When endoscopists frequently find polyps during their exams, there are fewer interval cancers diagnosed between tests.
The adenoma detection rate or the percentage of time that at least one polyp is found during all of the colonoscopies done by an individual endoscopist is one measure of quality performance. When that rate falls below 20 percent, the risk of colorectal cancer being diagnosed within the next five years goes up significantly.
When the rate was below 11 percent, the risk of an interval cancer was more than 10 times higher than when adenomas were found more than 20 percent of the time according to research published this week in The New England Journal of Medicine.
The same study found that reaching the cecum — or cecal intubation rate — had no impact on interval cancers.
Researchers analyzed records of 45,026 screening colonoscopies performed in Poland between 2000 and 2004, as well as national and regional cancer registries to identify people with negative screening who developed cancer before the next colonoscopy was due.
They discovered 42 interval cancers among nearly 190,000 patient years after colonoscopy.
The rate of interval cancer per 100,000 patient years was 2.4 per 100,000 for screenings done by endoscopists with a rate of polyps found to procedures done of 20 percent or more. When the polyp detection rate was less than 20 percent, the rate of cancers per 100,000 patient years ranged from 22.1 to 33.6 — a huge increase.
Hazard ratios comparing risk for having an interval cancer comparing detection rates under 2o percent to those over 20 percent:
- Less than 11%: 10.94
- 11% to 14.9%: 10.75
- 15% to 19.9%: 12.50
However, similar relationships weren’t found between records showing that the colonoscopy reached the cecum at the very top of the colon, another measure used to determine quality colonoscopy.
The research team had no information about withdrawal times.
Age was another significant risk for interval cancers with more than 13 times as many interval cancers found in patients from 60 to 66 as in those from 40 to 49.
Michal F. Kaminski, MD, of Maria Sklodowska-Curie Memorial Cancer Center in Warsaw, Poland, and his colleagues concluded,
The adenoma detection rate is an independent predictor of the risk of interval colorectal cancer after screening colonoscopy.
What This Means for Patients
Before you choose an endoscopist for your colonoscopy, ask about his or her adenoma detection rate. It should be at least 20 percent.