Familial Adenomatous Polyposis (FAP): A Rare But Real Risk Factor

Most Australians diagnosed with bowel cancer don’t have a strong family history. But for a small group of people, the risk is inherited. One of the most well-known genetic conditions that increases bowel cancer risk is called Familial Adenomatous Polyposis, or FAP.

It’s rare. But it’s real. And if it runs in your family, the consequences can be life-changing. Knowing what to look for can also be life-saving.

What is Familial Adenomatous Polyposis (FAP)?

FAP is a rare genetic condition that causes hundreds, sometimes thousands, of small growths called polyps to form in the lining of the colon and rectum. These polyps usually start appearing in the teenage years. If left untreated, they almost always lead to bowel cancer.

The condition is caused by a mutation in the APC gene, a tumour suppressor gene that normally keeps cell growth in check. When this gene stops working properly, cells in the bowel can grow out of control and form polyps.

There are two main forms of FAP:

• Classic FAP: Typically causes hundreds or thousands of polyps, often showing up during the teenage years or early adulthood.
• Attenuated FAP (AFAP): A milder version, with fewer polyps that appear later in life.

How Common Is FAP?

FAP is rare. It affects about 1 in 8,000 to 1 in 10,000 people. For those who have it, the risk of developing bowel cancer is close to 100 percent without treatment, usually before age 40.

Since it’s passed down genetically, knowing your family history is crucial. If one parent has FAP, each child has a 50 percent chance of inheriting the condition.

Signs FAP Might Be in Your Family

FAP can be tricky to detect early, especially when symptoms are mild. But there are some signs to watch for:

• Multiple relatives diagnosed with bowel cancer, particularly under age 50
• A known family history of FAP or an APC gene mutation
• A family member with hundreds of bowel polyps or polyps found at a young age
• Unexplained gut issues in teens or young adults

Sometimes, the first clue comes after a family member is diagnosed with bowel cancer or has an unusually high number of polyps found during a colonoscopy.

How Is FAP Diagnosed?

FAP is usually diagnosed using:

• Colonoscopy: To find and count polyps
• Genetic testing: To check for mutations in the APC gene

If a family member has already been diagnosed with FAP, you can access predictive genetic testing through a family cancer clinic or a genetic counsellor. This service is available in many parts of Australia.

What’s the Cancer Risk With FAP?

Without treatment, the chance of developing bowel cancer for someone with FAP is nearly 100 percent by age 40 to 50.

FAP can also increase the risk of other types of cancer, including:

• Small bowel or duodenal cancer
• Pancreatic cancer
• Thyroid cancer
• Brain tumours (in rare cases like Turcot syndrome)

Because of this, people with FAP are usually enrolled in a personalised screening program from a young age.

What Are the Treatment and Management Options?

Managing FAP is all about staying ahead of cancer. Some of the main strategies include:

1. Regular Screening

• Frequent colonoscopies, sometimes starting in early adolescence
• Upper GI endoscopies to check for duodenal polyps
• Thyroid ultrasounds or other screenings, depending on risk

2. Preventative Surgery

Because of the high number of polyps, surgery to remove the colon is often recommended. Common options include:

• Total colectomy with ileorectal anastomosis: Removes the colon but leaves the rectum
• Proctocolectomy with ileal pouch (J-pouch): Removes both the colon and rectum

These surgeries can significantly reduce or even eliminate the risk of bowel cancer.

3. Genetic Counselling

Genetic counsellors help families navigate FAP. They can support you with:

• Arranging testing and explaining results
• Understanding how FAP is inherited
• Making decisions about screening, surgery, and family planning

Living With FAP

FAP doesn’t just affect individuals. It affects families. When one person is diagnosed, it often leads to testing and diagnoses in close relatives too. That can feel overwhelming.

The good news is that early diagnosis and ongoing care can make a huge difference. Many people with FAP live long, fulfilling lives thanks to surgery and close monitoring.

Having a solid team, including genetic specialists, surgeons, gastroenterologists, and psychologists makes the journey easier to manage.

Where to Get Support in Australia

• Bowel Cancer Australia: Offers support and resources for people affected by hereditary bowel cancer.
• Centre for Genetics Education: Information about family cancer clinics and genetic testing in Australia.
• Cancer Council Australia: Support services, counselling, and helplines across the country.

Final Thought

Familial Adenomatous Polyposis might be rare, but the risk is serious. If bowel cancer runs in your family, or someone close to you has been diagnosed with FAP, it’s worth getting checked out.

Early screening and genetic testing could change your future, or even save your life. You don’t need to be scared. You just need to be proactive.