Do You Need a Colonoscopy

• Updated on: 2023-01-17
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But a recent study that has garnered much public attention has called into question the effectiveness of a common type of colorectal cancer screening: the colonoscopy. More than 15 million are performed in the U.S. each year.
Results from a  large, first-of-its-kind trial  published Oct. 9 in the New England Journal of Medicine found that colonoscopies only lowered the risk of colorectal cancer by a modest 18 percent in study participants invited to get one, and that the reduction in the risk of death from the cancer that was discovered was not significant. Many experts, however, are urging caution when it comes to interpreting the results, and a big reason has to do with the way the study was designed.
7 warning signs of colon cancer
• Blood in the stool (this could look dark brown or black)
• Rectal bleeding
• An urge to have a bowel movement when the bowel is empty
• Weakness or fatigue
Source: American Cancer Society
The team of European researchers randomly divided nearly 85,000 adults between the ages of 55 and 64 into two groups: One group was asked to get a colonoscopy, the other was not. And among those participants asked to get the test, only 42 percent opted for it. The researchers then compared the number of colorectal cancers and deaths from the disease in each group over a 10-year period.
“So you're talking about a comparison where [more than] half the people in the intervention group didn't actually have the actual intervention,” says Jeffrey Meyerhardt, M.D., chief clinical research officer at Dana-Farber Cancer Institute in Boston.
In a statement, William L. Dahut, M.D., chief scientific officer for the American Cancer Society, argued, “It’s hard to know the value of a screening test when the majority of people in the study didn’t get it done.” He pointed out, however, that study participants who did have a colonoscopy had a 31 percent decrease in the risk of colorectal cancer compared to the group that didn’t get screened. The risk of death was also cut by about 50 percent.
“This result points to the value of continued screening,” Dahut said.
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“It should not be interpreted that colonoscopies aren't helpful. And most importantly, it should not be interpreted that there's not a benefit to colon cancer screening,” Meyerhardt says.
Bottom Line: Get screened and stay up to date on screenings
Despite headlines touting disappointing study results, experts say colonoscopies and colorectal cancer screenings, more generally, absolutely saves lives and shouldn’t be skipped. “There's no question that colorectal cancer screening works,” says Carole Macaron, M.D., a gastroenterologist at Cleveland Clinic, who points out that this latest study was really trying to assess the effectiveness of a colonoscopy as a public health intervention when it's being offered to a large group of people.
If you are at average risk for colon cancer — meaning you don’t have a family history of the disease or another condition that increases your chances of getting it, like Crohn's disease — routine screenings should  start at age 45  and continue to 75. Whether you should continue screenings from age 76 to 84 is a decision you should make with your doctor. Adults 85 and older don’t need to be screened.
A colonoscopy is just  one type  of colorectal cancer screening. During this procedure, the doctor looks at the entire length of the colon using a flexible tool that has a camera attached at the end. One of the benefits to this screening is that if your doctor spots a polyp during the procedure (these are small clumps of cells that can be precancerous), they can take it out on the spot.
“If left inside 10, 15 years down the road [a polyp] could progress to cancer, so you want to remove them so that technically your risk of cancer from that polyp turns into zero,” Macaron says. If you opt for the colonoscopy, you should have it done every 10 years. If the test uncovers polyps your doctor might ask you to repeat the test sooner.
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