What is screening?
General Information About Colorectal Cancer
Colorectal Cancer Screening
Risks of Colorectal Cancer Screening
Changes to This Summary (09/13/2004)
Questions or Comments About This Summary
To Learn More
About PDQ

What is screening?

Screening is looking for cancer before a person has any symptoms. This can help find cancer at an early stage. When abnormal tissue or cancer is found early, it may be easier to treat. By the time symptoms appear, cancer may have begun to spread.

Scientists are trying to better understand which people are more likely to get certain types of cancer. They also study the things we do and the things around us to see if they cause cancer. This information helps doctors recommend who should be screened for cancer, which screening tests should be used, and how often the tests should be done.

It is important to remember that your doctor does not necessarily think you have cancer if he or she suggests a screening test. Screening tests are given when you have no cancer symptoms. Screening tests may be repeated on a regular basis.

If a screening test result is abnormal, you may need to have more tests done to find out if you have cancer. These are called diagnostic tests.

Refer to the following PDQ summaries for information about prevention, diagnosis, and treatment of colorectal cancer:

• Prevention of Colorectal Cancer ¹
• Colon Cancer Treatment ²
• Rectal Cancer Treatment ³

General Information About Colorectal Cancer

Key Points for This Section

Colorectal cancer is a disease in which malignant (cancer) cells form in the tissues of the colon or the rectum. Colorectal cancer is the second leading cause of death from cancer in the United States. Age and health history can affect the risk of developing colon cancer.

Colorectal cancer is a disease in which malignant (cancer) cells form in the tissues of the colon or the rectum.

The colon and rectum are parts of the body's digestive system. The digestive system removes and processes nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) from foods and helps pass waste material out of the body. The digestive system is made up of the mouth, throat, esophagus, stomach, and the small and large intestines. The first 6 feet of the large intestine are called the large bowel or colon. The last 6 inches are the rectum and the anal canal. The anal canal ends at the anus (the opening of the large intestine to the outside of the body).

Cancer that begins in the colon is called colon cancer, and cancer that begins in the rectum is called rectal cancer. Cancer that begins in either of these organs may also be called colorectal cancer.

Colorectal cancer is the second leading cause of death from cancer in the United States.

In recent years (1995-1999), the number of people diagnosed with colorectal cancer has stayed about the same, but the number of people who die from colorectal cancer has decreased. Colorectal cancer is found more often in men than in women.

Age and health history can affect the risk of developing colon cancer.

Anything that increases a person's chance of getting a disease is called a risk factor. Risk factors for colorectal cancer include the following:

• Being older than 50 years of age.
• Having a personal history of any of the following:
  • Colorectal cancer or adenomas.
  • Cancer of the ovary, endometrium, or breast.
  • Ulcerative colitis or Crohn's disease.
• Having a parent, brother, sister, or child with colorectal cancer or adenomas.
• Having certain hereditary conditions, such as familial adenomatous polyposis (FAP) and hereditary nonpolyposis colon cancer (HNPCC; Lynch Syndrome).

Refer to the PDQ summary on Genetics of Colorectal Cancer ⁴ for more information about family history and colorectal cancer screening.

Colorectal Cancer Screening

Key Points for This Section

Tests are used to screen for different types of cancer. Five tests are commonly used to screen for colorectal cancer: Fecal occult blood test Sigmoidoscopy Barium enema Colonoscopy Digital rectal exam Other screening tests are being studied in clinical trials. Virtual colonoscopy DNA stool test

Tests are used to screen for different types of cancer.

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 Cancer.gov Web site ⁵.

Five tests are commonly used to screen for colorectal cancer:

Fecal occult blood test

A fecal occult blood test (FOBT) checks 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.

Sigmoidoscopy

Sigmoidoscopy is a procedure to look inside the rectum and sigmoid (lower) colon for polyps, abnormal areas, or cancer. A sigmoidoscope (a thin, lighted tube) is inserted through the rectum into the sigmoid colon. Polyps or tissue samples may be taken for biopsy. A sigmoidoscopy and a digital rectal exam (DRE) may be used together to screen for colorectal cancer.

Barium enema

A barium enema (BE) 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

Colonoscopy is a procedure to look inside the rectum and colon for polyps, abnormal areas, or cancer. A colonoscope (a thin, lighted tube) is inserted through the rectum into the colon. Polyps or tissue samples may be taken for biopsy.

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.

Other screening tests are being studied in clinical trials.

Virtual colonoscopy

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.

