Health Letter, February 2022
By Azza AbuDagga, M.H.A., Ph.D.
Colorectal cancer involves the colon (large intestines) or the rectum (the lower part of the colon). Symptoms of this cancer include abdominal pain, changes in bowel habits and sometimes blood in the stool.
It is the third most commonly diagnosed non-skin cancer in men and women and the third leading cause of cancer death in the U.S. Overall, the lifetime risk of developing this cancer is about 4%.
Colorectal cancer occurs most commonly in older adults. However, the rate of new cases of colon cancer among American adults aged 40 to 49 years increased by at least 13% from 2000–2002 to 2014–2016. Additionally, colorectal cancer is more frequent in Black adults as wells as American Indian and Alaska Native adults than other racial groups.
The good news is that certain screening tests can find abnormal polyps (colorectal growths that may turn into cancer) early so they can be removed before they become cancerous. Screening also helps in detecting colorectal cancer at an early stage, when treatment is most effective.
The U.S. Preventive Services Task Force (USPSTF), a respected volunteer panel of national experts in evidence-based medicine and disease prevention that works independently of the pharmaceutical and medical-device industries, issued a final statement that summarizes its recommendations for routine colorectal cancer screening. These recommendations focused on determining what screening tests are accurate and their ideal screening intervals as well as determining the adult age groups that should be routinely screened using these tests.
The USPSTF statement and its supportive evidence review and modeling study were published in the May 18, 2021, issue of the Journal of the American Medical Association.
The USPSTF recommendation statement pertained only to adults aged 45 years or older with average risk of colorectal cancer who do not have any signs or symptoms of colorectal cancer (hereafter referred to as average-risk adults).
Therefore, the statement is not applicable to individuals who have a prior diagnosis of colorectal cancer, adenomatous polyps or inflammatory bowel disease or those with personal or family history of known genetic disorders that predispose them to a high risk of colorectal cancer (such as Lynch syndrome or familial adenomatous polyposis).
These excluded individuals may need to be screened more often and at a younger age than recommended by the USPSTF.
Recommendations regarding screening tests
The USPSTF found adequate evidence to recommend certain stool-based and direct visualization screening tests for colorectal cancer (see Table 1 for these tests and their recommended screening intervals).
In terms of stool-based tests, USPSTF recommended three tests that are noninvasive (the samples are collected at home and sent to a laboratory for testing) and do not require any bowel preparation before collecting the samples. These tests examine the presence of either blood or altered genetic material, which can be signs of colorectal cancer. These recommended tests are the high-sensitivity guaiac fecal occult blood test (HSgFOBT), fecal immunochemical test (FIT) and stool DNA-FIT test (which is the only stool DNA test approved by the Food and Drug Administration). Whereas the HSgFOBT and FIT tests should be conducted every year, the stool DNA-FIT test can be done every one to three years. Positive results from these tests require follow-up with colonoscopy (which involves looking at the colon and rectum using a scope and camera), according to the USPSTF.
In terms of direct visualization screening tests, the USPSTF recommended colonoscopy every 10 years, flexible sigmoidoscopy (which involves looking at the lower colon and rectum using a scope and camera) every five years or computed tomography (CT) colonography scan (which uses special x-ray equipment to examine the colon) every five years. Emptying the colon using laxatives is required before these tests. Sedation or anesthesia usually is used during colonoscopy, which requires recovery time after the procedure.
The USPSTF recommended that flexible sigmoidoscopy can be done every 10 years when it is combined with an annual FIT test. Additionally, abnormal findings identified by flexible sigmoidoscopy or CT colonography screening require follow-up colonoscopy, according to the USPSTF.
The USPSTF did not specifically prioritize any of its recommended screening tests over the others. Instead, it suggested that the best screening test for an individual is the one that he or she, along with their doctor, chooses, depending on how feasible and preferable a given screening test is for that individual.
Notably, the USPSTF did not recommend serum tests, urine tests or capsule endoscopy for colorectal cancer screening because of the limited available evidence about their accuracy.
|Colorectal Cancer Screening Test||Screening Interval|
|High-sensitivity guaiac fecal occult blood test (HSgFOBT) or fecal immunochemical test (FIT)||Every year|
|Stool DNA-FIT||Every one to three years|
|Computed tomography colonography||Every five years|
|Flexible sigmoidoscopy||Every five years|
|Flexible sigmoidoscopy and FIT||Every 10 years and annually, respectively|
|Colonoscopy||Every 10 years|
Screening recommendations by adult age group
Whereas the USPSTF previously recommended that routine colorectal cancer screening should start at age 50 for average-risk adults, its new statement recommended beginning screening at age 45 for this population (see Table 2 for all recommendations per age group). The USPSTF made this decision based on the data-modeling study which provided evidence with moderate certainty that starting screening at age 45 years may increase the net benefit of colorectal cancer screening.
The USPSTF continued to strongly recommend routine screening for average-risk adults aged 50 to 75 because there are substantially more potential benefits than potential harms for screening in this age group as shown in clinical trials.
Additionally, the USPSTF concluded that the decision to screen older adults aged 76 to 85 years for colorectal cancer should be an individual one, based on the overall health (such as life expectancy and presence of other health problems), prior screening status and preferences of each individual. Generally, adults who have never been screened for colorectal cancer are more likely to benefit than those who had previously received adequate screening.
The USPSTF recommended discontinuing routine colorectal cancer screening for average-risk older adults after age 85 because the evidence on benefits and harms of such screening in this age group is lacking, and because competing causes of death likely prevent any survival benefit that would supersede the harms of screening.
The harms of screening are primarily due to colonoscopy (done either initially or as a follow-up after abnormal results from other screening tests) and include perforation and bleeding. Usually, the risk of these harms increases with age.
|Age Groups||Colorectal Screening Recommendations|
|All average-risk adults aged 45 to 49 years||The USPSTF recommends screening for colorectal cancer in this age group.|
|All average-risk adults aged 50 to 75 years||The USPSTF recommends screening for colorectal cancer in this age group.|
|All average-risk older adults aged 76 to 85 years||The USPSTF recommends that health care professionals selectively offer screening for colorectal cancer for individuals in this age group. In determining whether this service is appropriate for an individual, he or she along his or her health care professional should consider the overall health, prior screening history and preferences of that individual.|
|All average-risk older adults aged 86 years and over||Discontinue screening.|
Advocate for your health
If you are older than 45 years, talk to your health care professional about your risk of colorectal cancer and the type of screening test that is best for you. If you have risk factors for colorectal cancer, discuss with him or her whether you should start routine screening sooner than age 45 years and whether you should undergo such screening at more frequent intervals than those recommended in the new USPSTF statement.
It also is important to try to reduce your risk of colorectal cancer by consuming a healthful diet, increasing your physical activity, not smoking and avoiding or limiting your alcohol consumption.