The Evolution of ERCP

CT Colonography
Wave of the Future or Possible Threat?

Computerized tomographic (CT) colonography offers a means of viewing the colon for polyps without sedating the patient. Just how safe and effective is this technique?

CT colonography, in limited use since 1994, has received a great deal of press, not all of it positive. But evidence shows that the procedure, although not a replacement for traditional colonoscopy, may be a viable option for those who cannot or will not undergo colonoscopy.

CT colonography is performed using rapid helical CT scanning and software to view the colon, which is inflated with room air or carbon dioxide. Its use has been controversial since the concept was first described in 1994.

“We’re trying to avoid using the term ‘virtual colonoscopy’ because it really isn’t anything like that,” clarifies Christopher J.

Gostout, MD, president of the American Society for Gastrointestinal Endoscopy (ASGE), and professor of medicine at the Mayo Clinic College of Medicine.

Asked if CT colonography is a valid approach to screening for colorectal cancer, Gostout replies, “It has a role. We have an obligation to effectively screen our population for colorectal cancer. All possibilities for screening should be looked at, and should be supported.

I don’t think we should have a negative view toward CT colonography. There are some shortcomings to it right now; we need a lot more experience with it. More refinement needs to go into the technique, to the software.”

In December 2003, researchers published a study in the New England Journal of Medicine (NEJM) showing that CT colonography with a three-dimensional approach was an accurate means of screening for colorectal neoplasia in asymptomatic average-risk patients.

“The article in the NEJM represents one of the latest developments in using this method, especially software and fly-through capability, but not everyone has that,” Gostout observes. “There are issues such as still needing to give a patient a full bowel prep.

It’s not necessarily a comfortable procedure; one’s colon is filled up with air like a balloon. I think gastroenterologists should embrace CT colonography and determine when to use it appropriately.

But right now, the issues of cost, the technology itself and the time involved for interpretation are keeping it from being a widespread screening technique.”

The American College of Gastroenterology (ACG) says its position and response to CT colonography depends on several factors; it will “support any colorectal cancer screening technology that is in the best interest of patients;” it will not support reimbursement for the procedure “until there is validation that the results of the recent NEJM trial are generalizable;” patients with polyps of 6 mm or larger detected by CT colonography will be referred for colonoscopy and polypectomy; and “conventional colonoscopy must be improved.” The NEJM paper is a “call to action”, the ACG says, and it encourages the gastroenterology field to view the technique as a challenge to improve more long-standing techniques.

“It’s an exciting technology, and it’s still in the process of evolution or development,” Gostout says. “Since we are attempting to in effect do a colonoscopy-like examination using CT scanning, who’s going to interpret CT colonography? Maybe it’s best off being interpreted by gastroenterologists as opposed to radiologists.

There are going to be some very interesting developments occurring as this technology moves along and gains experience.”

The green line in the center of the colon lumen shows the direction of endoluminal travel. Image by Hubert A. Shaffer, MD.

Gostout notes that even with its tremendous potential, “right now it’s hard to beat [diagnostic] colonoscopy, because it can be done relatively quickly, comfortably and safely. The endoscopists in the ASGE are highly skilled at colonoscopy, and it has a gold standard that is going to be tough to beat. The big plus for colonoscopy is you get your screening and removal of any polyps at the same time. That’s going to be very hard to supplant with even the most ‘wow’ type of technology. But again, the demand is for effective screening of our population, and if we can’t meet that, we need to embrace other methods that can at least screen the population; we can then decide what to do with polyps that get found.”

Gostout points out that gastroenterologists might be trained in reading films from CT colonography, saying, “We’re used to spending a lot of time looking inside the colon, and we’re very familiar with the internal architecture of the colon. As that’s reproduced in a CT scan, this may evolve into something similar to cardiologists interpreting coronary angiograms; this may ultimately fall into the bailiwick of a gastroenterologist as opposed to a radiologist.”

