the patient's prognosis and accordingly, of the treatment and follow-up.

[Periodic colonoscopic examinations of persons with a positive family history for colorectal cancer. Work Group 'Hereditary non-polyposis- colon-rectum cancers']

Individuals with one first-degree relative with colorectal cancer diagnosed before age 45 years and those with two first-degree relatives with colorectal cancer run a significantly increased risk (relative risk: 4-6) of developing colorectal cancer. Based on calculation of the mortality due to colorectal cancer for the age group 50-70 years (which is higher than the mortality due to breast cancer) surveillance may be justified, e.g. by colonoscopy at 5-year intervals from the age of 45-50. The total number of people in the Netherlands in this high risk group is estimated at 10,000. The authors conclude that prospective studies are needed to assess the cost-effectiveness of such a programme.

[Genetics of colorectal cancer. I. Non-polyposis and polyposis forms of hereditary colorectal cancer]

About 5% of colorectal cancer cases are due to an autosomal dominant genetic predisposition with high penetrance. In this condition, the patient is carrier of a pathogenic gene mutation present in all body cells which can be transmitted to descendants, a so-called germ line mutation. The mutation is usually present in a tumour suppressor gene. Three subgroups of hereditary colorectal cancer can be distinguished on the basis of the clinical characteristics: (a) syndromes without polyposis (mostly hereditary non-polyposis colorectal carcinoma; HNPCC), (b) syndromes with adenomatous polyposis (mostly familial adenomatous polyposis; FAP) and (c) syndromes with hamartomatous polyposis. Recently, the main gene defects which underlie these syndromes were identified. Consequently, it is possible in approximately half the families with HNPCC or FAP in patients with colorectal cancer to demonstrate the causative gene defect and subsequently, by blood testing of healthy relatives to determine who is and is not a carrier of this hereditary condition. Thus, preventive measures can be directed toward family members with a demonstrable high risk of large bowel cancer.

Suspected hereditary nonpolyposis colorectal cancer: International Collaborative Group on Hereditary Non-Polyposis Colorectal Cancer (ICG-HNPCC) criteria and results of genetic diagnosis

PURPOSE

The aim of this study was to determine the frequency of mutations in the mismatch repair genes in families suspected of having hereditary nonpolyposis colorectal cancer.

METHODS

We devised two criteria for families suspected of having hereditary nonpolyposis colorectal cancer (Criteria I and II). Criteria I consist of at least two first-degree relatives affected with colorectal cancer with at least one of the following: development of multiple colorectal tumors including adenomatous polyp, at least one colorectal cancer case diagnosed before the age of 50, and occurrence of a hereditary nonpolyposis colorectal cancer extracolonic cancer (endometrium, urinary tract, small intestine, stomach, hepatobiliary system, or ovary) in family members. Criteria II consist of one colorectal cancer patient with at least one of the following: early age of onset (<40 years); endometrial, urinary tract, or small intestine cancer in the index patient or a sibling (one aged <50 years); and two siblings with other integral hereditary nonpolyposis colorectal cancer extracolonic cancers (one aged <50 years). A questionnaire was mailed to members of the International Collaborative Group on Hereditary Non-Polyposis Colorectal Cancer to determine the mutation detection rate in mismatch repair genes from the families fulfilling these criteria. For comparison the mutation detection rate for families fulfilling the Amsterdam hereditary nonpolyposis colorectal cancer criteria in each institution was also obtained.

RESULTS

Data were obtained from eight different institutions (in 7 different countries). In a total of 123 patients from 123 families (67 families fulfilling Criteria I and 56 families fulfilling Criteria II), genetic testing for germline mismatch repair gene variants was performed. Germline mutations of the hMLH1 or hMSH2 genes were identified in 24 families (20 percent). Of these, the mutation detection rate for families fulfilling Criteria I was 28 percent (19/67). The mutation detection rate for families fulfilling Criteria II was 9 percent (5/56). In these eight institutions, the overall mutation detection rate for families fulfilling the Amsterdam hereditary nonpolyposis colorectal cancer criteria was 50 percent (77/154).

