Does bowel cancer run in families?
Most people who develop bowel cancer have no family history of bowel cancer. However, for around 25% of all bowel cancer cases diagnosed in the UK there is a family history. Generally speaking, the more members of the family affected by bowel cancer, and the younger they were at diagnosis, the greater the chance of a family link.
What is my risk of hereditary bowel cancer?
The following guidelines from the British Society of Gastroenterology may help you assess your personal risk:
High to moderate risk:
- at least 3 relatives in your family diagnosed over the age of 50 years, and over 2 generations on one side of the family, or
- 2 close relatives in your family diagnosed under the age of 60 years, or
- 1 immediate relative aged less than 45 at diagnosis of bowel cancer
The national guidelines in this case would be to recommend a colonoscopy at 35 years, and then follow up with a 5 year colonoscopy between ages 50 – 75 years for individuals with known risk.
Low to moderate risk:
- 1 close relative affected under age 50 years, or
- 2 close relatives affected over age 60 years
The national guidelines in this case would be to offer a one off colonoscopy at 55 years.
- 1 close relative diagnosed at over 50 years of age and no other family history of bowel cancer or non-polyposis related cancers.
Hereditary non-polyposis colorectal cancer (HNPCC)
Each person inherits genes from both their parents and HNPCC is caused by a fault in one of the genes, known as the 'mismatch repair' genes. Someone who inherits HNPCC from their parents has a normal gene and a faulty gene, which increases their risk of developing bowel cancer and other types of cancer.
HNPCC affects less than 5% of those who develop bowel cancer. Although rare, this risk relates to a clear family history of bowel or certain other related cancers such as some gynaecological cancers, digestive tract, urinary tract, brain or bowel cancer. The typical age of diagnosis of this kind of hereditary cancer (HNPCC or Lynch Syndrome) is usually between 40-50 years (compared to 60-70 years amongst the general population).
Familial adenomatous polyposis (FAP)
FAP is a rare, inherited condition which causes hundreds or thousands of polyps (pre-cancerous growths) to grow in the colon (large bowel). FAP most commonly runs in families, but it can also affect people who don’t have a family history of it. FAP is usually inherited from a parent who has the condition, and is caused by a mutation on the APC gene.
You can have FAP even if there are no other cases in your family. In about 1 in 4 cases, the gene mutation comes about by accident and not because you’ve inherited it. FAP is responsible for about 1 out of every 100 bowel cancers.
The polyps (sometimes called adenomas) usually start to appear when a person is in their teens, and if left untreated, one or more polyps will almost certainly develop into cancer, usually by the age of 40. In some people there are no symptoms until a polyp has changed into a cancer.
In families where there is a clear history of FAP, screening usually commences by the age of 13 with an annual sigmoidoscopy for the first few years, and then an annual colonoscopy using a special dye spray.
Doctors recommend that people with FAP have surgery to have their colon removed by the age of 25 to prevent them getting bowel cancer. This can be hard for a young person to cope with, and they will need the specialist help and support of an experienced colorectal team to help make the right decisions about their treatment.
Where FAP is suspected, your GP will refer you to the local Regional Genetics Centre for support and on-going management of the condition. Screening for the other complications of FAP is also possible, and the local Regional Genetics Centre will be able to advise about these on an individual basis, once they have seen you and your family in their clinic.
Do you know if anyone in your family has had bowel or any other kind of cancer? Talk to your family and make sure you all know your family history.
If you think you have a strong family history of bowel cancer, you should make an appointment with your GP to talk about your concerns. If your GP agrees with you, he/she will refer you to a specialist genetics service. The genetic specialist will go through your family history with you in great detail and ask you to provide accurate information about who has been affected, how old they were when they were diagnosed, and the site where their cancer developed. You may also have to have blood tests as part of this investigation.
If the genetic specialist agrees you are at increased risk, you will be referred to a bowel specialist to talk about what types of screening they recommend, at what age you (and/or other family members) should start being screened and how often you should be screened. Regular screening will ensure that any signs of bowel changes and early cancer are spotted and treated quickly.
For more information about family history and the national guidelines for screening people at higher risk of bowel cancer, please click here.
Last reviewed 11/6/2015