Genetics of Colorectal Cancer (PDQ®): Genetics - Health Professional Information [NCI] - Major Genetic Syndromes
Table 5. Extracolonic Tumor Risks in Familial Adenomatous Polyposis continued...
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. 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. 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.[85,86]
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.[16,79,87,88] 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 to attempt to identify those individuals with FAP at highest risk of developing duodenal adenocarcinoma. According to this system, known as the Spigelman Classification (see Table 6), 36% of patients with the most advanced stage will develop carcinoma.
Table 6. Spigelman Classification
|Points||Polyp Number||Polyp Size (mm)||Histology||Dysplasia|
|Stage I, 1–4 points; Stage II, 5–6 points; Stage III, 7–8 points; Stage IV, 9–12 points|
A baseline upper endoscopy, including side-viewing duodenoscopy, should be performed between ages 25 and 30 years in FAP patients. The subsequent intervals between endoscopy vary according to the findings of the previous endoscopy, often, based on Spigelman stage. Recommended intervals are based on expert opinion although the relatively liberal intervals for stage 0-II disease are based in part on the natural history data generated by the Dutch/Scandinavian duodenal surveillance trial (see Table 7).
The main advantages of the Spigelman Classification are its long-standing familiarity to and usage by those in the field, which allows reasonable standardization of outcome comparisons across studies.[71,89] However, there are several limitations on attempted application of the Spigelman Classification:
- Most pathologists do not currently employ the term moderate dysplasia, preferring a simpler low- versus high-grade dysplasia system.
- Because of the villous nature of normal duodenal epithelium, pathologists commonly disagree over the classification of "tubular," "tubulovillous," and "villous."
- Spigelman staging requires biopsy, which is not always essential when only a few small plaques are present; conversely, for larger adenomas, sampling variation leads to understaging.[90,91]