CONCLUSION

The Criteria I for suspected hereditary nonpolyposis colorectal cancer have the advantages that they can be applied to nuclear families and they can include extracolonic cancers. The results of this study suggest that families fulfilling Criteria I should be offered genetic testing. The relatively low mutation detection rate in those families fulfilling Criteria II suggests that, using current techniques, genetic testing in these families is not practical.

Cumulative risk of developing polyps or malignancy at the ileal pouch-anal anastomosis in patients with familial adenomatous polyposis

Restorative proctocolectomy with an ileal pouch-anal anastomosis is performed in an increasing number of patients with familial adenomatous polyposis (FAP). Two techniques are currently used to construct an ileal pouch-anal anastomosis: (1) a double-stapled anastomosis between the pouch and the anal canal and (2) mucosectomy with a hand-sewn ileoanal anastomosis at the dentate line. Although this procedure is thought to abolish the risk of colorectal adenoma, an increasing number of case reports have been published concerning the development of adenoma at the anastomotic site. The purpose of this study was to evaluate the overall cumulative risk of developing adenomatous polyps after ileal pouch-anal anastomosis and to compare the cumulative risk after either anastomotic technique. A total of 126 consecutive FAP patients undergoing a restorative proctocolectomy were identified from polyposis registries in The Netherlands, Denmark, Italy, Germany, and New York. Life-table analysis was used to calculate the cumulative risk of developing polyps in 97 patients with at least 1 year of endoscopic follow-up (median 66 months, range 12 to 188 months). A double-stapled anastomosis was used in 35 patients, whereas in 62 patients a hand-sewn anastomosis with a mucosectomy was performed. In 13 patients polyps developed at the anastomotic site, four with severe and four with moderate dysplasia. None of the patients developed a carcinoma at the anastomotic site. The cumulative risk of developing a polyp at the anastomotic site was 8% (95% confidence interval 2% to 14%) at 3.5 years and 18% (95% confidence interval 8% to 28%) at 7 years, respectively. The risk of developing a polyp at the anastomotic site within 7 years was 31% for patients with a double-stapled vs. 10% for patients with a hand-sewn anastomosis with mucosectomy (P = 0.03 [log-rank test]). Because FAP patients undergoing a restorative proctocolectomy with either a double-stapled or hand-sewn anastomosis have a substantial risk of developing adenomatous polyps at the anastomotic site, lifelong endoscopic surveillance is mandatory in both groups.

[The role of genetic factors in the development of gastric cancer]

In general, a genetic predisposition to a tumour disease such as gastric cancer is postulated in patients with cancer at an unusually early age or when several relatives are affected. A clear definition of hereditary gastric cancer is lacking. Two types of families may be distinguished: kindreds with gastric cancer only (site-specific), and kindreds with gastric as well as colorectal cancer, representing the hereditary non-polyposis colon cancer (HNPCC) syndrome. A genetic predisposition is presumed in young patients with a diffuse type of gastric cancer, in contrast to the intestinal type which is associated with atrophic gastritis and older age. A variety of genetic abnormalities in tumour tissue have been described, e.g. mutations in genes involved in DNA repair. Helicobacter pylori plays an important role in the aetiology, but the interaction with genetic factors is unknown.

Current policies for surveillance and management in women at risk of breast and ovarian cancer: a survey among 16 European family cancer clinics. European Familial Breast Cancer Collaborative Group

