What is Lynch syndrome?

Lynch syndrome is a genetic condition that puts you at a higher risk of developing certain types of cancers. Lynch syndrome was previously known as hereditary non-polyposis colorectal cancer (HNPCC).

The most common cancers associated with Lynch syndrome are bowel (colorectal) cancer and endometrial cancer.

Lynch syndrome also increases your risk of:

• ovarian cancer
• bladder cancer or kidney cancer
• brain cancer
• skin cancer
• stomach cancer or small intestine cancer
• liver cancer
• pancreatic cancer

If you have Lynch syndrome, you are also more likely to develop cancer at a younger age than the general population.

Having Lynch syndrome does not mean you will definitely develop cancer, but your risk is higher than in people who do not have Lynch syndrome.

What causes Lynch syndrome?

Lynch syndrome is caused by a change (mutation) in one of the genes responsible for repairing mistakes or damage that occur to your DNA. As some cancers are caused by changes to your DNA, if it functions normally, this gene helps protect you from developing cancer.

Your genes come in pairs. You inherit one from each of your biological parents. If you have Lynch syndrome, you have inherited one copy that works properly and one copy that does not work. If your working copy becomes defective, your repair system fails, making it more likely that you will develop cancer.

Who is at risk of Lynch syndrome?

If one of your parents has Lynch syndrome, you have a 1 in 2 chance of inheriting it.

Similarly, if you have been diagnosed with Lynch syndrome, any child you have will also have a 1 in 2 chance of inheriting it.

Lynch syndrome cannot 'skip a generation; if your children do not inherit Lynch syndrome, they cannot pass it on to your grandchildren.

Not all people with Lynch syndrome have a family history of the condition. You can be the first one in your family to be diagnosed with it.

How is Lynch syndrome diagnosed?

A blood test can diagnose Lynch syndrome.

Your doctor may recommend testing for Lynch syndrome if:

• at least 3 members of your family have had bowel cancer or other cancers associated with Lynch syndrome
• 2 consecutive generations are affected
• at least one family member was diagnosed with cancer before age 50
• a family member has had multiple bowel cancers, or several types of cancers that are linked to Lynch syndrome

Whenever possible, a sample of the cancerous tumour will be tested first. Then the person with cancer will have a blood test to identify the mutation.

If a gene mutation is found, other family members can choose to be checked too. Sometimes, it is not possible to find the mutation causing Lynch syndrome.

You will be offered genetic counselling with a genetic specialist before and after any tests you decide to have. They will explain the pros and cons of genetic testing and can help you decide if genetic testing is right for you.

You can only be tested for Lynch syndrome after you have given informed written consent. Your results are confidential and cannot be shared with anyone, including your family, without your permission.

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How is Lynch syndrome managed?

If you have Lynch syndrome, your doctor may recommend:

• regular check-ups to detect early signs of cancer
• preventative surgery
• taking aspirin daily

Your doctor will explain which check-ups are recommended and how often, depending on which gene mutation you have and your personal or family history of cancer.

Colonoscopy

The most recommended check-up is a colonoscopy to look for changes in your bowel. Your doctor can advise you when to have your first colonoscopy and how frequently you should have follow-up colonoscopies.

Risk-reducing surgery

To prevent endometrial and ovarian cancer, you may be advised to have a hysterectomy and oophorectomy when you have finished having children or when you are 40 years old.

You can discuss the advantages and disadvantages with your gynaecological oncologist (a specialist in cancers of the female reproductive system).

Managing cancer risk with lifestyle

You can reduce your risk of developing some cancers by:

• maintaining a healthy diet
• eating foods that are high in fibre
• avoiding red meat, processed meat and alcohol
• maintaining a healthy weight

There is also some evidence that:

• using hormonal contraceptives for more than a year may lower your risk of developing endometrial cancer
• taking multivitamins and calcium supplements for many years might reduce your risk of developing bowel cancer

Ask your doctor about measures you can take to reduce your risk.

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Resources and support

• Visit Cancer Australia to learn more about Lynch syndrome.
• You can learn more about genetic inheritance and bowel cancer at Bowel Cancer Australia.
• For information about cancer and cancer-related issues, visit the Cancer Council website or call 13 11 20.