About 30% of bowel cancers are considered to have an inherited component. The most prominent inherited condition is called Lynch Syndrome.
Although they are termed Inherited Tumours, that does not mean a person can inherit cancer. Conditions like Lynch Syndrome do not cause the cancer. They are inherited mutations in the genes that help to protect us from cancer – some control replication, others identify genetic errors and even repair them. So, if an actual cancer mutation occurs, these important genes may not be as effective at stopping the mutation from spreading out of control.
Lynch Syndrome is a catch-all term for a selection of mutations that can be inherited and can have a role in bowel cancers
Tests for genetic factors are often done after treatment. We argue that it should be done at the time of diagnosis, because it can affect the kind of treatment that is most appropriate.
About 30% of bowel cancers are considered to have an inherited component. However, Lynch only makes up about 5% of all bowel cancers and these are the only ones that are tested for. There are 25% of inherited cancers that we do not have specific tests for.
- Familial Adenomatous Polyposis
- This is an inherited genetic mutation that predisposes a person to grow a lot of polyps in the colon.
- FAP normally manifests itself in people under 50 years.
- Some people with FAP have slower development of polyps this is known as Attenuated FAP (aFAP)
- People with FAP have a very high risk of polyps becoming cancerous.
- FAP cancers are typically of a kind called APC Tumours.
- The APC protein is a tumour suppressor. It stops cells growing and dividing too fast. A mutation in this gene will allow cells to grow and replicate in an uncontrolled manner.
- APC tumours account for about 1% of bowel cancers and can be caused by external factors as well as inherited predisposition.
- MUTYH-Associated Polyposis
- This is a genetic mutation that predisposes a person to grow a lot of polyps in the colon.
- This involves mutations to the MUTYH gene.
- The MUTYH gene is involved with repairing DNA if it suffers from a mutation.
- Although mutations in the MUTYH gene are quite common (1 in 50 people), this kind of cancer only occurs if you inherit two copies of the mutation, one from each parent.
- MAP is implicated in 0/3% of bowel cancers.
Rare Genetic Conditions
- NTHL1 tumour predisposition syndrome;
- Peutz Jegher syndrome;
- PTEN Hamartoma tumour syndrome;
- Juvenile polyposis syndrome.
Implications of Inherited Factors
- If you are diagnosed with an inherited conditions it has implications for your family. Your elders, siblings and offspring. If they too have the same mutations, they will be more susceptible to bowel and other cancers, or be carriers (eg MUTYH).
- You should contact members of your family and advise them to get tested.
- Anyone with an inherited condition can reduce their cancer risk.
- People with inherited conditions are entitled to advanced cancer screening, to catch cancer early and cure it.
- Lynch Syndrome UK is a support group for people with this condition.
Some people say they would rather not know, and live without the ‘threat’ hanging over them. This represents an old fashioned view of cancer. In the past a diagnosis of bowel cancer was usually terminal. Today it is different. Most people survive bowel cancer and go on to live normal lives because we can spot it early and be successfully treated.
Reducing your risk.
What we know about bowel cancer today is that everyone is at risk of the disease and we can do something about it:
- Act to prevent cancer, by taking cancer risk reduction measures
- Be aware of symptoms and act on them early.
- Take up cancer screening in order to detect early cancer or pre-cancer, before symptoms.
Page Contributor: Stephen Rowley