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APC (Familial adenomatous polyposis) – risk management

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Familial adenomatous polyposis (FAP) is an autosomal dominant condition caused by a germline mutation in the APC gene.

Classical familial adenomatous polyposis (FAP) is defined by the presence of >100 colorectal adenomas (cumulative count), autosomal-dominant inheritance and young age of onset of polyposis (mean age approximately 15 years).  

Atypical/attenuated familial adenomatous polyposis (AFAP) is defined by the presence of fewer than 100 colorectal adenomas (cumulative count) and autosomal-dominant inheritance, with later onset of adenomas and cancer compared with classical FAP. 

This risk management guideline has been developed for individuals who have NOT been diagnosed with a relevant cancer/tumour. The care of affected individuals should be individualised based on their clinical situation, and the monitoring they need as part of their treatment and post-treatment follow up. 

  • Known APC mutation carrier.
  • Individuals meeting clinical criteria for FAP, who have uninformative genetic testing.

Exclusion criteria

  • Multiple mixed polyposis phenotype with no APC or MYH mutation identified.
  • Those at 50% risk of FAP who have not had genetic testing, or where genetic testing is not possible (refer to further information on risk management).
Tumour Familial adenomatous polyposis* General population to age 85 yrs
Colorectal cancer >95%r# 8% **
Duodenal or periampullary cancer 4.5% by age 57r <2%
Other neoplasms
Desmoid tumours 15%r^ <1%
Duodenal adenomas 90%r 0.3-4.6%
Gastric fundic gland polyps >50%r 6%

 *This data is from classical FAP and does not take the impact of surveillance into account
#Penetrance of colorectal adenoma is almost 100% by age 40 in the classical FAPrr
^there is a higher risk of desmoid tumour following surgery or pregnancy, with female gender, and with family history of desmoid tumoursrr

**Data source: NSW Central Cancer Registry 2008 final dataset and NSW Health Outcomes Information Statistical Toolkit (HOIST).

Cancer type Recommendationsa
Colorectal Surgical
  • Colectomyb is standard of care and is strongly recommended.
  • Timing of surgery: typically late teens for FAPc, often later for AFAPc, exact timing to be determined by individual patient factors and number of polyps present.
Surveillance Age to begin Strategy and frequency
  • FAP from 10-12 years
  • AFAP from 18-20 years
  • Annual flexible sigmoidoscopy or colonoscopy until polyps detected.
  • Then annual colonoscopy until colectomy done.
  • Annual surveillance of residual rectum or ileal pouch is required following colectomy.
  • Annual colonoscopy until colectomy done.
  • Annual surveillance of residual rectum or ileal pouch is required following colectomy.
Risk-reducing medication

No evidence that non-steroidal anti-Inflammatory drugs (NSAIDs) prevent colorectal cancer (CRC) in this situation.
Duodenum or periampulla Surgical

Consider duodenectomy for stage IV adenomas.r
Surveillance Age to begin Strategy and frequency

From 25 years
  • Upper gastrointestinal endoscopy frequency dependent on Spigelman criteria.r
  • Endoscopic surveillance should include side viewing endoscopy to ensure the medial wall and papilla are assessed.
  • Patients with adenomatous lesions larger than 10 mm to be reviewed in centres with both endoscopic and surgical expertise in duodenal and ampullary adenoma management.
Risk-reducing medication

No evidence that NSAIDs prevent small bowel tumours in this situation.
Desmoid tumours Risk-reducing medication

No evidence that NSAIDs prevent desmoid tumours in this situation.

athe impact of lifestyle on cancer risk should be discussed e.g. recommend regular exercise, maintain healthy weight, have a healthy diet, limit alcohol intake, do not smoke.
bthe two most common surgical options recommended are total colectomy with ileorectal anastomosis or total proctocolectomy with formation of ileal pouch anal anastomosis. 
cFAP = classical familial adenomatous polyposis; AFAP = atypical/attenuated familial adenomatous polyposis.

A systematic review found that registration, surveillance and colectomy have a consistent and significant reduction in incidence and CRC related mortality.r

Expert opinion is that children at risk for classic FAP are screened every 1 to 2 years by flexible sigmoidoscopy or colonoscopy, beginning at 10 to 12 years of age.rr 

Those initially screened at an older age should probably have colonoscopy for the first examination.r  If surgery is delayed longer than a year after polyps emerge, annual colonoscopy should be used for surveillance.

In AFAP the emergence of adenomas and cancer is delayed 10 to 20 years compared with classical FAP. People with AFAP have fewer adenomas than those with classical FAP, although polyp number is variable within kindreds.  As polyps have a more proximal colonic preponderance colonoscopy should be used for screening (not sigmoidoscopy), usually starting from late teens and repeated every 1 to 2 years depending on polyp burden.rr

The upper GI surveillance protocol is based on published literature and expert opinion.r

First degree (blood) relatives (parents/brothers/sisters/children) are at 50% risk of having inherited the gene mutation/or having the condition. First degree relatives should be referred to a local family cancer clinic.

