What is Lynch syndrome?
- If you have heard of genetic mutations and their link to cancer, you’ve probably heard about BRCA1/2 but less about Lynch syndrome (LS).
- Lynch syndrome was also known as “hereditary non-polyposis colorectal cancer (HNPCC)”, and is the most common cause of hereditary bowel cancer. It’s important to note though that only 5% of all bowel cancers are linked to Lynch syndrome. There are a number of genes that have been linked to Lynch syndrome, including MLH1, MSH2, MSH6, PMS2, and EPCAM which are called “mismatch repair genes”.
- These genes usually help to repair any DNA damage that happens when cells divide.
- If you have inherited a mutation in one of these genes though, this process doesn’t work properly. This is a bit like a spelling error in an instruction manual- the instructions don’t make sense so whatever you’re building won’t work properly. In this case, the mismatch repair genes don’t work, so the DNA errors aren’t repaired and the abnormal cells can continue to divide with these mistakes, which can lead to uncontrolled cell growth. This is why your risk of cancer is increased (see “what are genetic mutations” for more information about this).
How is it inherited?
Whilst we have two copies of each gene, one from each of our parents, we only need one mutated copy to be affected. This means if one of your parents has Lynch syndrome, it is 50/50 whether you inherit it too. You can inherit Lynch syndrome from your mother or your father. If you have Lynch syndrome, it is 50/50 whether each of your children inherits the mutation, whether they are boys are girls. The estimated prevalence in the population is 1/440 and it’s thought 95% of carriers of these mutations are unaware that they are at risk.
What are my risks if I have Lynch syndrome?
A genetic mutation like Lynch syndrome is not a guarantee that you will develop cancer, but it gives you an increased risk that you will be diagnosed with certain cancers in your lifetime.
The table below shows the estimated lifetime risk (up to age 70) for Lynch syndrome:
Lynch syndrome is also linked to an increased risk of other cancers including:
- Brain/ central nervous system
- Small bowel
- Liver/bile duct
- Urinary tract
It is important to speak to a genetic counsellor to understand your risks in more detail as this will vary depending on your exact mutation.
How do I get tested for Lynch syndrome?
I have colorectal cancer:If you have a personal diagnosis of colorectal cancer, you are eligible to be tested for Lynch syndrome.
This is because since February 2017, NICE Diagnostics guidance [DG27] has recommended that everyone with colorectal cancer, no matter their age, is offered tested of their tumour initially, followed by a blood testing for Lynch syndrome when necessary.
You can access testing even if you were diagnosed before these guidelines were introduced. Unfortunately, how easy this is to access does vary depending on the area you live in.
I don’t have colorectal cancer:If you don’t have a personal diagnosis of Lynch syndrome, you should make yourself aware of your family history of cancer.
Speak to your GP if you have:
- Two or more relatives on the same side of the family with colorectal cancer
- Any family members diagnosed with colorectal cancer under the age of 50
- Three or more relatives with Lynch syndrome-related cancers (see list above) on the same side of the family
If these apply to you, you can speak to your GP about being referred for genetic counselling where you can talk about your risks, screening and prevention options. If you did go ahead with genetic testing, this takes place through a simple blood test.
What are my options if I have Lynch syndrome?
Symptoms awareness: It is important for everyone, but particularly those with Lynch syndrome, to be aware of the symptoms of the cancers linked to these mutations. You can find materials about each of the symptoms here:
Screening: If you have Lynch syndrome, you will be eligible for earlier bowel screening, from the age of 25. This will involve a colonoscopy to examine the bowel for any abnormalities, biopsies and the removal of any growths (polyps) that are found.
Surgery: If you have Lynch syndrome you may have the option of having surgery to remove your ovaries and fallopian tubes (bilateral salpingo-oophorectomy), which will reduce your risk of developing ovarian cancer. If you are pre-menopausal, this operation will put you into immediate menopause. There are significant risks associated with going through the menopause early, even when HRT is taken, so speak to your medical team in detail about this option.
As Lynch syndrome also increases the risk of uterine cancer, it is recommended that women with Lynch syndrome have a hysterectomy to remove their womb in addition to their ovaries and fallopian tubes. Guidelines suggest Lynch syndrome women should consider these surgeries between the ages of 40-45.
Aspirin: there is some evidence that regular doses of aspirin can help reduce the chances of cancer in Lynch syndrome patients. However, research ongoing into the best dosage of aspirin to take and we do not advise taking aspirin without consulting your medical team.To find out about the CAPP3 trial into aspirin use and cancer risk, and who can be involved visit www.capp3.org
It’s important to note that none of these options guarantee that you will not get cancer and there will always be a risk. You should continue to be aware of any changes in your body and visit your GP if you notice anything that concerns you. Speak to your medical team to understand more.
It’s also important to note that there are no right or wrong decisions. You should take the time to find out as much as possible and make the best decision for you and your family.