ORLANDO – The rate at which physicians detect adenomas during colonoscopy is an independent risk factor for their patients’ risk of developing colorectal cancer following a negative colonoscopy, according to findings from a large observational study.
Physicians with low rates of adenoma detection during screening colonoscopies were more likely to have patients who developed interval colorectal cancers. For every 1% decline in the physician adenoma detection rate, colorectal cancer risk increased by about 3%, and the risk of death related to colorectal cancer increased by about 4%, Dr. Douglas A. Corley reported at the annual Digestive Disease Week.
The findings suggest that adenoma detection rates – the proportion of screening colonoscopies in which a physician detects at least one adenoma – could be a useful quality metric, he said.
Dr. Douglas Corley
The findings were noted in a study of 314,872 colonoscopy exams in which 8,708 colorectal cancers were detected. Interval colorectal cancers – cancers diagnosed at examinations that took place at least 6 months after the index colonoscopy – were seen in 712 patients, said Dr. Corley, of the Kaiser Permanente Division of Research, Oakland, Calif.
Most (60%) interval cancers were proximal. In total, 34% were advanced cancers, and about 20% led to colorectal cancer–related deaths. About one-third were diagnosed in the early interval period, between 6 months and 3 years. The remaining two-thirds were diagnosed 3-10 years after an initial negative screening colonoscopy, Dr. Corley said.
Physician adenoma detection rates ranged from 7% to 52%, which are rates consistent with prior reports in the literature. There was a linear association across five quintiles of physician adenoma detection rates and subsequent patient colorectal cancer risk. "There’s no threshold effect above which increases in adenoma detection rate were without benefit," Dr. Corley said.
After adjusting for colonoscopy indication and patient age, sex, race/ethnicity, family history of colorectal cancer, and Charlson comorbidity score, the risk was about 80%-90% higher among patients of physicians whose adenoma detection rates were in the first or second quintile, as compared with patients of physicians with detection rates in the highest quintile.
A similar pattern was seen for advanced colorectal cancers, and the correlation was even stronger. The risk was increased more than twofold among patients of physicians in the bottom two quintiles of adenoma detection rates, compared with patients whose physicians were in the top quintile, he said.
Risk of death from colorectal cancer followed a similar pattern. Patients of physicians in the first and second quintiles had more than a 2.5-fold increased risk of colorectal cancer death compared with patients of physicians in the top quintile. Risk did not differ by patient status or by cancer location, Dr. Corley said.
Patients included in the study were aged 50 years or older, had been members of the Kaiser Permanente Northern California health plan for at least 2 years, and had a negative colonoscopy for any indication between 1998 and 2010. Only those colonoscopies performed by experienced endoscopists – those who had performed more than 300 colonoscopies and more than 75 screening exams during the study period – were included in the study.
Patients were followed for 10 years or until another negative colonoscopy was performed, health plan membership was terminated, a diagnosis of colorectal cancer was made, or Jan. 31, 2011 – whichever came first.
Dr. Corley has received grant or research support from Pfizer Pharmaceuticals.