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Major Genetic Syndromes

    Table 5. Extracolonic Tumor Risks in Familial Adenomatous Polyposis continued...

    Level of evidence: None assigned

    Duodenum/small bowel tumors

    Whereas the incidence of duodenal adenomas is only 0.4% in patients undergoing upper gastrointestinal (GI) endoscopy,[68] duodenal adenomas are found in 80% to 100% of FAP patients. The vast majority are located in the first and second portions of the duodenum, especially in the periampullary region.[50,51,69] There is a 4% to 12% lifetime incidence of duodenal adenocarcinoma in FAP patients.[13,66,70,71] In a prospective multicenter surveillance study of duodenal adenomas in 368 northern Europeans with FAP, 65% had adenomas at baseline evaluation (mean age, 38 years), with cumulative prevalence reaching 90% by age 70 years. In contrast to earlier beliefs regarding an indolent clinical course, the adenomas increased in size and degree of dysplasia during the 8 years of average surveillance, though only 4.5% developed cancer while under prospective surveillance.[16] While this study is the largest to date, it is limited by the use of forward-viewing rather than side-viewing endoscopy and the large number of investigators involved in the study. Another modality through which intestinal polyps can be assessed in FAP patients is capsule endoscopy.[72,73,74] One study of computed tomography (CT) duodenography found that larger adenoma size could be accurately measured but smaller, flatter adenomas could not be accurately counted.[75]

    A retrospective review of FAP patients suggested that the adenoma-carcinoma sequence occurred in a temporal fashion for periampullary adenocarcinomas with a diagnosis of adenoma at a mean age of 39 years, high-grade dysplasia at a mean age of 47 years, and adenocarcinoma at a mean age of 54 years.[76] A decision analysis of 601 FAP patients suggested that the benefit of periodic surveillance starting at age 30 years led to an increased life expectancy of 7 months.[70] Although polyps in the duodenum can be difficult to treat, small series suggest that they can be managed successfully with endoscopy but with potential morbidity—primarily from pancreatitis, bleeding, and duodenal perforation.[77,78]

    FAP patients with particularly severe duodenal polyposis, sometimes called dense polyposis, or with histologically advanced duodenal adenomas appear to be at the highest risk of developing duodenal adenocarcinoma.[16,71,79,80] Because the risk of duodenal adenocarcinoma is correlated with the number and size of polyps, and the severity of dysplasia of the polyps, a stratification system based on these features was developed in order to attempt to identify those individuals with FAP at highest risk of developing duodenal adenocarcinoma.[80] According to this system, known as the Spigelman Classification (see Table 6), 36% of patients with the most advanced stage will develop carcinoma.[71]

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