By Dr Saravana K.
How common is colon cancer?
The colon is the final portion of the digestive tract, just before the anus. Colon cancer is the commonest cancer among men and the third commonest among women in Malaysia. Every year about four thousand new cases of colon cancer are diagnosed in Malaysia. Among the local ethnic groups, the Chinese appear to have the highest incidence of the disease, followed by Indians and then Malays. The incidence is even higher among the western population. It is estimated that one in twenty people will get colon cancer in their lifetime.
How does colon cancer happen?
Most colon cancers develop from precancerous polyps. Polyps are growths that arise in the lining of the colon and are visible when the bowel is examined by colonoscopy. There are two types of polyps: adenomatous polyps and hyperplastic polyps. Adenomatous polyps can become cancerous over time and this progression takes at least 10 years in most people. At age 50 about 30% of colonoscopies will detect adenomatous polyps. This adenoma detection rate continues to rise with age (45% of colonoscopies at age 70 will detect adenomatous polyps).
Are you at increased risk of getting colon cancer?
Several factors increase an individual’s risk of developing colorectal cancer. Having one or more of these factors will determine the age when you should begin screening: first degree relatives with colon cancers/adenomatous polyps; increasing age; smoking; heavy alcohol intake; sedentary lifestyle; obesity; diet that is high in red meat and low in fibre; or patients with inflammatory bowel disease (crohn’s disease or ulcerative colitis).
How do you know if you have colon cancer?
Unfortunately, most colon cancers are asymptomatic in the beginning. At a later stage, the patient may complain of abdominal pain, change in bowel habit (new development of diarrhoea/constipation or both), change in the texture of the faeces, passing bloody or black and sticky faeces, or present with symptoms of anaemia or low red blood level (easily tired, breathlessness, dizziness).
How can you prevent colon cancer?
Colon cancer can be prevented by doing screening tests. These are called screening tests because these tests are performed before the development of any symptoms or problems. The most effective and widely practised screening test is screening colonoscopy. The primary goal of screening colonoscopy is to prevent deaths from colon cancer. Screening colonoscopy prevents the development of colorectal cancer by identifying precancerous abnormal growths (adenomatous polyps), and removing them before they become malignant. The risk of developing colon cancer is reduced by 90% after a single screening colonoscopy done at age 50. Even if cancer is already present, a screening colonoscopy helps identify it at an early and potentially treatable stage. The age at which you should have the first screening colonoscope varies. An average risk person is recommended to have it done at age 50, regardless of the gender or ethnicity. The presence of risk factors and/or symptoms requires it to be done at an earlier age. If any first degree relative has colon cancer or adenomatous polyps, then screening should be done ten years before the age of detection or at fifty years old, whichever is earlier.
How is colonoscopy performed?
Prior to the procedure, you will be asked to take a medication to clean your entire colon so that it is free of obstructing faeces. You will also be asked to avoid fruits, vegetable, red meat and certain medications for a period of time before the procedure. A sedative and a painkiller will be given intravenously just before the procedure. After you are asleep the doctor will pass a thin flexible video endoscope through your anus into your colon. This video endoscope has a light source and a camera at its tip and this allows the doctor to see the inside of the colon. During this procedure, most polyps encountered will be removed and sent for microscopy. It normally takes 20 minutes to an hour to complete the colonoscope. Almost all patients do not experience any pain during or after this procedure and should be able to go back that very same day.