Evaluation of molecular genetic diagnosis in the management of familial adenomatous polyposis coli: a population based study

Familial adenomatous polyposis in children younger than age ten years: a multidisciplinary clinic experience

PURPOSE

Children with familial adenomatous polyposis have a greater mortality and morbidity in the first decade of life compared with the general population. Some children with a more severe disease phenotype present early with colorectal adenomata and may require colectomy at an early age. We present our multidisciplinary clinic experience with familial adenomatous polyposis in children younger than age ten years at the time of presentation.

METHODS

A cross-sectional analysis was performed on all patients with suspected or confirmed familial adenomatous polyposis presenting in the first decade of life and followed by the multidisciplinary Pediatric Hereditary Polyposis Clinic at our institutions. Analysis included demographics, clinical presentation and course, gene mutation testing, endoscopic-histologic findings, and surgical outcome.

RESULTS

Twenty-two children (11 males) presented with suspected or confirmed familial adenomatous polyposis. Two were discharged from follow-up after negative adenomatous polyposis coli gene mutation testing. The rest underwent annual hepatoblastoma surveillance through age ten years with negative findings. Twelve patients presented with symptoms: six had de novo familial adenomatous polyposis. Seven had gastrointestinal hemorrhage and went on to colonoscopy. Four patients with adenomatous polyposis coli gene mutation at codon 1309 were referred for colectomy before age ten years. Referral to colectomy was earlier in patients with 1309 mutation and with de novo familial adenomatous polyposis.

CONCLUSIONS

Children with familial adenomatous polyposis younger than age ten years may present presymptomatically for disease surveillance. Familial adenomatous polyposis with adenomatous polyposis coli gene mutation at codon 1309 entails a risk of a more aggressive phenotype; early colectomy may be indicated in children harboring this gene mutation.

Cancer genetics in primary care

The cloning of two major breast cancer susceptibility genes, BRCA1 and BRCA2, in 1994 and 1995 and the subsequent development of commercial genetic testing has brought hereditary cancer genetics into the public eye. In addition to DNA-based genetic testing, new strategies and treatments have been developed to provide accurate assessment of cancer risk and to reduce the chances of cancer developing in the future. This increasing scientific and public attention has prompted some cancer patients and their families to find out whether they "have the cancer gene" and has placed more responsibility on primary care clinicians to identify people who should be referred for specialized services of hereditary cancer genetics.

Cancer genetics services: a systematic review of the economic evidence and issues

This paper systematically reviews the published economic research upon cancer genetics services for families at risk of having familial breast, ovarian or colorectal cancer. A structured search was made of 15 electronic databases. The search identified 1030 papers, of which 31 fulfilled the inclusion criteria, two were cost–benefit studies, five were cost consequences, four were cost-effectiveness studies, one was a cost analysis, two were cost-minimisation studies, one was a cost–utility study, 10 modelled life years and six were reviews. Modelling studies indicate that surveillance, prophylactic and chemoprevention techniques extend survival for carriers of identified mutations. Genetic testing has been estimated to cost $70–2400 [£48^*–1591] and genetic counselling $129–800 [£89–£551]. The technology of genetic testing has been found to be cost effective. Cost effectiveness was particularly influenced by targeting genetic services for patients with a strong family history of cancer rather than screening the entire population. Future economic evaluation must go beyond merely assessing health outcomes and mutation identification, and account for the impact of genetic services upon the individual, the family and society, establish the value of services to these groups and determine the most effective ways of delivering genetic services.

The clinical spectrum of duodenal polyps in pediatrics

OBJECTIVES

The aim of this retrospective study was to determine the prevalence, clinical presentation, and histologic subclassification of duodenal polyps identified on endoscopy (EGD) in pediatric patients.

METHODS

We performed an 18-year retrospective study of all pediatric patients (< 21 years) with duodenal polyps diagnosed between 1983 and 2001 at The Johns Hopkins Children's Center. Our analysis includes a formal histologic evaluation of duodenal polyps either biopsied using cold-forceps or removed by snare cautery.

