NICE issues draft guidance for consultation on Lynch syndrome screening

NICE has issued draft guidance for consultation on molecular testing for Lynch syndrome in people with colorectal (bowel) cancer.

This is a public consultation, so anyone can register and make comments on the draft guidance.

I am an author on the Diagnostics Assessment Report, which collects data from the published scientific literature and other sources (such as national statistics), and produces an evaluation of the clinical effectiveness and cost-effectiveness of testing for Lynch syndrome in people with colorectal cancer.

What is Lynch syndrome?

Lynch syndrome is an inherited genetic disorder which affects the ability of the body to identify and correct errors which occur when DNA is replicated, i.e., when cells in the body divide. It leads to an increased risk of bowel cancer, cancer of the uterus, and a number of other cancers.

Lynch syndrome is caused by mutations in four of the DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6 and PMS2) or in a neighbouring gene to MSH2 called EPCAM. People with Lynch syndrome have one faulty copy of the gene and one working copy. People without Lynch syndrome have two working copies. Because people with Lynch syndrome only have one working copy, they are at a higher risk of losing DNA mismatch repair function.

If someone has Lynch syndrome, there is a 50:50 chance of passing it on to each of their children, so Lynch syndrome runs in the family.

If someone is known to have Lynch syndrome then it is recommended they have regular surveillance of their bowel to look for precancerous lesions and for early stage asymptomatic cancer. This reduces their risk of dying from bowel cancer.

What does the draft guidance say?

The draft guidance recommends that the tumours of all people newly diagnosed with colorectal cancer are tested using MMR immunohistochemistry or microsatellite instability testing. If these show that the cancer may have been caused by Lynch syndrome, then further testing may be done to rule out other likely causes.

People will then be offered genetic testing for the mutations that cause Lynch syndrome, after suitable genetic counselling to make sure they understand the condition, the test, and the risks and benefits of testing.