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Screening statement for Patients

Screening for Colorectal Cancer

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Overview of Screening
Colorectal Cancer Screening
Changes to This Summary (06/10/2003)
To Learn More
About PDQ

Overview of Screening

What is screening?

Screening for cancer is examination (or testing) of people for early stages in the development of cancer even though they have no symptoms. Scientists have studied patterns of cancer in the population to learn which people are more likely to get certain types of cancer. They have also studied what things around us and what things we do in our lives may cause cancer. This information sometimes helps doctors recommend who should be screened for certain types of cancer, what types of screening tests people should have, and how often these tests should be done. Not all screening tests are helpful, and most have risks such as tearing (perforation) of the lining of the colon during a colonoscopy. For this reason, scientists at the National Cancer Institute are studying many screening tests to find out how useful they are and to determine the relative benefits and harms.

If your doctor suggests certain cancer screening tests as part of your health care plan, this does not mean he or she thinks you have cancer. Screening tests are done when you have no symptoms. Since decisions about screening can be difficult, you may want to discuss them with your doctor and ask questions about the potential benefits and risks of screening tests and whether they have been proven to decrease the risk of dying from cancer.

If your doctor suspects that you may have cancer, he or she will order certain tests to see whether you do. These are called diagnostic tests. Some tests are used for diagnostic purposes, but are not suitable for screening people who have no symptoms.

Purposes of this summary

The purposes of this summary on colorectal cancer screening are to:

You can talk to your doctor or health care professional about cancer screening and whether it would be likely to help you.

Colorectal Cancer Screening

Cancer of the colon or rectum is often called colorectal cancer. The colon and the rectum are part of the large intestine, which is part of the digestive system.

Risk of colorectal cancer

Colorectal cancer is the second leading cause of death from cancer in the United States. It is common in both men and women; men are more likely to get rectal cancer. The number of colorectal cancer cases is decreasing each year. In addition, fewer deaths are resulting from colorectal cancer. You can talk to your doctor about whether you should have the screening tests described later in this summary.

Anything that increases a person’s chance of developing a disease is called a risk factor. Some of these risk factors for colorectal cancer are as follows:

Age: The risk of developing colorectal cancer rises after age 50 years.

Hereditary Conditions: You may have inherited a condition from your parents that puts you at a higher-than-average risk of developing colorectal cancer. For example, if you have inherited familial adenomatous polyposis, a condition characterized by many polyps on the inner lining of the colon, you have a greater-than-average chance of developing colorectal cancer. Your doctor may ask you medical questions about your relatives and may perform some tests to see if you have any hereditary conditions that might increase your risk of colorectal cancer.

Personal History of Colorectal Cancer: If you have already had colorectal cancer, you are more likely to develop colorectal cancer again.

Personal History of Polyps: If you have had polyps (adenomas), you have a higher-than-average risk of developing colorectal cancer.

Family History: If your mother, father, brother, or sister has had colorectal cancer or has had an adenoma diagnosed before 60 years of age, you have a higher-than-average risk of developing colorectal cancer.

Personal History of Ovarian, Endometrial, or Breast Cancer: If you have had ovarian, endometrial, or breast cancer, you have a higher-than-average risk of developing colorectal cancer.

Personal History of Chronic Ulcerative Colitis or Crohn’s Colitis: If you have longstanding chronic ulcerative colitis or Crohn’s colitis, you have a higher-than-average risk of developing colorectal cancer.

Screening tests for colorectal cancer

Fecal Occult Blood Test: Special cards are coated with a stool sample and returned to the physician or lab. This test examines a patient’s solid waste (stool) for occult (hidden) blood. Studies show that a fecal occult blood test performed every 1 or 2 years in people between the ages of 50-80 years decreases the number of deaths due to colorectal cancer.

Sigmoidoscopy: Sigmoidoscopy is an examination in which a doctor uses a thin, flexible tube with a light to look inside the rectum and colon for polyps, tumors, or abnormal areas. Studies suggest that fewer people may die of colorectal cancer if they have regular screening by sigmoidoscopy after the age of 50 years.

Digital Rectal Examination: A digital rectal examination is performed during an office visit or prior to sigmoidoscopy or colonoscopy. For this examination, the doctor or nurse inserts a lubricated gloved finger into the rectum and feels for lumps or abnormal areas. The evidence available does not suggest that digital rectal examination is effective in decreasing mortality from colorectal cancer.

