Your patient recently celebrated her 50th birthday. After a few weeks of partying, she’s ready to turn to the less glamorous work that comes with having lived half a century. First up is the colonoscopy.
She’s impressively well informed and so it’s not a surprise when she comes to your primary care office with a question. She read that the percentage of a gastroenterologist’s colonoscopies that find pre-cancerous polyps, the so-called “adenoma detection rate,” is an important marker of a doctor’s ability to perform high-quality colonoscopies. She wants to know what you think – is one colonoscopy as good as another, or should she care about the adenoma detection rate?
Your gut answer is yes. After all, various professional societies have recommended adenoma detection rate cut-offs of higher than fifteen percent for female patients and twenty-five percent for male patients as indicators of quality colonoscopies. And the Center for Medicare Services recently proposed that this rate become a reportable quality measure.
But the data supporting this assumption have been scant – until now. In this week’s issue of NEJM, Douglas Corley and colleagues report that yes, patients of physicians with a higher adenoma detection rate have lower rates of colon cancer in the years after colonoscopy.
To investigate their question, researchers examined the records of approximately 300,000 colonoscopies, performed by 136 gastroenterologists. They calculated the adenoma detection rate for each gastroenterologist and found this figure to range broadly between physicians, from a low of under 10 percent to a high of just over 50 percent. The researchers then followed the patients who’d undergone colonoscopies for up to 10 years and monitored for the development of interval cancers – defined as colon cancer diagnosed between six months and ten years after colonoscopy.
The findings are impressive. When researchers split the patients into five groups based on their physicians’ adenoma detection rates, they found that the risk of interval cancers – that includes advanced colon cancer and fatal colon cancer – decreased in a linear fashion as adenoma detection rates increased. That meant patients of physicians with the highest adenoma detection rates were nearly half as likely to be diagnosed with an interval cancer than those whose physicians were in the lowest group. In fact, each one percent increase in adenoma detection rate brought with it a three percent decrease in interval cancer risk and a five percent decrease in risk of fatal colon cancer.
In their discussion, the authors note that in addition to better detection of pre-cancerous lesions leading to decreased rates of subsequent cancers, it’s also possible that those physicians who detected more adenomas performed better resections. That question isn’t answered by the current results. We also don’t know the effect of different qualities of bowel preparation, length of the exams in the different groups, or differences in the complication rates.
Ultimately, these results establish an association between higher adenoma detection rates and decreased colon cancer incidence, not a causal link. Despite that limitation, the authors conclude that their findings “support the validity of adenoma detection rate as a quality measure of physicians’ performance of colonoscopy in community practice.”
For your patient? Just get the colonoscopy.