I’m overdue for a colonoscopy. The US Preventive Task Force advises Americans to have one every 10 years beginning at age 45. It has long been believed that if Americans followed that advice colon cancer would largely be a thing of the past. Now a European study casts doubt on that theory.
“This is a landmark study. It’s the first randomized trial showing outcomes of exposing people to colonoscopy screening versus no colonoscopy. And I think we were all expecting colonoscopy to do better,” said Samir Gupta, a gastroenterologist at the University of California, San Diego and the VA who didn’t work on the trial. And, he said, it raises an uncomfortable question for doctors. “Maybe colonoscopy isn’t as good as we always thought it is.”
The trial’s primary analysis found that colonoscopy only cut colon cancer risk by roughly a fifth, far below past estimates of the test’s efficacy, and didn’t provide any significant reduction in colon cancer mortality. Gastroenterologists, including Bretthauer, reacted to the trial’s results with a mixture of shock, disappointment, and even some mild disbelief.
Experts stress that this does not mean that colonoscopies are of no value.
Colonoscopies are still a good test, Gupta said, but it may be time to reevaluate their standing as the gold standard of colon cancer screens. “This study provides clear data,” he said, “that it’s not as simple as saying, ‘Colonoscopy is the most sensitive test, and therefore it is the best.’ It still prevented cancers.”
Researchers in Oslo, Norway identified roughly 80,000 people from Norway, Poland and Sweden. About 28,000 were randomized and invited to take a colonoscopy while an equal number were tracked but not offered the screening.
The researchers then kept track of colonoscopies, colon cancer diagnoses, colon cancer deaths, and deaths from any cause. After 10 years, the researchers found that the participants who were invited to colonoscopy had an 18% reduction in colon cancer risk but were no less likely to die from colon cancer than those who were never invited to screening. Of the participants who were invited to colonoscopy, only 42% actually did one. The team published their findings in the New England Journal of Medicine on Sunday.
It sort of makes me wonder if 10 years was enough time to track colon cancer deaths. Also, I wonder if the actual results were only for those 42% of the treatment group. For example, how many of the control group actually got a screening without being invited. How many of those who didn’t get a screening had one before the experiment began? That would seem to make a huge difference.