The headlines were brutal and the gastroenterologists cringed. One from MEDPAGE TODAY (October 9, 2022) captured the essence of a new study: “If you invite 455 people for a colonoscopy, you’ll stop one case of cancer – Colorectal cancer risk is reduced with screening in a randomized trial, but less than expected. Unsurprisingly, colonoscopies have been a hot topic on news shows this week. And many gastroenterologists were somewhat defensive about the study results. What’s the bottom line on the new research?
Colonoscopies in The New England Journal of Medicine:
Research reported in the New England Journal of Medicine (October 9, 2022) suggested that the effectiveness of colonoscopy in preventing colon cancers was surprisingly unimpressive. Among those invited for colonoscopy, the 10-year mortality rate from colorectal cancer was 0.28%. It compares to 0.31% among those who were not invited to undergo screening. If you are not a statistician, this difference is not statistically significant.
The study was large, including more than 84,000 volunteers in Norway, Poland and Sweden. Researchers guest 28,000 to undergo screening colonoscopies and nearly 12,000 Actually did it. Those not asked to have a colonoscopy received usual care, and investigators collected health data on everyone for ten years.
Colonoscopies and number needed to treat:
The researchers created a metric called the number needed to treat or NNT. It describes the number of people who would need to receive a particular treatment (or intervention) for one person to benefit. Here is the official explanation from NNT:
“The NST offers a measure of the impact of a drug or therapy by estimating the number of patients that need to be treated to have an impact on one person. The concept is statistical, but intuitive, because we know that not everyone is helped by a drug or intervention – some are beneficial, some are harmed, and some are unaffected. The NNT tells us how many of each.
The New England Journal of Medicine article describes the advantages of colonoscopies as follows:
“The number needed to invite for screening to prevent one case of colorectal cancer within 10 years was 455.”
Needless to say, it’s not terribly impressive. This means that 454 people will not receive any benefits.
The newspaper article adds:
“The risk of death from any cause was 11.03% in the invited group and 11.04% in the usual care group.”
You don’t have to be a statistical wizard to realize that there was no statistically significant difference in the death rate between those invited for colonoscopy and those in the usual care group.
Should you give up colonoscopies?
Before giving up on colonoscopies, however, there are a few caveats. In reality, not everyone who has been asked for a colonoscopy has done so. Remember that less than half of those invited followed the procedure.
The researchers point out that if you only compare those who actually have had a colonoscopy, there was a 30% less risk of developing colon cancer. The risk of death from cancer was reduced by 50%.
Wow! It looks impressive. And many gastroenterologists were quick to point out these relative risk benefits. But the absolute the risk reduction was small. Here’s how the researchers describe their data:
“In analyzes adjusted to estimate the effect of screening if all participants who were randomly assigned to screening had actually been screened, the risk of colorectal cancer was reduced from 1.22% to 0.84%, and the risk of death from colorectal cancer was reduced from 0.30% to 0.15%.Our results can be used to quantify the effectiveness of screening colonoscopy for the prevention of colorectal cancer and thus allow decision makers to prioritize appropriate cancer screening resources and health care services.
The authors also attempt to distinguish between relative risk reduction and absolute risk reduction:
“Although we observed appreciable reductions in relative risks, the absolute risks of colorectal cancer risk and even more colorectal cancer-related deaths were lower than in previous screening trials and lower than we expected when trial planning.”
We appreciate this openness among researchers.
So… Are colonoscopies a waste of time and money?
We don’t think you should give up on colonoscopies. People who have a family history of colon cancer should absolutely undergo regular colonoscopies from an early age. Guidelines suggest others should start at age 45. Anyone who has had polyps discovered during a colonoscopy should continue to have regular colonoscopies to prevent new ones from turning into something worrisome.
There are other ways to screen for colon cancer. Here is a link to an article on this topic.
What are the alternatives to colonoscopy?
How good are alternatives to colonoscopy, such as FIT or Cologuard, for detecting colorectal cancer? When should you start?
What do you think?
We appreciate your perspective on the new data published in the New England Journal of Medicine. We recently discussed new preparation strategies with one of the top gastroenterologists in the country. Many people avoid colonoscopies because they hate drinking a gallon of glop to clean out their colon.
We think you will find this podcast of great interest. Here is a link to the podcast. To listen, just click on the arrow in the green circle under the photo of Dr Nicholas Shaheen. Or scroll down the page and download the mp3 file. Please share this article with your friends and family. We suspect a lot of people were confused by the headlines.
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