Colorectal polyps and cancer
In classic FAP extensive colonic adenomatous polyposis is typically evident early in the second decade of life (but can develop earlier). In atypical FAP polyps typically develop at a later age, although the age at first polyps varies from adolescence to mid-to-late adulthood. Without polypectomy and/or colectomy polyps eventually become malignant. Colorectal cancer occurs most often in adulthood but is occasionally seen in childhood or adolescence.
Multiple studies have demonstrated that surveillance colonoscopy from early childhood with appropriately timed colectomy reduces CRC incidence and mortality.r The natural history of polyposis supports annual surveillance in classical FAP. It also supports surveillance by either sigmoidoscopy or colonoscopy until polyps are first detected, and then by colonoscopy.r
Some experts recommend less frequent (2-3 yearly) colonoscopy for individuals at risk of atypical FAP who have not developed polyps. They recommend an increase to 1-2 yearly colonoscopy once polyps have been detected, with the frequency guided by polyp burden.r Others recommend annual surveillance because of the variability in polyp phenotype that is seen both between and within families. In AFAP polyps have a more proximal colonic preponderance and colonoscopy should be used for surveillance (not sigmoidoscopy).
Gastric, duodenal and small bowel polyps and cancer
Gastric, duodenal and jejunal polyps may be evident by the second decade of life. Progression to malignancy is uncommon.r The recommended upper GI surveillance protocol is based on published literature and expert opinion.r
Although desmoid-type fibromatosis is a benign fibroblastic neoplasm, intra-abdominal desmoids can cause substantial morbidity in patients with FAP, and contribute to FAP-related mortality. Abdominal surgery, APC pathogenic variant site and positive family history for desmoid-type fibromatosis are consistent risk factors for development of desmoid-type fibromatosis.r There is conflicting evidence regarding female gender, pregnancy and oestrogen exposure. Some experts recommend annual surveillance using abdominopelvic MRI for patients who have had abdominal surgery and have a family history, but there is no evidence of benefit.
The American College of Gastroenterology recommends hepatoblastoma surveillance from birth to age 7 years. However, there is substantial controversy about surveillance as the absolute risk of hepatoblastoma is small and there is no evidence of benefit of surveillance.r
The cribriform-morular variant of papillary thyroid cancer is more common in FAP patients, especially females. Some experts recommend annual clinical examination of the neck from mid-teenage years,r others recommend periodic thyroid ultrasound. There is no evidence of benefit for either approach.