Adenoma Detection Rates in Colonoscopy: The Higher the Better

Caroline Helwick

July 2013, Vol 4, No 6 - Colorectal Cancer

Orlando, FL—In screening colonoscopies, high adenoma detection rates (ADRs) by physicians are associated with fewer missed cancers and with better survival from colorectal cancer (CRC), according to 2 studies presented at Digestive Disease Week 2013.

It is assumed that the higher the ADR, the more complete the colonoscopy examination. Although low ADRs have been linked to the occurrence of missed or “interval” cancers—those occurring within 3 years of a negative colonoscopy—this association needed further exploration, according to Douglas A. Corley, MD, PhD, MPH, a researcher at Kaiser Permanente in Oakland, CA, who presented one of the studies.

ADR an Important Quality Indicator
An ADR was defined as the percentage of colonoscopy screenings in which at least 1 adenoma or cancer was detected. Current guidelines recommend ADRs of 15% for females and 25% for males, but no data have provided a threshold ADR that should be targeted for intervention, Dr Corley said.

“We found a 3% increase in interval CRC risk and 4% increase in risk of CRC death for every 1% difference in ADR,” he reported.

“Patients whose colonoscopies were performed by endoscopists who had lower ADRs were more likely to be diagnosed with subsequent CRC than patients whose endoscopists achieved higher ADRs,” Dr Corley noted.

A total of 314,872 colonoscopies were performed by 136 experienced endoscopists, and 712 postcolonoscopy cancers were diagnosed within the next 10 years. The quartile of ADR, from a low of <19% to a high of 33%, was linked to these cancers as an independent predictor after a negative colonoscopy. Patients with the fewest adenomas had more than a 2.6-fold increased risk of dying within 10 years.

“Our findings support the validity of ADR as a quality metric for colonoscopy, and they support the evaluation of interventions to determine if improving ADR will improve outcomes,” Dr Corley concluded.

Characteristics of Missed CRCs
Investigators from the Huntsman Cancer Institute at the University of Utah, Salt Lake City, also examined the rate and the predictors of missed or interval CRCs in a population-based study of 126,936 adults aged ≥50 years. Of the 2659 patients who developed CRCs, 159 were diagnosed within 6 months to 5 years of the negative colonoscopy, and 91 were diagnosed within 6 months to 3 years. This yielded a missed or interval CRC rate of 6% for the 5-year window and 3.5% for the 3-year window, said N. Jewel Samadder, MD, MSc, Assistant Professor of Medicine at the University of Utah School of Medicine.

Philip S. Schoenfeld, MD, Associate Professor of Medicine at the University of Michigan, Ann Arbor, who is coauthoring a position paper on quality indicators in colonoscopy, commented that these findings suggest that current recommended ADRs may be too low.

“We have not upped the thresholds for recommending ADRs of 25% in men and 15% in women at screening colonoscopy, though I think the data from these papers could influence the ADR that we specify in the updated position statement,” Dr Schoenfeld pointed out.