Colon cancer screening
Author
Robert H Fletcher, MD, MSc Section Editor
Kenneth K Tanabe, MD Deputy Editor
Leah K Moynihan, RNC, MSN
H Nancy Sokol, MD
COLON CANCER SCREENING OVERVIEW — Colorectal cancer is a cancer that develops in the large intestine [colon] or rectum. The primary goal of colon cancer screening is to prevent deaths from colon cancer. Screening tests can help identify cancers at an early and potentially treatable stage. Some tests can also prevent the development of colorectal cancer by identifying precancerous abnormal growths called adenomatous polyps; these polyps can be removed before they become malignant.
All adults should undergo colon cancer screening beginning at age 50 or earlier, depending upon the person’s risk of developing colorectal cancer. Several tests are currently available, each of which has advantages and disadvantages. The optimal screening test depends upon a person’s preferences and his or her risk of developing colon cancer.
This topic review discusses colon cancer risks, available screening tests, and recommendations for screening based upon a person’s risk. There are additional topics about the screening tests themselves (see “Patient information: Flexible sigmoidoscopy” and see “Patient information: Colonoscopy”) as well as about particular conditions (see “Patient information: Colon polyps” and see “Patient information: Crohn’s disease” and see “Patient information: Ulcerative colitis”).
EFFECTIVENESS OF COLON CANCER SCREENING — Most colorectal cancers develop from precancerous adenomatous polyps. A small percentage of these polyps become cancerous and spread to other areas. This progression takes at least 10 years in most people.
Colon cancer screening tests work by detecting polyps or by finding early stage cancers. Regular screening for and removal of polyps can reduce a person’s risk of developing colorectal cancer by up to 90 percent. Early detection of cancers that are already present in the colon increases the chances of successful treatment and decreases the chance of dying as a result of the cancer.
COLON CANCER RISK FACTORS — Several factors increase an individual’s risk of developing colorectal cancer. Having one or more of these factors will determine the age at which screening should begin, the frequency of screening, and the screening tests that are most appropriate.
Small increases in risk — Several characteristics increase the risk of colorectal cancer. While each individual risk factor adds some risk, risk is substantially increased if several are present together.
Family history of colorectal cancer — Having colorectal cancer in a family member increases an individual’s risk of cancer, especially if the family member is a first degree relative (a parent, brother or sister, or child), if several family members are affected, or if the cancers have occurred at an early age (eg, before age 55 years). (See “Family history of colorectal cancer” below).
Prior colorectal cancer or polyps — People who have previously had colorectal cancer have an increased risk of developing a new colorectal cancer. People who have had adenomatous polyps before the age of 60 years are also at increased risk for developing colorectal cancer. Screening recommendations for these groups are discussed separately. (See “Patient information: Colon polyps” and see “Patient information: Colon cancer treatment”).
Increasing age — Although the average person has a 5 percent lifetime risk of developing colorectal cancer, 90 percent of these cancers occur in people older than 50 years of age. Risk increases with age throughout life.
Lifestyle factors — Several lifestyle factors increase the risk of colorectal cancer, including:
A diet high in fat and red meat and low in fiber
A sedentary lifestyle
Cigarette smoking
Factors that decrease risk — Factors that may decrease risk include:
A high calcium diet — Some studies suggest that it is possible to reduce the risk of colon cancer by consuming at least 1000 mg of calcium daily, either through diet or by taking a calcium supplement.
Aspirin, ibuprofen, and related nonsteroidal antiinflammatory medications may decrease the risk of developing colorectal cancer. However, there is not enough evidence to recommend NSAIDs as a preventive treatment for colon cancer.
Large increase in risk — Some conditions greatly increase the risk of colorectal cancer.
Familial adenomatous polyposis — Familial adenomatous polyposis (FAP) is an uncommon inherited condition that increases a person’s risk of colorectal cancer. Nearly 100 percent of people with this condition will develop colorectal cancer during their lifetime, and most of these cancers occur before the age of 50 years. FAP causes hundreds of polyps to develop throughout the colon.
