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A family history of bowel cancer

Many people worry about getting bowel cancer, sometimes because a relative has had it. About 1 in 20 people will get bowel cancer in their lifetime.

Bowel cancer is the third most common cancer in the UK for men and the second most common cancer for women. Every year more than 30,000 people will develop it.

The cause of most bowel cancers is not known, but we do know that some risk factors can increase your chances of developing cancer.

Having a particular risk factor for cancer, or being exposed to one, doesn’t mean that you will definitely get cancer - just as not having it doesn’t mean that you won’t. For example if you just have one elderly relative who had bowel cancer, it’s unlikely that you will have a significantly increased risk.

How does family history affect my bowel cancer risk?

Genes carry the biological information we inherit from our parents. They affect the way our bodies grow, work and look.

Changes (mutations) in certain genes can increase the risk of bowel cancer in family members who inherit the genetic change. However, only a small number of bowel cancers are thought to be due to an inherited altered gene (genetic mutation) running in the family.

A genetic mutation that could increase your risk of developing bowel cancer is only likely to be present in your family if you have:

One close relative who had bowel cancer at a young age (under 50). Your close relatives are your parents, children, brothers and sisters. They are also sometimes called your first degree relatives.
At least two first degree relatives on the same side of the family who developed bowel cancer.
Cases of bowel and womb cancer on the same side of your family.
Relatives with multiple (over 10) pre-cancerous growths (polyps) in the bowel.

If any of these apply to your family and you’re worried about your risk of developing bowel cancer, you may want to talk to your GP. If your GP thinks there’s a chance you may have an increased risk of developing bowel cancer because of your family history, they can refer you to a family history of bowel cancer clinic at West Middlesex University Hospital or elsewhere.

Inherited conditions which increase the risk of bowel cancer

Up to 30 per cent of people will have a close relative with bowel cancer, however, the degree of risk varies between individuals. There are some conditions in which inherited genetic changes greatly increase the risk of bowel cancer developing, such as polyposis and Lynch syndrome, where many people in a single family can be affected. Only about 5 per cent of bowel cancer cases occur in people who have a very strong inherited predisposition. On the other hand, if only one elderly relative has had bowel cancer, this does not greatly increase your risk.

How can screening reduce my risk of bowel cancer?

The Bowel Cancer Screening Programme (BCSP)

Everyone in England between the ages of 60 and 75 years of age is invited to take part in the National BCSP. This involves 2 yearly stool tests which are sent through the post, the Faecal Occult Blood Test (FOBT). People with an abnormal FOBT test will have a colonoscopy.

During a colonoscopy a long, flexible tube is inserted gently into the back passage to look at the inside of the bowel. Bowel screening aims to detect any precancerous changes to the bowel (known as polyps) that could develop into cancer. These polyps can be removed and cancer prevented. More information about the BCSP can be found at www.cancerscreening.nhs.uk/bowel/.

People with a stronger family history

For most people with a family history of bowel cancer the BCSP is an adequate level of screening. For some people with a stronger family history we recommend screening with colonoscopy directly rather than the stool tests. For example this may be from the age of 50 years and every five years for people with 2 close relatives with bowel cancer at a young age. The type of screening for an individual does vary depending on the degree of risk. We can discuss this with you in detail in the family history of bowel cancer clinic and work out what suits you best.

Think you have a strong family history of bowel cancer?

Do you know if anyone in your family has had bowel or any other kind of cancer? Talk to your family and make sure you all know your family history.

If you think you have a strong family history of bowel cancer, you should make an appointment with your GP to talk about your concerns. If your GP agrees with you, they can refer you to a specialist family history of bowel cancer clinic at West Middlesex University Hospital. The specialist will go through your family history with you in great detail and ask you to provide accurate information about who has been affected, how old they were when they were diagnosed, and the site where their cancer developed. You may also have to have blood tests as part of this investigation.

You will talk about what types of screening they would recommend, at what age you (and/or other family members) should start being screened and how often you should be screened. Regular screening will ensure that any signs of bowel changes and early cancer are spotted and treated quickly. You can also discuss other ways to reduce your risk through your lifestyle.

Who we are

Dr Kevin J Monahan (Service lead): I spent three years working at Cancer Research UK where I completed my PhD in cancer genetics with funding from the Bobby Moore Fund for Bowel Cancer Research. I worked in the Family Cancer Clinic at St Mark’s Hospital in Harrow during this time.

The other members of the team are from the Departments of Gastroenterology, Endoscopy, Colorectal Surgery and Cancer Services at West Middlesex University Hospital.

Risk factors – how to reduce your risk of bowel cancer

Risk factors other than family history can play a more important role in the development of bowel cancer. The main risk factor for bowel cancer is increasing age. Only 7 per cent of bowel cancer occurs before the age of 50 years. However, even if you have a family history or other genetic risk of bowel cancer, this risk can be reduced by leading a healthy lifestyle. This kind of healthy lifestyle can also reduce your risk of heart disease, stroke and other cancers.

Diet

A diet high in red meat and animal fat and low in fruit and vegetables increases your risk of bowel cancer. So if you want to reduce your risk of bowel cancer, whether or not you have a genetic risk, eat 5 pieces of fruit or vegetables daily, plenty of fibre, and don’t eat too much processed or red meat.

Normal Body weight

Having a healthy weight (or a body mass index (BMI) of between 20-25) will reduce your risk of cancer.

Regular exercise

Regular physical activity can reduce your risk of bowel cancer, this is clearly shown in many studies. We would recommend 2-3 30 minute sessions per week of dedicated exercise (rather than more ‘passive’ exercise such as being busy at work!).

Other risk factors

Not smoking and drinking less than the upper recommended limit of normal (less than 21 units for men and less than 14 units for women) may also be helpful.

Familial Adenomatous Polyposis (FAP)

FAP (familial adenomatous polyposis) is a rare disease that causes a family history of bowel cancer.

Click here to download an information sheet

Lynch Syndrome

Lynch Syndrome (also known as hereditary non-polyposis colorectal cancer or HNPCC) is a rare condition that may cause a family history of bowel cancer. Conditions that run in families are known as familial or hereditary.

Click here to download an information sheet