Every few years, the colon cancer screening guidelines are updated based on scientific evidence, new testing options, accessibility, and economic feasibility. The new guidelines, set forth by the American College of Gastroenterology, have divided screening methods into two categories: cancer prevention and cancer detection.
Tests for Cancer Prevention
Screening tests for colon cancer prevention aim to find irregularities in the colon before they turn cancerous. In the average person, it can take between 10 and 20 years for tissues to mutate from a small polyp or adenoma into an adenocarcinoma, which is the most common type of colon cancer.
Routine colon screening tests and the removal of benign (non-cancerous) masses can decrease your lifetime risk of developing colon cancer by 80 percent, according to the American Cancer Society. The routine screening exams for colon cancer prevention include:
- Computed tomography colonoscopy (virtual colonoscopy)
- Flexible sigmoidoscopy
- Double contrast barium enema (DCBE)
Average Risk Screening
The majority of people fall into the average-risk category for colon cancer prevention screening and are encouraged to begin testing at age 50 (or 45 if you are African American). You are labeled as having an average-risk of developing colon cancer:
- If you do not have a first-degree relative with colon cancer (if you do, they must be diagnosed with colon cancer after age 60 or you are in the increased-risk category)
- If you do not smoke or drink heavily
- If you do not have a personal history of cancer, colon cancer or polyps
- If you do not have any genetic conditions predisposing you to colon cancer (Peutz-Jeghers, familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer syndrome)
- If you do not have ulcerative colitis, Crohn's disease or any inflammatory bowel condition
Ultimately, the age that you begin colon cancer screening is not set in stone. Your doctor uses these guidelines as a frame of reference, but can encourage testing earlier if you have any symptoms of colon cancer or other gastrointestinal disorders.
For the average-risk individual, screening exam routines should follow this schedule, unless an abnormality is found:
- Colonoscopy -– Every 10 years
- Computed tomography colonoscopy (virtual colonoscopy) –- Every 5 years as an alternative test to endoscopic colonoscopy
- Flexible sigmoidoscopy –- Every 5 years as an alternative to colonoscopy
- Double contrast barium enema (DCBE) –- Every 5 years
If any test other than the colonoscopy has irregular findings, you will still need a colonoscopy to confirm those findings (and potentially remove any polyps or small growths, if needed).
Increased or High-Risk Screening
If you are at an increased or high-risk for developing colon cancer, your screening tests will occur more frequently. Talk to your doctor to see if your insurance covers the testing, as some companies require proof of your increased or high-risk status (such as genetic testing results). Although it is determined on a case-by-case basis by your physician, you may be in the increased or high-risk category:
- If you have a first-degree relative (or two second-degree relatives) with colon cancer diagnosed before age 60
- If you have a history of cancer
- If you have a history of polyps
- If you or a first-degree relative have Peutz-Jeghers, familial adenomatous polyposis, hereditary nonpolyposis, or other genetic colorectal cancer syndrome
- If you have ulcerative colitis, Crohn's disease or other inflammatory bowel condition
The screening guidelines for increased and high-risk individuals vary according to what put them in that category -– a personal history of colon cancer, polyps, colorectal cancer genetic syndromes, or an increased family risk.
For people with a family history of colon cancer, screening tests should begin at age 40 or 10 years prior to the youngest diagnosed case of cancer in your family. For instance, if your mother was diagnosed with cancer at 45, you should technically begin screening at 35 years old. Your doctor may encourage a colonoscopy every five years, depending on the strength of your familial risk factors.
If you have a personal history of colon polyps on prior exams (but not cancer), your screening frequency is dependent on the number and type of polyps that were found and removed. For instance, if you had one or two small, tubular adenomas, you will probably need a colonoscopy every five to 10 years after removal. However, if you had 10 or more polyps removed, you may need a colonoscopy every three years and your doctor may encourage genetic testing for colorectal cancer syndromes.
If you have a personal history of colon cancer, your screening frequency is dependent on the stage and grade of your cancer and the method used to remove it (surgery versus colonoscopy). Your screening exams may be as frequent as every six months or three years, depending on those factors, your health, and your doctor’s suggestion.
People with inflammatory bowel disease may require more frequent colon screening exams, but only if the large intestines are involved. Your doctor will have specific recommendations for you, based on your bowel disease progression.
If you have (or have a family history) of any genetic colorectal cancer syndromes, your screening may have to begin as young as age 12. Yearly flexible sigmoidoscopies are encouraged beginning at age 12 for people with known familial adenomatous polyposis syndrome. If you have hereditary nonpolyposis colorectal cancer syndrome (HNPCC or Lynch Syndrome), screening exams may start as early as age 20, with routine colonoscopies every one to two years.
Currently, there are no formal recommendations for people who are obese, smoke, or drink alcohol heavily. However, they are encouraged to consider screening exams starting a little earlier than average-risk people, to begin at the age of 45 years.
Tests for Cancer Detection
Stool tests are designed to detect cancer when it is present, not to prevent it or catch it early. There are two types of stool tests –- tests that check for trace amounts of blood in the stool and tests that check for shed cancer cells in the stool (DNA tests). These tests are usually completed at home, using a collection kit over several days. Your doctor will give you specific instructions prior to each exam, which include collection and return instructions for the samples.
The stool testing should be completed annually, following your 50th birthday for people of average and high risk:
- Fecal occult blood tests (FOBT) – Every year
- Fecal immunochemical test (FIT) – Every year
- Stool DNA test – Every three years
American Cancer Society. (2006). American Cancer Society's Complete Guide to Colorectal Cancer. Clifton Fields, NE: American Cancer Society.
American Cancer Society. (n.d.). Colorectal Cancer Early Detection. Accessed March 12, 2012.
American Cancer Society. (n.d.). American Cancer Society Recommendations for Colorectal Cancer Early Detection. Accessed March 13, 2012.
Rex, D.K., Johnson, D.A., Anderson, J.C., et al. (February 2009). American College of Gastroenterology Guidelines for Colorectal Cancer Screening 2008. Accessed March 13, 2012.