Colorectal cancer is the third most common cancer in adults and the second leading cause of cancer deaths in of men and women in the United States. Cancer of the colon and rectum is both preventable and treatable if detected early. Studies show that regular screening could prevent one-third of colorectal cancer deaths in the U.S.
Screening tests that look for and remove polyps and lesions in the colon can prevent colorectal cancer. Because these are found most often in people 50 years of age and older, experts recommend universal screening of average risk people in this age group. However, if you have one or more risk factors for colon cancer, described below, you should talk to your doctor about more rigorous or more frequent screening options.
The exact causes of colon and rectal cancer are not known, but risk appears to be associated with genetic, dietary, and lifestyle factors. More frequent screening is appropriate if you have risk factors. If you began screening before age 50 due to one or more of these risk factors, it is important that you continue screening at the interval recommended by your doctor.
- Average risk: People over 50 with no known risk factors.
- Increased risk: A family history of colorectal cancer or adenomatous polyps—a specific type of polyp associated with higher risk of colorectal cancer—increases your risk for colorectal cancer. Most of these cancers occur in people without a family history of colorectal cancer. However, as many as 1 in 5 people who develop colorectal cancer have other family members who have been affected by this disease.
Specifically, if you have any first-degree relatives (parents, siblings or children) who had colorectal cancer or adenomatous polyps before age 60, or two or more first-degree relatives who had either finding at any age, you are in this risk category. The risk is about doubled in those with one affected first-degree relative. It is even higher if the first-degree relative was diagnosed at a young age, or if multiple first-degree relatives were affected.
You may also be at increased risk for colorectal cancer if you have been diagnosed with colon cancer in the past or if you have had a history of polyps on a prior colonoscopy.
- High risk: If you have a genetic syndrome such as familial adenomatous polyposis (FAP) or hereditary non-polyposis colorectal cancer (HNPCC) or if you are at an increased risk of HNPCC based on your family history, you are at high risk for colorectal cancer.
If you have inflammatory bowel disease, including chronic ulcerative colitis or Crohn's disease, you are also in the high-risk category.
According to the Centers for Disease Control and Prevention (CDC), lifestyle factors that may contribute to increased risk for colon cancer include lack of regular physical activity, low fruit and vegetable intake, a low-fiber and high-fat diet, obesity, alcohol consumption, and smoking.
Types of Tests Used for Screening
Recommendations for colon cancer screening include laboratory tests performed on your stool samples to detect existing cancers and imaging tests on the inside of your colon that can detect pre-cancerous polyps and existing cancers.
- Laboratory tests find telltale blood or DNA—signs that cancer is present—in a stool sample. The three types of lab tests are:
If the findings are abnormal, you will need a colonoscopy.
- Imaging procedures show abnormalities—polyps and less conspicuous flat lesions—on the empty colon's lining.
- Two of these procedures use a scope with a video camera: colonoscopy views the entire length of the colon and flexible sigmoidoscopy views the lower third. These two approaches to screening are also able to remove any polyps that are found and allow them to be tested for the presence of cancer cells.
- The other two use x-rays: virtual colonoscopy—a computed tomography (CT) scan—combines many cross-sectional images into 2-D and 3-D views of the colon and a double-contrast barium enema (DCBE) provides x-ray views of lumps, polyps, and abnormalities in the outline of the colon. However, these approaches only allow visualization of the polyps. To remove the polyps would require a follow-up colonoscopy or flexible sigmoidoscopy.
Colonoscopy is the most accurate and thorough test, but also the most costly and invasive. However, it is especially appropriate for those with risk factors. Stool sample testing and sigmoidoscopy are easier than colonoscopy, but not as accurate. They are better used together.
Your doctor can help you assess your individual risk factors and which test(s) to use. No single test is preferred for all individuals. As the CDC notes, any of the recommended tests is better than no test.
Recommendations: Ages 50 to 75 | Over age 75
Several health organizations have their own colon cancer screening recommendations. While they may differ on which tests to use and how often, they each support screening for colon cancer.
- The American Cancer Society, U.S. Multi-Society Task Force on Colorectal Cancer and the American College of Radiology jointly recommend using one of the approaches described below. Any one can be appropriate for a person of average risk who is 50 years old or older, depending on the circumstances. The first four can find both polyps and cancer:
- Flexible sigmoidoscopy every 5 years
- Colonoscopy every 10 years
- Double-contrast barium enema every 5 years
- Virtual colonoscopy every 5 years
Particularly when the ease and safety of a sample-based test is desirable, one of the three laboratory tests can be used. They primarily find cancer rather than polyps:
- Fecal occult blood test (FOBT) or the simpler immunochemical fecal occult blood test (iFOBT or FIT) every year
- Stool DNA test—optimal frequency not yet known
The joint recommendations urge the use of a screening test such as colonoscopy or sigmoidoscopy that is good at finding both pre-cancerous polyps as well as cancer, as these procedures can help prevent cancer rather than only detect it after it has developed. They advise this as long as this type of procedure is available to you and that you are comfortable with undergoing an invasive test.