The recent isolation of breast cancer predisposing genes (BRCA1 and BRCA2) allows the identification of carriers within affected families. These carriers have a 50-85% risk of developing breast or ovarian cancer and need careful follow-up. The purpose of this study was to evaluate the management and screening protocols implemented in high risk families at various family cancer clinics in Europe. A questionnaire was mailed to the members of the European Familial Breast Cancer Collaborative Group (n = 30) requesting information on the following issues: indication for surveillance of breasts and ovaries, the recommended protocol, coordination of the screening examination, prophylactic surgery, the specific management of breast cancer in a mutation carrier and the use of oestrogen. 16 centres from nine countries responded. Most centres recommend surveillance of the breasts if the lifetime risk exceeds 15-20%. The surveillance protocol that is generally advised comprises monthly self breast examination, examination by a specialist every 6 months and annual mammography, all starting from an age between 25 and 35 years. Surveillance of the ovaries is recommended in BRCA1 and BRCA2-mutation carriers, in members from breast/ovarian cancer families and in some centres in 'breast cancer only' families with an early onset of breast cancer. The recommended protocol includes gynaecological examination, sonography and estimation of CA-125 at yearly intervals starting from the age 30-35 years. Prophylactic mastectomy is considered for proven mutation carriers in some centres. Most centres consider prophylactic oophorectomy in mutation carriers and some centres also consider it for members of breast/ovarian cancer families. This survey provides insight into the guidelines for surveillance and management of familial breast cancer used at various family cancer clinics in Europe; this insight may contribute to the appropriate management of these high risk women. It should be emphasised that most recommendations are based on experts' opinion rather than on any specific studies.

Occurrence of thyroid carcinoma in Dutch patients with familial adenomatous polyposis. An epidemiological study and report of new cases

OBJECTIVES

To assess the occurrence of thyroid cancer in Dutch patients with familial adenomatous polyposis (FAP) and to discuss the value of surveillance.

DESIGN

Retrospective analysis of medical records.

SETTING

The data were collected from the Dutch FAP registry.

PARTICIPANTS

601 patients with FAP, 339 males and 262 females.

RESULTS

The registry contained four female cases with a thyroid carcinoma. The mean age at diagnosis was 30 years (range: 16-46). In two patients it was the presenting symptom of FAP. None of the women died from their thyroid carcinoma during a mean follow-up of 13 years (range: 6-31). The histology revealed one papillary carcinoma, one follicular carcinoma and two mixed papillary/follicular carcinomas. The relative risk (RR) of developing thyroid carcinoma compared with the general Dutch population was 23 (95% confidence interval: 9-61). At the age of 60 years, the cumulative risk (CR) of thyroid carcinoma for female FAP patients was 2.8%.

CONCLUSIONS

Young female FAP patients have a significantly increased RR to develop a thyroid carcinoma. It may even be the presenting symptom of FAP. As the CR of thyroid carcinoma is low and the prognosis seems to be good, we recommend only periodical physical examination of the thyroid.

Clinical findings with implications for genetic testing in families with clustering of colorectal cancer

BACKGROUND

Germ-line mutations in DNA mismatch-repair genes (MSH2, MLH1, PMS1, PMS2, and MSH6) cause susceptibility to hereditary nonpolyposis colorectal cancer. We assessed the prevalence of MSH2 and MLH1 mutations in families suspected of having hereditary nonpolyposis colorectal cancer and evaluated whether clinical findings can predict the outcome of genetic testing.

METHODS

We used denaturing gradient gel electrophoresis to identify MSH2 and MLH1 mutations in 184 kindreds with familial clustering of colorectal cancer or other cancers associated with hereditary nonpolyposis colorectal cancer. Information on the site of cancer, the age at diagnosis, and the number of affected family members was obtained from all families.

RESULTS

Mutations of MSH2 or MLH1 were found in 47 of the 184 kindreds (26 percent). Clinical factors associated with these mutations were early age at diagnosis of colorectal cancer, the occurrence in the kindred of endometrial cancer or tumors of the small intestine, a higher number of family members with colorectal or endometrial cancer, the presence of multiple colorectal cancers or both colorectal and endometrial cancers in a single family member, and fulfillment of the Amsterdam criteria for the diagnosis of hereditary nonpolyposis colorectal cancer (at least three family members in two or more successive generations must have colorectal cancer, one of whom is a first-degree relative of the other two; cancer must be diagnosed before the age of 50 in at least one family member; and familial adenomatous polyposis must be ruled out). Multivariate analysis showed that a younger age at diagnosis of colorectal cancer, fulfillment of the Amsterdam criteria, and the presence of endometrial cancer in the kindred were independent predictors of germ-line mutations of MSH2 or MLH1. These results were used to devise a logistic model for estimating the likelihood of a mutation in MSH2 and MLH1.

