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It's important to understand how the cancer develops inside the colon to raise the awareness of this screening procedure.
Colon cancer is the third most effective killer in most countries. Overall the lifetime risk of developing colon cancer is about 1in20. In the US it's expected to kill 49,000 people this year.
The death rate has been dropping for more than 20 years, however. Screening for early occurrence and more effective treatments are the likely reasons.
Colon cancer is quite rare before 40 years of age, but the risk of getting it increases rapidly after 50, and the average age of diagnosis is 70.
The cancer starts silently, without few symptoms, over the course of months or years. Some signs should nevertheless be recognised. Seek medical consultation if there are changes in your bowel habits, especially alternating constipation and diarrhoea; if you have abdominal discomfort or bloating; and if you notice blood in the stool, even in small quantities.
Colon cancer often starts with a benign growth called a polyp, usually of the noncancerous adenomatous type. A few of these polyps can become a malignant tumour over five to 10 years. The more polyps and the bigger they are above one centimetre in diameter, the higher the risk of cancer.
Regular screening tests are the only approach to prevent cancer. If polyps are found they can be removed at the precancerous stage.
Besides older age, there are several predisposing factors that need to be taken into consideration for the frequency of screening: a family or personal history of colorectal cancer or polyps; the presence of diabetes or obesity; smoking and excessive alcohol consumption; previous radiation therapy for cancer.
A lowfibre, highfat diet that's high in red and processed meats, as well as a sedentary lifestyle, has also been found to increase the risk of colon cancer.
People without specific risk should have an annual "occult blood" screening after they reach 50. A simple stool sample on a card is sent to a laboratory but the test results are only 60 to 70 per cent accurate.
But this test is not appropriate for people at higher risk of developing colon cancer.
The reference test is the colonoscopy, which is about 95 per cent accurate. It's done with a long, flexible tube called a colonoscope, inserted into the rectum. A tiny video camera at its tip reveals the inside of the entire colon. Polyps or other abnormal tissue can be removed for analysis.
If no polyp is found, the procedure should be repeated every five years to 10 years. If polyps are found, depending on the number, size and cellular type, the tests will be more frequent.
Dr Gerard Lalande is managing director of CEOHealth, which provides medical referrals for expatriates and customised executive medical checkups in Thailand. He can be contacted at gerard.lalande@ceohealth.com.
