The study isn’t as cut-and-dry as it may seem, so don’t cancel any upcoming screenings.
Google “ways to prevent colon cancer” and colorectal screening will be at the top of that list. Colonoscopies have been hailed as a way to reduce incidences of and mortality for colon cancer, with a 2018 study finding that colonoscopy screenings were linked to as much as a 75 percent reduction in risk of death for adults ages 55-90. And it’s no secret that Katie is a huge proponent of cancer screenings, including colonoscopies — after allowing the TODAY show to film and air her colonoscopy in 2000, the rate of colonoscopies in the U.S. increased by 20 percent. But a new study is casting some doubt on the effectiveness of colonoscopies. Don’t go canceling your appointment just yet though, because there’s a lot to unpack about this study.
What is the new colonoscopy study?
The study, titled Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death, was published on Sunday in The New England Journal of Medicine. It examined 85,585 men and women between ages 55 and 64 living in Poland, the Netherlands, Norway, and Sweden between 2009-2014. The participants were randomly selected to either be invited to receive one colonoscopy screening, or to not be invited for screening. After ten years, follow-up data was collected: The study found that among the group who were invited to get a colonoscopy screening, 259 cases of colorectal cancer were diagnosed, compared to 622 cases in the group that were not invited to screen. It concluded that among the “intention-to-screen” group, a colonoscopy reduced the risk of colon cancer by 18 percent, but had no statistically significant reduction in death from colorectal cancer.
What do the results mean?
The authors of the study concluded that undergoing a screening reduced the risk of being diagnosed with colon cancer by 18 percent — which is definitely something, but not quite as big of a reduction as was previously believed. (A 2013 study that examined data from 88,902 U.S. healthcare professionals over 22 years found that colonoscopy screening was linked to a 40 percent risk reduction of getting colon cancer and a 68 percent reduction in mortality.) However, a key factor to note is that not every participant who was invited to screen for colon cancer underwent one — not by a long shot. While there were 28,220 people in that group in total, less than half of that — 11,843 people, or 42 percent — actually did undergo a screening.
When the researchers of the European study restricted for people who actually received colonoscopies (not just everyone who was invited to), they found that the risk of diagnosis was reduced by 31 percent and the mortality risk was reduced by 50 percent — which are pretty good numbers.
Why is the study controversial?
With headlines making sweeping claims like “In gold-standard trial, colonoscopy fails to reduce rate of cancer deaths” and “Screening Procedure Fails to Prevent Colon Cancer Deaths,” members of the medical community have some strong opinions about the ways the study is being interpreted — and the potential implications for screenings.
First, it’s important to note that although the results may seem to minimize the importance of getting screened, the authors do explicitly state, “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 does still reduce risk. More importantly, less than half of the participants who were invited to undergo a screening for colon cancer actually did so. “It basically shows that asking people to screen for colon cancer with colonoscopy isn’t as effective as we would expect,” Dr. Mark Pochapin, Director of Gastroenterology and Hepatology at NYU Langone Health, tells KCM. However, he says, “if someone has a colonoscopy, it actually shows very positive data.”
“A closer look at the NordICC study data presents a different picture than offered by many of the media headlines,” Dr. Paul Limburg, Chief Medical Officer of Screening for Exact Sciences, tells KCM. “If all invited participants had actually undergone colonoscopy screening, the expected CRC incidence and mortality rates would have been reduced by 31 percent and 50 percent, respectively — findings that are much more in line with results from previous studies.”
Another issue with the study is that it only examined participants over a period of 10 years. Dr. Aasma Shaukat, Robert M. & Mary H. Glickman Professor of Medicine and Gastroenterology at NYU School of Medicine and one of the reviewers for the study, tells KCM, “10 years is too short to look for a reduction in risk of dying from colorectal cancer — that generally takes a longer period of time.” She notes that we start to see a reduction in colorectal cancer mortality at about the 13 year follow-up point, but it can take as many as 30 years to see the instances of colon cancer that are reduced from taking out polyps during a colonoscopy that could have turned into cancer.
The fact that the study was not performed in the United States is also important, especially when it comes to trying to generalize the results, Dr. Shaukat says. For one, the patient data was collected from an all-white population, when race can be a risk factor for colon cancer incidence and mortality. And because the study didn’t collect information on patient demographics, we don’t know about other risk factors, such as smoking, Aspirin use, and prior screening history — all of which can play a role. Additionally, Sweden, Poland, and Norway only recently started screening people for colon cancer — in 2015 — so it wasn’t encouraged in those countries. (They didn’t have a Katie!) That could account for why less than half of invited participants did the screening.
“Over the last 30 years, the U.S. has celebrated major decreases in colorectal cancer cases and deaths attributed in large part to the effectiveness of CRC screening,” Limburg says. “There is a wealth of evidence supporting screening that has led all the major guideline-making bodies to issue consistently strong recommendations to screen average risk adults for CRC.”
The location of the study has other implications for the results as well, and it gets a bit technical. Dr. Shaukat says that a colonoscopy — where a tube is inserted into the rectum to identify and remove polyps or abnormal tissue — “is only as good as the person doing the high-quality exam.” To that effect, there are a number of indicators that show whether an endoscopist is considered “high-quality,” one of them being adenoma detection rate, or ADR (basically, the number of colonoscopies performed where at least one adenoma is found, divided by the number of colonoscopies performed in a given time period). In order for an endoscopist to be considered high-quality, their ADR needs to be at least 25 percent. The United States averages between 35 to 40 percent ADR, which is better than the standard. In the study, however, about one-third of the endoscopists were below that 25 percent benchmark. “So that also tells us there might be some component of operator variability, and the colonoscopies were just not high-quality exams,” Dr. Shaukat says.
In other words, as Dr. Pochapin puts it, “Imagine we’re studying a drug to prevent a disease that takes 10-15 years to develop. We evaluate the results of the drug where only 42 percent of participants took the drug, and of those who took it, many were assessed less than 10 years out. And, one-third of the tablets participants were taking were of less quality. Can we make any comment about the effectiveness of the drug to prevent the disease?”
What should be the takeaway from this study?
Dr. Shaukat notes that while these results were published at the 10-year mark, the study is still ongoing and the authors will do a longer follow-up. For now, it’s important to take the findings in context with the other bodies of evidence that are out there, and science does support screenings. The American Cancer Society recommends people of average risk get their first screening at age 45.
“I think the answer is we need to be better at getting people screened,” Dr. Pochapin says, adding, “the best test is the one that gets done,” whether it be a colonoscopy, a FIT test, or Cologuard.
“Encouragingly, major guidelines support multiple CRC screening strategies, including the noninvasive, home-based Cologuard test that has a reported completion rate of 66.8 percent,” says Dr. Limburg. “Understanding the strengths and limitations of all available CRC screening options, and allowing patients to make an informed choice, will help to ensure that more people realize the benefits of completed CRC screening.”
And Dr. Pochapin is concerned about the implications the interpretations of the study could have: “I worry that people who have been on the fence of getting screened, whether it’s colonoscopy or otherwise, might actually not get screened. I think it could potentially do a lot of damage.”
Dr. Shaukat agrees: “I think the takeaway is that screening works, and screening for colorectal cancer is both effective and cost-effective.” She warns, “It’s too premature, just on the basis of this study, to say that colonoscopy is not effective or to be discouraged about colorectal cancer screening.”