- In 2008, the U.S. Preventive Services Task Force (USPSTF) recommended routine screening with iFOBT, sigmoidoscopy with iFOBT, or colonoscopy for people aged 50 to 75 with average risk, stating that any of the three are effective screening techniques to decrease mortality:
- Fecal occult blood test (FOBT) or the simpler immunochemical fecal occult blood test (iFOBT or FIT) every year
- Flexible sigmoidoscopy every 5 years with FOBT every 3 years
- Screening colonoscopy every 10 years
- The USPSTF concluded that evidence was lacking to assess virtual colonoscopy or stool DNA testing.
- For people whose first-degree relatives had colorectal adenomas or cancer, the USPSTF states that the same recommendations for people of average risk can still apply.
- Some groups such as the American College of Gastroenterology recommend that people of African descent begin testing at age 45. However, the USPSTF states that its recommendations for average risk individuals are intended to apply to all ethnic and racial groups.
If you have increased or high risk for colorectal cancer due to family history, hereditary syndromes such as hereditary non-polyposis colorectal cancer (HNPCC) or familial adenomatous polyposis (FAP) or inflammatory bowel disease, you should talk to your health care provider about more aggressive and frequent screening.
Recommendations: Over age 75 | Ages 50 to 75
The U.S. Preventive Services Task Force (USPSTF) revised its guidelines in October 2008 to recommend against routine screening in people aged 76 to 85 who have had consistently negative screening results since they were age 50 and against screening for anyone over the age of 85 years.
Talk to your health care provider about the screening tests recommended for you. Some employers, health plans, and health care providers offer decision aids.
Also, don't neglect the protection of getting re-tested at the interval recommended by your health care provider. Ask or sign up for a mailed or e-mailed reminder (see Links below) or mark your calendar or date book.
Sources Used in Current Review
(Last Review 2011 March 2). Colorectal Cancer Early Detection. American Cancer Society [On-line information]. PDF available for download at http://www.cancer.org/acs/groups/cid/documents/webcontent/003170-pdf.pdf through http://www.cancer.org. Accessed March 2012.
(Published online 2008 February 13). Screening and Surveillance for the Early Detection of Colorectal Cancer and Adenomatous Polyps, 2008: A Joint Guideline From the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. American Gastroenterology Association [On-line information]. Available online at http://www.gastrojournal.org/article/S0016-5085%2808%2900232-1/fulltext through http://www.gastro.org/practice/medical-position-statements. Accessed March 2012
National Cancer Institute. Colon and Rectal Cancers. Available online at http://www.cancer.gov/cancertopics/types/colon-and-rectal through http://www.cancer.gov. Accessed October 2011.
(Current as of February 2010). Enhancing Use and Quality of Colorectal Cancer Screening [On-line information]. U.S. Preventative Services Task Force. Available online at http://www.ahrq.gov/clinic/tp/crcprotp.htm through http://www.ahrq.gov/clinic/uspstfix.htm. Accessed March 2012.
U.S. Preventive Services Task Force. Screening for Colorectal Cancer: U.S. Preventive Services Task Force Recommendation Statement. Annals of Internal Medicine Volume 149, Issue 9. November 4, 2008. Available online at http://www.annals.org/cgi/content/full/0000605-200811040-00243v1 through http://www.annals.org. Accessed March 2012.
Kushi et al. 11 Jan. 2012 (e-pub). American Cancer Society guidelines on nutrition and physical activity for cancer prevention. CA Cancer J Clin 62. Available online at http://onlinelibrary.wiley.com/doi/10.3322/caac.20140/abstract through http://caonline.amcancersoc.org. Accessed March 2012.
Smith et al. 19 Jan. 2012 (e-pub). Cancer screening in the United States 2012. CA Cancer J Clin 62 Available online at http://onlinelibrary.wiley.com/doi/10.3322/caac.20143/abstract through http://caonline.amcancersoc.org. Accessed March 2012.
(Last updated 19 Aug. 2011) Colorectal Cancer Risk Factors. Centers for Disease Control and Prevention. Available online at http://www.cdc.gov/cancer/colorectal/basic_info/risk_factors.htm through http://www.cdc.gov. Accessed March 2012.
(Last updated 19 March 2012). Colon Cancer Screening. Medline Plus. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/002071.htm. Accessed March 2012.
(Last reviewed 2 March 2011). American Cancer Society recommendations for colorectal cancer early detection. American Cancer Society Available online through http://www.cancer.org. Accessed March 2012.
(March 2009). American College of Gastroenterology Guidelines for Colorectal Cancer Screening 2008. American College of Gastroenterology. PDF available for download at http://s3.gi.org/physicians/guidelines/CCSJournalPublicationFebruary2009.pdf through http://gi.org/clinical-guidelines/clinical-guidelines-sortable-list/. Accessed March 2012.