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Multifaceted effort propelsCT colonography forward

Diagnostic ImagingDiagnostic Imaging Vol 31 No 1
Volume 31
Issue 1

The creators of CT screening colonographyhave not waited for the medicalestablishment and insurers to accept itas an alternative to optical colonoscopy.

The creators of CT screening colonography have not waited for the medical establishment and insurers to accept it as an alternative to optical colonoscopy. Dr. Elizabeth G. McFarland described during RSNA's Annual Oration in Diagnostic Radiology how they have established the necessary training, practice management, and governance mechanisms to aid its growth once it is routinely reimbursed.

Whether Medicare will grant reimbursement remained an open question, as McFarland, medical director of CT colonography at the Center for Diagnostic Imaging in Minneapolis, described past achievements and ongoing initiatives she believes will lead to the modality's acceptance.

CT colonography was given a mixed reception at a Nov. 19 hearing before the influential Medicare Evidence Development & Coverage Advisory Committee (MedCAC). A rating of "insufficient" by the U.S. Preventive Health Task Force contradicted a new American Cancer Society guideline issued in September. The guideline concluded that enough data have accumulated to consider CTC an acceptable alternative to optical colonoscopy for colorectal cancer screening.

The ACS's willingness to wait for a confidential briefing on the results of a major American College of Radiology Imaging Network trial on colonography partially explains the differences in findings, McFarland said.

The advisory committee appeared to be more influenced by the task force's assessment, she said. It recently concluded that three tests are acceptable: fecal occult testing, flexible sigmoidoscopy, and colonoscopy.

But CT colonography was scored as insufficient, based largely on the premise that the potential harm from radiation exposure and extracolonic findings could outweigh the benefits.

"This is a little bit neutralizing," McFarland said.

The MedCAC opinion increases the likelihood that the Centers for Medicare and Medicaid Services will mandate a "coverage with evidence development" requirement if it decides to grant Medicare coverage for colonography. CMS's decision is expected in February.

Yet McFarland believes that the cohesive group of radiologists who first developed colonography will eventually win over the doubters.

"The community of CT colonography has been like a family. . . It revitalizes energy. It focuses direction. It gives us purpose. It is the culture of the effort that will motivate the future," she said.

Additional research is validating the use of computer-aided diagnosis to improve the detection of colorectal disease. Conscious of the FDA's rigorous validation standards, CAD researchers have developed ways to detect polyps and reduce false positives before case findings are graphically presented to the interpreting physician. At least four studies since 2006 have shown that CAD enhances the sensitivity of CTC, according to McFarland.

Electronic cleansing techniques promise to reduce the need for catharsis, fasting, and tagging requirements that discourage at-risk adults from screening, she said.

In terms of practice governance, ACR Practice Guidelines will be published in 2009, McFarland said. The standards will cover low-dose CT, training and competency, and results reporting requirements.

The ACR's National Radiology Data Registry will gather clinical data to measure quality and patient outcomes.

The program, thus far tested at five sites, will track radiation dosage, bowel preparation, proper insufflation, and outcomes measures including extracolonic findings, McFarland said.

Proper training requires work with a competent instructor to master workstation evaluations across a range of known morphologies, McFarland said. The Society of Gastrointestinal Radiologists, the Society of Computed Body Tomography and Magnetic Resonance, the Center for Virtual Colonoscopy at Boston Medical Center, and the ACR Training Facility at Reston, VA, have all established training programs.

Dr. Michael E. Zalis, director of CT colonography at Massachusetts General Hospital, and colleagues introduced the C-RAD reporting lexicon for colonography in 2005 (Radiology 2005;236[1]:3-9). Inspired by the BI-RADS breast imaging lexicon, it offers a standardized way to report colorectal findings. Additional efforts are directed at concerns about radiation dose and extracolonic findings.

Ultimately, CT colonography involves a radical change from optical colonoscopy. Unlike the invasive approach, suspicious polyps are detected but not necessarily removed. CTC aims at eliminating costly, unnecessary polypectomy, McFarland said.

"The emphasis now is to take these findings, but then to put them into the clinical context of patient age, comorbidity, colorectal risk, and then manage the patient," McFarland said. "This is done instead of just being inside the colon and taking everything out that you see."

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