U.S. Doctors Rebuke the New Study That Questions Colonoscopy's Effectiveness

A contentious new study published in the New England Journal of Medicine cast doubts on how useful colonoscopies can be at preventing sickness and death from colon cancer. But some experts are pushing back against the study's conclusions.

A colonoscopy is a preventive screening tool in which a doctor inserts a tiny camera scope at the end of a long flexible tube into the rectum. They look for small polyps and other abnormalities which can be removed before the suspicious growths become cancerous.

The study was the largest randomized clinical trial of colon cancer screening so far, involving nearly 85,000 participants in Europe. It affirmed that colonoscopies are somewhat helpful in preventing colon cancer, but the researchers indicated that the procedure didn't significantly reduce colon cancer deaths among participants.

Some gastroenterologists in the United States have rebuked these conclusions, pointing out limitations that make the findings misleading to patients in the U.S.

Most notably, the researchers reported outcomes for people who intended to get a colonoscopy, regardless of whether or not they underwent the procedure.

They compared a group that was invited to undergo a colonoscopy with those who didn’t. But fewer than half of those "invited" to screen never actually underwent the procedure. When they were removed from the analysis, colonoscopies slashed the risk of getting colorectal cancer by an estimated 31% and reduced the risk of death by about 50%.

“I don't think this is representative of what happens in the United States. The limitations of this article really make it non-applicable," Adam Lessne, MD, a gastroenterologist at Gastro Health in Florida, told Verywell. "When you take away the limitations, it's proven again that colonoscopies do save lives and they do reduce the risk of death.”

Organizations including the American Cancer Society and American Gastroenterological Association have responded to the study by underscoring the importance of colon cancer screening.

“We recognize that this study is generating a lot of attention and could have the effect of discouraging some from getting life-saving colonoscopy screenings. We firmly stand behind the science that has unequivocally demonstrated the benefits of these screenings,” Heidi Nelson, MD, FACS, medical director of the American College of Surgeons cancer programs, said in a statement.

Making Sense of the Study

The researchers recruited nearly 85,000 men and women 55 to 64 years old from Poland, Norway, Sweden, and the Netherlands. Between 2009 and 2014, the participants were invited to undergo a single colonoscopy, or they received the usual care and did not undergo the procedure.

Of the more than 28,000 people invited to get a colonoscopy, only 11,800—or 42%—of them did.

After 10 years, 0.98% of people who were invited to get a colonoscopy were at risk of colorectal cancer, compared to 1.2% in the usual care group, showing an 18% risk reduction. The risk of death from that cancer was similar in each group, at about 0.3% in each.

Earlier research indicated that colonoscopies can reduce the risk of colon cancer and related death by as much as 61%.

Many of the existing studies on the benefits of colon cancer screening are cohort studies. In an editorial response to the recent study, a group of scientists wrote that these study types “probably overestimate the real-world effectiveness of colonoscopy” because healthier people are more likely to seek colonoscopies, among other reasons.

The Europe study was the first randomized clinical trial to directly compare patients who received a colonoscopy to those who don’t. This type of study is considered the “gold standard” of clinical data and the findings were published in one of the most prestigious journals.

In the U.S., it is standard for patients to undergo sedation during the procedure—a practice that's less common in Europe. Sedation minimizes patient discomfort and keeps providers from rushing through it.

“If I’m being offered a colonoscopy and I'm told it's going to be a 20-minute procedure, I'm going to be completely asleep, I’ll have no pain or discomfort, and I’ll wake up and it's going to reduce my risk of colon cancer, I'm going to say yes,” Lessne said. “But if I'm going to have a lot of discomfort during the procedure, I'm going to be a lot more hesitant to get it.”

Additionally, it’s important that the provider is well-trained in performing colonoscopies. In the U.S., doctors strive to meet the benchmark by detecting one or more precancerous polyps, called adenomas, in at least 25% of their procedures. Studies have shown that the procedures are of better quality if a physician has a higher detection rate.

In the Europe study, nearly a third of the surgeons failed to meet this threshold, meaning they may have been less likely to detect and remove precancerous polyps.

How the Findings May Affect Current Recommendations

Since the mid-1990s, the U.S. Preventive Services Task Force has recommended that adults be screened for colon cancer via colonoscopy every 10 years. Last year, in response to data showing that more people are now being diagnosed with colon cancer at a younger age, the group said people should start getting screened at 45 years old. Adults ages 76 to 85 should speak with their doctor about whether to be screened.

Improving access to screening can reduce cancer rates, especially among groups in the U.S. who are more likely to be affected. Black Americans experience the highest rate of new colon cancer cases compared to other racial and ethnic groups.

Under the Affordable Care Act, health insurance plans must cover routine colonoscopies even for people who are at average risk of colorectal cancer, including those with no familial history of the cancer or personal history of certain gastrointestinal conditions.

While the U.S. colonoscopy recommendations are unlikely to change as a result of the new study, it could open a conversation about bolstering less invasive screening approaches for people who are unlikely to get screened if colonoscopy is their only option.

“Easier alternatives such as home stool DNA tests should be considered in low-risk patients,” Anton Bilchik, MD, PhD, MBA, FACS, a surgical oncologist and division chair of general surgery at Providence Saint John’s Health Center and chief of medicine at Saint John’s Cancer Institute, said in an email.

Colonoscopies are invasive, but they’re generally safe. In the Europe study, no participants experienced a perforation, or tear in the large intestine. And only 0.13% of people experienced major bleeding.

Besides, the procedure has become much easier in recent years—the bowel-cleansing agents are lower volume and better tasting than they once were.

“People wake up with minimal symptoms and they're surprised that we're done,” Lessne said. “A lot of this issue is a lack of access because people are scared about a colonoscopy and then when they're done with the procedure, they're kind of like, ‘this isn't a big deal.’”

The bottom line, Lessne said, is that screening of any type is better than none.

“You can be healthy, you can be fit, you can eat well, you can have no symptoms, and yet you can have precancerous polyps that turn into cancer,” Lessne said. “That is completely preventable if you have a screening test.”