One of the leading cancers affecting both men and women in Singapore is colon cancer, with approximately 1200 new cases diagnosed each year. Also referred to as bowel or colorectal cancer, majority of the disease develop from adenomatous polyps. The process of malignant transformation of adenomatous polyps takes between 5 to 10 years through multiple gene mutations.
Some of the signs and symptoms of colon cancer include rectal bleeding or blood in the stool, incomplete evacuation of bowels, persistent abdominal discomfort and unexplained weight loss. While surgery is the mainstay treatment for colon cancer, an early diagnosis can improve the likelihood of a cure.
There are several risk factors involved that may increase your chances of colon cancer such as:
- Older age
The risk of colon cancer goes up as you age. Majority who are diagnosed with colon cancer are over the age of 50. While younger adults can still get the disease, cases occur much less frequently.
- Personal history of colon cancer or polyps
If you have a history of adenomatous polyps (adenomas), you face a higher risk of developing colon cancer in the future. They are benign non-cancerous growths that develop in the colon and rectum, but may be a precursor lesion to colon cancer especially when they are greater than 1cm in diameter. If the polyps are not removed, they can continue to grow with a great risk of becoming cancerous.
If you’ve had colorectal cancer before, there is a likelihood of developing new cancers in other parts of the colon and rectum especially if it had occurred when you were younger.
- Family history of colon cancer
While colorectal cancers occur in people without a family history of colorectal cancers, you are more likely to develop it if you have a child, parent or sibling with the disease. You will be at increased risk if more than one family member has colon cancer.
Getting screened for colon cancer
Those with an average risk of colon cancer can consider screening at age 50, however for those with increased risks, they should go for screening sooner. Going for regular colon screening shouldn’t be skipped because it can prevent cancer by removing polyps at colonoscopy and there is a good chance of a cure when cancers are detected early. Colon cancer screening also reduces cancer-related deaths especially by screening asymptomatic individuals.
There are two screening methods used routinely – the faecal occult blood test to check for blood in the stool, and imaging or scans to visualize the inner and outer folds of the colon for polyps and lesions.
Immunochemical faecal occult blood test detects human haemoglobin from partially digested blood in the stool. For this testing, it is more specific and sensitive than guaiac-based tests which were used in the past, and dietary restriction is also not required.
If necessary, further specialised tests will be performed by specialists for colon cancer screening such as:
Colonoscopy – enables a complete large bowel evaluation, to check for colorectal cancer and spot any abnormalities. Patients will need to undergo full bowel preparation and sedation. This is also recommended for screening for high-risk patients.
CT Colonography – a technique that is used to generate images of the colon and rectal wall. Patients will also need to do bowel preparation. However, the disadvantage is that it cannot pick up small or flat lesions. Thus, colonoscopy may be needed to rule out any suspicious lesions.
It should be noted that for any abnormal test result from screenings that are done with tests other than colonoscopy, it should be followed up with a timely colonoscopy to rule out suspicious lesions and complete the screening process.
People older than 50 years old are typically advised to go for a colonoscopy once every 10 years, while those who are at a high risk of developing the disease are advised to get tested more often (i.e. every 3 years).