Practice parameters for the identification and testing of patients at risk for dominantly inherited colorectal cancer--supporting documentation

The Natural History of Hereditary Colorectal Cancer Syndromes: From Phenotype to Genotype? Where Do We Stand and What Does the Future Hold?

Applying the concept of a "natural history" to hereditary colorectal cancer is an interesting exercise because the way the syndromes are approached has changed so drastically. However, the exercise is instructive as it forces us to think in depth about where we are, where we have been, and, most helpfully, about where we may be going. In this article the diagnosis, along with endoscopic and surgical management of hereditary colorectal cancer are discussed in the context of their history and the changes in genomics and technology that have occurred over the last one hundred years.

Colonic adenomatous polyposis syndromes: clinical management

Colorectal cancer is one of the major causes of cancer deaths in both men and women. It is estimated that 5 to 10% of patients with colorectal cancer have an inherited germline mutation that predisposes them to cancer. Hereditary colorectal cancer syndromes can be divided into those associated with colonic polyposis - familial adenomatous polyposis (FAP), attenuated familial adenomatous polyposis (aFAP), and MYH associated polyposis (MAP), and those not associated with colonic polyposis - hereditary nonpolyposis colon cancer (HNPCC). The hereditary polyposes are usually easier to diagnose than HNPCC, but their higher penetrance and variable phenotype pose some difficult problems in management and surveillance. The timing and type of surgical intervention, the management of desmoid risk, the treatment of rectal or pouch neoplasia, and the management of duodenal neoplasia are all questions that must be addressed in patients with FAP or MAP.

Colon cancer screening update and management of the malignant polyp

Colorectal carcinoma is common, but screening for this cancer has found less acceptance with the public than screening for breast, prostate, and cervical cancer. Available methods include fecal occult blood tests (FOBTs), flexible sigmoidoscopy (FOS), double-contrast barium enema, colonoscopy, computed tomographic colography, and fecal DNA. Evaluation of these options demonstrates that colonoscopy at ages 55 and 65 offers the best combination of reduction in colorectal cancer at the lowest cost. However, when compliance with screening recommendations is very high, costs are high, and the proportion of cancers arising from adenomas is low, the combination of FOS and FOBT is most cost effective. Malignant polyps look friable and irregular and feel hard. Sessile malignant polyps need to be treated by formal resection. Patients with pedunculated polyps with favorable histology (clear margin, well or moderately differentiated, no lymphovascular invasion) can be observed, and those whose polyps show unfavorable histology should have the polyp-bearing segment of colon resected along with its draining lymph nodes.

Family history? The forgotten question in high-risk colorectal cancer patients

AIM

The aim of the study was to investigate the frequency and detail of family history recorded for patients diagnosed with potentially high-risk colorectal cancer, and to determine the proportion of these patients referred to a high-risk assessment clinic.

METHOD

Medical records of patients diagnosed with colorectal cancer under the age of 50 admitted to a major Sydney teaching hospital were reviewed. The proportion of records containing information about family history was calculated. Associations between recording of family history and demographic and clinical characteristics of patients were investigated. Logistic regression modelling was performed to identify significant, independent predictors of study outcomes.

RESULTS

Of 113 patients with colorectal cancer diagnosed under the age of 50 years, 61 (54%, 95% CI: 44-63%) had an entry in their hospital medical record about family history. Family history was significantly less likely to be recorded for females, for those admitted via the Emergency Department, and for those with shorter lengths of stay. A significant family history was found in 51% of the 61 patients who had a family history recorded. Records of patients attending specialist colorectal surgeons were significantly more likely to contain information about family history than those who attended other specialists (P = 0.04). Only 14 patients (12%, 95% CI: 7-20%) were formally referred for further genetic assessment.

CONCLUSION

These results suggest that family history is still being neglected in routine clinical practice, and high-risk assessment services are underutilized, implying the need for further dissemination of guidelines with regard to the recognition and management of hereditary colorectal cancer.

[Familial adenomatous polyposis]

Familial adenomatous polyposis is a rare genetic disease characterized by the development of more than a hundred adenomatous polyps in the colorectal area, as well as by extracolonic manifestations. Without treatment, this inherited disease, usually transmitted by autosomal dominant inheritance, predisposes to colorectal cancer. Treatment must be preceded by counseling about the nature of the syndrome and by recommendations for the optimal management and surveillance of the disease. Currently, prophylactic surgical therapy is imperative. However, the type of surgical technique used depends mainly on the severity of the polyposis phenotype, the age of the patient at diagnosis, and a series of special clinical circumstances. Lifetime follow-up of all patients is required. This article reviews the main studies published on familial adenomatous polyposis in order to provide an update on the most appropriate management of these patients.