“[CT colonography] is not going to replace traditional colonoscopy; it’s going to augment it, or be complimentary to it,” says David Beck, chairman of the department of colon and rectal surgery at Ochsner Clinic Foundation in New Orleans.

“There are some limitations that are going to limit the widespread availability of it. First of all, there are not a lot of CT scans sitting around that nobody’s using; they’re usually fairly busy. Second, the software is still being developed. Third, it takes a lot of expertise for the radiologist to interpret films.

Unfortunately, this is not currently widespread. The fourth issue has to do with reimbursement and payment.”

Cross-sectional 2-dimensional view of a polyp (on the left) and a 3-dimensional endoluminal view of the same polyp (on the right). Miniature colon model (left upper) showing the location of the polyp (blue arrow) within the colon. Image capture by Hubert A. Shaffer, MD.

Beck continues, “It takes a radiologist more time to read the films than it takes the average colonoscopist to do the procedure. It would currently be cheaper to pay a physician to do the colonoscopy than to read X-rays.”

However, there are certain patients who may benefit significantly from the procedure: “a patient with an obstructive tumor of lower bowel. This lesion prevents the colonoscopist from examining the proximal colon. Another type of patient is the one who is anticoagulated. It is risky to do colonoscopy or remove polyps in anticoagulated patients, and it is difficult, expensive and risky to take them off anticoagulation,” Beck says. “In some ways, this is like a super-duper barium enema, and that’s why ‘virtual colonoscopy’ is not a good term. It is virtual, but it is not colonoscopy. Most radiologists call it ‘CT colonography’, which is a more accurate term. The limitation is, if you find something, you can’t do anything about it, whereas with colonoscopy, there is a therapeutic option. Many centers, ours included, have arranged that if patients have an abnormal colonography, they will scope them the same day, as the patient is already cleaned out. A lot of places don’t have that capability.”

Beck points out that the researchers in the NEJM study had cutting-edge software, which is not yet widespread. “They were in a military (government) center, where reimbursement was not an issue,” he adds.

“It would be harder to do at your local hospital, because if they spent a day doing CT colographies and they weren’t going to get paid for them, the lost revenue for the procedures they could have done would be significant, so it’s kind of a double hit. You lose the money if you don’t get paid for [CT colonography]; you also lose the money you would have gotten had you done a procedure you were going to get paid for.”

Asked whether CT colonography is less expensive than traditional, diagnostic colonoscopy, Beck responds, “There’s two issues. One is the equipment you’re using, because the CT scanner itself is about $1.5 million, and then there’s the time for the radiologist to review the film. Going through the machine is pretty quick now, but the current hang-up is the time for radiologists to interpret the studies. That’s compared to colonoscopy, where you have lower equipment costs and less physician time. With colonoscopy, you do require medications and recovery time, but as this is done by nurses, the extra expense is limited.

Currently, as best I can tell, most people are charging more for CT colonography than for colonoscopy, but that’s real variable and there’s no good data on it.” CT colonography can have benefits for certain core groups of patients, “but only if it’s done correctly,” says Hubert A.

Shaffer, Jr., MD, FACR, professor of Radiology and Internal Medicine and cohead of the Division on Thoracoabdominal Imaging at the University of Virginia Health Sciences Center. “The way Pickhardt reported in NEJM in December, that’s the correct way.

Radiology has been doing it for a number of years, but it has been very time-consuming, labor-intensive, and it required a long learning curve. But with the Pickhardt procedure using the Viatronix software and hardware, I think everything has changed and now the results can be reproduced by people with much less training,” Shaffer says.

“Several things make it different. One is that we are doing the primary evaluation in three dimensions, and doing problem-solving in two-dimensional images. Secondly, we are marking as much stool and liquid as possible in advance as part of the preparation and then electronically removing it, so it creates a better bowel preparation,” he observes. “[CT colonography] never will be a substitute for all colonoscopy. I would say those patients who are already known to have polyps or cancer from past experience, those who are in family groups who have inherited disease that would make it likely or almost certain that they have or will have polyps, such as familial adenomatous polyposis, and patients with inflammatory bowel disease — those would go right on to standard colonoscopy.”

