Key Takeaways:
- The recommended age for a first screening colonoscopy is 45.
- The decision about whether to continue to undergo colonoscopies after age 75 should be based on a discussion with an individual’s physician.
- A colonoscopy remains the “gold standard” screening test for colorectal cancer.
Until recently, health authorities recommended that most individuals have their first colonoscopy at age 50 to screen for colorectal cancer or precancerous growths, which can often be removed to prevent cancer development. But a worrying rise in colorectal cancer in younger people in recent years has prompted a federal task force to recommend the initial colorectal screening at age 45 – or earlier, for some patients with high risk conditions.
“A concerning increase in colorectal cancer incidence among younger individuals has been documented since the mid-1990s, with 11% of colon cancers and 15% of rectal cancers in 2020 occurring among patients younger than 50 years, compared with 5% and 9%, respectively, in 2010,” Dana-Farber’s Kimmie Ng, MD, MPH, said in an editorial in JAMA accompanying the article about the guideline changes. Ng is the director of the Young-Onset Colorectal Cancer Center at Dana-Farber.
As a result, the U.S. Preventive Services Task Force (USPSTF) now recommends the following:
- Adults age 45 to 75 should be regularly screened for colorectal cancer.
- Adults age 76 to 85 should discuss with their doctor whether they should be screened. Since colorectal cancer is a slow-growing disease, the risks and benefits of screening after age 75 should be weighed against the individual’s overall health, life expectancy, and prior screening history. Adults in this age group who have never been screened for CRC are more likely to benefit, especially if they are healthy enough to undergo treatment if colorectal cancer is detected.
How often should I be screened?
If the initial screening test is a colonoscopy that doesn’t detect cancer or a precancerous growth called an adenoma, the next test is normally recommended for 10 years later. If a colonoscopy finds one or two low-risk adenomas and they are removed at that time, the next exam should be done in five years.
If you have more adenomas or larger and advanced adenomas, it may be recommended that you have another screening test sooner than five years — possibly in just one to three years for patients with very high-risk conditions, such as inherited cancer predisposition syndromes like Lynch syndrome.
What does a colonoscopy involve?
A colonoscopy is considered the “gold standard” screening test for colorectal cancer. It requires the patient to adhere to a cleansing regimen of a liquid diet and laxatives the day before the procedure, which is done in a clinic or hospital, usually under sedation. The doctor passes a long, flexible tube with a light and camera through the anus and along the entire length of the colon, which is about five feet. The tube is then withdrawn, and the physician examines the walls of the colon for any abnormal growths, such as polyps, or tumors.
Polyps can be removed using long, thin instruments that snip the polyps, which are subsequently sent to a laboratory for analysis. Removing precancerous polyps can prevent the development of cancer; a colonoscopy is the only procedure in which this is possible.
Because of the sedating drugs, the patient usually doesn’t feel any pain and remembers little or nothing about the procedure. Because of the drugs used, however, someone must accompany the patient on the return home, and resting for the remainder of the day is recommended.
Are there alternatives to a colonoscopy?
Alternatives to colonoscopies may be easier for the patient and in some cases can be done at home.
One alternative to colonoscopy is a flexible sigmoidoscopy, in which a shorter tube, about two feet long, is inserted into the lower part of the colon, and usually doesn’t require sedation for the patient. However, less than half of the colon can be examined with a flexible sigmoidoscopy, which is one reason it is not frequently performed.
Another alternative screening procedure, a “virtual colonoscopy,” is a specialized type of CT scan that does not require any instrument to be inserted into the colon and can be done without sedation. However, it requires the same type of bowel cleansing preparation as a conventional colonoscopy, and if abnormal growths are detected, a colonoscopy would then have to be performed.
There are several types of stool-based screening tests that involve a sample collected at home and analyzed in a laboratory. These tests are effective at detecting colorectal cancer but are much less sensitive than colonoscopy at detecting precancerous polyps. Such tests need to be done more often than a colonoscopy. A positive test result of a stool-based test also calls for a follow-up colonoscopy and biopsy.
Types of stool-based tests include:
- A test that looks for occult (hidden) blood in the stool that could be caused by bleeding from fragile vessels in a polyp or tumor.
- The fecal immunochemical test (FIT), which also looks for blood in the stool. It must be done every year.
- A multitargeted stool DNA test, which in addition to looking for occult blood, can identify abnormal segments of DNA from a tumor or polyp and can also detect DNA mutations in certain genes associated with colorectal cancer. The only such test available in the United States is Cologuard, which should be done every three years.