DNA stool test

This test checks DNA in stool cells for genetic changes that may be a sign of colorectal cancer.

Screening clinical trials are taking place in many parts of the country. Information about ongoing clinical trials is available from the NCI Cancer.gov Web site ⁵.

Risks of Colorectal Cancer Screening

Key Points for This Section

Screening tests have risks. The risks of colorectal cancer screening tests include the following: Damage to the colon can occur. False-negative test results can occur. False-positive test results can occur.

Screening tests have risks.

Decisions about screening tests can be difficult. Not all screening tests are helpful and most have risks. Before having any screening test, you may want to discuss the test with your doctor. It is important to know the risks of the test and whether it has been proven to reduce the risk of dying from cancer.

The risks of colorectal cancer screening tests include the following:

Damage to the colon can occur.

Infection or tears in the lining of the colon can result from sigmoidoscopy, colonoscopy, or the removal of polyps found by screening.

False-negative test results can occur.

Screening test results may appear to be normal even though colorectal cancer is present. A person who receives a false-negative test result (one that shows there is no cancer when there really is) may delay seeking medical care for symptoms.

False-positive test results can occur.

Screening test results may appear to be abnormal even though no cancer is present. A false-positive test result (one that shows there is cancer when there really isn't) can cause anxiety and is usually followed by more tests (such as biopsy), which also have risks.

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

Changes to This Summary (09/13/2004)

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.

Questions or Comments About This Summary

If you have questions or comments about this summary, please send them to Cancer.gov through the Web site’s Contact Form ⁶. We can respond only to email messages written in English.

To Learn More

Call

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 Cancer.gov ⁷ 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.

Publications

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 ⁸. 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.

LiveHelp

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.

Write

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Bethesda, MD 20892-8322

About PDQ

PDQ is a comprehensive cancer database available on Cancer.gov.

PDQ is the National Cancer Institute's (NCI's) comprehensive cancer information database. Most of the information contained in PDQ is available online at Cancer.gov ⁷, 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 Cancer.gov ⁹. 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.

Glossary Terms

Not normal. In referring to a lesion or growth, may be cancerous or premalignant (likely to become cancer).

A noncancerous tumor.

The opening of the rectum to the outside of the body.

A procedure in which a liquid with barium in it 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.

The removal of cells or tissues for examination under a microscope. When only a sample of tissue is removed, the procedure is called an incisional biopsy or core biopsy. When an entire lump or suspicious area is removed, the procedure is called an excisional biopsy. When a sample of tissue or fluid is removed with a needle, the procedure is called a needle biopsy or fine-needle aspiration.

The long tube-shaped organ in the abdomen that completes the process of digestion. There is both a small and a large bowel. Also called the intestine.

A term for diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues and can spread through the bloodstream and lymphatic system to other parts of the body. There are several main types of cancer. Carcinoma is cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the bloodstream. Lymphoma is cancer that begins in the cells of the immune system.

A sugar molecule. Carbohydrates can be small and simple (for example, glucose) or they can be large and complex (for example, polysaccharides such as starch, chitin or cellulose).

The individual unit that makes up all of the tissues of the body. All living things are made up of one or more cells.

A type of research study that uses volunteers to test new methods of screening, prevention, diagnosis, or treatment of a disease. The trial may be carried out in a clinic or other medical facility. Also called a clinical study.

The longest part of the large intestine, which is a tube-like organ connected to the small intestine at one end and the anus at the other. The colon removes water and some nutrients and electrolytes from partially digested food. The remaining material, solid waste called stool, moves through the colon to the rectum and leaves the body through the anus.

Cancer that develops in the tissues of the colon.

A thin, lighted tube used to examine the inside of the colon.

An examination of the inside of the colon using a thin, lighted tube (called a colonoscope) inserted into the rectum. If abnormal areas are seen, tissue can be removed and examined under a microscope to determine whether disease is present.

Having to do with the colon or the rectum.

CT scan. A series of detailed pictures of areas inside the body taken from different angles; the pictures are created by a computer linked to an x-ray machine. Also called computerized tomography and computerized axial tomography (CAT) scan.

Chronic inflammation of the gastrointestinal tract, most commonly the small intestine and colon. Crohn's disease increases the risk for colorectal and small intestine cancer.

The process of identifying a disease by the signs and symptoms.

A method used to identify a disease.

The organs that take in food and turn it into products that the body can use to stay healthy. Waste products the body cannot use leave the body through bowel movements. The digestive system includes the salivary glands, mouth, esophagus, stomach, liver, pancreas, gallbladder, small and large intestines, and rectum.

