ABOUT BOWEL CANCER
Lynch syndrome
Lynch syndrome is an inherited genetic condition that increases the risk of developing bowel cancer and some other cancers. It is the most common inherited bowel cancer syndrome and is sometimes called hereditary non-polyposis colorectal cancer (HNPCC).
Most bowel cancers are diagnosed after the age of 50, but people with Lynch syndrome can develop bowel cancer at a younger age.
What causes Lynch syndrome?
Lynch syndrome is caused by an inherited change in one of the genes that normally helps repair damage to DNA.
When cells grow and divide, small errors can occur in their DNA. Usually, the body has genes that identify and repair these errors. In people with Lynch syndrome, this repair process does not work as it should, which allows errors to build up over time and can increase the risk of developing bowel cancer.
Lynch syndrome is most commonly associated with bowel and endometrial (uterine) cancers, but it can also increase the risk of some other cancers including ovarian and stomach cancers.
How does Lynch syndrome affect cancer risk?
Not everyone with Lynch syndrome will develop cancer, but having the condition increases the risk of developing bowel and some other cancers.
Bowel cancer can also develop at a younger age in people with Lynch syndrome than in the general population.
The level of cancer risk varies depending on the genetic change involved and other individual factors. Your healthcare team or genetic counsellor can help you understand what Lynch syndrome may mean for your individual cancer risk.
How do you know if you have Lynch syndrome?
Lynch syndrome does not cause symptoms itself. Genetic testing is used to confirm whether someone has an inherited genetic change associated with the condition.
Because Lynch syndrome runs in families, your family history can help identify whether you may be at risk. If a parent has Lynch syndrome, each of their children has a 50% chance of inheriting the genetic change.
Talk to your GP if:
- a close family member developed bowel or another Lynch syndrome-associated cancer at a younger age
- two or more people on the same side of your family have had bowel cancer
- there is a history of both bowel and endometrial cancer on the same side of your family
- several relatives on the same side of your family have had cancers associated with Lynch syndrome
Your GP can discuss your family history with you and whether further assessment or genetic testing may be appropriate.
Genetic testing for Lynch syndrome
If your family history suggests you may have Lynch syndrome, you may be referred to the New Zealand Familial Gastrointestinal Cancer Service. The government-funded service assesses people and families who may have an inherited risk of gastrointestinal cancers. It can help determine whether genetic testing or ongoing bowel surveillance may be appropriate.
You may also be referred to Genetic Health Service New Zealand, which provides genetic testing and counselling.
Genetic testing can identify whether you have an inherited genetic change associated with Lynch syndrome. If Lynch syndrome is confirmed, other family members may also be offered genetic testing.
Genetic counselling may be offered alongside testing to help you and your family understand what the results may mean and any decisions you may need to make.
Knowing you have Lynch syndrome means you can be offered appropriate surveillance from a younger age. Regular surveillance can help find and remove precancerous changes or detect bowel cancer at an earlier stage.
There is also some evidence that taking aspirin regularly may reduce the risk of bowel cancer for people with Lynch syndrome. Aspirin isn’t suitable for everyone and can cause side effects, so talk to your GP or cancer specialist about the potential benefits and risks before taking it regularly.
Bowel surveillance
People with Lynch syndrome have a higher risk of developing bowel cancer, so regular bowel surveillance is important.
A colonoscopy can find and remove polyps before they develop into cancer and can help detect bowel cancer at an earlier stage.
For people with Lynch syndrome, regular bowel surveillance by colonoscopy is generally recommended to start from 25 years of age. How often you need a colonoscopy will depend on your individual history and the findings from previous colonoscopies.
The New Zealand Familial Gastrointestinal Cancer Service may help coordinate ongoing bowel surveillance for people and families with Lynch syndrome.
Gynaecological management
Lynch syndrome can increase the risk of uterine (endometrial) and ovarian cancers.
For some people with Lynch syndrome, risk-reducing surgery, such as a hysterectomy and removal of the ovaries and fallopian tubes, may be an option once they have completed their family.
Talk to your healthcare team about your individual risk and whether any additional surveillance or risk-reducing options may be appropriate for you.
More information and support
Finding out you have Lynch syndrome can raise questions about what it means for you and your family. Your healthcare team or genetic counsellor can help you understand your individual risk, surveillance options and whether other family members may benefit from assessment.
There is a private Facebook group for people with Lynch syndrome, where members can connect with others who have the condition and share their experiences. As the group is private, you’ll need to request to join.
For more detailed information about research into Lynch syndrome, you can also explore research published through the New Zealand Medical Journal.