Doctors' Skill at Colonoscopy May Affect Patients' Colon Cancer Risk: Study

WEDNESDAY April 2, 2014, 2014 -- Your risk of developing colon cancer may depend partly on having a doctor who often spots precancerous growths during patients' colonoscopy screenings, a new study suggests.

Colonoscopy is one of the ways doctors screen for colon cancer. It's effective because it can detect not only tumors, but also precancerous polyps -- which can be removed then and there.

Doctors vary in how often they pick up precancerous polyps, or adenomas. But it hasn't been clear whether a doctor's adenoma detection rate is actually related to patients' risk of eventually developing colon cancer.

New findings, reported in the April 3 New England Journal of Medicine, points to an association.

Looking at records for more than 224,000 California patients, researchers found that when doctors had a higher adenoma detection rate, their patients had a lower risk of developing or dying from colon cancer.

For every 1 percent increase in a doctor's adenoma detection rate, patients' risk of developing cancer over the next decade dipped by 3 percent.

Presumably, that's because precancerous growths are being removed and never have a chance to progress, said Dr. Douglas Corley, a gastroenterologist at Kaiser Permanente in Oakland, Calif., who led the study.

Corley called the findings a "first step" toward using doctors' adenoma detection rates as a quality-of-care measure that's reported to Medicare and made widely available to the public.

Until then, patients can ask their doctors what their detection rate is, Corley said.

A gastroenterologist not involved in the study agreed.

"Many (doctors) make quality measures available to their patients," said Dr. Lawrence Kim, who serves as the community private practice councilor for the American Gastroenterological Association (AGA).

That information may be in the written materials your doctor gives you, or even on the practice's website, Kim said.

And what is a "good" adenoma detection rate? Some "benchmarks" have been proposed, Kim noted: a 25 percent rate or higher for men, and 15 percent or higher for women. (Adenomas are more common in men.)

But those recommendations are based on limited research evidence. And Corley said that's one reason his team did this study.

The researchers were able to scour electronic health records for more than 224,000 Kaiser Permanente patients who underwent colonoscopy screenings between 1998 and 2010. Among the 136 gastroenterologists who performed those procedures, the adenoma detection rate varied widely -- from a low of 7 percent of all colonoscopies, to more than 52 percent.

Corley's team then broke the doctors into five groups: In the group with the highest adenoma detection rate -- finding them in 33 percent to 52 percent of all colonoscopies -- patients developed colon cancer at a rate of about 0.05 percent per year.

That compared with almost 0.1 percent per year among patients whose doctors had the lowest adenoma detection rates -- finding the growths in around 7 percent to 19 percent of all the colonoscopies they performed.

There are several potential reasons that doctors' adenoma detection rates would range widely, Corley said. One, he noted, is "just the random variation in the patients doctors see."

If one doctor has more female patients, or younger patients, than another doctor, it makes sense that their adenoma detection rates would be different, Corley explained.

But skills count, too. "There may be differences in how well doctors are able to see and remove adenomas," Corley said. His team is now studying whether "enhanced training" helps improve adenoma detection rates among doctors with lower numbers.

Colonoscopies should be done every 10 years beginning at age 50 through age 75, when screening then becomes an individual decision to be made with your doctor, according to the U.S. Centers for Disease Control and Prevention.

While the new study found a link between doctors' rates of detecting adenomas and patients' risk of later developing colon cancer, it didn't establish a cause-and-effect relationship.

The AGA's Kim noted that the detection rate is only one measure of colonoscopy quality. Some others include the percentage of procedures where a doctor visualizes the entire colon, and whether he or she follows professional guidelines on patients' overall care.

"In the future, we expect that quality measures for colonoscopy will be reported to external entities such as Medicare, and made publicly available," Kim said.

Until then, he and Corley said you can ask for any figures your doctor already provides. And if your doctor is voluntarily offering such information, that's probably a good sign.

"The fact that a (doctor) is willing to measure her own performance, in itself, likely indicates a commitment to quality care," Kim said.

More information

The U.S. Centers for Disease Control and Prevention has more on colon cancer screening.

Posted: April 2014


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