Hereditary nonpolyposis colon cancer — Hereditary nonpolyposis colon cancer (HNPCC) is another inherited condition associated with an increased risk of colorectal cancer. It is slightly more common than FAP, but is still uncommon, accounting for about 1 in 20 cases of colorectal cancer. About 70 percent of people with HNPCC will experience colorectal cancer by the age of 65. Cancer also tends to occur at younger ages and in the part of the colon on the right side of the body (the ascending colon).
HNPCC is suspected in those with a strong family history of colon cancer; several family members from different generations may have been affected, some of whom developed the cancer relatively early in life. People with HNPCC are also at risk for other types of cancer, including cancer of the uterus, stomach, bladder, kidney, and ovary.
Inflammatory bowel disease — People with Crohn’s disease of the colon or ulcerative colitis have an increased risk of colorectal cancer. The amount of increased risk depends upon the amount of inflamed colon and the duration of disease; pancolitis (inflammation of the entire colon) and colitis of 10 years’ duration or longer are associated with the greatest risk for colorectal cancer. The risk of colon cancer is not increased in people with irritable bowel disease.
COLON CANCER SCREENING TESTS — Several tests are available for colorectal cancer screening, including tests that can detect cancers at an early treatable stage (eg, stool tests), and tests that also detect pre-cancerous polyps (adenomas) and can lead to cancer prevention.
Guidelines from expert groups recommend that patients and their healthcare provider discuss the available options and choose a testing strategy that makes sense for the individual. Tests that detect pre-cancerous polyps are generally preferred; these include colonoscopy, CT colonography, flexible sigmoidoscopy, and double contrast barium enema. Stool tests that detect blood or abnormal DNA are another option [1] .
Colonoscopy — Colonoscopy allows a physician to see the lining of the rectum and the entire colon (show figure 1). (See “Patient information: Colonoscopy”).
Procedure — Colonoscopy requires that the patient prepare by cleaning out the entire colon and rectum. This usually involves consuming a liquid medication that causes diarrhea temporarily. The patient is given a mild sedative drug before the procedure. During colonoscopy, a thin, lighted tube is used to directly view the lining of the rectum and the entire colon. Polyps and some cancers can be removed during this procedure.
Effectiveness — Colonoscopy detects most small polyps and almost all large polyps and cancers [2] .
Risks and disadvantages — The risks of colonoscopy are greater than those of other screening tests. Colonoscopy leads to serious bleeding or a tear of the intestinal wall in about 1 in 1,000 people. Because the procedure usually requires sedation, the person must be accompanied home after the procedure and the person should not return to work or other activities on the same day.
CT colonography — Computed tomography colonography (CTC) is a test that uses a CT scanner to take images of the entire bowel. These images are in two- and three-dimensions, and are reconstructed with other enhancements to allow a radiologist to determine if polyps or cancers are present (show radiograph 1). The major advantages of CTC are that it does not require sedation, it is non-invasive, the entire bowel can be examined, and abnormal areas (adenomas) can be detected about as well as with traditional (optical) colonoscopy.
There are several disadvantages of CTC. Like traditional colonoscopy, CTC requires a bowel prep to clean out the colon. If an abnormal area is found with CTC, a traditional colonoscopy will be needed to see the area and take a tissue sample (biopsy). CTC may detect abnormalities other than polyps and colorectal cancer. Many of these incidental findings will have no clinical significance, although most will require further testing. This test may not be covered by health insurance plans in the United States.
Sigmoidoscopy — Sigmoidoscopy allows a physician to directly view the lining of the rectum and the lower part of the colon (the descending colon, show figure 1). This area accounts for about one-half of the total area of the rectum and colon. (See “Patient information: Flexible sigmoidoscopy”).
