Lynch syndrome Q & A

Some bowel cancers are caused by an inherited condition, which means that having a family history of bowel cancer may mean you are at an increased risk of developing cancer yourself.

As part of Bowel Cancer Awareness Month we sat down with Dr Anju Kulkarni, Consultant Clinical Geneticist, to understand more about inherited bowel cancer.

What is inherited cancer?

Cancer is a common condition with approximately one in two people developing it in in their lifetime, so everyone has some risk of developing cancer. In most cases the disease develops by chance and the risk increases as we get older. 

Cancer usually develops when one or more of the genes in a cell are not working properly due to a specific change in the genetic code. We refer to this clinically as a mutation. These gene changes, called somatic mutations, mostly happen during our lifetime as a natural consequence of ageing. 

However, in a small percentage of people with cancer, the disease is driven by a different type of mutation called a hereditary or germline mutation. These gene mutations, which can be inherited from one or both parents, cause the person who carries them to be genetically predisposed to developing certain types of cancer.

The most common cause of hereditary bowel cancer is Lynch syndrome, also known as hereditary non-polyposis colorectal cancer (HNPCC).

How does Lynch syndrome lead to bowel cancer?

Lynch syndrome is due to inherited changes (mutations) in genes that affect DNA mismatch repair, which is a process that fixes mistakes made when a cell’s DNA or genetic code is copied. These genes (MLH1, MSH2, MSH6 and PMS2) normally protect you from getting certain cancers, but mutations in these genes prevent them from working properly. As a result, individuals who carry these inherited mutations are more susceptible to cancer and may develop the disease at a younger age or multiple times.

Lynch syndrome also increases the risk of developing other cancers including womb and ovarian cancer in women. More rarely Lynch syndrome may also cause cancer in the stomach, small bowel, pancreas, gallbladder, brain and urinary tract system.

How common is Lynch syndrome?

Lynch syndrome is more common than we previously thought, it is just that people and families with the condition probably went unrecognised. Lynch syndrome accounts for about 3 out of every 100 bowel cancers or 3%. However, what is concerning is that in people with Lynch syndrome, up to 60% can develop bowel cancer during their lifetime, and a significant number of these people may be diagnosed under the age of 50 years. 

This is why it’s so important that we raise awareness of the condition. If you have a confirmed diagnosis of Lynch syndrome, whilst it can be scary, knowing this information can empower you and your doctors to safeguard your future health. People with a confirmed diagnosis of Lynch syndrome will be put on a regular screening programme which will aim to prevent or catch cancer at its earliest stage, when treatment is most effective. If an inherited mutation is confirmed in you, it is also possible to offer testing in your wider family so any relatives who also carry the mutation can access cancer surveillance in a timely way.

How do I know if I am at risk?

You and your family members are more likely to have Lynch syndrome if your family has a strong history of bowel cancer and other Lynch-related cancers. If a first-degree relative – a mother, father, brother or sister – had bowel cancer under the age of 50, this may also be an indicator of Lynch syndrome.

If a parent has a Lynch syndrome gene mutation, then each child has a 1 in 2 chance (50%) of inheriting it. Some children will have the gene change and therefore an increased risk of developing cancer and some children won’t, which is why genetic testing is important.  

It’s also worth noting that even if you have a strong family history, it doesn’t necessarily mean you will have Lynch syndrome. There are many different factors, environmental and genetic, that can increase cancer risk. Also, importantly, people with Lynch syndrome do not always develop cancer, it is just that their risk of developing the disease at some point during their lifetime is higher than average. 

What should people do if they think they are at risk?

If you are concerned that you could have Lynch syndrome, or another mutation related to bowel cancer, the first step is to collect your family health history and share this information with your doctor.

If necessary, they can refer you to a genetics specialist, who can give you more advice about your level of risk and may recommend genetic testing.

Inherited cancer genetic testing

An inherited cancer genetics test is a blood test to discover whether you are carrying a genetic mutation that could increase your risk of cancer. The results can help you and your doctor make important decisions about your medical care and could also have implications for your relatives.

If you have a family history of cancer, or if you would like to find out whether you or a family member has an increased likelihood of developing cancer, I would encourage you to consult with a genetic specialist.

What would you say to somebody who is nervous about testing?

Understanding and dealing with your own or a family member’s bowel cancer or bowel cancer risk can be challenging. Genetic counselling can help by providing information, resources, and support for you and your family, so you can make an informed decision. 

Deciding whether to undergo genetic testing is a personal choice and it’s important that you understand all the options available to you, before you choose to go ahead with any tests. If you are feeling nervous about testing make sure you raise this with your genetic specialist who can answer any questions you may have.

What would you like people to remember?

There has been amazing progress in the treatment of bowel cancer but early diagnosis is a significant priority for the medical community. If detected early, it's one of the most curable types of cancer. 

If you are diagnosed with an inherited risk of developing bowel cancer, then risk reducing strategies such as surveillance can significantly increase the chances of catching cancer early or even at a pre-cancerous stage.

More about hereditary cancer genetic testing