RESULTS

Duodenal polyps were reported in 22 of 5766 EGDs (0.4%) performed in 16 (M:F; 1:1) patients with a mean (SD) age of 14.1 (5.1) years. Polyps were equal in both the Caucasian and African American population (adjusted ratio 1.2:1). The histologic subtypes included Adenomatous (42%), Brunner's gland hyperplastic (33%), hamartomatous (17%), and heterotopic gastric gland polyps (8%). The most frequent indication for EGD was surveillance in patients with polyposis syndromes; most of these patients were asymptomatic at the time of their EGD. In comparison, the most frequent indication for an EGD in patients without polyposis syndromes was abdominal pain and vomiting.

CONCLUSIONS

Duodenal polyps are most frequently encountered in children with polyposis syndromes, most of whom are asymptomatic. In nonsyndromic patients, the most common histologic subtype is Brunner's gland hyperplastic polyp and presenting symptoms include abdominal pain and vomiting.

Familial adenomatous polyposis and extracolonic cancer

Our purpose is to focus attention on the cancer family history, coupled with an understanding of the natural history and extracolonic tumor spectrum of familial adenomatous polyposis (FAP), through a family study. This family report provides an example of how colorectal cancer (CRC) can be prevented by knowledgeable gastroenterologists and colorectal surgeons who educate and compassionately counsel members of high-risk families so that their compliance with diagnostic screening and, ultimately, with protection through prophylactic colectomy, is achieved. A working pedigree of this extended family was constructed through interviews with the proband, followed by questionnaires sent to all primary and secondary relatives. Appropriately signed permission forms enabled us to secure pertinent medical and pathology records in order to ensure accuracy of historical information. Integral extracolonic tumors included medulloblastoma, papillary thyroid carcinoma, hepatoblastoma, and desmoid tumors. We conclude that, due in part to improved longevity as a result of being spared CRC, several family members have developed certain FAP integral extracolonic cancers.

Common hereditary cancers and implications for primary care

The identification of genes that place individuals at high risk of breast, ovarian, and colorectal cancer has greatly advanced our understanding of cancer predisposition over the past decade. This knowledge has received much attention from the media, and referrals to geneticists and surgeons, and requests for genetic testing, have risen. We review the published evidence for the management of people at increased risk of hereditary cancers, to draw attention to areas of uncertainty and to discuss implications for primary care. We focus on common inherited cancers, since they will have the greatest effect on clinical practice over the next decade. Cancer genetics offers a model of how information on the genetics of other common diseases could affect primary care in the future. Strategies to support the integration of genetic medicine in primary care are needed to enable primary-care practitioners to identify individuals at raised genetic risk and to reassure patients for whom genetic testing and increased surveillance offer little benefit.

Calcium and vitamin D. Their potential roles in colon and breast cancer prevention

The geographic distribution of colon cancer is similar to the historical geographic distribution of rickets. The highest death rates from colon cancer occur in areas that had high prevalence rates of rickets--regions with winter ultraviolet radiation deficiency, generally due to a combination of high or moderately high latitude, high-sulfur content air pollution (acid haze), higher than average stratospheric ozone thickness, and persistently thick winter cloud cover. The geographic distribution of colon cancer mortality rates reveals significantly low death rates at low latitudes in the United States and significantly high rates in the industrialized Northeast. The Northeast has a combination of latitude, climate, and air pollution that prevents any synthesis of vitamin D during a five-month vitamin D winter. Breast cancer death rates in white women also rise with distance from the equator and are highest in areas with long vitamin D winters. Colon cancer incidence rates also have been shown to be inversely proportional to intake of calcium. These findings, which are consistent with laboratory results, indicate that most cases of colon cancer may be prevented with regular intake of calcium in the range of 1,800 mg per day, in a dietary context that includes 800 IU per day (20 micrograms) of vitamin D3. (In women, an intake of approximately 1,000 mg of calcium per 1,000 kcal of energy with 800 IU of vitamin D would be sufficient.) In observational studies, the source of approximately 90% of the calcium intake was vitamin D-fortified milk. Vitamin D may also be obtained from fatty fish. In addition to reduction of incidence and mortality rates from colon cancer, epidemiological data suggest that intake of 800 IU/day of vitamin D may be associated with enhanced survival rates among breast cancer cases.

Ophthalmic and genetic screening in pedigrees with familial adenomatous polyposis

PURPOSE

To study the possible association between ophthalmic findings, genetic status, and clinical course of the disease in Austrian pedigrees with familial adenomatous polyposis (FAP).

