Colorectal Cancer Screening
Key Points for This Section
- Tests are used to screen for different types of cancer.
- Studies show that screening for colorectal cancer helps decrease the number of deaths from the disease.
- Four tests are used to screen for colorectal cancer:
- Studies have not shown that screening for colorectal cancer using digital rectal exam helps decrease the number of deaths from the disease.
- New screening tests are being studied in clinical trials.
Some screening tests are used because they have been shown to be helpful both in finding cancers early and decreasing the chance of dying from these cancers. Other tests are used because they have been shown to find cancer in some people; however, it has not been proven in clinical trials that use of these tests will decrease the risk of dying from cancer.
Scientists study screening tests to find those with the fewest risks and most benefits. Cancer screening trials also are meant to show whether early detection (finding cancer before it causes symptoms) decreases a person's chance of dying from the disease. For some types of cancer, finding and treating the disease at an early stage may result in a better chance of recovery.
Clinical trials that study cancer screening methods are taking place in many parts of the country. Information about ongoing clinical trials is available from the NCI Web site.
A fecal occult blood test (FOBT) is a test to check stool (solid waste) for blood that can only be seen with a microscope. Small samples of stool are placed on special cards and returned to the doctor or laboratory for testing. Blood in the stool may be a sign of polyps or cancer.
A new colorectal cancer screening test called immunochemical FOBT (iFOBT) is being studied to see if it is better at finding advanced polyps or cancer than the FOBT.
Sigmoidoscopy is a procedure to look inside the rectum and sigmoid (lower) colon for polyps, abnormal areas, or cancer. A sigmoidoscope is inserted through the rectum into the sigmoid colon. A sigmoidoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove polyps or tissue samples, which are checked under a microscope for signs of cancer.
A barium enema is a series of x-rays of the lower gastrointestinal tract. A liquid that contains barium (a silver-white metallic compound) is put into the rectum. The barium coats the lower gastrointestinal tract and x-rays are taken. This procedure is also called a lower GI series.
Colonoscopy is a procedure to look inside the rectum and colon for polyps, abnormal areas, or cancer. A colonoscope is inserted through the rectum into the colon. A colonoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove polyps or tissue samples, which are checked under a microscope for signs of cancer.
A digital rectal exam (DRE) may be done as part of a routine physical exam. A digital rectal exam is an exam of the rectum. A doctor or nurse inserts a lubricated, gloved finger into the lower part of the rectum to feel for lumps or anything else that seems unusual. Study results have shown that there is no evidence to support DRE as a screening method for colorectal cancer.
Virtual colonoscopy is a procedure that uses a series of x-rays called computed tomography to make a series of pictures of the colon. A computer puts the pictures together to create detailed images that may show polyps and anything else that seems unusual on the inside surface of the colon. This test is also called colonography or CT colonography. Clinical trials are comparing virtual colonoscopy with commonly used colorectal cancer screening tests. Other clinical trials are testing whether drinking a contrast material that coats the stool, instead of using laxatives to clear the colon, shows polyps clearly.
Screening clinical trials are taking place in many parts of the country. Information about ongoing clinical trials is available from the NCI Web site.