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What is meant by screening and surveillance for colorectal cancer?

Polyps and cancers of the colon and rectum do not always produce symptoms until they become large. Accurate screening involves one or more tests performed to identify whether a person with no symptoms has a disease or condition that may lead to the diagnosis of colon or rectal cancer. Our goal is to identify the potential for disease or the condition early when it is easier to prevent and/or cure. Surveillance involves testing people who have previously had colorectal cancer or are at increased risk.

Why should testing be done?

Colorectal cancer is considered by many healthcare professionals as being a "silent" disease. Many patients do not develop classic symptoms, such as bleeding or abdominal pain until the cancer has spread and grown in size. The possibility of curing patients after symptoms develop is roughly 50%. If colorectal cancer is found and treated at an early stage, before symptoms develop, the percentage rate of complete recovery is 80% or better in some cases. Most colon cancers start as non cancerous growths called polyps. If the polyps are removed, then cancer may be prevented.

What screening tests should be done?

A simple screening test for colon and rectal cancer is testing of the stool for traces of blood; this is called fecal occult blood testing (FOBT). This test can only detect cancer or polyps which are actively bleeding at the time of the test. Only about 50% of cancers and 10% of colon polyps bleed enough to be detected by this test. Therefore, further screening is necessary for an accurate diagnosis of cancers and polyps.

A Flexible sigmoidoscopy is a test which allows our physicians to examine the lining of the colon and rectum visually. During this test, the lining of the lower one-third of the colon and rectum can be seen through a scope. This is the portion of the lower intestine which accounts for most polyps and cancers. When flexible sigmoidoscopy is combined with stool testing, many cancers and polyps can be detected.

When a polyp or cancer is detected by flexible sigmoidoscopy, or if a person is at high risk to develop colon and rectal cancer, colonoscopy provides a safe, effective means of visually examining the full lining of the colon and rectum. Colonoscopy procedures are used to diagnose colon and rectal problems and to perform biopsies and remove colon polyps. Most colonoscopies are done on an outpatient basis with minimal inconvenience and/or discomfort.

A barium enema or x-ray of the colon is almost as good as a colonoscopy in detecting large tumors, but it is not as accurate for small tumors or polyps. The combination of barium enema and sigmoidoscopy is better than either test alone, but not as good as a colonoscopy.

Table for the screening guideline

Surveillance Colonoscopy

For patients who have had colon or rectum resected for cancer, they should follow up on a much more regular basis than those with no history. The goal of the surveillance for colon and rectal cancer is to detect treatable recurrent cancers, identify and remove metachronous polyps and identify possible hereditary influence in development of a colon and rectal cancer.

The Standards Task Force of the American Society of Colon and Rectal Surgeons (ASCRS) has recommended colonoscopy surveillance to begin 3 years after surgery assuming pre-operative or intra-operative clearance was done and was negative. If pre-operative clearance could not be done, post-operative colonoscopy within 6 months of surgery is recommended. If multiple synchronous polyps are identified during the clearance examination, initial surveillance should be done at 1 year. Follow up surveillance colonoscopy every 3 years can be done for the duration of the individual’s active life. It is also acceptable to have colonoscopy at 5 years after a negative colonoscopy at 3 years.