Familial Adenomatous polyposis (FAP) is a rare genetic condition characterised by the development of hundreds to thousands of adenomatous colorectalrelating to the colon or rectum in the large bowel/intestine polyps and a predisposition to malignancy (cancera disease where abnormal cells split without control and spread to other nearby body tissue and/or organs), most notably colonthe longest portion of the large bowel that absorbs water and salts from ingested food cancer. It is caused by an alteration in the adenomatous polyposis coli (APC) gene, which is a type of tumoura tissue mass that forms from groups of unhealthy cells suppressor gene.
Familial cancer syndromes, also known as hereditary cancer syndromes, are rare conditions that cause an increased riskthe possibility that something bad will happen of cancer as the result of inherited genetic mutations in certain cancer-related genes. They can affect both adults and children, however they generally develop in people at a younger age than normal. While familial cancer syndromes are not classified as cancer, they are equally as severe and can be life-threatening as they are associated with the development of various tumours throughout the body. Having a familial cancer syndrome does not guarantee the development of cancer, however the risk of developing cancer is higher than those who do not have a familial cancer syndrome.
FAP is generally diagnosed equally among the sexes, and is often diagnosed around the age of 40. However, people with this condition may start developing colon polyps at approximately 16 years of age, and anyone can develop this disease.
Types of Familial Adenomatous Polyposis
There are several types of FAP, which are categorised by the number of colorectal polyps that develop and by any disease manifestations outside of the gastrointestinal tract.
FAP Subtypes
There are two distinct subtypes of FAP that present with polyps solely in the gastrointestinal tract.
Classic FAP
Classic FAP is the most common subtype of this disease, and is characterised by the development of over 100 colorectal polyps (benignnot cancerous, can grow but will not spread to other body parts tissuea group of cells that work together to perform a function growths) that generally start developing around the age of 16. People with classic FAP may require an annual colonoscopyan examination of the large intestine/bowel with a small, flexible instrument known as a colonoscope to screen for colorectal cancer.
Attenuated FAP (AFAP)
Attenuated FAP (AFAP) is a less common subtype of this disease, and is characterised by the development of less than 100 colorectal polyps (generally between 20-100). People with this subtype tend to develop polyps later in life, and the polyps are generally found in the proximal colon. While AFAP is considered a milder form of FAP, regular monitoring is still important to ensure the polyps don’t become cancerous.
FAP Variants
There are two distinct variants of FAP that also present with polyps in the gastrointestinal tract, however they also present with tumours in other areas of the body.
Gardner Syndrome
Gardner syndrome is a variant of familial adenomatous polyposis (FAP) that has the characteristics of FAP with additional tumours outside of the gastrointestinal tract, including osteomas (benign bone tumours), as well as various skin and soft tissuetissue/the material that joins, holds up or surrounds inside body parts such as fat, muscle, ligaments and lining around joints tumours. For more information on Gardner syndrome, please refer to the Rare Cancers Australia Gardner Syndrome page.
Turcot Syndrome
Turcot syndrome is a variant of familial adenomatous polyposis (FAP) that has the characteristics of FAP with an additional risk of developing brain tumours such as glioblastomas and medulloblastomas. For more information on Turcot syndrome, please refer to the Rare Cancers Australia Turcot Syndrome page.
Familial Adenomatous Polyposis Related Tumours
FAP is most commonly associated with the development of colorectal cancers, however it has also been linked to other types of tumours. Some examples include:
- Colorectal cancers (bowel cancers).
- Hepatoblastomas.
- Stomach cancers.
- Small bowel cancers.
- Pancreatic cancers.
- Cholangiocarcinomas.
- Desmoid tumours.
- Papillary thyroid cancers.
- Benign growth and tumours, such as:
- Epidermal cystsabnormal growths that are usually filled with liquid or air (benign growths beneath the skin).
- Osteomas (benign bone tumour).
- Fibromas (benign growths made up of fibrous connective tissue).
Treatment
When cancers are detected, they are staged and graded based on size, metastasiswhen the cancer has spread to other parts of the body, also known as mets, and how the cancer cellsthe basic structural and functional unit of all living things look under the microscope. Stagingthe process of determining how big the cancer is, where it started and if it has spread to other areas and grading helps your doctors determine the best treatment for you. However, each patient with FAP will present with a unique disease behaviour, with varying tumour locations and symptoms. As such, there is no one treatment method that will work for everyone, and there is no standard staging system for this disease. Instead of staging and grading, your doctor will recommend a treatment plan based on the following factors:
- Type of tumours present.
- Whether the tumours are malignantcancerous, may grow and spread to other areas of the body (cancerous) or benign (non-cancerous).
- Tumour location.
- Whether or not malignant tumours have metastasised.
- Your age.
- General health.
- Your treatment preferences.
