The Finds of a Great European to study published in the New England Journal of Medicine this week seemed to call into question how beneficial a colonoscopy is in preventing colorectal cancer, which is a cause of cancer deaths in the US. The results have generated much controversy and headlines in the popular press, such as “Screening Procedure Fails to Prevent Colon Cancer Deaths in Large Study.”
But that’s not the whole story.
A colonoscopy is a widely recommended cancer screening tool that involves placing an endoscope into the colon to look for potentially cancerous growths, called polyps, and remove them. Sometimes these slow-growing polyps, or adenomas – would have becometo cancer, so by regularly examining and removing any polyps, the procedure serves as both a cancer screening tool and an intervention to prevent a tumor from developing in the first place.
Research going back more than a decade has shown that colonoscopies can life jacket; A 2018 study from Kaiser Permanente, for example, found a 67% reduction in cancer deaths among people who had a screening colonoscopy.
In contrast, the main findings of this week’s NEJM study point to an 18% reduction in colorectal cancer among thousands of men and women in Europe who were “invited” to have a colonoscopy. And, as some media reports pointed out, the reduction in deaths was too small to be considered statistically significant. Sounds pretty disappointing, right?
A hitch in the studio.
But here’s the big picture: It turns out that more than half of the research participants who were ‘invited’ to have a colonoscopy never showed up for the procedure.
“A colonoscopy will only work if the patient does it,” he says. Brett Peterson, a Mayo Clinic gastroenterologist and president of the American Society for Gastrointestinal Endoscopy, a leading group of gastrointestinal physicians. Peterson says it’s important to focus on the results of people who actually had the procedure, which was about 42% of the participants who lived in European countries, including Norway and Poland.
Among this group, people who actually had a screening colonoscopy, the risk of developing colon cancer decreased by about 31%. “And deaths were significantly reduced by a significant proportion, about 50%,” says Peterson. He rejects the suggestion that the study published this week calls into question the effectiveness of colonoscopies. “On the contrary, I don’t think we have data from this study to suggest that it is less valuable,” says Peterson. “Based on currently available studies, colonoscopy remains the gold standard for detecting and preventing colorectal cancer,” she says. Peterson’s group, ASGE, issued a statement doubled down on the claim that a colonoscopy “remains the the best and most proven way for patients to be screened for colorectal cancer.
American Cancer Society: ‘This result points to the value of continued screening’
The American Cancer Society also weighed in on the study, also noting the large number of participants who did not undergo the procedure. “It’s hard to know the value of a screening test when most people in the study didn’t get it,” he says. Dr William Dahut, scientific director of ACS. He highlights the 31% reduction in risk among those tested.
“This result points to the value of continuous screening,” says Dahut. The ACS also says it’s important to note that the study participants were examined sometime between 2009 and 2014, so some had their colonoscopy as little as 8 years ago. “The time from polyps to cancer and mortality is almost always longerr than this, so much longer follow-up is needed,” concludes a statement from the ACS. Over time, the reduction in cancer or deaths could be greater.
The controversy created by this study is unlikely to lead to changes in screening recommendations in the US “Preventive cancer screening is the best and most reliable way to save lives,” says Karen Knudsen, CEO of the American Cancer Society. The ACS recommends colorectal cancer screening for adults age 45 and older. “There’s no reason to change that direction,” says Knudsen.
Some doctors have been quick to point out that the methods used by endoscopists (doctors performing the procedure) have improved, compared to 2009, when the European study began.
“The polyp detection rate is much higher than it was 10 or 15 years ago,” he says. Douglas Corley, research scientist and gastroenterologist at Kaiser Permanente. He says equipment is better and preparation methods have also improved (patients must fast and drink a specially formulated laxative drink to help cleanse the GI tract before the procedure). Also, “the doctor’s ability to detect and remove polyps is better,” says Corley. So if a study started now, “the benefit we would expect to find now would be greater.”
Differences between the United States and Europe
Also, colonoscopies are not as common in the European countries where the study was conducted, and Bret Petersen says that some of the doctors who performed the tests did not identify the number of polyps that would be considered an acceptable rate in the US.” About 30% of the endoscopists who were included in the NordICC trial did not meet the adenoma detection rate,” says Peterson. He says this calls into question whether there were actually “just some of the lesions missing that might otherwise have been detected and therefore removed.”
The lead author of the study says he is aware of all the criticism of his paper. But he rejects the idea that the endoscopists did not find the expected levels of polyps. “In the two countries that contributed the largest number of participants, which are Norway and Poland, the detection rate, which is the quality metric for finding polyps, was 30%, well above the current threshold for good quality” says Dr. Michael Brethauer from the University of Oslo in Norway. The detection rate was much lower in Sweden, which contributed to fewer study participants because, she says, not as many people in Sweden have polyps. “So I don’t think that argument is valid.”
Bretthauer says the paper may be getting so much attention because it challenges commonly held assumptions in the US about how protective colonoscopies can be. “I think our findings suggest that colonoscopy is not a magic bullet against colorectal cancer,” says Bretthauer. But he points out that, with up to a 50% reduction in mortality risk, it’s still more beneficial than almost any other cancer-screening tool.
Another challenge with the new Europa study is that it was not designed to answer the questions many people have when trying to evaluate screening options. “There are different methods of screening for colon cancer,” explains Kaiser Permanente’s Corley. Because the European researchers only evaluated colonoscopies, their study offers no direct comparison with the increasingly popular alternative to the once-a-decade colonoscopy: stool-based home tests that are performed more frequently.
Alternative Screening Tests for Colon Cancer
The US Preventive Services Task Force recommends any of several different types of colorectal screeningg methods, including colonoscopy, a sigmoidoscopy (a less invasive test to evaluate part of the colon), or stool-based tests, usually taken at home and mailed to a lab, that look for blood or abnormal cells in the samples of feces
“It’s not clear if any one of these approaches is better than another at reducing colon cancer deaths,” says Corley.
A fecal immunochemical test, called a FIT, can detect small amounts of blood in the stool and is typically done annually. Another option is a combined test, such as Cologuard –– which can detect changes in both the blood and DNA that may come from a cancerous or precancerous polyp in the stool. People who choose this option are generally recommended to get tested every three years.
Kaiser Permanente patients opt for FIT testing more often. Sometimes the biggest hurdle is remembering to get tested, so Corley says Kaiser mails stool-based tests to patients and then stays in touch with patients until the tests are shipped.
Each detection approach “has its advantages and disadvantages,” says Corley. If the stool sample test is positive, a colonoscopy will likely be recommended to better see and remove the polyps. Colonoscopies carry small risks, including the risk of a perforation or tear in the colon, bleeding at the biopsy site (if the doctor removes a polyp or takes a biopsy), and the possible side effects of sedation during the procedure.
Generally, “if you’re at increased risk for colon cancer, such as if you’ve had close family members who have had colon cancer, especially if they’re young, then it’s recommended that you get a colonoscopy,” says Corley. she says. If you’re not at high risk, she says, you should choose the test you’ll be able to complete, whether it’s a colonoscopy or one of the less invasive and more frequent stool-based tests.
Regardless of which colon cancer screening method you choose, Corley says, the important thing is to go ahead and get tested.
You can find Allison Aubrey via Twitter @AubreyNPR.