METHODS

Thirty-nine members of 16 consecutive FAP families with 20 affected patients and 19 relatives with a 50% a priori risk to develop the disease were examined ophthalmologically. The intestinal status of all persons was established by colonoscopy. Direct or indirect molecular genetic analysis, or both, was possible in eight of the 16 FAP families.

RESULTS

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) was discovered in 15 (75%) of the 20 persons affected by familial adenomatous polyposis. Five (25%) of the patients with an established FAP were CHRPE-negative. Four of the 19 at-risk individuals were CHRPE-positive. According to DNA analysis, five of the 19 at-risk relatives had a high risk to develop a manifest disease. The ophthalmoscopic tests were in complete agreement with the molecular risk estimation. Furthermore, the combined results of endoscopy and ophthalmoscopy suggested a relationship between a positive CHRPE status and the severity of FAP.

CONCLUSIONS

Ophthalmic examinations facilitate predictive diagnosis in FAP patients and first-degree relatives, permitting a noninvasive, highly reliable risk assessment. When present, CHRPE lesions are a reliable clinical marker for FAP in CHRPE-positive families. In CHRPE negative families, negative ophthalmic examinations are of no predictive value. The CHRPE status can add information about the location of the genetic mutation. The combination of an ophthalmic examination with DNA analysis and endoscopy improves the risk assessment of FAP carriers.

Overview of the epidemiology of colorectal cancer

INTRODUCTION

The epidemiology of colorectal cancer has generated more interest recently, because recent developments in genetics, molecular biology, and genetic epidemiology have increased our understanding of the role of genes in the etiology of colorectal cancer. Interactions between genetic susceptibility and environmental factors in the etiology of cancer may be easier to define.

EPIDEMIOLOGY

Colorectal cancer is common in the Western world and is rare in developing countries. A sharp increase is seen in Eastern Europe and Japan.

ETIOLOGY

Molecular genetics has shown that accumulation of genetic changes is important in the development of colorectal cancer. Mutations in at least four to five genes are required for the formation of a malignant tumor. Environmental mutagenic factors may determine which susceptible individuals grow carcinomas. Environmental risk factors for colorectal cancer are found in a western diet, rich in fat, meat, and animal protein and low in fiber, fruit, and vegetables. The complex interrelations between food components make it difficult to define the precise role of specific food factors.

PREVENTION

Conclusive evidence of the effectiveness of primary prevention of colorectal cancer via dietary measures or nonsteroidal anti-inflammatory drugs is lacking. Secondary prevention by interrupting the adenoma carcinoma sequence is an actual possibility, its effectiveness, however, needs to be determined. Molecular genetics holds a promise for identifying populations at high risk for colorectal cancer, therefore, targeting the screening to make it more cost-effective.

Congenital hypertrophy of the retinal pigment epithelium in familial adenomatous polyposis. Novel criteria of assessment and correlations with constitutional adenomatous polyposis coli gene mutations

BACKGROUND

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) is the most common extracolonic manifestation of familial adenomatous polyposis (FAP) and is an early clinical marker of the disease. It seems to be correlated with the position of constitutional mutations of the adenomatous polyposis coli (APC) gene.

METHODS

The authors investigated the expression of CHRPE and its correlation with the position of the APC gene in FAP patients and in "at risk" relatives from 31 FAP kindreds. To obtain comparable data on CHRPE expression, the authors developed a novel scoring system based on morphologic and dimensional criteria.

RESULTS

A positive CHRPE score was obtained in 29 of 39 FAP patients (74%) and in 16 of 53 relatives who showed no clinical evidence of FAP (30%). Colonoscopy revealed polyps in 20 of the 47 relatives who could be examined. The cumulative sensitivity and specificity of CHRPE were 72.88% and 96.29%, respectively. APC gene mutations were characterized in 34 subjects from 17 kindreds. In 28 of the subjects, mutations were detected in exon 15, between codons 876 and 1324. Mutations were found in exon 9 in 6 subjects. In 3 of the 6 subjects, they were found at the site where both forms of alternative splicing of the exon occur (codon 437). In the other 3 subjects (another kindred), mutations were found in the portion of exon 9 in which alternative splicing occurs (codon 367). Only 1 of the 6 subjects (16.6%) with mutations in exon 9 had a positive CHRPE score, compared with 28 of 28 subjects (100%) with mutations in exon 15. None of the 3 subjects with mutations in codon 437 had a positive CHRPE score. The CHRPE scores of exon 15 mutation carriers varied markedly both within and among kindreds, irrespective of the mutation site.

