Colon cancer (cancer of the colon and/or rectum) is the uncontrolled growth of abnormal cells within the layers of tissue that line the colon. It is the third most common non-skin cancer in adults and the third leading cause of cancer deaths in men and women in the United States. The lifetime risk of developing colon cancer is about 1 in 21 (or 4.7%) for men and 1 in 23 (4.4%) for women, according to the American Cancer Society (ACS).
Over the last several years, the number of deaths from colon cancer has dropped significantly. Improved screening has led to removal of more pre-cancerous polyps, preventing the development of cancer. Likewise, better screening has detected more cancers in the earlier stages, when they are most treatable.
But while the incidence of colon cancer has decreased over the last several years in people age 55 and older due in part to effective screening, there has been a 51% increase in colon cancer among people younger than age 50 since 1994. In 2018, the ACS lowered their recommended starting age for colon cancer screening to age 45 for people with an average risk of colon cancer. If you haven’t already begun screening, you may consider it now.
Furthermore, if you have one or more risk factors for colon cancer you should talk to your healthcare practitioner who can help you assess your individual risk factors and determine if you should get screened more frequently. As the Centers for Disease Control and Prevention (CDC) notes, any of the recommended tests is better than no test.
Screening Recommendations
Several health organizations have colon cancer screening recommendations. In 2017, screening guidelines for the early detection of pre-cancerous polyps and colon cancer were released by the US Multi-Society Task Force (MSTF) on Colorectal Cancer. The US Preventive Services Task Force released updated similar recommendations in 2016 and the American Cancer Society (ACS) updated their guidelines in 2018. While these groups may differ on which tests to use and how often, they each support screening for colon cancer. Recommendations are based on your age and level of risk.
Increased and High Risk:
Risk of colon cancer increases with age, being overweight or obese, and with the occurrence of cancers in other parts of the body. Examples of other risk factors include:
- Family history—having one or more family members with colon cancer or multiple polyps, especially if they were younger than age 60 at diagnosis
- Diet—high fat and meat diets are risk factors, especially combined with not eating enough fruits, vegetables, and/or high-fiber foods
- Lifestyle—these risk factors include cigarette smoking, drinking excessive amounts of alcohol, and lack of regular exercise
- Having ulcerative colitis, a form of inflammatory bowel disease
- Having type 2 diabetes
- Racial or ethnic background—African Americans and Ashkenazi Jews have higher risk and rates of colon cancer compared to others.
- Having a personal history of colon cancer and/or high risk precancerous polyps
- Having a rare inherited disease called familial adenomatous polyposis (FAP)—this causes benign polyps to develop early in life and causes cancer in almost all affected persons unless the colon is removed. (See the Genetics Home Reference article on FAP)
- Having a genetic syndrome called Lynch syndrome (hereditary non-polyposis colon cancer or HNPCC) (See the Genetics Home Reference article on Lynch syndrome.)
People with increased or high risk of colon cancer may be advised to start screening at a younger age (e.g. age 40). A colonoscopy is usually recommended because it is the most accurate and thorough. Also, the recommended screening interval for high-risk individuals is shorter than for people with average risk (such as every 1-2 years compared to every 10 years).
Additionally, people who have been screened and found to have colon cancer or high risk pre-cancerous polyps also need more frequent re-testing, usually at least every 3 years. (This is called surveillance.) For example, the MSTF guidelines advise enhanced surveillance for people with 3-10 small tubular adenomas as well as those with 1 or more high-risk polyps (i.e., villous features, larger than 10 mm diameter tubular adenoma or serrated sessile polyp, or any polyp that has very atypical features, called high grade dysplasia). On the other hand, those with 1-2 small (less than 10 mm) tubular adenomas in the colon can be re-screened at normal intervals (i.e., every 10 years). Another common polyp, termed a hyperplastic polyp, is not felt to increase risk of colon cancer.
For more information on these types of polyps, read the American Cancer Society’s webpage Understanding Your Pathology Report: Colon Polyps
Average Risk
Ages 50 to 75:
This includes people with no known risk factors other than age. The ACS recommends that all average-risk people begin screening at age 45. Both the MSTF and the USPSTF recommend that people with average risk for colon cancer begin screening at age 50. MSTF recommends that African-Americans begin at age 45.
In 2016, the Canadian Task Force on Preventive Health Care (CTFPHC) issued colon cancer screening recommendations that differ in part from U.S. groups. It recommends that adults aged 50 to 74 years be screened with guaiac-based fecal occult blood test (gFOBT) or FIT every 2 years or flexible sigmoidoscopy every 10 years and recommends against using colonoscopy for primary screening.
Ages 76 to 85:
The MSTF and USPSTF have similar guidelines recommending that the decision to screen for colon cancer in people aged 76 to 85 should be an individual one based the overall health of the individual and prior screening history. Screening would be most beneficial for those who have never had screening. It is also most appropriate for people healthy enough to undergo treatment if necessary and for those who do not have other underlying conditions that would affect their life expectancy.
The Canadian Task Force on Preventive Health Care recommends against screening people age 75 and older.
