Colonoscopies may not reduce cancer deaths, study finds – but experts say you still need to get it

CNN
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Colonoscopies may reduce the risk of dying from colorectal cancer by as much as 50%, but there are pitfalls.

that is, first randomized trial colonoscopy, open on sunday In the New England Journal of Medicine.

Colonoscopy is the recommended screening test for adults over the age of 50 from the mid-1990sand approximately 15 million colonoscopies are performed each year in the United States. This recommendation is based on evidence from retrospective observational studies to compare the frequency of colorectal cancer diagnoses in people who underwent colonoscopy with those who did not. However, these studies can be subject to bias, so scientists use randomized trials that blindly divide people into two groups: those who are assigned to receive interventions and those who are not. These studies will then follow both groups over time to see if there are differences. These studies have been difficult to do against colon cancer, which is slow-growing and can take years to be diagnosed.

The NordICC study, which stands for the Nordic Initiative on Colon Cancer, involved more than 84,000 men and women between the ages of 55 and 64 in Poland, Norway and Sweden. None had previously had a colonoscopy. Participants were randomly invited to undergo colonoscopies between June 2009 and June 2014, or were followed for the study without screening.

Ten years after enrollment, the group invited to undergo colonoscopy had an 18% lower risk of colorectal cancer than the unscreened group. Overall, the screening-invited group also had a slightly reduced risk of dying from colorectal cancer, although the difference was not statistically significant.

The researchers say they plan to continue following the participants for another five years. Screening endoscopy may provide greater benefit.

Usually such disappointing results from such large and powerful studies are considered conclusive enough to change medical practice.

However, this study has significant caveats that limit how the results can be applied. Of the participants invited to undergo colonoscopy, only 42% of him underwent colonoscopy.

“I think it would be difficult to know the value of screening tests if the majority of people who participated in screening did not get tested,” the study said.

The procedure was found to be more effective when the study authors limited the results to people who had actually had a colonoscopy (about 12,000 out of over 28,000 invited to do so). I was. A 31% reduction in the risk of colorectal cancer and a 50% reduction in the risk of dying from that cancer.

However, experts say the results for this subgroup can be biased, so it’s hard to rely on this result alone.

For example, in clinical trials, researchers often worry about the “healthy volunteer effect.” Those who volunteer for exams are more likely to take good care of themselves by eating healthy and doing other things that research can’t measure. It may reduce their risk.

As a gastroenterologist, the study’s investigator, Dr. Michael Brettthauer, who heads the clinical efficacy group at the University of Oslo in Norway, said he was disappointed with the results.

But as a researcher, he has to follow science, so “I think you have to embrace it,” he said.

“And over the last decade or so, we may have oversold the message and need to rewind a bit,” he said.

Brettauer believes that the full set of study results, including those who did not have a colonoscopy, is the minimum benefit one can expect, while the narrower results are limited to the subset of people who did. increase. Colonoscopy – the biggest benefit people can expect.

Based on his results, he expects that colonoscopy screening probably reduces the chance of colorectal cancer by 18% to 31% and reduces the risk of death from 0% to 50%. . I think everyone thought it would.

Other research estimated The benefits of colonoscopy are significant, with reports that these procedures may reduce the risk of dying from colorectal cancer by as much as 68%.

There are other caveats that may limit the applicability of the study results.

First, Dr. Douglas Corey, a gastroenterologist who leads delivery sciences and applied research at Kaiser Permanente Northern California, said it’s not clear how much follow-up people had after colonoscopies. increase. Part of the value of screening comes from close follow-up when an abnormality is detected, he said.

Corey not involved in research, It also states that colonoscopies have improved since the study was conducted. The findings may not reflect the performance of currently available screening tests, as the techniques are better, and doctors are just as well trained to perform them.

The question of the most effective method to screen for colon cancer is important.

Colorectal cancer will be the fourth leading cause of cancer in the United States in 2022 and the second leading cause of cancer deaths. according to National Cancer Institute.

Several other ongoing studies may help answer the question of how effectively colonoscopies detect cancer. The other is based in the US and is called Confirm. The Spanish study will finish follow-up of the patients in late 2021. The US trial will follow patients through 2027.

Dr. Jason Dominitz is the National Director of Gastroenterology for the Veterans Health Administration. He conducts his Confirm study comparing colonoscopy with stool immunochemistry (FIT), which detects blood in the stool and looks for problems.

Dominitz, who co-authored an editorial alongside new research published Sunday in The New England Journal of Medicine, says colonoscopies should not be canceled based on these results.

“We know colon cancer screening works,” he told CNN. Previous studies of FIT and a test called sigmoidoscopy, which looks only at the lower part of the colon, have shown a reduction in both cancer incidence and death from colorectal cancer.

“These other tests work with colonoscopies,” Dominitz said. “They identify people who are at high risk of benefiting from colonoscopies. Colonoscopies are then performed to remove polyps. prevent colon cancer from developing or identify colon cancer at a treatable stage.”

Polyps are benign tumors that can become cancerous. They are usually removed when identified during colonoscopy screening and can lower the risk of future colorectal cancer.

Dominitz said the randomized controlled trial is both a test of the value of colonoscopy and a test of advice.

“If you ask the public to do something, how much impact will it have?” he said.

Overall, the study found that simply inviting people to undergo colonoscopies did not have a significant beneficial impact across these countries.

Dominitz believes that the low participation rate can be partly explained by the study setting. Colonoscopies are less common in the countries participating in the study than in the United States. According to him, Norway did not have official colorectal cancer screening recommendations until last year.

“They don’t see the public service announcements. They don’t hear Katie Couric talking about getting screened for colon cancer. They don’t see billboards at airports or anything like that,” he said. Told. “So I think it’s likely that an invitation to a screening in Europe would be somewhat different than an invitation to a screening in the US.”

in the United States, according to the data According to the US Centers for Disease Control and Prevention, about 1 in 5 adults between the ages of 50 and 75 have not been screened for colorectal cancer.

The US Preventive Services Task Force states that various methods and regimens are effective in detecting colorectal cancer.this Recommend screening Tests to check for blood and/or cancer cells in stool every 1 to 3 years, colon CT scan every 5 years, flexible sigmoidoscopy every 5 years, flexible sigmoidoscopy every 10 years Colonoscopy combined with a stool test to check for blood Annual or 10-year colonoscopy.

In 2021, the task force lowered the recommended age to begin routine colorectal cancer screening from 50 to 45.

When considering the best screening tests for his patients, Dominitz says he remembers advice from a mentor: “The best tests are the ones that are completed.”

As evidence, he points to early results from a large Swedish randomized trial that did not test colonoscopies, FIT tests, and screening at all.

Results collected from more than 278,000 people enrolled between March 2014 and the end of 2020 show that 35% of the group assigned to undergo a colonoscopy actually did. 55% of those assigned to the FIT stool testing group.

To date, slightly more cancers have been detected in the group assigned to the stool examination than in the group undergoing the colonoscopy. “So your participation in the screening is really important!” said Dominitz.