There were around 42,000 new cases of bowel cancer a year in the UK between 2014 and 2016, according to Cancer Research UK. One in 15 men in the UK and one in 18 women will be diagnosed with bowel cancer during their lifetime. It is the third most common type of cancer in the UK.
Your risk of developing the disease depends on many different factors, one of which is your genes. While only one in 20 incidence of bowel cancer is due to inherited cancer genes, it pays to be aware if you are at risk of hereditary cancer so you can take proactive steps to protect yourself.
To mark DecemBeard – a campaign which sets out to raise awareness of bowel cancer – we are looking at genetic causes of bowel cancer and how genetic testing can help to establish if you are at risk.
What is hereditary and familial bowel cancer?
Familial bowel cancer is when there is a family history of bowel cancer, whether it is a single member of the family or multiple family members. There can be a number of reasons why the disease runs in families, from shared lifestyle influences (eating a similar diet, for example) through to inherited faulty genes.
Inherited genetic mutations are what cause hereditary bowel cancers. You may be at risk if a first-degree relative (parent, sibling or child) was diagnosed with the disease below the age of 50 or you have relatives with certain types of cancer, including bowel, pancreatic, ovarian, womb or stomach cancer.
Genes linked to bowel cancer
Inherited genetic mutations can cause conditions that may lead on to bowel cancer. One of these is Lynch syndrome (also called hereditary non-polyposis colorectal cancer). Most types of bowel cancer that occur before the age of 50 are caused by Lynch syndrome, which can also increase the risk of other cancers such as womb cancer.
Familial adenomatous polyposis (FAP) is caused by a mutation in the APC gene. Like Lynch syndrome, FAP is inherited. It leads to hundreds or even thousands of polyps (growths) in the bowel. If they are not removed, one of these growths will almost certainly become cancerous.
While these are the two most common inherited bowel cancer genes, there are others that occur less frequently, including MUTYH-associated polyposis (MAP), juvenile polyposis syndrome, serrated polyposis syndrome and Peutz-Jeghers syndrome.
Genetic testing for bowel cancer
If you suspect you may be at greater risk of developing bowel or other type cancer, genetic testing analyses your DNA to determine your cancer risk. Myogenes, which makes one of the most comprehensive tests currently available, tests 98 genes that are known to be associated with 25 different types of hereditary cancers, including bowel cancer.
Using only a saliva sample, it tests for a wide range of genetic mutations including BRCA1, BRCA2, ALK and EPCAM. Samples are sent off to a CLIA-certified laboratory for testing and a detailed report is provided detailing the presence of absence of genetic mutations linked to an increased risk of cancer.
Who should get tested?
You may wish to undergo genetic testing for bowel cancer if you:
- Have a family history of the disease.
- Have a family member who developed the disease below the age of 50 or who had a rare cancer at any age.
- Have been diagnosed with cancer and want to establish if it had a genetic cause (which may increase your and your family’s risk of other cancers).
- Are healthy but want to know if you have an increased risk of cancer.
Using genetic testing results
If genetic testing reveals you have an increased cancer risk, there are a number of steps you can take to protect yourself, from making lifestyle changes to undergoing regular screening. For certain types of cancer, it may be possible to take preventative medication.
You may also want to discuss with your family the increased risk they also face and possibly encourage them to undergo genetic testing as well. In this way, families are able to support and empower one another and keep on top of any increased risk.
The earlier cancer is detected, the greater your chances of survival so being aware of your risk and monitoring for early signs of the disease could make a significant difference to your lifespan.