Screening Tests
The following table summarizes the screening tests that are options for people with average risk. Tier 1 tests are the tests of choice, according to the MSTF, while tier 2 tests have some disadvantages compared to tier 1 tests. The ACS guidelines do not prioritize a particular screening test and instead says patients and their healthcare practitioners should choose from among several tests based on the patient's preference.
| TEST |
DESCRIPTION |
SCREENING INTERVAL FOR PEOPLE AT AVERAGE RISK |
PROS |
CONS |
| Tier 1 tests |
|
|
|
|
| Colonoscopy |
Examination of the rectum and entire colon with a lighted instrument |
Every 10 years |
Can examine the entire colon
Detects pre-cancerous polyps and cancer
Can remove polyps and take biopsies for pathological testing
|
Extensive full bowel preparation ahead of time
Sedation needed to perform
Takes at least one day for prep and recovery
Risk of bleeding, infection or bowel tears |
| Fecal Immuno-chemical test (FIT) |
Test to detect hidden blood in stool samples |
Annually |
No dietary or drug restrictions
No bowel preparation
No direct risk to bowel
Samples can be collected at home |
Cannot detect precancerous changes
May miss some cancers
May need to have colonoscopy if positive result |
| Tier 2 tests |
|
|
|
|
| Flexible sigmoidoscopy |
Examination of the rectum and lower colon with a rigid or flexible lighted instrument |
Every 5-10 years |
Minimal preparation ahead of time
Detects pre-cancerous polyps and cancer
Does not usually need sedation
Fairly quick and safe |
Only examines about 30% of colon
Small risk of bleeding, infection or bowel tear
May need to have colonoscopy if abnormal result found |
| Virtual colonoscopy (CTC, or computed tomographic colonography) |
Examination of the rectum and entire colon to the small intestine using x-rays and computers; tube inserted in rectum and bowel is inflated with air |
Every 5 years |
No sedation required
Can view entire colon
Detects pre-cancerous polyps and cancer
Relatively safe; minimal risk of tear to colon |
Full bowel preparation required
May need standard colonoscopy if abnormal results
Effectiveness as a screening tool is not fully accepted |
| Fecal Immunochemical test (FIT)-DNA |
Detects blood and mutations in specific genes associated with colon cancer in DNA isolated from a stool sample |
Every three years, according to the American Cancer Society and MSTF |
No bowel preparation or dietary restrictions
Sample can be collected at home
No risk of bowel tear |
Cannot detect precancerous changes
Not as effective as annual FIT
Adequate stool sample must be obtained
Special handling needed
May need colonoscopy if abnormal result found
|
| Capsule colonoscopy |
Examination of the colon performed by swallowing an indigestible pill with embedded video cameras |
Every 5 years per MSTF |
Detects pre-cancerous polyps and cancer
No sedation required
Relatively safe |
May need standard colonoscopy if abnormal results
Not approved by the FDA for screening people at average risk |
| No Tier recommendation |
|
|
|
|
| Guaiac-based fecal occult blood test (gFOBT) stool test |
Test to detect hidden blood in stool sample |
Annually |
No bowel preparation
No direct risk to bowel
Sample can be collected at home |
Dietary restrictions before testing
Cannot detect precancerous changes
Detects any blood, not just from cancers but from food or dental procedures
May need colonoscopy if positive result |
In addition to screening tests, a healthcare practitioner may perform a digital rectal examination (DRE) to feel for a rectal mass with a gloved finger. The DRE is primarily performed to examine the prostate gland, but also allows for the examination of the lower rectum, pelvis, and belly. Most colon cancers, however, are beyond the detection range of a DRE.
If a test other than colonoscopy gives a result suggestive of polyps or cancer, a colonoscopy is often done to examine the full colon and remove polyps or potentially cancerous areas.
Decision Aids
Because any invasive procedure carries some level of risk, you should talk to your healthcare provider about the screening tests recommended for you. Some employers, health plans, and health practitioners offer decision aids.
Also, don't neglect the protection of getting re-tested at the interval recommended by your healthcare provider.
Links
Tests: Fecal Occult Blood Test and Fecal Immunochemical Test
Condtions: Colon Cancer
Sources Used in Current Review (September 17, 2018)
(2016 June). Colorectal Cancer: Screening. US Preventive Services Task Force. Available online at https://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/colorectal-cancer-screening2?ds=1&s=colon. Accessed on September 2018.
Rex DK, Boland CR, Dominitz JA, et al. Colorectal Cancer Screening: Recommendations for Physicians and Patients from the U.S. Multi-Society Task Force on Colorectal Cancer. Am J Gastroenterol. 2017; 112(7):1016–1030. Available online at http://www.nature.com/articles/ajg2017174. Accessed on 9/12/2018.
Canadian Task Force on Preventive Health Care. Recommendations on screening for colorectal cancer in primary care. Canadian Med Assoc J. 2016 Mar 15; 188(5): 340–348. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4786388/. Accessed 9/12/2018.
Wolf AMD, Fontham ETH, Church TR, et al. Colorectal cancer screening for average‐risk adults: 2018 guideline update from the American Cancer Society. CA Cancer J Clin. 2018; 68(4):250-281. First published: 30 May 2018. Available online at https://doi.org/10.3322/caac.21457 https://onlinelibrary.wiley.com/doi/full/10.3322/caac.21457. Last accessed 9/12/2018.
