Predictive genetic testing for Lynch Syndrome

We all have more than 20,000 genes. Each gene is an instruction within our body. Changes in that instruction can affect how it works. Lynch syndrome is caused by a change in one of several genes. We have two copies of every one of our genes, one from our mother and one from our father. For Lynch syndrome, a change in just one of those two copies will lead to the condition.

When we have our children we pass only one copy of each gene on, with the other copy coming from our partner. If a parent has Lynch syndrome, there is a 50% chance for each of their children of inheriting the gene change and a 50% chance of not inheriting it. Lynch syndrome affects males and females. There is no way at present to reverse the gene change but there is screening and surgery available to help protect against the chance of cancer developing.

Not everyone who has Lynch syndrome will develop cancer. Over a person’s lifetime there is:

• Up to 80% chance of developing bowel polyps or cancer for men.
• Up to 60% chance of developing bowel polyps or cancer for women.
• Up to 60% chance of developing cancer of the uterus (womb) in women.
• Up to 10% chance of developing ovarian, stomach or urinary tract (e.g. kidney, ureter or bladder) cancers.
• A slightly increased risk of small bowel, gall bladder, bile duct, pancreas, skin and brain cancer.

The cancer risks are thought to be significantly lower for families with Lynch syndrome caused by a PMS2 gene change. This will be discussed with you, if applicable.

Bowel polyps and bowel cancer

People with Lynch syndrome are more likely than the general population to develop bowel polyps. They tend to develop more polyps and at a younger age than people without Lynch syndrome. Bowel cancers can arise from polyps. Removal of the polyps in Lynch syndrome reduces the chance that a bowel cancer will develop.

People with a Lynch syndrome gene change (or who have a 50% risk of having one) are offered screening of their bowel by colonoscopy, every two years, from the age of 25 or 35, depending on the specific cause of Lynch syndrome in your family.

To prepare for a colonoscopy, the bowel needs to be cleared with laxatives. During colonoscopy, a narrow tube with a small light and camera is carefully passed through the back passage into the large bowel. Polyps can then be removed, if seen. Colonoscopy can be uncomfortable but sedation is offered. It is usually done as an outpatient procedure.

The aim of colonoscopy screening is to prevent bowel cancer developing, or, if it has already developed, to detect it at an early stage. The earlier a cancer is found, the better the chance of successful treatment.

It is important to be aware of bowel symptoms. If you have any of the following symptoms you should see your GP for a check-up:

• Bleeding from the back passage.
• Increase in the amount of mucus in the stool.
• Change in bowel habit such as persistent diarrhoea or constipation.
• Abdominal pain or bloating.
• Unexplained weight loss.
• Feeling of incomplete emptying of the bowel.

There is increasing evidence that a diet low in animal fats (particularly red meat and processed meats) and high in fresh fruit and vegetable is protective for the bowel.

Stomach cancer

It is recommended to check for an infection with a bacterium called Helicobacter Pylori, which may be found in the stomach and is linked to an increased risk of stomach cancer. If present, it can be treated with a course of antibiotics. This test can be organised through the GP. People with a Lynch syndrome gene change (or who have a 50% risk of having one) are not routinely offered endoscopy of their stomach.

Endometrial (uterine or womb) cancer

The chance of developing endometrial cancer in Lynch syndrome is low under the age of 35 but increases after this age. Symptoms to watch for include: any abnormal bleeding; for example, between periods or if periods become heavier than normal. For a woman who has already had her menopause, any vaginal bleeding should be brought to the attention of the GP or gynaecologist so it can be investigated.

Surgical removal of the womb (hysterectomy) is an option for women with an Lynch syndrome gene change, to reduce the risk of endometrial cancer. It may be offered together with surgery to remove the ovaries (see below). It would not usually be considered until a woman has reached her mid to late 30’s and has finished her family.

Although there is no proven effective screening for endometrial cancer in Lynch syndrome, from the age of 35, it may be possible to arrange annual checks with a local gynaecologist. This would continue until a woman has a hysterectomy.

Ovarian cancer

Symptoms of ovarian cancer can be difficult to notice. They include persistent abdominal (tummy) pain, bloating, difficulty eating, feeling full very quickly and the need to pass urine more frequently. Ovarian screening is not effective. The chances of developing ovarian cancer can be reduced by surgical removal of the fallopian tubes and ovaries (prophylactic bilateral salpingo-oophorectomy (BSO)). It would not usually be considered until a woman has reached her mid to late 30’s and has finished her family. BSO will cause an immediate menopause if a woman has not already reached her natural menopause. This can increase the risk of other problems including osteoporosis (thinning of the bones). Hormone Replacement Therapy (HRT) may be prescribed.

Urinary tract screening

This is not proven to be of benefit but may be considered for some families, depending on their specific gene change, or if there is a strong family history of urinary tract cancer.

Aspirin

Research suggests that taking a daily low dose of aspirin can reduce the risks of bowel cancer in people with Lynch syndrome. Regular aspirin should only be taken on the advice of a doctor. If this is relevant for you we will discuss the recommended dose and duration of treatment.

Genetic testing

If the specific gene change causing Lynch syndrome has been found in a family member, others in the family can have a ‘predictive’ genetic test. This allows them to find out whether they have inherited it or not. This testing is only offered to adults. There is a one in two chance of inheriting the gene change from a parent who has Lynch syndrome.

If it has not been inherited, then the chances of developing the cancers discussed above are not increased and screening or surgery to reduce the risk is not needed. Someone who has not inherited the gene change cannot pass it on to their own children.

If the gene change causing Lynch syndrome has been inherited, then all the options described above could be considered, where appropriate.

Most people with Lynch syndrome will have their children as normal. Some people with an Lynch syndrome gene change want to ensure that it is not passed on to the next generation. They may consider the possibility of testing a pregnancy or Pre-implantation Genetic Diagnosis (PGD). This incorporates In-Vitro Fertilisation (IVF) with genetic testing, aiming to implant an embryo without an Lynch syndrome gene change. It is a complicated process with a success rate of about one in three per cycle of IVF. Further information about this is available on request.

This information may be relevant to other adult members of your family. If they wish to be seen in the Genetics Clinic to discuss Lynch syndrome, they can be referred by their GP quoting the family reference number given on your clinic summary letters.

Further information

You may find the following websites helpful: