Many people in the U.S. may now be thinking that they’ve received a blessed reprieve from a middle age rite of passage: the colonoscopy. After all, a large study just made headlines for suggesting the procedure isn’t nearly as effective at lowering the risk of colon cancer as previously thought. Worse, it didn’t seem to have any impact on lowering the risk of dying from the disease.
But no one should cancel their colon cancer screen.
The trial was important and well run, but it would be a mistake to take it as an indictment of the colonoscopy. Rather, the study should reinforce the need to closely compare the real-world risks and benefits of preventative testing — and serve as a reminder that those benefits might look less impressive as the overall population gets healthier.
The study, published over the weekend in the New England Journal of Medicine, involved nearly 85,000 people in Norway, Poland and Sweden, who were randomly assigned to be invited to get a colonoscopy or to not be offered one. That might sound odd, and we’ll come back to that idea of an invitation, because it’s critical to interpreting the results. The volunteers were then followed for a decade to see if a colonoscopy lowered their risk of getting cancer and dying from it.
The risk of colon cancer was about 18% lower in the group that was invited to get a colonoscopy, and deaths from colon cancer were roughly equal among the two groups. Previous studies, which weren’t done in this randomized, controlled fashion, had suggested colonoscopies reduced the risk of colon cancer by anywhere from 40% to 69%, and lowered the risk of death by anywhere from 29% to 88%.
There’s no sugarcoating it: The colonoscopy’s modest effect was a surprise and disappointment. But the takeaway shouldn’t be that colonoscopies don’t work or aren’t worthwhile.
Instead, the takeaway from the trial is that very few people are going to RSVP enthusiastically to an invitation to get a colonoscopy.
The study was designed to gauge how well a population-level screening program worked in the real world — not to understand the difference between getting or not getting a colonoscopy. And it turns out that only 42% of the 28,000 people in the arm of the trial invited to get the screen actually booked it and showed up.
It’s not hard to imagine why motivation was low. The preparation is notoriously unpleasant. Because the procedure is performed under sedation, the patient can’t drive home. It can easily suck up nearly two days of someone’s time. Even in the U.S., where colonoscopies are far more routine than in the countries where the study was run, nearly 20% of people aged 50 to 75 in have never had any kind of colon cancer screen.
In the end, the main thing that the study clearly shows is that widespread efforts to screen the population with colonoscopy “may have limited benefit,” says Benjamin Rome, a general internist and health policy researcher at Harvard Medical School. But that benefit is still important when it comes to lowering the risk of colon cancer, and the study also suggests it might grow over time.
The study did not show that getting a colonoscopy can increase the chances of surviving colon cancer. But it’s also possible that effect hasn’t appeared yet in the population studied. Many gastroenterologists pointed out that it looks like differences in the colon cancer survival rates between groups that were and weren’t invited to get colonoscopies were starting to appear around year 8. It’s possible that when the data is revisited at year 15, the colonoscopy group will have fared better. We’ll have to wait a few more years to find out.
And while it’s always dangerous to pluck data out of an arm of a study, it’s worth taking a closer look at what happened to the people who did accept that invitation for a colonoscopy. For that slice of the population, the risk of colon cancer was about 30% lower, and their risk of death was roughly cut in half compared to the people who did not receive one.
One last thing that’s worth considering: Sometimes good news can be buried in the bad news. Rates of colon cancer and deaths in the study were lower overall than the researchers had expected when designing the trial. That could be due in part to changes in lifestyle and better treatment options for colon cancer, or even increasing awareness over that decade in the value of screening among participants in the trial.
But that means that those older studies that made colonoscopies look so good at preventing cancers and deaths might be overestimating their benefits in today’s world, says Barry Kramer, who previously served as the director of the National Cancer Institute’s Division of Cancer Prevention. And on the flip side, he says, this study might be underestimating the benefits of colonoscopy if more people in the control arm were being screened than anticipated.
To be crystal clear: The results do not mean there’s no value in screening for colon cancer. The question, rather, is whether a colonoscopy is the best way to do it, or if a non-invasive and cheaper test like the also-recommended stool-based testing is as good or better for most people. The answer to that is particularly important in an era of ballooning health care costs. A giant trial comparing the two is being run, but unfortunately the results aren’t due for several more years.
For now, as Kramer likes to say, the most effective cancer screen is the one you choose to take. Rather than be deterred from that colon cancer screen, people should see this study as a good reason to talk with their doctor about their testing options.
Lisa Jarvis is a Bloomberg Opinion columnist covering biotech, health care and the pharmaceutical industry. Previously, she was executive editor of Chemical & Engineering News.