DRE. An examination in which a doctor inserts a lubricated, gloved finger into the rectum to feel for abnormalities.

Deoxyribonucleic acid. The molecules inside cells that carry genetic information and pass it from one generation to the next.

The layer of tissue that lines the uterus.

The muscular tube through which food passes from the throat to the stomach.

A test result that indicates that a person does not have a specific disease or condition when the person actually does have the disease or condition.

A test result that indicates that a person has a specific disease or condition when the person actually does not have the disease or condition.

An inherited condition in which numerous polyps (growths that protrude from mucous membranes) form on the inside walls of the colon and rectum. It increases the risk of colorectal cancer. Also called familial adenomatous polyposis or FAP.

FOBT. A test to check for blood in stool. (Fecal refers to stool; occult means hidden.)

The stomach and intestines.

Inherited; having to do with information that is passed from parents to offspring through genes in sperm and egg cells.

Transmitted from parent to child by information contained in the genes.

HNPCC. An inherited disorder in which affected individuals have a higher-than-normal chance of developing colorectal cancer and certain other types of cancer, often before the age of 50. Also called Lynch syndrome.

Invasion and multiplication of germs in the body. Infections can occur in any part of the body, and can be localized or systemic (spread throughout the body). The germs may be bacteria, viruses, yeast, or fungi. They can cause a fever and other problems, depending on the site of the infection. When the body's natural defense system is strong, it can often fight the germs and prevent infection. Cancer treatment can weaken the natural defense system.

The long, tube-like organ that is connected to the small intestine at one end and the anus at the other. The large intestine has four parts: cecum, colon, rectum, and anal canal. Partly digested food moves through the cecum into the colon, where water and some nutrients and electrolytes are removed. The remaining material, solid waste called stool, moves through the colon, is stored in the rectum, and leaves the body through the anal canal and anus.

A nutrient required to maintain health.

A chemical compound (such as protein, fat, carbohydrate, vitamins, or minerals) that make up foods. These compounds are used by the body to function and grow.

A part of the body that performs a specific function. For example, the heart is an organ.

One of a pair of female reproductive glands in which the ova, or eggs, are formed. The ovaries are located in the pelvis, one on each side of the uterus.

A growth that protrudes from a mucous membrane.

A molecule made up of amino acids that are needed for the body to function properly. Proteins are the basis of body structures such as skin and hair and of substances such as enzymes, cytokines, and antibodies.

By or having to do with the rectum. The rectum is the last several inches of the large intestine and ends at the anus.

The last several inches of the large intestine. The rectum ends at the anus.

Something that may increase the chance of developing a disease. Some examples of risk factors for cancer include age, a family history of certain cancers, use of tobacco products, certain eating habits, obesity, exposure to radiation or other cancer-causing agents, and certain genetic changes.

Checking for disease when there are no symptoms.

The S-shaped section of the colon that connects to the rectum.

A thin, lighted tube used to view the inside of the colon.

Inspection of the lower colon using a thin, lighted tube called a sigmoidoscope. Samples of tissue or cells may be collected for examination under a microscope. Also called proctosigmoidoscopy.

The part of the digestive tract that is located between the stomach and the large intestine.

The extent of a cancer within the body. If the cancer has spread, the stage describes how far it has spread from the original site to other parts of the body.

An organ that is part of the digestive system. It helps in the digestion of food by mixing it with digestive juices and churning it into a thin liquid.

The waste matter discharged in a bowel movement; feces.

An indication that a person has a condition or disease. Some examples of symptoms are headache, fever, fatigue, nausea, vomiting, and pain.

A group or layer of cells that are alike and that work together to perform a specific function.

Chronic inflammation of the colon that produces ulcers in its lining. This condition is marked by abdominal pain, cramps, and loose discharges of pus, blood, and mucus from the bowel.

A method under study to examine the colon by taking a series of x-rays (called a CT scan) and using a high-powered computer to reconstruct 2-D and 3-D pictures of the interior surfaces of the colon from these x-rays. The pictures can be saved, manipulated to better viewing angles, and reviewed after the procedure, even years later. Also called computed tomography colography.

A key nutrient that the body needs in small amounts to grow and stay strong. Examples are vitamins A, C, and E.

A type of high-energy radiation. In low doses, x-rays are used to diagnose diseases by making pictures of the inside of the body. In high doses, x-rays are used to treat cancer.