You may have seen last week’s headlines questioning the importance of colonoscopies as a cancer screening test that saves lives. Yes, a recent study of nearly 85,000 people in four European countries (known as the NordICC study) concluded that people between the ages of 55 and 64 who were offered a colonoscopy had a similar likelihood of dying from colon cancer as did those not offered the procedure, and the risk of being diagnosed with colon cancer was reduced by a disappointingly small 18%. But there are several reasons why the latest results shouldn’t tempt you to postpone colon cancer screening if you’re 45 or older (or if you’re younger and your doctor recommends it).
Reason 1: invitations can’t detect cancer
The study randomly assigned people to “usual care” in these countries (no screening) or “an invitation” to undergo a screening colonoscopy, and the results compared the people in the two groups. But only 42% of the people who received the invitation showed up for the colonoscopy.
The study authors were attempting to create a real-world scenario and avoid bias by analyzing the entire invitation group, but it doesn’t take a statistician to realize that an invitation alone can’t detect cancer. In fact, when the analysis was restricted to the people who had a colonoscopy, the risk of a colon cancer diagnosis fell by 31%, and the risk of dying from colon cancer fell by 50%.
Reason 2: short follow-up time
The people in the NordICC study underwent colonoscopies between 2009 and 2014 and have been followed by the study authors for an average of 10 years. But colon cancer often develops from precancerous polyps over more than a decade, so additional time may be required to realize the full number of lives saved. The authors plan to update us in another five years.
Reason 3: low adenoma detection rates
A colonoscopy is a procedure that requires training and practice, and there are quality standards that have been developed over the years. For example, a doctor performing colonoscopies should detect precancerous polyps at least 25% of the time (referred to as an acceptable “adenoma detection rate”). In the NordICC trial, 29% of the doctors had adenoma detection rates below 25%, suggesting that some cancers could have been missed.
Reason 4: colonoscopy is only one tool
Most importantly, colonoscopy is only one strategy for colon cancer screening, with others including stool tests for microscopic bleeding and DNA shed from undiagnosed tumors in the colon (referred to as FIT testing and Cologuard®, respectively). Unlike colonoscopy, stool tests are completed at home. Every screening test has advantages and disadvantages that should be discussed between each person and that person’s doctor. Although only colonoscopy allows the doctor to directly inspect the entire colon and remove polyps, it is an invasive test that requires bowel preparation prior to the procedure and time off from work that can cause significant hardship for some people.
Although it’s important to point out that a colonoscopy is necessary in the event of a positive stool test, most people who choose one of these tests will never need a colonoscopy. Guidelines from professional organizations including the United States Preventive Services Task Force, the American College of Gastroenterology and the American Cancer Society emphasize that options are available and that patients should be given a choice. Studies show that this is the best way to maximize the number of people screened. The best test is the one that gets done! Don’t risk your life by putting off screening.