# Familial adenomatous polyposis-associated colorectal cancer

Source: https://onco.cc/cancers/fap-associated-colorectal-cancer/  
OnCo record `fap-associated-colorectal-cancer` (Cancer). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

In familial adenomatous polyposis a person inherits a fault in the APC gene and grows hundreds or thousands of polyps in the large bowel from their teens. Left alone, almost all of them become cancer by about 40, so the bowel is watched from childhood and usually removed before that happens; the cancers that do occur are treated like ordinary bowel cancer.

## Summary

What it is. Familial adenomatous polyposis is an inherited condition caused by a germline variant in APC, the gatekeeper of the Wnt pathway whose loss also opens the sporadic adenoma-carcinoma sequence. Carriers develop hundreds to thousands of colorectal adenomas from adolescence; an attenuated form produces fewer polyps later in life. The World Health Organization lists it among the genetic tumour syndromes of the digestive system. It is not only a bowel condition: duodenal and gastric polyposis occurs in almost all patients, desmoid tumours are a leading cause of death after colectomy, and thyroid cancer, hepatoblastoma and medulloblastoma occur (Nagtegaal 2020; Gastrointest Endosc Clin N Am 2022).

How it differs from its parent. The cancer that arises in polyposis is an ordinary colorectal adenocarcinoma; what differs is everything before and after it. Cancer Research UK records that almost all untreated patients develop bowel cancer by age 40, against a median age at diagnosis of 66 in the United States for colorectal cancer generally. The tumours are the endpoint of a field of hundreds of adenomas rather than of one, which is why segmental resection is rarely enough and why surveillance of the retained rectum or ileal pouch continues for life after surgery (Best Pract Res Clin Gastroenterol 2022).

How common it is. Fewer than 1 percent of bowel cancers (Cancer Research UK). Because carriers are identified and operated on before cancer develops, the share of cancers is much smaller than the share of the polyp burden.

How it is treated. Colonoscopy is recommended from about age 10 to 12 at intervals of one to two years, and prophylactic colectomy is the intervention that prevents the cancer; after colectomy, endoscopic surveillance of the retained rectum or the ileal pouch continues, as does upper gastrointestinal surveillance with visualisation of the ampulla, because duodenal and ampullary cancer becomes the leading gastrointestinal risk once the colon is gone (Gastrointest Endosc Clin N Am 2022; Best Pract Res Clin Gastroenterol 2022). The type and timing of colectomy are not settled by consensus. A cancer that does occur is staged and treated as colorectal adenocarcinoma, with the systemic rows of the parent page. UK surveillance and surgical practice follow the British Society of Gastroenterology, ACPGBI and UK Cancer Genetics Group guidelines (Monahan 2020).

## Fields

- Kind: Cancer
- Last checked: 2026-09-24
- Also known as: Familial adenomatous polyposis-associated colorectal cancer (inherited APC variant; fewer than 1 percent of bowel cancers); FAP colorectal cancer; Polyposis coli; Adenomatous polyposis coli bowel cancer; Attenuated familial adenomatous polyposis
- Tags: gi; colorectal; subtype-page
- Group: gastrointestinal
- Burden: Familial adenomatous polyposis accounts for fewer than 1 percent of bowel cancers, and almost all untreated patients develop bowel cancer by age 40 (Cancer Research UK).
- Subtypes: Classic familial adenomatous polyposis (hundreds to thousands of colorectal adenomas from adolescence); Attenuated familial adenomatous polyposis (fewer adenomas, later onset, more proximal); Familial adenomatous polyposis with duodenal or ampullary neoplasia (the leading gastrointestinal risk after colectomy); Familial adenomatous polyposis with desmoid disease (a leading cause of death after colectomy)
- Biomarkers: Germline APC variant, and MUTYH testing when polyposis is present without an APC variant; Polyp count and distribution at colonoscopy, which set the timing of surgery; Spigelman stage of duodenal polyposis and the state of the ampulla, which set upper gastrointestinal surveillance

## Sections of this record

The page is a hub with ten sections in reading order; large sections have their own page. The same plan as JSON: https://onco.cc/api/v1/cancers/fap-associated-colorectal-cancer/sections.json

- Overview (on the hub): The TL;DR, the family this cancer belongs to, the organ, who gets it and what the state of the art is. https://onco.cc/cancers/fap-associated-colorectal-cancer/#overview
- What it is (on the hub): Anatomy, the subtypes and how they differ, how it is staged, and where advanced disease spreads. https://onco.cc/cancers/fap-associated-colorectal-cancer/#what-it-is [4 subtypes]
- Finding it (on the hub): How it shows itself, how it is confirmed, what screening exists, and the biomarkers clinicians test for. https://onco.cc/cancers/fap-associated-colorectal-cancer/#finding-it [3 biomarkers]
- Treating it (on the hub): The standard of care by setting, the medicines, surgery and radiotherapy named in it, and the regimens behind them. https://onco.cc/cancers/fap-associated-colorectal-cancer/#treating-it [2 settings, 1 decision with options]
- Evidence (on the hub): Trials recruiting now, the landmark trials, the key papers and what they mean, the latest literature, and the milestones year by year. https://onco.cc/cancers/fap-associated-colorectal-cancer/#evidence
- The science (on the hub): The molecular landscape: the targets and how often each appears, the pathways, the mechanics stages and the preclinical models. https://onco.cc/cancers/fap-associated-colorectal-cancer/#science [1 pathway]
- Where you are (own page): Cases by country, the UK and NHS pathway and other country lenses, and the expert centres with trials on record. https://onco.cc/cancers/fap-associated-colorectal-cancer/where-you-are/
- Living with it (on the hub): The decisions you may face, the aids that walk through them, the warnings on record, the first sixty days and the questions to ask. https://onco.cc/cancers/fap-associated-colorectal-cancer/#living-with-it [9 questions, 2 red cards]
- What is coming (own page): Everything in development, the open problems and what is being done about them, the roadmaps, and what changed on this record. https://onco.cc/cancers/fap-associated-colorectal-cancer/coming/ [2 medicines]
- Data (own page): Every connected record, the notes, the JSON, Markdown and RDF twins, and where the record came from and when it was checked. https://onco.cc/cancers/fap-associated-colorectal-cancer/data/ [14 connected records]

