CT colonography experts assess new screening guidelines

March 17, 2008
Shalmali Pal

The American Cancer Society’s green light for CT colonography as a preferred modality for colon cancer screening is a major victory for proponents, but they are not resting on their laurels. Imaging and gastroenterology experts must gear up for widespread dissemination of the procedure, according to Drs. Judy Yee and Beth McFarland.

The American Cancer Society's green light for CT colonography as a preferred modality for colon cancer screening is a major victory for proponents, but they are not resting on their laurels. Imaging and gastroenterology experts must gear up for widespread dissemination of the procedure, according to Drs. Judy Yee and Beth McFarland.

Last week, the ACS released updated colorectal cancer screening guidelines, adding CTC to its approved list of methods. The five-year guidelines are available online. They highlight CTC as a test that "finds polyps and cancer" and should be performed every five years.

"I think this is a new day for CTC," said Yee, vice chair of radiology at the University of California, San Francisco. "The guidelines recognize a lot of the science. The ACRIN 6664 colonography trial created huge momentum to get CTC out there to the public. "

Released in late 2007, outcomes from that trial deemed CTC comparable to standard colonoscopy for screening intermediate and large-sized polyps. In the trial, the prevalence of lesions 6 mm or larger came in at a low 8.3%.

A major thrust of the ACS guidelines is that certain tests, including CTC, are better at finding polyps and cancer, while others, such as fecal occult blood testing, are less likely to pinpoint polyps but still adept at cancer detection.

"The current guidelines break the tests down into two broad categories: those that detect cancer versus those that prevent cancer with the detection of polyps, the precursors to cancer," said McFarland, chair of the American College of Radiology's colon cancer committee. "We still need further research and multidisciplinary consensus in specific areas, but these are reasonable recommendations from the data that we have."

A number of interested parties weighed in on the updated guidelines: the ACR, ACS, American Gastroenterological Association, and American College of Gastroenterology.

"I think it's a tremendous step forward that we could write this kind of multisociety collaborative guideline. It was quite a feat to keep everyone at the table and work through this, but it's a very rewarding and satisfying result," said McFarland, who is also with St. Luke's Hospital/Center for Diagnostic Imaging in Chesterfield, MO. "I think it is an objective document that honestly evaluates the strengths and weaknesses across all the colorectal cancer screening modalities."

The question of which specialty should perform CTC has been the source of friction, and the guidelines may de-escalate some of that discord. Ideally, radiologists and gastroenterologists will continue to work together, but other circumstances may ultimately influence who performs CTC screening, Yee said.

"You have to take into consideration local resources, expertise, and interest in performing CTC. These parameters will be different depending on the site. Obviously, radiologists developed the technique, and we receive our training in imaging. Gastroenterologists are the experts at looking at the colon lumen on colonoscopy," she said. "I'm certain that there are gastroenterologists who could excel at performing CTC, but so many patients are currently underscreened for colon cancer. I think gastroenterologists will be kept quite busy with referrals from the radiologists who perform CTC screening."

McFarland agreed with Yee that different practice patterns will decide who performs CTC screening. Of course, economics will also play a large part in making that determination, she said.

"We will all depend on getting appropriate reimbursement for the time and expertise needed to do CT colonography in clinical practice," she said.

Currently, there are two CPT 3 billing codes in place for CTC. The hope is they will be bumped up to CPT 1 codes.

"But that won't happen for 2009. In the meantime, I think there should be an effort for a national coverage determination for screening CTC," Yee said. "The current ACS guidelines help to justify the development of this NCD. In almost all states, there are already local coverage determinations for diagnostic CTC, with very specific limitations, using ICD 9 codes. The NCD can be a way to bridge screening codes until CPT 1 codes are approved."

Regardless of who conducts the exams, McFarland and Yee stressed that proper training is a must. To that end, the ACR is slated to open a training facility in April for CTC and other imaging procedures. The society is currently working on a certification process for physicians who wish to perform CTC. The AGA also offers CTC training modules. "Hands-on" should be the operative word in any educational offering, according to Yee.

"Attendance at an interactive training course where participants actually get to independently manipulate cases at a workstation, with close supervision by experienced faculty, is necessary to start learning CTC. Continued education is also needed," said Yee, author of the textbook Virtual Colonoscopy.

Mastering CTC technique is crucial, but so is learning about the modality from a more global perspective, McFarland said.

"Quality assurance is key to ensure proper use and quality of CTC service, including proper selection of patients, using low-dose protocols and good bowel preparation for patients. We know that there were learning curves during the technology development, so it's very important that as (CTC) becomes more broadly implemented, clear and helpful QA guidelines are laid down," she said.

Finally, there is the matter of public awareness. According to the ACS, less than half of U.S. patients who are eligible for colon cancer screening actually have any kind of test done. With regard to colonoscopy in particular, Canadian researchers found that perceived pain was the number one reason people gave for shying away from the procedure. Even those patients who had undergone colonoscopy and no longer worried about pain were still not inclined to follow a recommended screening schedule (Can J Gastroenterol 2008;22:41-47).

The ACS guidelines offer screening options to patients and their physicians rather than forcing the same exam on everyone.

"In general, raising public awareness and equipping primary-care physicians with an understanding of the different tests out there will be key," McFarland said. "It's not just a matter of doing CTC because it's less invasive than colonoscopy. It's a collaborative message to the community that there is an array of tests ... and (that) different tests are better, depending on the patient's age, comorbidity, and symptoms."

For more information from the Diagnostic Imaging archives:

American Cancer Society blesses virtual colonoscopy for screening

CTC pushes for rightful place in colorectal cancer screening

CT colonography matches gold standard in eagerly awaited ACRIN trial results

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