Procedure — Sigmoidoscopy requires that the patient prepare by cleaning out the lower bowel. This usually involves consuming a clear liquid diet and an enema shortly before the examination. Most people do not need sedative drugs and are able to return to work or other activities the same day. During the procedure, a thin, lighted tube is advanced into the rectum and through the left side of the colon to check for polyps and cancer; the procedure may cause mild cramping. Biopsies (small samples of tissue) can be taken during sigmoidoscopy. Sigmoidoscopy may be performed in a doctor’s office.
Effectiveness — Sigmoidoscopy can identify polyps and cancers in the descending colon and rectum with a high degree of accuracy. Studies suggest that sigmoidoscopy, performed periodically, reduces death from cancers in the lower half of the colon and rectum (the area directly examined) by two-thirds [3] .
Risks and disadvantages — The risks of sigmoidoscopy are small. The procedure creates a small tear in the intestinal wall in about 2 per every 10,000 people; death from this complication is rare. A major disadvantage of sigmoidoscopy is that it cannot detect polyps or cancers that are located in the right side of the colon.
Additional testing — Finding polyps or cancers in the lower colon increase the likelihood that there are polyps or cancer in the remaining part of the colon. Thus, if sigmoidoscopy reveals polyps or cancer, colonoscopy is recommended to view the entire length of the colon.
Double contrast barium enema — A barium enema test provides a detailed x-ray picture of the rectum and the entire colon (show figure 1). This test has largely been replaced by other options. Polyps or cancers cannot be removed during a barium enema, and CT colonography is more accurate for detecting abnormalities [4] .
Stool tests — Colorectal cancers often bleed, releasing microscopic amounts of blood and abnormal DNA into the stool. Stool tests can detect blood or abnormal DNA makers.
Guaiac tests (typically Hemoccult®) and immunochemical tests evaluate the stool for blood, which may be present if there is bleeding from a colon cancer (or other source of blood).
With guaiac testing, the person collects two samples of stool from three consecutive bowel movements, which are applied to home collection cards. The cards are usually mailed back to the healthcare provider. Red meat and vitamin C should not be consumed for 3 days before testing. Nonsteroidal antiinflammatory medications (eg, aspirin, ibuprofen, naproxen) should be avoided for 7 days before testing. These medications/foods may affect the accuracy of guaiac testing.
With immunochemical testing, the person uses a long handled tool to brush the surface of the stool in the toilet bowl after two consecutive bowel movements. The brush is applied to a card, which is usually mailed to a laboratory. No dietary or medication restrictions are needed.
With stool DNA testing, the person collects an entire bowel movement and mails it to a laboratory with an ice pack. No dietary or medication restrictions are needed. The stool DNA test evaluates stool for several DNA markers, which can be associated with colon cancers.
Effectiveness — Guaiac testing, when performed once per year, can reduce the risk of dying from colorectal cancer by at least one-third [5] .
Risks and disadvantages — Because polyps seldom bleed, guaiac testing is less likely to detect polyps than other screening tests. In addition, only 2 to 5 percent of people with a positive stool test actually have colorectal cancer.
Additional testing — If the stool test is positive, the entire colon should be examined with colonoscopy.
Fecal occult blood test and sigmoidoscopy — Combined screening with a fecal occult blood test (guaiac) and sigmoidoscopy is a possible screening strategy and may be more effective than either test done alone.
COLON CANCER SCREENING PLANS — The recommended colon cancer screening plan depends upon a person’s risk of colorectal cancer.
Average risk of colorectal cancer — People with an average risk of colorectal cancer should begin screening at age 50. The following screening strategies are recommended [1] :
Colonoscopy every 10 years
Computed tomographic colonography every 5 years
Flexible sigmoidoscopy every five years
Double contrast barium enema every five years
Stool testing is an alternative option and is recommended once per year (for guaiac and immunologic tests, less frequently for DNA-based tests). Testing should begin at age 50.
