News · Longevity & Aging
Waiting five years instead of three for a follow-up colonoscopy was just as safe, in a 10,799-person trial
After risky polyps are removed, guidelines call for another colonoscopy at three years. A European trial found that waiting until five left cancer rates no higher, at least so far.
- A randomized trial of 10,799 people in eight European countries who had high-risk polyps removed.
- Half were scheduled for their next colonoscopy at five years, half at three years as guidelines advise.
- After 5.5 years, bowel cancer had been found in 0.77% of the five-year group and 0.82% of the three-year group.
- That met the trial's test for five years being no worse; deaths from bowel cancer were very rare in both.
- This is an early look at a 10-year trial, and nobody should change their own schedule without their doctor.
Anyone who has had polyps removed during a colonoscopy knows the next step: a letter, a date, and another bowel preparation a few years down the line. For people whose polyps looked riskier, guidelines set that date at three years. The interval is based on caution and expert judgment more than on direct evidence, and colonoscopy units in many countries are stretched.
A trial across eight European countries, published in the New England Journal of Medicine, tested whether waiting five years is just as safe. In an early analysis of 10,799 people, it was.
What happens when polyps are removed at colonoscopy
MedlinePlus explains that if you have polyps, your doctor may remove them and send them to a lab for testing. The reassuring part follows: most polyps aren’t cancer, but removing them can prevent them from becoming cancer later on.
The polyps that matter most are adenomas, the kind that can slowly turn into cancer. People whose adenomas were large, numerous or showed advanced changes are asked to come back sooner, because they are thought to be more likely to grow new ones.
How the colonoscopy interval trial worked
Everyone had high-risk polyps removed. The trial randomly assigned patients with high-risk adenomas to undergo a first colonoscopy at 5 years after polyp removal or at 3 years, noting that surveillance at 3 years is currently recommended in guidelines.
The three-year group had a second colonoscopy at five years too, so everyone was examined at the five-year mark. The trial is designed to run for ten years, and the question it asks is precise: is waiting five years no worse than three, within a margin set before the trial began? That margin was 0.7 percentage points of extra cancer risk.
What the colonoscopy trial found at five years
The two groups were almost indistinguishable. The 5-year cumulative incidence of colorectal cancer was 0.77% with less-frequent surveillance and 0.82% with more-frequent surveillance, a difference of 0.05 percentage points that slightly favored the longer wait.
The statistical test the trial set itself was met, and the cancers that were found did not appear to be more advanced in the five-year group. Deaths from bowel cancer were rare in both arms: 3 patients in the 5-year group and 2 in the 3-year group out of more than 5,000 people each.
Why spacing out colonoscopy matters
Colonoscopy is safe but not risk-free, it takes a day of preparation that many people dread, and endoscopy units in many health systems have long waiting lists. Every follow-up that can safely be pushed back frees an appointment for someone with symptoms or a positive screening test.
If the final results hold, moving high-risk patients from three years to five would remove a large number of procedures from the system without costing anyone protection. In this trial the three-year group had two colonoscopies in the first five years where the five-year group had one, and each examination that does not happen is a bowel preparation not endured and a small procedural risk not taken. That is the kind of change guideline committees look for evidence to support, and until now it was largely missing.
What an interim bowel cancer analysis cannot settle
This is an interim result. The analysis was conducted after 5.5 years of follow-up, and the main end point is cancer at ten years. The final analysis could still look different, particularly for cancers that take longer to appear.
Not everyone turned up for their five-year colonoscopy, and the researchers used statistical weighting to account for the missing examinations. A thorough first colonoscopy, with every polyp found and removed, is part of what makes a longer wait safe, so how well the result carries over depends on the quality of that first examination.
What this changes for your next follow-up colonoscopy
For now, individual schedules stay as they are. Guidelines have not changed on the strength of an interim analysis, and the right interval depends on what was found at your own colonoscopy.
What the trial offers is strong early evidence that the three-year rule for high-risk polyps may be more cautious than it needs to be. If the ten-year results confirm it, many people will be able to wait longer for their next procedure, and the appointments saved can go to people who need them sooner.
People also ask
What did the study find?
The 5-year cumulative incidence of colorectal cancer was 0.77% with less-frequent surveillance and 0.82% with more-frequent surveillance (difference -0.05 percentage points); the upper boundary of the 99.12% confidence interval was 0.68, which met the criterion for noninferiority. Five patients died of colorectal cancer: 3 in the 5-year group and 2 in the 3-year group.
What is an adenoma?
A type of polyp, a small growth on the lining of the bowel, that can slowly turn into cancer if left alone. Removing adenomas during colonoscopy is one of the main ways the test prevents cancer.
What made these polyps high-risk?
At least one adenoma 10 mm or larger, one with advanced changes under the microscope, or between 3 and 10 adenomas of any kind. These are the patients currently told to return after three years.
What does noninferior mean?
That the new approach was shown to be no worse than the standard one, within a margin agreed before the trial started. Here the margin was 0.7 percentage points of extra cancer risk, and the result stayed inside it.
Should I cancel my three-year colonoscopy?
No. This is an interim result, guidelines have not changed, and your schedule depends on your own findings. Raise it with your doctor if you want to discuss timing. This is general information rather than medical advice.
Why does the interval matter?
Colonoscopy capacity is limited and the procedure carries small risks. Safely spacing out follow-ups would free appointments for people who need them sooner.