CONCLUSIONS

The results of this study indicate that the site of APC gene mutation influences CHRPE expression but is not the only factor responsible for the presence and level of retinal lesions in FAP patients.

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) and familial adenomatous polyposis (FAP)

Familial adenomatous polyposis (FAP) is a genetically transmitted disease affecting the colon. It is characterized by the presence of several (at least 100) adenomatous polyps, each able to develop into carcinomas, and by other extra-colonic signs such as skin and bone lesions. Within the framework of research studies to identify phenotyphic markers for early detection of subjects at risk within a family affected by FAP, attention has recently been paid to congenital hypertrophy of the retinal pigment ephitelium (CHRPE). With the aim of evaluating the relationship between FAP and CHRPE, 36 members of 7 FAP families were examined. We found that 43.75% of the subjects presenting CHRPE areas were also affected by FAP, whereas 58.33% of patients affected by FAP had CHRPE. Our findings indicated a lower incidence of CHRPE in FAP patients, compared to other studies reported so far. Moreover, in a control group of 160 healthy individuals we found a CHRPE prevalence of 5.5%.

Screening by genomic linkage studies and mutation analysis of hereditary adenomatous polyposis coli: usefulness for clinical practice

A heterogeneous group of patients suffering from adenomatous polyposis coli (APC) were evaluated by clinical and genetic investigations for the first time in Austria. The patients belonged to eight unrelated APC families. In six families several family members were affected with APC, and linkage analysis with highly informative markers was used to estimate the risk of single individuals in these families to develop APC. All index patients were also tested for the most frequent mutation in the APC gene (mutation cluster region, exon 15). Clinical investigations included ophthalmologic tests for congenital hypertrophy of retinal pigment epithelium and colonoscopy. According to DNA analysis, 5 of 19 at-risk individuals had to be considered to be at high risk of having inherited the disease. Four of them underwent proctocolectomy, one patient at risk is under colonoscopic surveillance. The predictive value of indirect genotype analyses reached 83.3%; direct mutation analyses allowed risk estimation in 50% of cases. Ophthalmologic investigation was informative in 75% of the families. Direct and indirect genotyping using a panel of highly polymorphic, closely linked microsatellite markers is a valuable, rapid, reliable method for establishing a presymptomatic diagnosis of APC, especially in families in which more than one affected individual is available for analysis. With regard to the onset of APC and extracolonic manifestations, the variability of APC demands clinical investigations in addition to the molecular tests for all patients and their first-degree relatives.

Presymptomatic diagnosis in Portuguese FAP families using intragenic RFLPs and (CA)n flanking markers by fluorescence based semiautomated DNA analysis

Owing to the large size of the APC gene, responsible for familial adenomatous polyposis, direct screening for individual mutations is not a practical approach. In the present study we establish the methodology of fluorescence based semi-automated DNA analysis to perform presymptomatic diagnosis of members at risk from 11 Portuguese FAP families with three (CA)n markers flanking the APC gene, MBC, CB26, and YN5.64, and four intragenic RFLPs. Haplotypes were constructed on the basis of individual genotypes and their segregation through generations were followed. The study was informative for 12% of subjects using only intragenic RFLPs and increased to 90% when we used the three (CA)n flanking markers. We report two of the 11 families under study in our laboratory and show recombinant events leading to a precise localisation of the CB26 marker between D5S82 and the APC gene. In one family there was a loss of (CA) units of one allele of the CB26 marker from an unaffected mother to her son.

Prophylaxis against colorectal cancer

Colorectal cancer is diagnosed in more than 3000 people every year in Denmark, with a population of 5 million, and 2000 die from this disease every year. The aetiology of the disease is complex, but an increasing number of cancers have been related to genetics and Denmark is contributing with a well-established register of familial adenomatous polyposis and a recently founded register for hereditary nonpolyposis colorectal cancer, both with major international relationships. The Danish tradition of epidemiology and clinical trials has also been demonstrated in population screening trials for colorectal cancer in average-risk persons as well as high-risk groups with precursors of the disease. The present review places Danish contributions within the prophylaxis of colorectal cancer during the last decade in an international context.