CONCLUSIONS

Assessment of clinical findings can improve the rate of detection of mutations of DNA mismatch-repair genes in families suspected of having hereditary nonpolyposis colorectal cancer.

Urinary tract cancer and hereditary nonpolyposis colorectal cancer: risks and screening options

PURPOSE

We investigate the risk of the different types of urinary tract cancer in hereditary nonpolyposis colorectal cancer families and review screening options.

MATERIALS AND METHODS

We retrospectively calculated the relative and cumulative risks of developing urinary tract cancer by comparing tumor occurrence in patients and their first degree relatives in the Dutch hereditary nonpolyposis colorectal cancer registry with those in the general Dutch population. A person-year analysis was used, including data on 1,321 individuals from 50 hereditary nonpolyposis colorectal cancer families.

RESULTS

The relative risk of developing transitional cell cancer of the renal pelvis or ureter was 14.04 (95% confidence interval 6.69 to 29.45, p <0.05) and the cumulative risk was 2.6%. The risks of renal (excluding renal pelvis) and bladder cancers were not significantly increased. Urinary tract cancer was diagnosed at a relatively young age and many women were affected. Some familial clustering was observed.

CONCLUSIONS

Our findings indicate that hereditary nonpolyposis colorectal cancer is associated with an increased risk of transitional cell cancer of the upper urinary tract. The cumulative risk is relatively low, although a subset of hereditary nonpolyposis colorectal cancer families may be exposed to a much higher risk. As yet nothing is known of the clinical impact of screening for urinary tract cancer in cases of hereditary nonpolyposis colorectal cancer. In a research setting screening by excretory urography of hereditary nonpolyposis colorectal cancer families with a strong history of upper urinary tract cancer should be considered.

Characteristics of small bowel carcinoma in hereditary nonpolyposis colorectal carcinoma. International Collaborative Group on HNPCC

BACKGROUND

Small bowel carcinoma is uncommon. However, hereditary nonpolyposis colorectal carcinoma (HNPCC) patients are at increased risk of small bowel carcinoma. The purpose of this study was to characterize small bowel tumors in HNPCC patients.

METHODS

A questionnaire was mailed to the members of International Collaborative Group on HNPCC (ICG-HNPCC) requesting clinicopathologic data in their registries on HNPCC patients with small bowel carcinoma. Survival was estimated utilizing the Kaplan-Meier method.

RESULTS

Forty-two individuals from 40 HNPCC families developed 42 primary and 7 metachronous small bowel tumors. There were 46 adenocarcinomas and 3 carcinoid tumors. The median age at diagnosis of the index small bowel tumor was 49 years. Mismatch repair gene mutations were present in 15 of 42 patients (36%). There were nine hMLH1 and six hMSH2 mutations. The small bowel was the first site of carcinoma in 24 patients (57%). The median survival for the 42 patients was 47 months (range, 0-447 months). The overall 5- and 10-year survival rates were 44% and 33%, respectively.

CONCLUSIONS

Small bowel tumors can be the presenting neoplasms in HNPCC patients. Similar to colorectal carcinoma in HNPCC, small bowel adenocarcinomas in HNPCC patients occur at an earlier age and appear to have a better prognosis than those occurring in the general population.

Familial and hereditary non-polyposis colorectal cancer: issues relevant for surgical practice

About 15% of patients with colorectal cancer report a family history of this disease. An estimated 1%-5% of patients have hereditary non-polyposis colorectal cancer (HNPCC). Recently, DNA mismatch repair genes associated with this syndrome were identified. For about 50% of families in which HNPCC occurs, DNA-based diagnosis and presymptomatic DNA testing are now feasible. Diagnosis of a hereditary tumour syndrome is relevant for both the patient with cancer and his or her close relatives. The complexities of family studies warrant the forming of a multidisciplinary team which may choose to work within a specialized cancer family clinic.

