Familial Adenomatous Polyposis (FAP) is an inherited condition in which non-cancerous polyps (small growths, usually benign, protruding from the lining of human tissue) grow in the colon and rectum. The polyps can become cancerous over time, resulting in colorectal cancer.
- FAP is caused by a mutation of the adenomatous polyposis coli (APC) gene.
- People with FAP usually develop colorectal cancer by their 40s.
- While there is no cure for FAP, surveillance and treatment can prevent cancer.
FAP is the result of changes to the DNA, which results in the APC gene being unable to do its job of suppressing tumors. Because of the mutations in the APC gene, rectal and colon polyps grow out of control. These polyps are also known as adenomas. People with FAP develop multiple polyps, and the number can actually be used to subclassify patients, aiding as a roadmap to their treatment.
The APC gene mutation that causes FAP is usually inherited from a parent, but in some people the mutation can occur spontaneously. When it is inherited from a parent, it is passed on in an autosomal dominant manner, meaning that the child of someone with FAP has a 50% chance of inheriting the mutated gene from their parent.
Symptoms can vary from person to person, even when the condition exists within the same family, and range from mild to severe. For people with FAP, the development of polyps within their colon and rectum usually begins in their teens. Polyps aren’t typically painful, but they can bleed and lead to the appearance of blood in stool. Bleeding from polyps can also lead to the gradual development of anemia.
The mutated APC gene that causes FAP can also lead to issues with other organs, like bones, the brain, the thyroid gland, and the retinas of the eye. Some of the most common other organs to develop polyps in FAP are the stomach and the duodenum (the first part of the small intestine). Rarely, the polyps in the stomach and the duodenum can develop into stomach cancer and duodenal cancer, respectively.
Some of the specific issues beyond polyps in the rectum and colon include:
- Benign tumors in the connective/scar tissue (desmoid tumor)
- Noncancerous tumors in the bones (osteomas)
- Tooth decay
- Pigmentation just outside the retina (Congenital hypertrophy of the retinal pigment epithelium)
- Noncancerous skin abnormalities
- Cancer in additional parts of the body, including the small bowel, thyroid, pancreas, and other areas.
If the polyps associated with FAP develop into malignant cancers, other symptoms may develop, including:
- Weight loss
- Altered bowel habits
FAP is typically diagnosed through colonoscopy and genetic testing.
A colonoscopy is a procedure that uses a tiny camera attached to a flexible tube to examine the inside of the colon and rectum. A colonoscopy can allow healthcare workers to see the polyps lining the rectum and colon, and to also take cell samples from them to test for cancer. If it’s confirmed that the person carries the APC mutation, they begin colonoscopy screenings by age 10 or 11. Yearly colonoscopies continue until colon surgery is required.
Genetic testing can confirm the diagnosis of FAP by showing that the APC gene is mutated in a DNA sample. The DNA used for a genetic test for FAP can come from a blood sample or from a cheek swab. Since FAP is a genetic condition, family members of those with FAP may want to be tested for the mutation as well.
Other Forms of Diagnosis
- Sigmoidoscopy: A procedure where a doctor uses a lighted tube to examine the tissue and cells of the rectum and lower colon. It is similar to a colonoscopy but it does not examine the full length of the colon. A sample may be taken at this time for further testing.
- Barium Enema: This is a procedure that allows healthcare workers to visualize the colon through an x-ray. Before the x-ray is taken, a preparation of liquid barium is inserted into the rectum through a small tube. The barium can be seen on x-rays and helps create a clear outline of the bowels.
FAP is not a condition that can be cured, but it can be managed. Treatment for FAP is centered around preventing cancer and/or promptly intervening with surgery once it develops.
Regular cancer screening and surveillance tests for FAP include:
- Colonoscopy: Along with being a tool for diagnosis, subsequent yearly colonoscopies help to control the polyps, by allowing the surgeon to track their presence, number, and sizes, until they become too numerous and surgery is planned.
- Stomach & Duodenum Checks: In patients with FAP, keeping a close watch on the number of polyps in the stomach and duodenum, starts at the age of 20. The stomach and duodenum can be checked through upper endoscopy (a test similar to a colonoscopy, except the thin, flexible tube enters through the mouth and examines the upper part of the digestive system) every one to three years. Similar to the colonoscopy, if large numbers of polyps are detected, surgery may be recommended.
- Thyroid Checks: Thyroid ultrasounds are performed at the point of diagnosis, and then every other year. Large lumps (over half an inch) are biopsied, and removed if cancerous.
Medications alone cannot prevent colon cancer due to FAP, but they can reduce the number of polyps and slow down the development of cancer. Sulindac and celecoxib, two nonsteroidal anti-inflammatory drugs, are known to potentially reduce the size and amount of polyps found in the rectal stump (pouch that remains after a colostomy, the surgical removal and/or diversion of the damaged part of the colon).
Before cancer develops in the colon, treatment may come in the form of surgical removal of the colon.
Surgery is the best treatment for polyps that can’t be treated endoscopically and for polyps that have developed into cancer. Colorectal surgeons can remove the cancerous portion of the colon and/or rectum. Experienced surgeons can reconstruct the digestive tract so that the patient can avoid needing a permanent stoma (an opening between the digestive tract and the skin, which allows the bowels to be drained into an attached bag). The exact timing, approach and scope of surgery will depend on the number, size, and position of cancerous polyps.
In general there are three surgical options:
- Take the colon out and join the small bowel to rectum, creating what is called an Ileorectal anastomosis, or IRA for short.
- Take the colon and rectum out and make a pouch (J, S or K pouch ). This is called an ileal pouch-anal anastomosis, or IPAA.
- Take the colon and rectum out and make a bag (ileostomy).
Patients with an IRA don’t need an external bag and have an average of 4 bowel movements a day with good control. Patients with an IPAA have more bowel movements a day, usually have good control, but may need a temporary bag.
Patients who have had surgery need to have their pouch or rectum checked once a year.
Specialists involved in the diagnosis and treatment of FAP include:
- Colorectal Surgeons
Certified Wound Ostomy Continence Nurses and Nutritionists may play a role in post-surgical management.
Even after surgery, people with FAP have a risk of developing colorectal cancer again. Regular colonoscopies, upper endoscopies, and check ups can help maintain health and catch any future complications. Patients with FAP can have a normal life expectancy when they follow all screening recommendations.
About 1 in 3 patients with FAP get desmoid disease. These are tumors of scar tissue that don’t spread but can grow very quickly. They usually follow surgery. Risk factors for desmoid disease include a family history of desmoids, being a woman, showing bone or skin lumps, and certain gene mutations. Desmoid tumors often do not cause any issues, but in some cases they may produce symptoms like pain, bloating, and constipation. In those cases, they can be removed by surgery. If they are irremovable then medical therapy or chemotherapy is given.
At the Hereditary Colorectal Cancer Center, our doctors and nurses have extensive experience creating personalized treatment plans to help manage FAP and keep you feeling your best. We can help your family members screen for disease as well. Our team features true pioneers in the fields of FAP surgery and research who will use their experience and expertise to bring you the latest and best in endoscopy, surgery and overall coordinated care.
Call us at (212) 342-1155 or use our online form to schedule an appointment.