A study comparing computed tomography colonography (CTC) and traditional optical colonoscopy (OC) using an endoscope for colorectal cancer screening may put the argument over whether CTC is useful as a screening tool to rest — or perhaps not.

The study, published in the Oct. 4 edition of the New England Journal of Medicine, concluded that “primary CTC and OC screening strategies resulted in similar detection rates for advanced neoplasia, although the numbers of polypectomies and complications were considerably smaller in the CTC group.”

One of the researchers at the University of Wisconsin School of Medicine and Public Health (Madison), Perry Pickardt, MD, told Diagnostics & Imaging Week that this study goes beyond validation of the technology.

OC is performed by a gastroenterologist who snakes an endoscope into the rectum and through the colon. CTCs and the images they produce are analyzed by radiologists, much like any other diagnostic imaging procedure. Both CTC and OC require bowel cleansing prior to the procedures, which is one aspect of either procedure that most patients do not like.

Gastroenterologists say that OC is both diagnostic and therapeutic, since polyps, whether benign or pre-cancerous, can be removed during the procedure, potentially preventing colon cancer from ever occurring by removing such polyps before they can turn into the disease.

The study compared primary CTC screening in 3,120 adults (mean age 57) with primary OC screening in 3,163 adults (mean age 58.1).

According to the study, “The main outcome measures included the detection of advanced neoplasia (advanced adenomas and carcinomas) and the total number of harvested polyps.”

In the study, the researchers report advanced neoplasia was confirmed in 100 of the CTC group, or 3.2%, and in 107 of the patients in the OC group, or 3.4%, “not including 158 patients with 193 unresected CTC-detected polyps of 6 mm to 9 mm who were undergoing surveillance.”

While 561 polyps were removed in the CTC group, 2,434 were removed in the OC group. According to the study, there were seven “colonic perforations” in the OC group and none in the CTC group. Perforation of the colon with the endoscope used by gastroenterologists is one of the potential problems associated with traditional colonoscopy.

In the study, “important outcome measures included detection rates for advanced adenomas and adenocarcinomas for various categories of polyp size and overall polpectomy rates.

“Those observations provided an assessment of CTC as a selective filter for therapeutic OC in the detection of advanced neoplasia,” the study reported.

Pickhardt said the University of Wisconsin study, along with a study completed by the American College of Radiology Imaging Network (ACRIN; Philadelphia) reported in late September, should erase any remaining doubt about CTC’s usefulness.

The ACRIN study has not been published, although results were reported for those attending the ACR fall meeting.

The results of the two studies may convince the federal government that CTC should be reimbursed by the Centers for Medicare & Medicaid Services (CMS). Lack of reimbursement has been one of the primary stumbling blocks to greater adoption by radiologists, Pickhardt said.

For example, Viatronix’s (Stony Brook, New York) device for CTC, which was used in the University of Wisconsin study, was approved by the FDA in April 2004.

However, since traditional colonoscopy is covered by payors, Pickhardt said that patients often don’t want to pay $1,000 or more out-of-pocket for the CTC procedure. Until that procedure is covered, there isn’t likely to be wide utilization, he said.

In fact, federal recommendation and coverage of CTC as a screening tool for colorectal cancer would have to be passed via legislation in the U.S. House and Senate, he said, and there are efforts under way to make that happen.

As a result of the ACRIN study, MGT Capital Investments issued a statement as the parent company of Medicsight (London), a company providing computer-aided detection (CAD) and image analysis software, including ColonCAD.

Commenting on the ACRIN study, Medicsight CEO David Sumner said it confirmed “that CT colonography is a genuine and robust option in the armamentarium that physicians have at their disposal when screening for colorectal cancer.

“This is likely to lead to a material increase in the use of CT colonography for screening populations aged 50 or more who are most at risk of developing this devastating condition,” Sumner said.

Meanwhile, the American College of Gastroenterology (Bethesda, Maryland), which represents gastroenterologists who conduct the traditional optical colonoscopy, issued comments offering their own perspective on the results of the University of Wisconsin researchers’ CTC study, not unexpectedly putting an emphasis on caution.

“While all of us on the front lines of battling colorectal cancer will welcome effective and clinically proven new tools, the evidence needs to be closely evaluated, and patients need to recognize that a virtual test is not without significant potential risks in its own right,” said David Johnson, MD, president of the ACG. He also said that the organization saw a “major limitation” in the fact that the study was nonrandomized.

Johnson noted that in the Wisconsin study, about 8% of CTC screenings resulted in referrals for OC for removal of suspicious polyps. He also noted that the total numbers of polypectomies in the CTC and OC groups were 561 and 2,434, respectively, so “far more potentially cancerous polyps were removed by colonoscopy.”

Regarding the seven perforations that occurred in the OC group, Johnson said this is “twice what is expected in a screening population,” but that more information is needed before the group can interpret those results.

“The nonrandomized design of this study is problematic,” he said. “The higher rate of cancer in the OC group suggests that the study populations were different ...”

The ACG said that an “important reality” of CT colonography is that patients most likely will need a follow-up with a traditional colonoscopy, and that the organization has concerns about the “economic impact to the healthcare system of separate diagnostic and therapeutic exams.”