Why was that major colonoscopy study so badly misinterpreted?

Updated: Oct 28, 2022

Last week, news headlines screamed out a glaring accusation: A study published in the New England Journal of Medicine that examined a group of people who got colonoscopies and a group that didn’t, seemed to suggest that colonoscopies don’t prevent colorectal cancer. But as many journalists, medical experts, and careful readers have since pointed out, this is a totally incorrect interpretation.

With cases of colorectal cancer on the rise, patient education and research are more important than ever. So how were the results of this important study so egregiously misinterpreted?

The study’s Abstract, which can be freely accessed online, is written in easy-to-understand language. Its Conclusion clearly states: “In this randomized trial, the risk of colorectal cancer at 10 years was lower among participants who were invited to undergo screening colonoscopy than among those who were assigned to no screening.”

So, screening for colorectal cancer is an advantage. Where did the message get garbled?

You could put the blame on the press - after all, most news outlets do like to sensationalize things for views and clicks. You might also consider that colonoscopies aren’t easy or pleasant, so maybe we’re all looking for an excuse not to get one.

But the problem ultimately comes down to a lack of clear communication from the researchers themselves.

One of the findings that got readers’ attention was this: “The risk of death from colorectal cancer was 0.28% in the invited group and 0.31% in the usual-care group” - in other words, the group that was invited to get a colonoscopy and the group that did not get one had a similar risk of death from colorectal cancer.

Taken on its own, this information, as well as something that follows: “The risk of death from any cause was 11.03% in the invited group and 11.04% in the usual-care group” would indeed seem to show that, contrary to the way they’re presented as a life-saving procedure, colonoscopies don’t do much to prevent colorectal cancer deaths.

But a closer look at what the study is saying shows that the true diagnosis here is easily misinterpreted data.

Medical news site STAT called on several health experts who weren’t involved with the study to examine what went wrong in reporting the results. While several brought up fascinating nuances about screening for colorectal cancer and other issues, all agreed that, as gastroenterologist and cancer researcher Folasade May puts it:

“The study wasn’t an effectiveness of colonoscopy study but effectiveness of invitation to colonoscopy.”

There are a lot of statistics and figures in the study’s abstract, but if you read closely, you’ll see that while the study technically involved two groups -- a group that got colonoscopies and a group that didn’t -- not all of the the colonoscopy group actually got colonoscopies.

Participants in this group were invited to get colonoscopies, but only 42% of them did.

So, the study didn’t really compare a randomized group of people who got colonoscopies and a randomized group that didn’t; it compared a group who was offered colonoscopies against a group that wasn’t.

This means, as gastroenterologist Samir Gupta observes, “It doesn’t answer the question of: if you’re in front of a patient and they do colonoscopy, will that reduce their risk of dying from colon cancer?”

Reporter Angus Chen adds, “That makes this trial more of a population or public health study,” rather than a test of colonoscopies’ effectiveness.

It almost seems as though researchers started out with one goal and should have modified or changed it along the way, maybe only following the 42% who got colonoscopies instead of the entire invited group. If they had, they might have been able to better present their other findings, which indicate that colonoscopies are a very effective way of discovering and preventing colorectal cancer.

For instance, Gupta notes,“this study suggested that colonoscopy can reduce cancer risk by 30% and mortality by 50%,” a success rate he deems “excellent” by modern medical standards.

The confusion over the study’s results could have terrible repercussions. While a colonoscopy isn’t the only method of screening for colorectal cancer, numerous health experts consider the procedure “the gold standard”, and it’s highly recommended, especially for those most at risk.

Since the study’s publication, May says, “I have patients texting and calling me and saying, ‘should I come in for that colonoscopy on Thursday?’ That’s a devastating result of this publication. The reality is that every day, there are people with polyps and cancer growing because colorectal cancer is so asymptomatic and it’ll grow for years. You will never know. Hopefully we get the message through that colorectal screening saves lives.”

The misinterpretation of this study show why it’s so important to read carefully, and between the lines, whenever medical news is being shared. Unfortunately, not everyone will do this. Some may not have the time, or may be confused by medical jargon, or blocked by a paywall. Others inherently trust the press, something that shouldn’t be a fatal flaw, but, sadly in cases like this, may be.

Contact Our Writer – Alysa Salzberg