If you’re at the age where colorectal screening is recommended to prevent colon cancer (between 45 and 75), you might see the new, landmark study published in the New England Journal of Medicine as somewhat of a reprieve since it found little to no decreased death risk from the screening method.
Not so fast, experts say. There are some reasons why this study — the first randomized controlled trial of colonoscopy — might have not have answered that question.
First, some details about the study if you haven’t already read about it.
New study finds colonoscopy has little impact on risk of death from colon cancer
In the trial that included 84,585 European participants between 55 and 64 years old and had a median follow-up of 10 years, researchers randomly assigned 28,220 of the participants to be invited to get screened with colonoscopy while the rest went about their lives as usual (the control group). Of the colonoscopy group, just 11,843 (42%) of those who were offered it got one.
During follow-up, 259 participants who received a colonoscopy developed colon cancer as compared to 622 in the control group, which had 56,365 members. These findings translated into a risk of 0.98% of developing colon cancer in the colonoscopy group as compared to 1.2% in the control group. The risk of death from colon cancer was .28% in the colonoscopy group versus .31% in the control group. The risk of death from any cause was 11.03% in the colonoscopy group and 11.04% in the control group. Researchers concluded that for every 455 people invited to undergo screening, one death from colorectal cancer will be prevented.
But it's important to note that the above findings are based on an analysis that included everyone in the colonoscopy group, including those who didn't actually accept the invitation to get a colonoscopy.
When researchers compared only those who did get colonoscopies to the members of the control group, the risk of death among those who got a colonoscopy was half that of those in the control group. Still, that finding might not tell the whole story, either, because the people who decided to get the colonoscopy may've had symptoms that convinced them to get screened for colon cancer.
So, should you still get a colonoscopy?
“My advice to the public is to get some type of colon cancer screening, whether it’s a stool test or a colonoscopy, starting at age 45,” said Dr. Otis Brawley, a cancer screening expert and professor at Johns Hopkins School of Public Health in Baltimore.
People who test positive on the stool test are then recommended to get a colonoscopy to determine whether that positive indicates an actual cancer.
“The strongest evidence we have that screening works comes from clinical trials of annual stool testing,” Brawley said. “The way we ended up recommending colonoscopy is that over 10 years 43% of people getting the stool test were recommended to get a colonoscopy because of the positive findings on the stool test.”
Gastroenterologists figured that 43% was close to 50% and if you were going to do colonoscopies in 50% of people you might as well do them in 100%, Brawley said.
There’s no question that any kind of screening saves lives, Brawley said. But the public has been oversold on just how many lives are saved, he added.
“The studies have shown that screening can prevent one-third of colon cancer deaths,” Brawley said. “Two-thirds of people will still die from colon cancer.”
The reason, Brawley said, is that some cancers grow very fast, and in the 10 years between colonoscopies, they can get to a very late stage. Moreover, some polyps are flat and missed by the medical professional performing the colonoscopy, he added.
Currently there is 30 years of data on people who use the stool test. Brawley suspects that if the authors of the new study were to follow the participants for another 10 or 20 years, their data would show that colonoscopy saves lives.
The lack of improvement in mortality was “somewhat surprising” to Dr. Jason Dominitz, a professor of medicine at the University of Washington School of Medicine and executive director for the National Gastroenterology and Hepatology Program at the Veterans Health Administration in Seattle. Dominitz co-authored the editorial accompanying the new report, which suggested a number of reasons that the study failed to show a mortality benefit, including too short of a follow-up period.
“Part of the reason for it is the rate of colonoscopy was fairly low,” Dominitz said. “Colonoscopy can’t be effective if it’s not done, and the study did show a significant decrease in cancer incidence with colonoscopy, and this will ultimately lead to a decrease in deaths.”
Because the study was structured around an invitation to receive a colonoscopy, some doctors have said it reveals more about the public's fear of colonoscopy than the effectiveness of the procedure.
"All this study shows is that many are hesitant to go for colonoscopy, but for the ones who undergo colonoscopy, there is a decrease in colon cancer mortality. In other words, we need to intensify efforts to educate people about the importance of colonoscopy!" tweeted Dr. Leonidas Platanias, director of Robert H. Lurie Comprehensive Cancer Center of Northwestern University.
"Better title for this study might have been: 'Colonoscopies prevent cancers and deaths only if people do them.' Must recognize that study was more about 'invitation for colonoscopy' than 'effectiveness,'" added Dr. Fola May, associate director of the UCLA Kaiser Permanente Center for Health Equity, via Twitter.
The bottom line, Dominitz said, is: “Don’t cancel your colonoscopy.”
This paper is part of a set of ongoing studies “helping to fill in gaps in our knowledge as to how effective colonoscopy is, but it remains the case that colon cancer screening is lifesaving," said Dr. Benjamin Lebwohl, a gastroenterologist and an associate professor of medicine and epidemiology at the Columbia University Vagelos College of Physicians and Surgeons.
“I very much suggest that people who are planning to get a colonoscopy not let this trial result dissuade them,” Lebwohl said. “No test is perfect, and a common adage in our community is the best test is the one that gets done. The question of whether screening can be lifesaving has been answered. The question that remains is whether colonoscopy should be the first line test.”
