Low Adenoma Detection Linked to Colorectal Cancer, Death

Caroline Helwick

May 19, 2013

ORLANDO, Florida — Low adenoma detection rates (ADRs) were linked to increased risk for interval colorectal cancers and related deaths in a large analysis of a Kaiser Permanente network that involved only experienced endoscopists.

"Physician colonoscopy ADRs vary widely and may impact subsequent colorectal cancer risk due to missed early cancers and adenomas," said Douglas Corley, MD, from Kaiser Permanente in Oakland, California. "There has been, however, no data on advanced cancers, location of the cancers, and subsequent deaths, and no data on whether a threshold ADR exists that should be targeted for intervention."

To address these issues, the study evaluated the association between physician ADR quartiles and the risk for subsequent colorectal cancer among a large group of patients and endoscopists in a community-based setting.

The findings were presented here at Digestive Disease Week (DDW) 2013 during the Presidential Plenary Session of the American Gastroenterological Association (AGA) and the American Society for Gastrointestinal Endoscopy (ASGE).

Patients had been Kaiser Permanente Northern California health plan members for at least 2 years, were 50 years of age or older, and were followed for up to 10 years.

The investigators evaluated only colonoscopies performed by 136 experienced endoscopists.

Physician ADR was the percentage of screening examinations performed during the full study period in which at least 1 adenoma or a colorectal cancer was detected. The outcome was colorectal cancer occurring 6 months to 10 years after any colonoscopy that did not initially detect cancer.

Investigators excluded colorectal cancers occurring within 6 months after the index colonoscopy.

The study evaluated potential predictors of subsequent cancer risk, including physician ADR, examination type, and patient sex, age, race, ethnicity, family history, and Charlson comorbidity score.

Investigators identified 314,872 colonoscopy examinations and 712 occurrences of postcolonoscopy interval cancers. Physician ADR was an independent predictor of subsequent colorectal cancer risk following a negative colonoscopy, Dr. Corley reported.

"Patients whose colonoscopies were performed by endoscopists with lower ADRs were more likely to be diagnosed with subsequent colorectal cancer than patients whose endoscopists had a higher ADR," he said. "Cancer risk increased linearly with decreasing physician ADR, and there was no clear threshold above which there was no further improvement."

Table. Risk of Interval Cancer by Adenoma Detection Quartiles

Adenoma Detection Rate Quartile (%) Hazard Ratio 95% Confidence Interval
<19 1.91 1.44 - 2.52
19 - 24 1.77 1.27 - 2.47
24 - 28 1.64 1.23 - 2.18
28 - 33 1.34 0.97 - 1.84
>33 1.00 Reference


The analysis was also able to link ADR quartiles and risk for death. The hazard ratio was 2.63 for patients whose physicians fell into the lowest ADR quartile, compared with those with the highest ADRs, he reported.

"We found a 3% increase in interval colorectal cancer risk and 4% increase in risk of colorectal cancer death for every 1% difference in ADR," he noted.

The inverse relationships were observed for male and female patients, distal and proximal interval cancers, early- and late-interval disease, advanced-stage interval, and interval colorectal deaths.

Among the strengths of the study, according to Dr. Corley, are its "comprehensive capture of procedures and pathology and its ability to adjust for patient demographic mix per provider." In addition, it involved a large pool of experienced, community-based providers and followed patients for up to 10 years.

Its limitations included the inability to adjust for bowel preparation or extent of examination, he acknowledged.

"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.

Asked by Medscape Medical News to comment on the findings, Kenneth McQuaid, MD, from the University of California, San Francisco, and Program Chair of the ASGE, said that the study "confirms, with a large number of gastroenterologists and health organizations involved, the importance of ADR."

The data are suggesting our thresholds are too low. Dr. Kenneth McQuaid

Dr. McQuaid noted the lack of an upper threshold or limit to the benefit of high detection rates. "The higher the ADR, the better," he said. "We should probably be shifting these ADR standards up higher to determine what is a quality endoscopic exam. The data are suggesting our thresholds are too low."

The ASGE currently suggests ADRs of 15% in women and 25% in men as thresholds for quality assurance in screening colonoscopies.

Although ADR has not yet become a formal metric that is linked to physician payment, "it may come to that," Dr. McQuaid predicted.

Dr. Corley reported grant and research support from Pfizer Pharmaceuticals, which was unrelated to the current study. Dr. McQuaid has disclosed no relevant financial relationships.

Digestive Disease Week (DDW) 2013. Abstract 9. Presented May 18, 2013.


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