Does lynch syndrome always lead to cancer?

Posted in lynch, cancer risk, ovarian cancer, endometrial cancer; Posted 15 months ago by Andreas Obermair

Lynch syndrome is an inherited cancer syndrome associated with a genetic predisposition to developing different cancer types.

Women and men who carry Lynch syndrome have a significantly increased risk of developing colorectal cancer. For women carrying Lynch, endometrial cancer is the most common cancer type. There is also an increased risk of developing other types of cancers, gastric (stomach), ovarian, small bowel (small intestines), pancreatic, prostate, urinary tract, kidney, bile duct, and brain cancers.

For a person with Lynch, they have about a 70% chance of developing a Lynch-related cancer. However, it does not always lead to cancer. Lynch syndrome is among the most common hereditary cancer syndromes.

Lynch syndrome is caused by a mutation in one of the body’s mismatch repair (MMR) genes. These include four genes: MLH1, MSH2, MSH6, and PMS2. Everyone is born with two copies of these genes, one inherited from their mother, and the other from their father. If one of these copies is faulty, the person carrying the gene mutation has a higher risk of developing one or more of the above cancers. The risk of certain cancers will differ depending on which of the four genes are mutated. Table 1 summarises the cumulative lifetime risk (to age 70) of a first cancer for a female now aged 30 years.

Table 1 Female cumulative cancer risk for each MMR gene

Table adapted from Lynch Syndrome Australia Consumer Report

Approximately 85,000 people in Australia carry a mismatch repair gene fault associated with Lynch syndrome.  Although, because the condition is usually only found when people undergo genetic testing, there may be many people with Lynch syndrome who carry Lynch, but don’t know because they have not yet been diagnosed. Lynch Syndrome Australia reports that over 90% of the 85,000 people remain undiagnosed and vulnerable to the increased cancer risks.

Cancers associated with Lynch syndrome develop at a younger age compared to non-Lynch cancers. The average age that people with Lynch syndrome develop their first cancer is about 40 years, although younger cases are also possible (compared with average age of cancer diagnosis being 60 years in the general population).

Lynch syndrome can increase the risk of developing multiple types of cancers during a person’s lifetime, and they can also develop more quickly. For example, in the general population it takes about 10 years for a polyp in the bowel to potentially develop into bowel cancer. For those with Lynch syndrome the average time is 30 months.

Someone with Lynch syndrome will often have a strong family history of cancer. A parent with Lynch syndrome has a 50% (1 in 2) chance of passing the condition on to their children. Men and women have an equal chance of inheriting Lynch syndrome. However, sometimes I have seen patients with Lynch-related cancers without a relevant family history.

Lynch syndrome doesn’t skip generations. This means if your children do not carry Lynch, your grandchildren will not be affected either. 

Lynch syndrome is named after an American doctor, Dr Henry T. Lynch who first discovered the hereditary link between the genes and cancers in the 1960s.

I recommend all patients diagnosed with endometrial cancer have their tumour tested for any of the four MMR genes that are capable of causing Lynch. This has to be done irrespective of the patient’s age. The result of the tumour testing then determines whether the patient should be referred to a Family Cancer Clinic or a clinical geneticist.

Once the specific Lynch syndrome gene has been identified in a person, a confirmatory blood test will check whether other immediate family members have also inherited Lynch.

Why do we look for Lynch?

While there is no cure for Lynch, people who carry Lynch syndrome can manage their cancer risk so as to prevent cancer developing, knowing the signs and symptoms to diagnose cancer at the earliecanst possible stage. The earlier the cancer is found the better the prognosis and less invasive treatment is.

Secondly, now we have medicines available that are especially effective in tumours that are Lynch-related. Some patients who were deemed incurable, now can live for many years if they can have targeted medication, which is targeted specifically at Lynch patients.

You can read my article on signs and symptoms of endometrial cancer and ovarian cancer.

Read more information on diagnosis and clinical management of Lynch Syndrome here

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