## Standard of care

- Surveillance and prophylactic surgery in carriers: Colonoscopy from about age 10 to 12 at one to two-yearly intervals; prophylactic colectomy before cancer develops, with the type and timing decided case by case; lifelong endoscopic surveillance of the retained rectum or ileal pouch afterwards; upper gastrointestinal endoscopy with ampullary visualisation at intervals set by duodenal and gastric findings. ([Colonoscopy](https://onco.cc/terms/colonoscopy/), [Colectomy](https://onco.cc/terms/colectomy/), [Endoscopy (EGD, EUS, ERCP)](https://onco.cc/terms/endoscopy/), [Germline (hereditary) testing](https://onco.cc/technologies/germline-testing/), [Surveillance intervals after polypectomy](https://onco.cc/terms/colonoscopy-surveillance-intervals/))
- Cancer arising in polyposis: Staged and treated as colorectal adenocarcinoma of the same stage, with the extent of resection decided by the field of polyps rather than by the single tumour; the parent record carries the systemic therapy rows. ([Colectomy](https://onco.cc/terms/colectomy/), [CAPOX (capecitabine, oxaliplatin)](https://onco.cc/drugs/capox/), [FOLFOX (5-FU, leucovorin, oxaliplatin)](https://onco.cc/drugs/folfox/))

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Familial_adenomatous_polyposis
- CRUK: bowel cancer risk factors (professional): https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/bowel-cancer/risk-factors
- Gastrointest Endosc Clin N Am 2022: endoscopic management and surgical considerations for familial adenomatous polyposis: https://doi.org/10.1016/j.giec.2021.08.007
- Best Pract Res Clin Gastroenterol 2022: management of familial adenomatous polyposis and MUTYH-associated polyposis, new insights: https://doi.org/10.1016/j.bpg.2022.101793
- Monahan, Gut 2020: BSG, ACPGBI and UKCGG guidelines for the management of hereditary colorectal cancer: https://doi.org/10.1136/gutjnl-2019-319915
- Nagtegaal, Histopathology 2020: the 2019 WHO classification of tumours of the digestive system: https://doi.org/10.1111/his.13975
- NICE NG151: colorectal cancer, recommendations (Lynch 1.1, local disease 1.3, biomarkers 1.4, metastatic disease 1.5, ongoing care and support including follow-up 1.6): https://www.nice.org.uk/guidance/ng151/chapter/Recommendations

## Connected records

- cancers: [Adenoma-like adenocarcinoma of the colon and rectum](https://onco.cc/cancers/colorectal-adenoma-like-adenocarcinoma/), [Colon cancer (adenocarcinoma of the colon)](https://onco.cc/cancers/colon-cancer/), [Colorectal cancer](https://onco.cc/cancers/colorectal/), [Early-onset colorectal cancer (under 50)](https://onco.cc/cancers/early-onset-colorectal/), [Lynch syndrome-associated colorectal cancer](https://onco.cc/cancers/lynch-associated-colorectal-cancer/), [Rectal cancer](https://onco.cc/cancers/rectal-cancer/)
- terms: [Adenoma-carcinoma sequence](https://onco.cc/terms/adenoma-carcinoma-sequence/), [Colectomy](https://onco.cc/terms/colectomy/), [Colonoscopy](https://onco.cc/terms/colonoscopy/), [Endoscopy (EGD, EUS, ERCP)](https://onco.cc/terms/endoscopy/), [Germline vs somatic mutations](https://onco.cc/terms/germline-vs-somatic/), [Polyp types in the bowel](https://onco.cc/terms/colorectal-polyp-types/), [Surveillance intervals after polypectomy](https://onco.cc/terms/colonoscopy-surveillance-intervals/)
- technologies: [Germline (hereditary) testing](https://onco.cc/technologies/germline-testing/), [Histopathology & immunohistochemistry](https://onco.cc/technologies/histopathology-ihc/)
- pathways: [Wnt / β-catenin](https://onco.cc/pathways/wnt/)
- drugs: [CAPOX (capecitabine, oxaliplatin)](https://onco.cc/drugs/capox/), [FOLFOX (5-FU, leucovorin, oxaliplatin)](https://onco.cc/drugs/folfox/)

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JSON: https://onco.cc/api/v1/entities/fap-associated-colorectal-cancer.json