Ask radiology experts and virtually all of them will say that virtual colonoscopies are a less expensive, less invasive and effective alternative to conventional colonoscopies to screen for colorectal cancer. Yet there’s a flip side to that view – that CT colonography, as it is more formally known, is inefficient, since a regular colonoscopy must follow if the CTC finds anything suspicious.

 

That debate, raging in medical circles for some time, seemed to abate last

 

September, when results of a national clinic trial demonstrated that the noninvasive technique is as accurate as conventional colonoscopies at detecting cancer and large precancerous polyps. That calm was short-lived, however. In February, the federal Centers for Medicare and Medicaid Services announced a tentative decision to end Medicare coverage for the procedure, citing among other things a desire to rein in the program’s skyrocketing imaging costs. CMS held off on a final decision, allowing a 30-day comment period. At press time, a final decision hadn’t been announced.

 

First with the patient on his or her back and then on the stomach, CT colonography uses graphical software to transform the information gathered through multiple imaging slices into two- and three-dimensional images.

 

Are the results as reliable? Judy Yee, MD, professor and vice chair of radiology at the University of California, San Francisco, answered that question with a quick “yes.” A member of the American College of Radiology’s Colon Cancer Committee, Yee said in an interview with Medical News that CTC holds multiple advantages over conventional colonoscopies, not the least of which is a dramatically decreased chance of perforating the colon wall. “The chance is about 20 times lower than for a colonoscopy,” she said, adding that there’s also a decreased risk of complications such as bleeding and infection with the “less-invasive” procedure.

 

With CTC, the patient’s colon is still distended with either room air or carbon dioxide. He or she still must undergo bowel cleansing similar to colonoscopy, “although researchers, including myself, are working on a nonlaxative version of CT colonography, where patients ingest a tagging agent and then, using specific software, we can subtract out that tagged material,” Yee said.

 

While conventional colonoscopy patients must be sedated, that’s not the case for CTC patients. “With the regular colonoscopy, the patient is put to sleep, and they need somebody to drive them to the site and drive them home. So usually, they lose a full day’s worth of work, and somebody else does as well,” she said. What’s more, the procedure is shorter, usually just 15 to 30 minutes.

 

Yet Yee said one of the top advantages of CTC is the bonus view afforded physicians. “Because it is a regular CT scan, we get to see everything outside of the colon as well,” she said. “So let’s say a patient comes in with abdominal pain. The reason may not be the colon – it may be something else. We’re able to detect other types of lesions like abdominal aortic aneurisms or masses in the organs of the abdomen.”

 

As for CTC’s effectiveness, the ACRIN national trial looked to be the final word. On Sept. 18, 2008, results of the American College of Radiology Imaging Network trial, sponsored by the National Cancer Institute, were published in the New England Journal of Medicine, recommending adoption of CTC “into the mainstream of clinical practice as a primary option for colorectal cancer screening.” The trial enrolled more than 2,600 patients at 15 sites nationwide, the largest multi-center study to compare CTC’s accuracy against conventional colonoscopy. CTC was found to be “highly accurate” for the detection of intermediate and large polyps. In fact, 90 percent of the polyps 1 centimeter or larger were detected by CTC, and even polyps as small as one-half centimeter were detected “with a high degree accuracy.”

 

The number of private payers agreeing to foot the bill for CTC, at least under some circumstances, is slowly growing. That’s one reason why Medicare’s reversal of its position shocked many in radiology circles, who rallied after the February announcement to flood CMS with objections.

 

Yet there was a warning flag: Last October, the U.S. Preventive Services Task Force, an independent advisory board that makes recommendations regarding clinical prevention services, said that “evidence is insufficient to assess the benefits and harms.”

 

CMS cited several reasons for its tentative denial of payment: that CTC isn’t as effective in detecting small polyps, that evidence is lacking for CTC’s effectiveness in the age group Medicare covers, that follow-up conventional colonoscopy might still be required and that findings not related to the colorectal screening would require additional healthcare expenditures. “Yes, we do see things outside of the colon, and that can be very much a positive and can help patients,” Yee said, arguing against Medicare’s view.

 

Adding to the equation is Medicare’s bill for medical imaging: In 2008, the Government Accountability Office said that Medicare in 2006 spent more than $14 billion on imaging services, twice the amount it spent in 2000. In today’s budget-hawk environment, imaging has been identified as a category to scrutinize.

 

Yee said the most important point, however, is CTC’s efficacy with patients, that those averse to a conventional colonoscopy might just give CTC a try. “Currently, the American population remains underscreened for colon cancer, and studies have shown that less than 40 percent of the American public actually comes in for any kind of colon-cancer screening,” she said. “CTC can save lives.”