Detecting colorectal cancer

The main screening method for people at high risk of colorectal cancer is a colonoscopy. During this test, an endoscope, a flexible fibre-optic tube, is inserted into the colon to look for bleeding, polyps, or tumours. Although the procedure can be a bit uncomfortable, it should not be painful. If any growths are found, the doctor will take a tissue sample (biopsy).

A new technology called a virtual colonoscopy has recently been developed. Virtual colonoscopy takes a picture of the inside of the colon using a CT scanner. Other new screening methods being developed include DNA tests and blood serum tests.

Fecal occult blood tests are used for people who are at a low-to-average risk of colorectal cancer. This test, which is done using a take-home test kit, can detect tiny amounts of blood in the stool, amounts that are too small to be seen. If there is a positive result, a colonoscopy is used to check for polyps or cancer.

Check with your doctor to find out if you should be screened for colorectal cancer.

Staging colorectal cancer

In order to determine your prognosis (chances of recovery) and the most appropriate treatment, your cancer will need to be staged by a doctor. Staging a cancer involves determining whether the cancer has spread, and if so, how far and where it has spread to. The cancer is then assigned a "stage" that describes where the cancer has spread within the body and how advanced it is.

There are two main staging systems for colorectal cancer:

Dukes system: This system assigns a letter from A to D. A is the least advanced and D is the most advanced form of colorectal cancer. For example, a cancer that is stage D has grown through the colon wall and spread to lymph nodes and distant parts of the body (such as the liver and lungs).

TNM system: This system assigns letters and numbers based on how deeply the tumour has grown into the wall of the bowel (T), how many lymph nodes it has spread to (N), and whether it has spread elsewhere in the body (M). For example, a cancer that is staged T4N2M1 has grown through the colon wall and from there it has spread to lymph nodes and distant parts of the body.

Your doctor can explain the stage of your cancer and what this means to you for prognosis and treatment. For more detailed information on colorectal cancer staging, talk to your doctor or contact the Colorectal Cancer Association of Canada.