What is FAP?

Hereditary Cancer Registry
Familial Adenomatous Polyposis (FAP)

What is FAP?

• FAP is an inherited bowel cancer syndrome.
• The most common indication of FAP is the development of 100s to 1000s of polyps in the large bowel (intestine). Polyps are small mushroom-like growths with stalks that vary in size from a tiny pinhead to 2 cm or more.
• Most people with FAP develop polyps in their bowel by their late teens, although polyps may develop at any age.
• Some polyps may become cancerous if left untreated, while others may remain benign growths.
• People with FAP are at high risk of developing bowel cancer much earlier than the general population.
• FAP is caused by a change in the APC gene. Everyone has two copies of the APC gene, but people with FAP have one working copy and one non-working copy. 
• If your parent or a brother or sister has FAP, you are at risk. If you have FAP, your children are at risk. An affected person has a 50% chance of passing the condition on to each of their children.
• Not all people with FAP have a family history of FAP. Some people may be the first in their family to have FAP. If you are the first one in your family to have FAP, each of your children still have the same 50% chance of inheriting the gene change.

Are there other signs of FAP?

• Freckles in the Eye
  Some people with FAP have tiny freckles at the back of the eye (known as congenital hypertrophy of the retinal pigment epithelium - CHRPE). The freckles will not affect your vision or develop into cancer. Not all individuals affected by FAP have freckles in the eye.
• Polyps in other places
  Polyps can develop in other parts of the gut, including the stomach and duodenum. See your doctor for further information.
• Gardner ’s syndrome
  Gardner’s syndrome is a variation of FAP caused by changes in the same APC gene. The main indication of Gardner’s Syndrome is small cysts and benign (non-cancerous) growths in the bones, particularly on the jaw. Lumps also occur below the skin, on the face, or the scalp. Occasionally individuals have missing or extra teeth, or impacted teeth.
• Desmoid tumours
  Desmoid tumours are benign tumours (non-cancerous) and are commonly found within the wall or lining of the abdomen (belly). Desmoids are slow growing and only become a problem as they get larger and interfere with the functioning of other organs. Desmoids do not spread to other parts of the body.  

Management

Talk to your specialist about the best screening service for you.

Regular check-ups

• If you are diagnosed with FAP but have not yet had a colectomy (removal of all or part of the colon), you should have a colonoscopy every year to check for polyps.  This is a procedure where a long flexible tube is used to examine the lining of your colon (large intestine). See diagram below.

Figure 1: Anatomy of the bowel
Source: CancerBackup (UK) 5/12/2006

• A colectomy is recommended in most cases by the age of 20.
• Following surgery, a sigmoidoscopy (a procedure in which a long flexible tube is used to view the sigmoid colon and or/rectum) should be performed every six months.
• If a pelvic pouch operation was performed when the colon was removed, the pouch should be examined annually.
• If a close relative in your family is diagnosed with FAP, you and other relatives should begin screening from age 12-15 years with a sigmoidoscopy every year until the age of 35. After age 35, continue screening with sigmoidoscopy every 3 years.

Types of surgery

Talk to your surgeon about the best treatment for you.

• Ileorectal Anastomosis and Colectomy : removal of the entire colon. The end of the small bowel (ileum) is joined to the rectum. See Diagram.
• Restorative Proctocolectomy: removal of the entire colon, most of the rectum and its lining. A new rectum (called a pouch) is made and this is joined to the anus.
• Proctocolectomy & Ileostomy: removal of the entire colon, rectum and anus. The end of the small bowel (ileum) is joined to the wall of the abdomen, opening to the outside (known as a stoma) to allow bowel motions to pass out.

Genetic testing

• Researchers have identified a gene associated with FAP, the APC gene. Changes in the APC gene can lead to the development of FAP.
• If a causative APC gene change is identified amongst your family (in someone who has FAP), other relatives at risk of carrying the gene change can be offered genetic testing.
• Sometimes a gene change is not found in the family. This means that in your family, FAP may be due to other gene changes that research has not yet identified. If the family gene change is not found, genetic testing is not able to be offered to other family members.
• If a family gene change is found, the rest of the family can be offered predictive genetic testing. This means testing to see if you have inherited FAP by checking whether or not you have the gene change even though you may not have any signs or symptoms yet.
• A blood test is needed for genetic testing. For further information speak with a Genetic Counsellor.

What is attenuated FAP?

A rare form of FAP called attenuated FAP occurs in some people. Attenuated FAP involves less than 100 polyps. If you are diagnosed with this condition, you are still strongly predisposed to colorectal cancer. The primary difference is that people with attenuated FAP will typically develop cancer later than people with classic FAP. Speak to your doctor or Genetic Counsellor about your risks and management.

What if I suspect I have FAP?

Speak to your doctor, a Genetic Counsellor or call the Hereditary Cancer Registry on 1800 505 644.

For more information on hereditary cancer, please visit eviQ and click on the Cancer Genetics tab.