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Early screening of this common yet treatable cancer can save your life, says Parkway Cancer Centre’s Dr Zee Ying Kiat.

Colorectal cancer, which occurs in the colon or rectum, does not develop overnight. It can take many years to develop, and therefore can be detected and treated early.

Typically, it starts off as benign growths, called polyps, on the inner lining of the colon or rectum. Although polyps are not cancerous, they can develop into cancer over a long period of time. In fact, most colorectal cancers develop from a polyp. Polyps are quite common, with about 1 in 4 people having at least one by age 50. However, only a small fraction of polyps develop into cancer and it takes years to happen. A polyp that is 1 cm across has roughly a 1 in 6 chance of growing into a cancer over 10 years.

Regular colorectal cancer screening is one of the most powerful weapons for preventing colorectal cancer. Precancerous polyps can be present, often without symptoms, in the colon for years before invasive cancer develops. Colorectal cancer screening can find precancerous polyps so they can be removed before they turn into cancer. In this way, colorectal cancer is prevented.

Screening can also potentially detect colorectal cancer at its earliest stage. This is important as colorectal cancer is generally more treatable when it is found early, before it has had a chance to spread.

Of course, apart from early detection and screening, a healthy lifestyle can also reduce the risk of developing colorectal cancer.

Faecal Occult Blood Test (FOBT)

This test, which checks for hidden blood in faeces (stool), is a basic screening test. The FOBT is simple and non-invasive, and can be performed by a family physician or at a polyclinic. Studies have shown that FOBT, when performed every 1-2 years in people aged 50-80, can help reduce the number of deaths due to colorectal cancer by 15-33 per cent.

If blood is detected, more tests are required to find the source, which may not be cancer. Haemorrhoids and other benign conditions can also produce blood in the stool.

Colonoscopy

In this test, the rectum and entire colon are examined using a lighted instrument called a colonoscope. Precancerous and cancerous growths throughout the colon can be found and either removed or biopsied. A thorough cleansing of the colon is necessary before this test, and most patients receive some form of sedation.

Other screening methods

Other methods to detect polyps include flexible sigmoidoscopy, double contrast barium enema, and CT colonography (virtual colonoscopy).

Colon cancer: Common but treatable

Colorectal cancer is now the most common cancer among men and the second most common cancer among women in Singapore. It can occur at any age, but is diagnosed mostly in those over 50 years old. It can be prevented or effectively treated if detected early.

Colorectal cancer does not usually produce symptoms early in the progress of the disease. In fact, more than half of the people diagnosed with colorectal cancer have no symptoms. When symptoms appear, they are likely to vary, depending on the size and location of the cancer. The more common symptoms of colorectal cancer are:

• A change in bowel habits, including diarrhoea or constipation
• Presence of blood in the stool
• Persistent abdominal discomfort, such as cramps, bloating or pain
• A feeling of incomplete bowel emptying
• Unexplained weight loss
   

Screening: What and when to do it

According to the Singapore Cancer Society, screening for colon cancer should start when you are aged 45 to 50:

• Faecal occult blood test: yearly
• Sigmoidoscopy: every 5 years
• Or colonoscopy: every 10 years
• Or barium enema X-ray: every 10 years
• Digital rectal examination: every 5 to 10 years
   

Individuals in the high risk group (e.g. if one or more close relatives are diagnosed with colorectal cancer) should have screening earlier and/or more frequently.