Shaffer continues, “I disagree with those who say that the virtual study is not good for screening. I think it’s excellent for screening and I think that will be its ultimate use, screening asymptomatic averagerisk persons. It will be useful for doing completion colonoscopy for those who have had a conventional study but have failed to have a complete study.”

Shaffer asserts that CT colonography should remain in the hands of radiologists, and offers several reasons in explanation:

“One is that there are extra-colonic abnormalities that can be detected. That’s not the main reason we’re doing that study, but the information is there to find significant disease in somewhere between 5 and 10 percent of the population.

Gastroenterologists are not trained or qualified to read the other information on the films or on the images. The other thing is that CT scanning is a radiologic procedure, and we are probably most knowledgeable and most concerned about radiation exposure. As long as we’re developing it, we’re going to work toward reducing the radiation dose to the patient, and improving the palatability of the procedure.”

Asked how long it might be before insurance companies begin reimbursing for CT colonography, Gostout can only hazard a guess. “Based upon my own efforts at developing new devices and methods, it generally translates into millions of dollars, and it also translates into several years. Is it going to be within three to five years? Yes, I think so. Is it going to be one to two years? I’m not certain.”

“It’s my belief that third-party payors will pay for it when it becomes cost effective, or when they recognize that it’s cost effective to do it,” Shaffer says. “The charges being charged for virtual colonoscopy are much less than the total charge for traditional colonoscopy, if you include all things, such as the cost of conscious sedation, nurse monitoring, recovery, facility charges as well as physician charges. There have been several studies that have shown roughly that if the cost of a virtual study is 46 percent or lower than the cost of colonoscopy, it becomes cost effective. Recognizing that there will still be a number of patients who will have virtual study and then need to go on to have traditional colonoscopy, that number is 30 percent or less, depending on your threshold on how big a polyp a gastroenterologist should go after and remove.”

“We develop policies based on evidence in peer-reviewed medical literature,” says Robert McDonough, MD, JD, MPP, medical director of clinical policy unit at Aetna U.S. Healthcare. “Our guidelines on preventive services are based on recommendations of the U.S.

Preventive Services Task Force and the leading primary care medical professional organizations. Our current policy is that we consider virtual colonoscopy to be experimental and investigational.”

McDonough explains, “As far as the NEJM article, I think one of the things we should note is that there was an editorial accompanying that article that did explain that there are some unanswered questions about virtual colonoscopy, about the appropriate size threshold and surveillance of smaller polyps. I think another important issue is that, at present, none of the leading medical professional organizations have endorsed the use of virtual colonoscopy for colorectal cancer screening.”

Gastroenterologists might feel threatened by CT colonography, as screening colonoscopy is often the bread and butter of a clinical practice. “I’m sure there’s an element of turf, feeling that your business may be encroached upon,” Gostout says.

“Gastroenterologists are spending a considerable amount of time performing both diagnostic or screening colonoscopy and therapeutic colonoscopy, removing polyps.

I think if our goal is truly to screen the U.S. population, we need to embrace all potential methods that can allow us to do that.

There’s going to be lots of polyps identified by alternative methods of screening, and endoscopists will still be busy, except it may shift colonoscopy from diagnostic to more therapeutic.”

Shaffer says, “Most of our [gastroenterologists] do not feel threatened, because they figure that if there are more people being screened, they will then have more patients to have interventional colonoscopies on, which have a higher value of reimbursement, and are more interesting, too, than just doing screening test after screening test.”

The CT colonography may even increase the number of people being screened, observes Shaffer. “If we’re looking altruistically at it, we say that it’s a good thing. I can’t think of any other major cancer we screen for or treat that we can actually prevent as well as cure if we catch it in an early state,” he says.

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