High resolution genetic map of the adenomatous polyposis coli gene (APC) region

Familial adenomatous polyposis coli (APC) is a dominantly inherited colorectal cancer susceptibility disease caused by mutation in a gene called APC and located on chromosome 5q21. Presymptomatic diagnosis of this condition is recommended because it enables restriction of the efficient but demanding prevention program to those relatives that are genetically affected. The large size of the APC gene makes the direct search for the causal alteration difficult to implement in routine diagnostic laboratories. Because APC appears to be genetically homogeneous with alteration in a single locus causing the disease, cosegregation analysis may represent an alternative efficient method for presymptomatic diagnosis. However, the reliability of the risk estimation by linkage analysis in APC families is hampered by the lack of a short range genetic map of the APC locus. A combined approach including genotyping of 65 APC families, analysis of the CEPH database, and complementary typing of both APC and CEPH families has made it possible to derive the following genetic map: Centromere-[D5S82-D5S49]-0.02-D5S122-0.01-D5S136 -0.01-D5S135-0.02-[APC-D5S346-MCC]-0.04-[D5S81-D5S6 4]-Telomere. This order, which differs from previously proposed genetic maps, is fully compatible with recent physical mapping data. These data should contribute to increase the reliability of the presymptomatic test for APC.

Familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an autosomal dominant condition resulting in the development of more than 100 adenomatous polyps in the large bowel. In addition, a number of extracolonic manifestations of the condition may occur. Recently, increasing knowledge relating to the extracolonic abnormalities, and localization and sequencing of the gene for FAP, have had important implications for screening and long-term follow-up of those affected. In this review the natural history of the disease and the extracolonic manifestations associated with it are considered. Surgical management and advances in understanding at a molecular level are discussed, as well as the problems relating to screening for FAP and the implications of the new knowledge.

Presymptomatic diagnosis in families with adenomatous polyposis using highly polymorphic dinucleotide CA repeat markers flanking the APC gene

A panel of five multiallelic and highly informative dinucleotide CA repeat markers flanking the APC gene was used for presymptomatic diagnosis of familial adenomatous polyposis coli (FAP). Marker regions were amplified by PCR. DNA fragments were separated by electrophoresis in denaturing polyacrylamide gels and visualised by ethidium bromide staining. Two or more markers were found to be informative in all nine families tested, and all 23 persons at risk could be diagnosed as affected or unaffected by the disease gene, the probability being > 99.9% in 14 cases from six families in which flanking markers were informative. We found no indication for locus heterogeneity of the disease in our sample. The polyposis phenotype and its extracolonic manifestations co-segregated with a distinct haplotype determined by the markers flanking the APC gene. In one family with no remaining living affected members, we could infer the high risk haplotype from genotyping of first degree relatives. The segregation of this haplotype is consistent with the occurrence of CHRPEs in the progeny. In a sporadic case we made use of the typical early extracolonic manifestations of the disease (osteomas, desmoids) to identify the high risk haplotype. We conclude from our experience that indirect genotyping of FAP with this particular panel of closely linked and highly polymorphic microsatellite markers is a rapid, efficient, and highly reliable method for presymptomatic diagnosis of FAP.

Knowledge of the adenomatous polyposis coli gene and its clinical application

Familial adenomatous polyposis (FAP) is one of the most clearly defined and well understood of the inherited colorectal cancer syndromes. It is an autosomal dominant condition with high (> 90%) penetrance. Clinically, it is characterized by multiple (> 100) adenomatous polyps in the colon and rectum; variant features in addition to the colonic polyps may include polyps in the upper gastrointestinal tract and other extracolonic manifestations. Since the risk of colorectal cancer in untreated FAP is virtually 100%, screening and intervention for at-risk persons has consisted of annual colon examinations by endoscopy beginning around puberty. The objective of this regimen is early detection of colonic polyps in those who have FAP, followed by preventive colectomy. Because of recent findings that most cases of FAP are due to mutations of the adenomatous polyposis coli gene at chromosome 5q21, genetic testing will probably be incorporated as the first step in the management of individuals at risk for this condition, and screening regimens can be modified. Genetic counselling about the consequences of presymptomatic gene testing is an important component of this process.