Characteristics of small bowel carcinoma in hereditary nonpolyposis colorectal carcinoma. International Collaborative Group on HNPCC

BACKGROUND

Small bowel carcinoma is uncommon. However, hereditary nonpolyposis colorectal carcinoma (HNPCC) patients are at increased risk of small bowel carcinoma. The purpose of this study was to characterize small bowel tumors in HNPCC patients.

METHODS

A questionnaire was mailed to the members of International Collaborative Group on HNPCC (ICG-HNPCC) requesting clinicopathologic data in their registries on HNPCC patients with small bowel carcinoma. Survival was estimated utilizing the Kaplan-Meier method.

RESULTS

Forty-two individuals from 40 HNPCC families developed 42 primary and 7 metachronous small bowel tumors. There were 46 adenocarcinomas and 3 carcinoid tumors. The median age at diagnosis of the index small bowel tumor was 49 years. Mismatch repair gene mutations were present in 15 of 42 patients (36%). There were nine hMLH1 and six hMSH2 mutations. The small bowel was the first site of carcinoma in 24 patients (57%). The median survival for the 42 patients was 47 months (range, 0-447 months). The overall 5- and 10-year survival rates were 44% and 33%, respectively.

CONCLUSIONS

Small bowel tumors can be the presenting neoplasms in HNPCC patients. Similar to colorectal carcinoma in HNPCC, small bowel adenocarcinomas in HNPCC patients occur at an earlier age and appear to have a better prognosis than those occurring in the general population.

A cost-effectiveness analysis of colorectal screening of hereditary nonpolyposis colorectal carcinoma gene carriers

BACKGROUND

It has been estimated that the prevalence of carriers of a mutated mismatch repair (MMR) gene among the general population in Western countries is between 5 and 50 per 10,000. These carriers have a risk of >85% of developing colorectal carcinoma (CRC) and therefore need careful follow-up. The objective of this study was to analyze the cost-effectiveness of CRC surveillance of carriers of a mutated MMR gene.

METHODS

The authors constructed a model to estimate the potential health effects (life expectancy) and healthcare costs of two strategies: 1) surveillance, with colonoscopy every 2-3 years, and 2) no CRC surveillance. Estimates of the lifetime risk of developing CRC and the stage distribution of CRC for symptomatic patients were derived from the Dutch hereditary nonpolyposis colorectal carcinoma (HNPCC) registry. The CRC stage specific relative survival rates and the effectiveness of surveillance in preventing or detecting cancer early were based on Finnish studies. The costs of surveillance and treatment were derived from recent American studies.

RESULTS

The results showed that 1) surveillance of gene carriers led to an increase in life expectancy of 7 years, and 2) the costs of surveillance under a wide range of assumptions are less than the costs of no CRC surveillance.

CONCLUSIONS

CRC surveillance of HNPCC gene carriers appears to be effective and considerably less costly than no CRC surveillance and therefore deserves to be supported by governmental agencies and health insurance organizations.

Extracolonic manifestations of familial adenomatous polyposis: desmoid tumours, and upper gastrointestinal adenomas and carcinomas

