Finding colorectal cancer early

Colorectal cancer, also known as bowel cancer, occurs in the colon or rectum. It can take many years to develop, and therefore can be detected and treated when found early.

Bowel cancer typically 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 one in four people having at least one by age 50. However, only a small fraction of polyps develop into cancer and this takes years to happen. A polyp that is 1cm across has roughly a one in six chance of growing into a cancer over 10 years.

Regular colorectal cancer screening is one of the most powerful weapons for preventing this type of cancer. Precancerous polyps can be present, often without symptoms, in the colon for years before invasive cancer develops. Regular screening can therefore find these polyps so they can be removed before they develop into bowel cancer, therefore preventing the disease.

Screening also has the potential to detect colorectal cancer at its earliest stage. This is important, as bowel cancer is generally more treatable when it is found early, before it has the chance to spread.

In addition to early detection and screening, a healthy lifestyle can also reduce the risk of developing bowel cancer.

Screening methods for colon cancer

Faecal Occult Blood Test (FOBT)

This test, which checks for hidden blood in the 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 to 33 percent.

If blood is detected, more tests are required to find the source, which may not necessarily 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 during the procedure.

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 typically in those over 50 years of age. It can be prevented or effectively treated if detected early.

In most cases, colorectal cancer does not produce symptoms in the early stages of the disease. In fact, more than half of those diagnosed have no symptoms. When symptoms do 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

When to screen for colon cancer

According to the Singapore Cancer Society, screening for colon cancer should start between the ages of 45 and 50.

• Faecal occult blood test (FOBT): 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 

It’s important to note that those individuals in the high-risk group, that is, those with one or more close relatives who have been diagnosed with colorectal cancer should commence screening earlier and more frequently.

Dr Zee Ying Kiat is a specialist in medical oncology at Parkway Cancer Centre. He conducted research on novel targeted therapies for colorectal, gastric, liver and pancreatic cancer.

Parkway Cancer Centre
Tel: +65 6738 9333
Email: enquiry@pcc.sg
www.parkwaycancercentre.com

Material provided by Parkway Cancer Centre