Frequently Asked Questions
Summary
Colon cancer is an abnormal (or malignant) growth arising from the inner lining (mucosa) of the large bowel. Like a person with many names, colon cancer can also be called large bowel cancer or colorectal cancer. If left untreated, colon cancer can grow larger and spreads through the wall to the outer surface of the bowel. It may also spread via the blood stream or lymphatic system to other parts of the body. Secondary growths may develop in distant organs, such as the liver or lung.
Colon cancer is one of the commonest cancers affecting both man and women. In Hong Kong, it is the third commonest cancer and the third commonest cause of cancer death. Every year, more than 2,000 Hong Kong people are found to have colon cancer. People over 40 years of age are more likely to develop this cancer, and the risk increases as we grow older. The average age of colon cancer sufferers in Hong Kong is 60 years old.
The large bowel consists of two main parts : the colon and the rectum. Colon is a muscular tube forming the last two metres of the body’s digestive system. Rectum is the short tube leading down from the end of the colon to the back passage.
What Causes Colon Cancer?
We don’t know for certain what causes colon cancer. Majority (80%) of colon cancers are related to environmental causes particularly our diet. Some food may help protect us from colon cancer, while others may help it develop. There is growing evidence that a high fat and low fibre diet is related to colon cancer. On the other hand, eating plenty of fruits, vegetables and produce high in fibre (such as cereals, brown rice/bread) may help prevent colon cancer.
About 20% of colon cancer are related to heredity. People with close relative(s) (parents, brothers, sisters or children) having colon cancer are more likely to develop it. The level of risk depends on the number of close relatives with colon cancer and their age of developing cancer.
What are the Symptoms of Colon Cancer?
Colon cancer may develop the following symptoms :
- Blood or mucus (or both) in the bowel movements
- Unexplained changes in bowel habits lasting more than two weeks, such as constipation or diarrhoea or both
- Persistent 'colicky pain' in the abdomen
- Tiredness or paleness from anaemia
Sometimes, symptoms appear only after the colon cancer has spread.
On the other hand, in many cases these symptoms do not mean cancer, but tests may be needed to make sure. The older you are, the more likely that the symptoms could mean cancer.
What are Polyps?
Polyps are mushroom-shaped growths on the inner lining of the large bowel. Although they are non-cancerous, one type of polyp called adenoma is the precursor of colon cancer. If untreated, some adenoma will grow bigger and become cancerous in a number of years.
Polyposis is a hereditary condition in which an individual develops hundreds of polyps in the large bowel. For more information, please go to the section on FAP.
Who is Most At-Risk?
For an average person, the risk of colon cancer increases with age from 50 years onwards. Individuals having close relatives with colon cancer are at-risk. The risk increases with increasing number of affected close relatives. A person with a history of large or numerous colonic adenoma or a history of extensive ulcerative colitis for more than ten years are also at risk of colon cancer.
Those most at-risk are individuals with hereditary colon cancer syndromes caused by abnormal change (mutation) of known genes. This includes : polyposis syndrome which is a rare but easily recognizable condition; non-polyposis syndrome which has no easily recognizable features except a strong family history of colon cancer. Genetic testing is helpful in pinpointing this condition.
Who should have a check-up?
Studies have shown that regular check-up (screening) is the most effective way to prevent colon cancer. Whether you are at-risk of colon cancer or not, regular screening is your best bet against this very common cancer.
I am over 50 – Should I have a check up?
Even if you have no risk factor for colon cancer, we recommend you to have regular check-up from age 50 onwards. The World Health Organization (WHO) recommends the following scheme to you :
· Stool test for occult blood annually; and
· Telescopic examination of the lower part of colon (called sigmoidoscopy) every 3 to 5 years.
If you have a family history of colon cancer, your check-up may have to start earlier, say from age 40 or earlier. Instead of stool test and sigmoidoscopy, you may need a complete telescopic examination of the whole colon (called colonoscopy).
I would like to have a check up – how do I start?
If you live in Hong Kong, stool test can be arranged through the Hong Kong Crusade Angels (telephone and address provided). If your family history fits in our Registry’s recruitment criteria (click to recruitment criteria), you can contact us for check-up arrangement.
If you live elsewhere, you can contact your local cancer registry for check-up information and arrangement.
This site has a list of registries around the world.