Estado actual del seguimiento del área gastroduodenal en la poliposis adenomatosa familiar

Familiar adenomatous polyposis (FAP) is a hereditary disease characterized by the development of multiple adenomatous polyps in the gastrointestinal tract and colorectal cancer in practically all patients who do not receive appropriate treatment. Although the most commonly involved region in this disease is the colorectal area, it is well known that adenomas can also develop in the upper gastrointestinal tract, mainly in the periampullary area of the duodenum. Because of the possibility of malignant transformation of these polyps, adequate monitoring is required, even though the optimal follow-up schedule has not yet been defined. In the present article, we report a case of a gastric adenocarcinoma detected during the follow-up of a patient diagnosed with FAP, as well as a review of the literature on this subject. We stress the need for early detection and appropriate management of this disease. Sufficient information is available to support the use of upper gastrointestinal endoscopy with lateral vision and serial biopsies of the periampullary region in these patients. The first endoscopy in patients with FAP should be performed at the age of 20 years or at diagnosis. Subsequently, a follow-up schedule should be designed, according to the number and histological characteristics of the polyps observed.

Adenomatous polyposis families that screen APC mutation-negative by conventional methods are genetically heterogeneous

PURPOSE

One third of families with classical adenomatous polyposis (FAP), and a majority of those with attenuated FAP (AFAP), remain APC mutation-negative by conventional methods. Our purpose was to clarify the genetic basis of polyposis and genotype-phenotype correlations in such families.

PATIENTS AND METHODS

We studied a cohort of 29 adenomatous polyposis families that had screened APC mutation-negative by the protein truncation test, heteroduplex analysis, and exon-specific sequencing. The APC gene was investigated for large genomic rearrangements by multiplex ligation-dependent probe amplification (MLPA), and for allelic mRNA expression by single nucleotide primer extension (SNuPE). The AXIN2 gene was screened for mutations by sequencing.

RESULTS

Four families (14%) showed a constitutional deletion of the entire APC gene (three families) or a single exon (one family). Seven families (24%) revealed reduced or extinct mRNA expression from one APC allele in blood, accompanied by loss of heterozygosity in the APC region in six (75%) of eight tumors. In 15 families (52%), possible APC involvement could be neither confirmed nor excluded. Finally, as detailed elsewhere, three families (10%) had germline mutations in genes other than APC, AXIN2 in one family, and MYH in two families.

CONCLUSION

"APC mutation-negative" FAP is genetically heterogeneous, and a combination of MLPA and SNuPE is able to link a considerable proportion (38%) to APC. Significant differences were observed in clinical manifestations between subgroups, emphasizing the importance of accurate genetic and clinical characterization for the proper management of such families.

Inherited colorectal cancer syndromes

Colorectal cancer is one of the major causes of cancer deaths in both men and women. It is estimated that approximately 5% to 10% of patients with colorectal cancer have an inherited germline mutation that predisposes them to cancer. Clinically, hereditary colorectal cancer syndromes can be divided into those associated with colonic polyposis (familial adenomatous polyposis, attenuated familial adenomatous polyposis, and MYH-associated polyposis) and those not associated with colonic polyposis (hereditary nonpolyposis colon cancer). Treatment options for these patients include multiple aggressive screening regimens, chemopreventive medications, and prophylactic surgery. Selection of the appropriate management approach is best made using information obtained from the patient's clinical examination, the family medical history, and genetic evaluation. Compliance is improved when patients completely understand their disease and participate fully in the formulation of the treatment plan. Although not proved, it seems reasonable that this approach may prevent the poor outcomes so frequently associated with inherited cancer syndromes.

Three new mutations in hereditary nonpolyposis colorectal cancer (Lynch syndrome II) in Uruguay

Hereditary nonpolyposis colorectal cancer (HNPCC) is the most common hereditary form of colorectal cancer (CRC). Our purpose is to describe three extended HNPCC families, each of which manifests novel germline mutations in Uruguay, a small country that is a study model for cancer investigation given its high cancer incidence and mortality rate. This is a study of three extended HNPCC families in which extensive genealogic information, medical history, and pathology findings are critically reviewed. DNA testing was performed for evidence of HNPCC mutations. The findings reveal three novel germline mutations, namely MLH1, with a deletion resulting in a frameshift and a premature stop codon (codon 228) in one of the families; in the second family, MSH2 exon 1, codon 61 at nucleotide 181, which results in immediate stop of translation; and in the third family, a mutation in MSH2 at exon 3: the amino acid at nucleotide 530, codon 117, causing a frameshift and a premature stop codon eight base pairs later. We conclude that it is important to study HNPCC mismatch repair genes because of emerging evidence for genotypic and phenotypic heterogeneity, which will harbor the potential to eventually translate this knowledge into specific screening and management protocols. Future projections for such mutations could even contribute to the emergence of molecular-based designer drugs developed through advances in genomics, proteomics, high-throughput screening, and bioinformatics, which would be effective therapeutically for these high-cancer risk patients.