The Case for Keeping Colonoscopy

When a story breaks in The New York Times about a major health issue, such as colon cancer, we pay attention. So when Gina Kolata had a story Tuesday morning with the headline "Colonoscopies Miss Many Cancers, Study Finds," we needed to take a look.

The Times reported that a Canadian study published in the Annals of Internal Medicine had concluded that the common test, which scans the inside of the colon for cancers, "missed just about every cancer in the right side of the colon, where cancers are harder to detect but is where about 40 percent arise."

"And it also missed roughly a third of the cancer in the left side of the colon," the report said. "Instead of preventing 90 percent of cancers, as some doctors have told patients, colonoscopies might actually prevent more like 60 [percent] to 70 percent."

VIDEO: Colonoscopy Effectiveness Debated Play

ABC News medical editor Dr. Tim Johnson discussed the story briefly on "Good Morning America," but he focused more on practical questions, such as the need for complete bowel preparation.

We had seen a summary of the study Monday and nothing suggested as dramatic a finding as the Times story. What made the Times story sound so worrisome were the phrases such as "much less accurate than anyone expected" and quotes that included "a shock," "a really dramatic result" and "it makes you step back and worry, 'what do we really know?'"

So we used the network of experts we regularly e-mail and took another look at the study.

A Closer Look at Colonoscopy

We asked three questions of three groups: colorectal surgeons, gastroenterologists and primary-care physicians. We wanted to know what primary-care physicians thought because there was a suggestion that perhaps the Canadian study did not reflect the best quality colonoscopy because only one-third of the doctors who did the procedure were gastroenterologists.

We asked these questions:

1. What was their view of whether the statement by Gina Kolata was an accurate summary of the study?

2. What were their views on the limitations of the study?

3. What is their advice to people about bowel preparation?

We expected to hear about "shock" and fears of the procedure being less accurate than thought. We did not hear that.

On the "90 percent" expectation figure, Dr. Dennis Ahnen, gastroenterologist and staff physician at the Denver VA Medical Center, said that this effectiveness statistic comes from the National Polyp Study done in the United States.

What this study found was that subjects whose polyps had been removed once they were found through a colonoscopy (a procedure called colonoscopic polypectomy), and who were subsequently monitored by their doctors for additional polyps, had a 75 percent to 90 percent or so decreased risk of subsequent colorectal cancer compared to historic control groups.

"There are, however, several other study groups that have had colonoscopic polypectomy and surveillance who have not had nearly as a beneficial effect as those in the National Polyps study and are more consistent with the results of the Annals paper," Ahnen said.

In other words, there are plenty of studies that suggest the effectiveness may be lower than 90 percent.

And the primary-care doctors had some warnings about depending upon the results from studies done at academic institutions. Dr. Lee Green, professor in the Department of Family Medicine at the University of Michigan, said the claims of 90 percent effectiveness cited in the Times story "is yet another demonstration of the difference between theory and real world practice."

"In theory, if the test were always done perfectly, it could prevent 90 percent of cancers," Green said. "The real world is a much messier place than the theories of academic sub-specialists."

Joanna Schaffhausen, a doctoral degree holder, reviews our studies day to day. She saw several problems with the study. One she mentioned was "the overall poor rate of colonoscopy screening in this study, period."

"Just 7 percent of the patients in the group that died of colon cancer were screened with colonoscopy compared to just 10 percent of those in the control group," she said. "This is an extremely low rate of screening and represents just a 3 percent difference between the study population and the control group. Because of the size of the analysis, they were still able to do their calculations, but really if you are trying to detect the effectiveness of colonoscopy you would like to see much higher screening rates."

And there were other concerns. Dr. John Petrini, president of the American Society for Gastrointestinal Endoscopy, cited several.

"The colonoscopies were performed primarily by nongastroenterologists -- family practice, surgeons and primary-care doctors -- who are not trained to the extent of gastroenterologists," he said. "Second, it is a retrospective study and may not reflect current practices, where better preparations and slower examinations techniques are being employed, as well as the increased recognition of right-sided lesions."

As for the study findings that nearly all the cancers on the right side were missed, there was a lot of comment about how these results in the right side suggest there is a problem with the study.

Dr. Douglas Rex, director of endoscopy at Indiana University Hospital in Indianapolis, who was extensively quoted in the Times story, said the study "doesn't reflect the overall literature in that there is no protection against right-sided colon cancer in this study. Other studies suggest the same trend but not a complete lack of effect in the right colon."

And colorectal surgeon Dr. Eric Kaplan of Plano, Texas, said, "I believe that some right-sided lesions may be missed, but I would be surprised at the rate being as high as quoted in the study."

Importance of an Experienced Hand

Many of the gastroenterologists said you need to seek out someone who is experienced doing colonoscopy. Dr. James Church, a colorectal surgeon at the Cleveland Clinic, said people should ask their doctors about the number they have done.

"Most colonoscopists worth their salt should know their completion rate," he said. "If they don't know, move on to the next one."

How many is enough to be experienced? "I think 1,000 minimum, which is about three years' experience for a not-very-busy endoscopist," Church said.

Everybody agreed bowel preparation was critical, and Rex, who was quoted in the Times story, emphasized in the article that split preparation -- taking half of the laxative the night before the screening test and the rest in the morning -- was important.

Dr. Roshini Rajapaksa, a gastrointestinal specialist and assistant professor of medicine at the New York University School of Medicine, agreed that this is "a great idea -- and one that many of us are currently adopting."

But, she added, "patients are not so crazy about it because they are worried about having 'accidents' on their way to the office or hospital."

So the Times story provided a valuable service by raising some important issues about bowel preparation and experience of the colonoscopist. However our medical experts were not convinced that there was the need for the urgent sense of the story providing us with scary news about a test that is pretty darn effective.

Roger Sergel is head of the ABC News Medical Unit in Needham, Mass.