Colorectal Cancer Screening

What is colorectal cancer?

Colorectal cancer is cancer that arises from the inner lining (mucosa) of the large intestine and the rectum. In Canada, colorectal cancer is the third most common cancer and is the second most common cause of cancer death. As Asian countries have become developed and adopt a more Western style diet, the rates of colorectal cancer have risen and are approaching Western rates. As you can see in the tables below, the rate of colorectal cancer in China is steadily increasing in both males and females. (Figures taken from Chen, W et. al., 2015, CA)

rates of cancer in females in China

Figure 1: Rates of Cancer in Females in China (2000-2011)

Rates of Cancer in Males in China

Figure 2: Rates of Cancer in Males in China (2000-2011)

Why do screening?

Unfortunately, like most cancer, colorectal cancer in its early stages are usually asymptomatic; that is, they have no symptoms whatsoever. As the cancer enlarges, it can cause:

  1. Bleeding
  2. Alterations in the bowel pattern
  3. Unexplained weight loss
  4. Unexplained anemia

However, these symptoms usually do not occur until the cancer is more advanced. Therefore screening, that is, testing patients without symptoms, is the best way to try to detect for colorectal cancer. As well, colorectal cancers usually arise out of small growths on the inner lining of the intestine call polyps. Screening can detect for these polyps. Removal of these polyps may then prevent future cancer.

Who should be screened?

The biggest risk factor for colorectal cancer is age. The risk of cancer steadily rises with increasing age as can be seen in Table 1.

table 1

What methods are there to do screening?

FIT Test / Stool Test

Currently, the Provincial government recommends stool testing using a FIT test for initial screening for patients who are over 50 with no family history of either a first degree relative under 60 or 2 first degree relatives. FIT testing is used to detect for the presence of abnormal amounts of blood in the intestines that may be due to a cancer or large polyps.

FIT testing is very safe and does not require any preparation of the intestines. A positive FIT test requires a colonoscopy to confirm if there is a cancer or polyps. A FIT test can miss a cancer or large polyp in around 5% of patients. It cannot detect for early or smaller polyps.


Colonoscopy is considered the gold standard for screening by most Surgeons and Physician groups. It is also recommended for patients with a family history of colorectal cancer in a first degree relative under 60 or two first degree relatives. It utilizes a long, flexible tube with a camera at the end to allow for visualization of the entire colon.

Colonoscopy picks up 99% of all cancers. It is also able to perform biopsies as well as removal of polyps at the same time. However, it does require preparation of the bowel with cleansing. It also requires IV sedation as it can cause pain. Lastly, there is a known risk of causing an injury or perforation of the colon in 1:1000 patients with a mortality risk of 1:10000. The risk appears to increase with age.

PillCam Colo2- Capsule endoscopy

Capsule endoscopy is a newer technology whereby a patient swallows a capsule that has a camera on both ends and allows for complete visualization of the colon and rectum. It is considered an alternative to colonoscopy for patients unwilling or who are concerned about the risk of perforation.

Capsule endoscopy does require a full bowel preparation but does not require sedation. There is no risk of perforation. There is a small 1% risk of a retained capsule as well. If an abnormality is found, colonoscopy may be required for biopsy. Capsule endoscopy may not see abnormalities smaller than 5-6mm.

CT Colonography

CT colonography is a specialized CT scan that focusses on the intestines. It is considered an alternative to colonoscopy. In this test, patients also require a bowel preparation to cleanse the intestines and also need to drink some x-ray contrast to coat the lining of the intestine. During the test, CO2 is pumped into the colon via the anus and then a CT scan is performed.

CT colonography does have a small risk perforation due to the need for CO2 inflation. As well, it cannot see abnormalities under 6mm. Lastly, the images are only computer generated and thus do not have color and hence, inflammation cannot be reliably assessed.

Do you need colon screening or want to ask about the various methods available? At Pacific Executive Health, we can offer the full range of screening methods.