Your doctor may also recommend genetic testinga procedure that analyses DNA to identify changes in genes, chromosomes and proteins, which can be used to analyse tumour DNA to help determine which treatment has the greatest chance of success, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment options for tumours associated with FAP may include:
- Surgerytreatment involving removal of cancerous tissue and/or tumours and a margin of healthy tissue around it to reduce recurrence to remove as much of the tumour(s) as possible – these will vary based on tumour type and location.
- Chemotherapya cancer treatment that uses drugs to kill or slow the growth of cancer cells, while minimising damage to healthy cells.
- Radiation therapya treatment that uses controlled doses of radiation to damage or kill cancer cells.
- Hormone therapymedication that alters the levels of certain hormones in the body, such as oestrogen and progesterone.
- Nonsteroidal anti-inflammatory drugs (NSAIDs).
- Clinical trialsresearch studies performed to test new treatments, tests or procedures and evaluate their effectiveness on various diseases.
- Palliative carea variety of practices and exercises used to provide pain relief and improve quality of life without curing the disease.
Cancer Screening
Once a diagnosisthe process of identifying a disease based on signs and symptoms, patient history and medical test results of FAP has been confirmed, implementing a targeted screeningtesting for cancer or conditions that can lead to cancer before symptoms appear, also known as cancer screening plan becomes essential due to the increased risk of developing certain cancers. The content of this plan will vary from person to person based on the genetic mutation involved, your family’s history of cancer and the types of cancers that may be present. It will also outline the routine tests you should have and how regularly you should have them. Some recommendations for FAP may include:
- Annual physical examinationan examination of your current symptoms, affected area(s) and overall medical history.
- Annual colonoscopy or flexible sigmoidoscopyexamination of the lower portion of the large intestine and rectum with small, flexible instrument known as a sigmoidoscope starting at age 10-12.
- Gastroscopyexamination of the stomach and part of the small bowel with a small, flexible instrument known as a gastroscope every four years starting around 20-25 or after colonic polyps have been detected.
- Thyroid ultrasounds every 2-5 years starting in late adolescence.
- Abdominal ultrasounda type of medical imaging that uses soundwaves to create detailed images of the body every 3-6 months until age five in patients with a family history of hepatoblastoma.
Screening options for FAP may evolve as new technologies are developed and our understanding of the condition grows. It is essential to discuss your individual circumstances with your healthcare team to determine the most appropriate screening plan for you.
Risk factors
FAP is caused by a genetic mutation in the APC tumour suppressor gene, which acts to inhibit cell growth to prevent overproduction of cells and the development of tumours. It is an autosomal dominant disease, which means that you have a 50% chance of developing the condition if one of your parents carries the mutation.
Symptoms
The symptoms of FAP often vary by the type(s) of tumours present. General symptoms of FAP may include:
- The presence of hundreds of polyps in the colon.
- Abdominal pain and/or discomfort.
- Changes in bowelportion of the digestive system that digests food (small bowel) and absorbs salts and water (large bowel); also called intestines movements, potentially including:
- Diarrhoeafrequent discharge of watery or loose stools from the body.
- Constipationa condition where a person has difficulty passing faeces/stools.
- Feeling of incomplete bowel movement.
- Thin bowel stools.
- Bloodthe red bodily fluid that transports oxygen and other nutrients around the body in stools.
- Rectal bleeding.
- Unexplained weight loss/loss of appetite.
- Fatiguea state of extreme tiredness or exhaustion, can be physical or mental.
- Anaemiaa condition where there aren't enough red blood cells in the blood, causing fatigue, weakness and pale skin and affecting how the body responds to infection.
- Nauseato feel sick or likely to vomit and/or vomiting.
Symptoms related to specific tumours can be found on our knowledgebase.
Not everyone with the symptoms above will have cancer, but see your general practitioner (GP) if you are concerned.
Diagnosis
If your doctor suspects you have tumours associated with FAP, they may order some of the following tests to confirm the diagnosis and refer you to a specialist for treatment. The tests required for diagnosis will often vary based on the symptoms present, and where the tumour(s) are suspected to be located.
- Physical examination.
- Genetic testing.
- Blood teststesting done to measure the levels of certain substances in the blood.
- Imagingtests that create detailed images of areas inside the body tests, potentially including:
- Ultrasound.
- MRI (magnetic resonance imaging)a type of medical imaging that uses radiowaves, a strong magnet and computer technology to create detailed images of the body.
- CT (computed tomography) scana type of medical imaging that uses x-rays and computer technology to create detailed images of the body.
- Exploratory procedures, such as:
- Colonoscopy.
- Flexible sigmoidoscopy.
- Other types of endoscopya procedure that involves inserting a long, flexible tube with a light and small camera (endoscope) into the body to view internal organs as indicated.
- Biopsyremoval of a section of tissue to analyse for cancer cells.