Link to information sheet on Informing family members about hereditary cancer. 

Centre for Genetics Education NSW Health
Genetic Alliance Australia
Cancer Institute NSW FAP Information

Further References

For further references used to develop this protocol please see the History icon.

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Version 7

Date Summary of changes
18/10/2009 Approved on CI-SCaT.
26/07/2010 Updated and approved on eviQ.
19/10/2011

Reviewed and addition of

  • Lifetime risk of duodenal and periampullar cancer changed from 1.6 to 5%  to 4.5%.
  • Surgical recommendations for duodenal or periampullary tumours.
  • New reference Bulow, S, Bjork, J, Christensen, I, et al. 2004. "Duodenal adenomatosis in familial adenomatous polyposis." Gut 53: 381-386
17/04/2013

Discussed at October 27 2011 reference committee meeting, review continued via email and the following changes made:

  • Target group - added - first degree relatives of an individual with proven FAP (i.e. individuals at 50% risk of FAP)
  • Exclusion criteria - deleted -
    - attenuated familial adenomatous polyposis (AFAP)
    - families of individuals with a clinical diagnosis of FAP and no mutation identified
    **surveillance in accordance with age and previous colonoscopic findings
  • Lifetime risk of cancer table - updated.
  • Cancer risk management guidelines table - colorectal - surveillance - risk reducing medication - updated.
  • Management of associated health problems and side effects - deleted. - NSAIDS may be considered as an addition to surveillance and surgical management, but should not replace it.
04/09/2013

Following discussion the cancer risk management guidelines table - duodenum or periampulla - surveillance has been updated.
24/02/2015

Discussed at March 5, 2014 reference committee meeting, review continued via email and the following changes made:

  • Target group - Individuals at 50% risk moved to exclusion criteria link to 'Risk Management protocol for untested individuals at 50% risk of FAP'.
  • Lifetime risk of cancer/other neoplasm table - figures and references updated.
  • Cancer risk management guidelines table - colorectal - surveillance - added 
    • 'prophylactic' removed from colectomy 
    • age to begin colectomy changed to 10-15 yrs
    • annual surveillance of residual rectum or ileal pouch is required following colectomy.
  • Evidence for risk management guidelines - evidence section updated.
  • References - updated.

Approved for publication.
31/07/2015 Link to AGSA changed to Genetic Alliance Australia.
07/01/2016 Sentence added to Risk Management template: "The impact of lifestyle on cancer risk should be discussed".
14/04/2016 This risk management guideline has been developed for individuals who have NOT been diagnosed with a relevant cancer/tumour.  The care of affected individuals should be individualised based on their clinical situation, and the monitoring they need as part of their treatment and post-treatment follow up. 
06/12/2016

Discussed at the October 20, 2016 reference committee meeting and the following changes made:

  • Summary - updated
  • Cancer risk management guidelines - updated 
  • Evidence - updated
  • References - updated

Approved for publication with 2 yearly review.
31/05/2017 Transferred to new eviQ website. Version number changed to V.6.
28/08/2019 Protocol title changed from 'Risk management for familial adenomatous polyposis' to 'APC (Familial adenomatous polyposis) – risk management' in accordance with Cancer Genetics Reference Committees' consensus. Version number increased to V.7.
 

 Further references used to develop this protocol:

Bulow, S. 2003. "Results of national registration of familial adenomatous polyposis." Gut. 52(5):742-746.

Burn, J., P. Chapman, J. Delhanty, et al. 1991. "The UK Northern region genetic register for familial adenomatous polyposis coli: use of age of onset, congenital hypertrophy of the retinal pigment epithelium, and DNA markers in risk calculations." J Med Genet 28(5):289-296.

Clark, S. K. and R. K. Phillips. 1996. "Desmoids in familial adenomatous polyposis." Br J Surg 83(11):1494-1504.

Klemmer, S., L. Pascoe and J. DeCosse. 1987. "Occurrence of desmoids in patients with familial adenomatous polyposis of the colon." Am J Med Genet 28(2):385-392.

The information contained in this document is based on the highest level of available evidence and consensus of the eviQ reference committee regarding their views of currently accepted approaches to care or treatment. Any clinician seeking to apply or consult this document is expected to use independent clinical judgement in the context of individual clinical circumstances to determine any patient's care or treatment. Use is subject to eviQ’s disclaimer available at www.eviQ.org.au

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https://www.eviq.org.au/p/178

19 Jan 2021