BowelGene

Most bowel cancer occurs by chance, however, less than 30% is familial. In families where bowel cancer is hereditary it may be possible to find the genetic change (variant) which is responsible for the cancers. This allows appropriate cancer screening and risk-reducing options to be offered to the family.

Individuals with hereditary bowel cancer generally show one or more of the following:

• Bowel cancer diagnosed at a young age (before the age of 50)
• Bowel cancer that has screened positive for Lynch syndrome (abnormal IHC/ MSI)
• Several relatives with bowel cancer
• Relatives with bowel cancer and related cancers (such as womb or ovarian cancer)
• Multiple bowel polyps* in an individual
• Multiple generations with cancer

* Cancer usually starts as a benign growth known as a polyp. Not all polyps will become cancerous and they can often be removed during screening.

The following genes have been shown to be associated with bowel cancer and are tested as part of Bowelgene:

• APC
• BMPR1A
• EPCAM
• MLH1
• >MSH2
• MSH6
• MUTYH
• NTHL1
• PMS2
• POLD1
• POLE
• PTEN
• SMAD4
• STK11
• TP53

Genetic testing can help determine the risk of cancer within a family and guide appropriate cancer treatment and screening. Clinical management, in terms, of surgery and chemotherapy may be altered based on the results of genetic testing. Depending on the specific genetic risk different screening tests can be arranged and risk-reducing strategies considered. Colonoscopies in particular have been shown to lower the risk of bowel cancer in families with an inherited risk.

There are three possible results:

1. A pathogenic variant is found in one of the genes which is known to increase the risk of bowel cancer. Increased screening and/or risk-reducing techniques will be recommended.
2. A genetic variant of uncertain significance is found, but whether or not this is the cause of cancer is unknown. Screening will be recommended based on the family history.
3. No variant is found. It is possible that there may be an undetectable variant or a variant in a different gene. Cancer screening may still be beneficial.

If you have a pathogenic variant this means that you have an increased risk of bowel cancer and possibly other cancers. Your exact risks will depend on which gene variant has been found.  Extra screening and/or risk-reducing strategies will be discussed. It will also be possible to offer predictive testing to other people in your family to see if they also have the mutation.

When someone has an increased risk of bowel cancer it is usual for them to have colonoscopies. A colonoscopy is when a flexible telescope is inserted into the anus to examine the entire bowel (rectum and colon).  If any polyps are found these can usually be removed to prevent them developing into cancer. The frequency of colonoscopy will depend on which gene mutation is found. 

Screening for other cancers may also be needed and will be discussed if necessary.

Aspirin has been shown to lower the risk of bowel cancer in some circumstances and is currently recommended for LS carriers.

In some situations, people may wish to consider risk-reducing surgery.  This is dependent on the condition. 

In Lynch syndrome women have an increased risk of womb and ovarian cancer and may therefore consider hysterectomy and removal of the ovaries.

Colectomy (removal of the colon) may be considered if an individual has FAP but is rare for other conditions.

It is important for everyone to be bowel aware and inform their doctor if they notice any signs that they are concerned about.

Signs of bowel cancer are:

• Bleeding from the anus and/or blood in the poo
• A change in bowel habit (needing to go to the toilet more or less often) lasting for 3 weeks, and particularly looser stools
• Unexplained weight loss
• Extreme tiredness for no obvious reason
• A pain or lump in the tummy

Most of the time people with these signs will not have cancer but is always important to get them checked out.

The risk of bowel cancer increases as a person becomes older which is why bowel screening for the general population currently starts at 60.  A personal history of bowel polyps, type 2 diabetes, ulcerative colitis, Crohn’s, and a condition called Acromegaly also increase the risk of bowel cancer and you should consult your doctor regarding screening if you have these.