The bowel is the longest part of the digestive system. Food passes through it and is broken down and absorbed. It is a long tube made up of 2 sections: the small bowel where food is absorbed into the body. This leads to the large bowel where only salts and water are absorbed.
The large bowel has 2 parts: the colon and the rectum. The rectum leads to the outside of the body via the anus (back passage).
Bowel cancer generally refers to cancer of the large bowel. Bowel cancer is therefore also known as colorectal cancer. Bowel cancer starts in the lining of the bowel (the mucosa). If untreated, it spreads deeper into the wall of the bowel. From there, it can spread to lymph nodes and later it may spread to other parts of the body. Sometimes bowel cancer starts in polyps, which can look like small mushrooms and grow in the lining of the bowel. There are different types of bowel polyps and not all polyps have the potential to become cancer.
Cancer of the small bowel is rare.
Australia has one of the highest rates of bowel cancer in the world. It is the second most common cause of death from cancer in Australia.
In Australia about 1 in 17 men and 1 in 26 women will develop bowel cancer before the age of 75. The older you are the greater your chance of bowel cancer. While it mainly affects people over 50, bowel cancer can occur at any age.
Everyone over the age of 50 should discuss with their doctor the bowel cancer tests (see below) that might be best for them so that any evidence of bowel cancer can be picked up early.
Bowel cancer is common. Many people have someone in their family who has had bowel cancer. More than one person in the family with bowel cancer can occur:
If you have a family history of bowel cancer (no matter what your age) it's important to talk with your doctor. Knowing which of your relatives has had bowel cancer and the ages at which they were diagnosed can help your doctor estimate your risk. It may also be helpful for your doctor to know whether there have been any other cancers (apart from bowel cancer) in your family.
If you find out about any new diagnoses of cancer in your family, it's important to discuss this with your doctor as this may change their advice to you.
First degree relatives are your mother, father, brothers, sisters and children. Second degree relatives are your grandparents, aunts, uncles, nieces, nephews and grandchildren.
Average risk: This will apply if you have:
Slightly above average: Applies if you have:
Speak to a doctor if you fit into the average risk or slightly above-average risk category for advice about the type of tests needed and at what age.
Moderately increased risk: Some people have an increased chance of bowel cancer because of their family history. This includes people with:
Speak to your doctor if you fit into the moderately increased risk category.
Potentially high risk: A few people may have a potentially higher chance of bowel cancer. These are people with:
Speak to a doctor if you fit into the potentially high risk category. They can discuss appropriate bowel checks for you and may refer you to a family cancer centre.
This condition runs in families, causing people to develop large numbers of 'adenomatous' or pre-cancerous polyps in the bowel. Polyps are small growths, often on stalks like a mushroom. They vary in size from a tiny pinhead to two centimetres or more.
If FAP is not treated, a bowel cancer will almost always develop in one or more polyps.
FAP is caused by a change in a gene called APC. Our genes carry the instructions that control how our bodies grow, develop and work. APC controls the way the lining of the bowel develops. Everybody has this gene, although only people with a change in the gene (called a mutation) develop FAP. Once this mutation has occurred, it can be passed from parent to child.
If you have a parent with FAP, you have a 50/50 chance of having FAP. If you have a brother or sister with FAP, you may also be at risk. The risk is the same for males and females.
Genetic testing is available for most people at risk of FAP. This can tell you with certainty whether you have the FAP gene. If you have not inherited the gene change, it is very unlikely that you will develop FAP.
Contact your nearest family cancer centre for further information.
Booklet - Familial Adenomatous Polyposis (FAP) - 1.4MB
HNPCC is also known as Lynch Syndrome. It is another inherited bowel cancer. People who have HNPCC have a high risk of bowel cancer. Women are also at increased risk of cancer of the uterus (also known as endometrial cancer or cancer of the womb). More rarely, other cancers can occur. People with HNPCC can develop polyps in the bowel, although these occur in fewer numbers than in FAP.
HNPCC is caused by a gene change (mutation) which affects how the gene works. Our genes carry the instructions that control how our bodies grow, develop and function. There are at least 4 genes connected with HNPCC and normally they are involved in preventing cancers. Everybody has these genes, but if a person has a change in one of these genes they have HNPCC. This gene change can be passed on from parent to child. If you have a parent with HNPCC you have a 50/50 chance of inheriting the changed gene. If you are aware of any member of your extended family with HNPCC, you may be at risk and you should contact a family cancer centre.
Having HNPCC does not necessarily mean you will develop cancer. Not all people who carry the gene develop cancer.
Genetic testing is available for some people at risk of HNPCC. For further information contact your nearest family cancer centre.
Booklet - Hereditary Non-Polyposis Colorectal Cancer (HNPCC) - 890kb
Depending on which category you fit into, there are tests that can pick up bowel cancers at an early stage before there are any signs. Your doctor will advise which tests are appropriate for you and how often these should be done.
Research shows about 90% of bowel cancer can be cured if picked up at the earliest stage.
Types of tests that might be done include:
Further information about bowel cancer is available from the Cancer Council Victoria’s Cancer Helpline on 13 11 20. If you're worried about your risk based on your family history, contact your doctor or nearest family cancer centre.