Barium Enema: Barium enema is a procedure in which a liquid containing barium is put into the rectum and colon by way of the anus. Barium is a silver-white metallic compound that helps to show the image of the lower gastrointestinal tract on an x-ray. Barium enema may be effective in detecting large polyps.

Colonoscopy: Colonoscopy is an examination of the inside of the colon and rectum using a thin, lighted tube (called a colonoscope) inserted into the rectum. If the doctor sees polyps or other abnormal tissue during the procedure, they can be removed and further examined under a microscope. Studies suggest that colonoscopy is a more effective screening method than barium enema.

Changes to This Summary (06/10/2003)

The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.

Editorial changes were made to this summary.

To Learn More


For more information, U.S. residents may call the National Cancer Institute's (NCI's) Cancer Information Service toll-free at 1-800-4-CANCER (1-800-422-6237) Monday through Friday from 9:00 a.m. to 4:30 p.m. Deaf and hard-of-hearing callers with TTY equipment may call 1-800-332-8615. The call is free and a trained Cancer Information Specialist is available to answer your questions.

Web sites and Organizations

The NCI's Web site provides online access to information on cancer, clinical trials, and other Web sites and organizations that offer support and resources for cancer patients and their families. There are also many other places where people can get materials and information about cancer treatment and services. Local hospitals may have information on local and regional agencies that offer information about finances, getting to and from treatment, receiving care at home, and dealing with problems associated with cancer treatment.


The NCI has booklets and other materials for patients, health professionals, and the public. These publications discuss types of cancer, methods of cancer treatment, coping with cancer, and clinical trials. Some publications provide information on tests for cancer, cancer causes and prevention, cancer statistics, and NCI research activities. NCI materials on these and other topics may be ordered online or printed directly from the NCI Publications Locator. These materials can also be ordered by telephone from the Cancer Information Service toll-free at 1-800-4-CANCER (1-800-422-6237), TTY at 1-800-332-8615.


The NCI's LiveHelp service, a program available on several of the Institute's Web sites, provides Internet users with the ability to chat online with an Information Specialist. The service is available from 9:00 a.m. to 10:00 p.m. Eastern time, Monday through Friday. Information Specialists can help Internet users find information on NCI Web sites and answer questions about cancer.


For more information from the NCI, please write to this address:

About PDQ

PDQ is a comprehensive cancer database available on

PDQ is the National Cancer Institute's (NCI's) comprehensive cancer information database. Most of the information contained in PDQ is available online at, the NCI's Web site. PDQ is provided as a service of the NCI. The NCI is part of the National Institutes of Health, the federal government's focal point for biomedical research.

PDQ contains cancer information summaries.

The PDQ database contains summaries of the latest published information on cancer prevention, detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries are available in two versions. The health professional versions provide detailed information written in technical language. The patient versions are written in easy-to-understand, nontechnical language. Both versions provide current and accurate cancer information.

The PDQ cancer information summaries are developed by cancer experts and reviewed regularly.

Editorial Boards made up of experts in oncology and related specialties are responsible for writing and maintaining the cancer information summaries. The summaries are reviewed regularly and changes are made as new information becomes available. The date on each summary ("Date Last Modified") indicates the time of the most recent change.

PDQ also contains information on clinical trials.

People who are at high risk for a certain type of cancer may want to take part in a clinical trial. A clinical trial is a study to answer a scientific question, such as whether a method of finding cancer earlier can help people to live longer. Trials are based on past studies and what has been learned in the laboratory. Each trial answers certain scientific questions in order to find new and better ways to help cancer patients and those who are at risk for cancer. During screening clinical trials, information is collected about screening methods, the risks involved, and how well they do or do not work. If a clinical trial shows that a new method is better than one currently being used, the new method may become "standard."

Listings of clinical trials are included in PDQ and are available online at Descriptions of the trials are available in health professional and patient versions. Many cancer doctors who take part in clinical trials are also listed in PDQ. For more information, call the Cancer Information Service 1-800-4-CANCER (1-800-422-6237); TTY at 1-800-332-8615.

Physicians version: CDR0000062753
Date last modified: 2003-06-10

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Dr. G. Quade
This page was last modified on Tuesday, 28-Feb-2006 11:01:12 CET