Cancer Institute A national cancer institute
designated cancer center

Prevention of Colorectal Cancer

Lowering Your Risk

Although the exact cause of colorectal cancer is not known, it may be possible to lower your risk of colorectal cancer by addressing the factors listed below.

The following screening guidelines can lower the number of cases of the disease, and can also lower the death rate from colorectal cancer by detecting the disease at an earlier, more treatable stage.

Screening Tests

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.

Studies show that screening for colorectal cancer helps decrease the number of deaths from the disease.

A picture of a phone
Fecal Occult Blood Test (FOBT) kit to check for
blood in the stool, a symptom of colorectal cancer.

Commonly Used Screening Tests for Colorectal Cancer

Fecal Occult Blood Test
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
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 sigmoidoscopy and a digital rectal exam (DRE) may be used together to screen for colorectal cancer.

Illustration of a sigmoidoscopy
Sigmoidoscopy. A thin, lighted tube is inserted through the anus and rectum and into th
lower part of the colon to look for abnormal areas. (click to enlarge)

Barium Enema
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.

Illustration of a barium enema procedure to check for colorectal cancer
Barium enema procedure. The patient lies on an x-ray table. Barium liquid is put into the
rectum and flows through the colon. X-rays are taken to look for abnormal areas. (click to enlarge)

Colonoscopy
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.

Digital Rectal Exam
A digital rectal exam (DRE) is an exam of the rectum. The 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.

New Screening Tests in Clinical Trial

Screening clinical trials are taking place in many parts of the country. Information about ongoing clinical trials is available from the NCI Web site.

Risks of Colorectal Cancer Screening

Specific Risks of Different Tests for Colorectal Cancer

Your doctor can advise you about your risk for colorectal cancer and your need for screening tests.


What is Colorectal Cancer | Symptoms | Diagnosis | Staging | Risk Factors | Prevention

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