It is well known that patients with familial adenomatous polyposis (FAP) are at considerable risk of developing extracolonic manifestations of the disease. Particularly, desmoid tumours of the abdominal cavity, and duodenal adenomas and carcinomas are the most serious ones. It is estimated that some 10% of the FAP patients will develop desmoids, whereas 50-90% of the FAP patients will get duodenal adenomas predominantly concentrated on or around the major papilla. Desmoid tumours and duodenal carcinomas are major causes of death in those patients in whom a prophylactic (procto)colectomy has been performed. Desmoids are histologically benign tumours, composed of mature fibroblasts. They usually grow slowly but they can become quite large and may compress or infiltrate surrounding viscera, which might cause significant morbidity as well as mortality. Successful treatment of these tumours is extremely difficult as surgical therapy often requires the removal of considerable lengths of small bowel. Moreover, surgical therapy may lead to uncontrollable bleeding and is seldom radical. Chemotherapy with cytoxic agents seems promising but so far the data are too few for firm conclusions to be drawn. The same holds true for drug regimens which interfere with the metabolic and hormonal metabolism of the tumour. Although various lines of evidence suggest that the adenoma-carcinoma sequence, which is generally accepted for colorectal adenomas, also applies for the duodenal adenomas in FAP patients, it is not clear whether we should screen these patients for upper gastrointestinal adenomas or not. As these polyps are usually small, sessile, multiple and difficult to remove, the benefit of endoscopic surveillance would be the early detection of cancer rather than eradication of the polyps. In addition, evidence that screening and early treatment leads to improvement of the prognosis is not available. Although the role of (procto)colectomy in the treatment of large-bowel polyps is well established in FAP patients, the treatment of their duodenal counterparts is still open for debate. The risk of the development of periampullary cancer is not high enough to warrant an aggressive prophylactic surgical approach, i.e. a Whipple's procedure, immediately after the discovery of duodenal adenomas. The considerable morbidity and mortality rates of this procedure must be weighted against a putative benefit of screening.

BRCA1 genomic deletions are major founder mutations in Dutch breast cancer patients

To date, more than 300 distinct small deletions, insertions and point mutations, mostly leading to premature termination of translation, have been reported in the breast/ovarian-cancer susceptibility gene BRCA1. The elevated frequencies of some mutations in certain ethnic subpopulations are caused by founder effects, rather than by mutation hotspots. Here we report that the currently available mutation spectrum of BRCA1 has been biased by PCR-based mutation-screening methods, such as SSCP, the protein truncation test (PTT) and direct sequencing, using genomic DNA as template. Three large genomic deletions that are not detected by these approaches comprise 36% of all BRCA1 mutations found in Dutch breast-cancer families to date. A 510-bp Alu-mediated deletion comprising exon 22 was found in 8 of 170 breast-cancer families recruited for research purposes and in 6 of 49 probands referred to the Amsterdam Family Cancer Clinic for genetic counselling. In addition, a 3,835-bp Alu-mediated deletion encompassing exon 13 was detected in 4 of 170 research families, while an deletion of approximately 14 kb was detected in a single family [corrected]. Haplotype analyses indicated that each recurrent deletion had a single common ancestor.

Mutations predisposing to hereditary nonpolyposis colorectal cancer: database and results of a collaborative study. The International Collaborative Group on Hereditary Nonpolyposis Colorectal Cancer

BACKGROUND & AIMS

Germline mutations in four DNA mismatch repair genes are known to cause susceptibility to hereditary nonpolyposis colorectal cancer (HNPCC). The rapidly increasing information about these mutations needs to be collected and appropriately stored to facilitate further studies on the biological and clinical significance of the findings.

METHODS

The International Collaborative Group on HNPCC has established a database of DNA mismatch repair gene mutations and polymorphisms. In this report, 126 predisposing mutations were analyzed.

RESULTS

A majority of the mutations affected either the Mut L homologue (MLH) 1 (n = 75) or the Mut S homologue (MSH) 2 (n = 48) and were quite evenly distributed, with some clustering in MSH2 exon 12 and MLH1 exon 16. Most MSH2 mutations consisted of frameshift (60%) or nonsense changes (23%), whereas MLH1 was mainly affected by frameshift (40%) or missense alterations (31%). Although most mutations were unique, a few common recurring mutations were identified. Of the families studied (n = 202), 82% met the Amsterdam criteria and 15% did not; the general mutation profile was similar in both groups.

CONCLUSIONS

The construction of mutation profiles will facilitate the development of diagnostic strategies in HNPCC.