Increased risk of colorectal cancer — Screening plans for people with an increased risk may entail screening at a younger age, more frequent screening, and/or the use of more sensitive screening tests (usually colonoscopy). The optimal screening plan depends upon the reason for increased risk.
Family history of colorectal cancer
– People who have one first-degree relative (parent, brother, sister, or child) with colorectal cancer or adenomatous polyps at a young age (before the age of 60 years), or two first-degree relatives diagnosed at any age, should begin screening for colon cancer earlier, typically at age 40, or 10 years younger than the earliest diagnosis in their family, whichever comes first. Screening usually includes colonoscopy, which should be repeated every five years.
– People who have one first-degree relative (parent, brother, sister, or child) who has experienced colorectal cancer or adenomatous polyps at age 60 or later, or two or more second degree relatives (grandparent, aunt, uncle) with colorectal cancer should begin screening at age 40, and screening should be repeated as for average risk people.
– People with a second-degree relative (grandparent, aunt, or uncle) or third-degree relative (great-grandparent or cousin) with colorectal cancer are considered to have an average risk of colorectal cancer (See “Average risk of colorectal cancer” above).
Familial adenomatous polyposis — People with a family history of familial adenomatous polyposis (FAP) should consider genetic counseling and genetic testing to determine if they carry the affected gene. People who carry the gene or do not know if they carry the gene should begin screening with sigmoidoscopy once every year, beginning at puberty.
Colectomy (surgical removal of the colon) should be considered if multiple polyps are seen or genetic testing shows that the person carries the abnormal gene; colectomy is the only way to prevent colorectal cancer in people with FAP.
Hereditary nonpolyposis colon cancer — People with a family history of hereditary nonpolyposis colon cancer (HNPCC) should consider genetic counseling and genetic testing to determine if they carry the affected gene. People who carry the gene or who do not know if they carry the gene should be screened with colonoscopy because HNPCC is associated with cancers of the right-sided colon (which cannot be seen during sigmoidoscopy).
Depending upon the family history and what is found, colonoscopy is usually repeated every one to two years between age 20 and 30 years, and every year after age 40. Because polyps can progress more rapidly to cancer in people with HNPCC, more frequent screening may be recommended.
Inflammatory bowel disease — In people with ulcerative colitis or Crohn’s disease of the colon, the optimal screening plan depends upon the amount of colon affected and the duration of the disease. (See “Patient information: Crohn’s disease” and see “Patient information: Ulcerative colitis”).
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.
National Cancer Institute
1-800-4-CANCER
(www.nci.nih.gov)
The American Society of Clinical Oncology
(www.cancer.net/portal/site/patient)
National Comprehensive Cancer Network
(www.nccn.com)
American Cancer Society
1-800-ACS-2345
(www.cancer.org)
National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
The American Gastroenterological Association
(www.gastro.org)
The American College of Gastroenterology
(www.acg.gi.org)
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REFERENCES
1 Levin, B, Lieberman, DA, McFarland, B, et al. Screening and Surveillance for early detection of colorectal cancer and adenomatous polyps, 2008: A joint guideline from the American Cancer Society, The U.S. Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. Ca Cancer J Clin 2008; :.
2 Rex, DK, Cutler, CS, Lemmel, GT, et al. Colonoscopic miss rates of adenomas determined by back-to-back colonoscopies. Gastroenterology 1997; 112:24.
3 Selby, JV, Friedman, GD, Quesenberry, CP Jr, Weiss, NS. A case-control study of screening sigmoidoscopy and mortality from colorectal cancer. N Engl J Med 1992; 326:653.
4 Winawer, SJ, Stewart, ET, Zauber, AG, et al. A comparison of colonoscopy and double-contrast barium enema for surveillance after polypectomy. National Polyp Study Work Group. N Engl J Med 2000; 342:1766.
5 Mandel, JS, Bond, JH, Church, TR, et al. Reducing mortality from colorectal cancer by screening for fecal occult blood. Minnesota Colon Cancer Control Study. N Engl J Med 1993; 328:1365.
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