The ACRIN CT colonography study proves the efficacy of the noninvasive test

The results are in—and they should make everyone cheer. CT colonography can be as effective as colonoscopy in discovering cancer. That was the finding of the recently completed ACRIN trial, which was sponsored by the National Cancer Institute.

The study’s results could signal a sea change in the way colon cancer is found, how it’s treated, and, more important, how many people are screened in the first place. Colon cancer is the third most frequently diagnosed cancer and the second leading cause of cancer death, according to the American College of Radiology.

But that could change if radiologists, gastroenterologists, and patients embrace CT colonography as the first line of defense against colon cancer.

The efficacy of the ACRIN study and the impact of its results are due to the fact that it was tested over a long time and in a large, diverse population.

The ACRIN Study

The ACRIN study was performed over a 2-year period and involved 15 sites nationwide that scanned more than 2,600 patients. Richard Obregon, MD, a radiologist at Radiology Imaging Associates, Denver, was a principal investigator for the study. Each site had a single investigator who oversaw and coordinated the study at their site and read the results.

Study participants had to be at least 50 years old, scheduled for a colonoscopy, and not have received a scan in the last 5 years. After having the colonography, the participant would then receive a colonoscopy. The key to the effectiveness of colonography lies in the speed at which it is read, according to Obregon. “[The findings] should be read within an hour,” he said. “If the patient has a positive finding less than one centimeter, they should be counseled [about their options]. If it’s more than that size, they should have a colonoscopy and then a polypectomy.” The latter two steps should take place on the same day as the colonography to eliminate the need for a second round of preparation. The screening test involved overnight prep identical to that for traditional colonoscopy. The following morning, the patients had CO2 pumped into their bowel and then they were scanned in a 16-slice CT scanner. The entire screening process took about 15 minutes—with the actual scan taking just a few seconds.

While the ACRIN trial has been creating a lot of buzz, this was not the first time a large population has been evaluated for the effectiveness of colonography. Several years ago, the Department of Defense (DOD) initiated a massive study of US armed forces personnel to evaluate the effectiveness of colonography. Obregon said that this study, though successful, had some inherent flaws. Since all of the participants were active military, factors such as age and, most important, willingness could have skewed the results. Because of these factors, “it’s still considered a single-site study,” said Obregon.

The ACRIN study built off of the DOD and other single-site studies that showed the high potentiality of the test and brought it to a more diverse, geographically dispersed population. From a medical perspective, it held more weight, but wasn’t as clean as the DOD study. “Multifacility studies aren’t typically as exquisite,” Obregon said. “This is a factor of reader experience, technology, [and other variables] that you won’t find in a single-center study.”

The trial showed, in theory, that colonography is a worthwhile and safe first line of defense against colon cancer. The next step is proving it on a day-to-day basis.

In the Trenches

Karen Horton, MD, associate professor of radiology at Johns Hopkins University, Baltimore, also was a principal investigator for the ACRIN study and has continued using colonography in her daily practice to scan patients. “It’s still not a huge volume [because of limited reimbursement], but once insurance starts to pay, there’ll be a spike,” she said. In fact, there has been a small increase because the Johns Hopkins employee health system—in response to the ACRIN trial—has begun reimbursing for the scan.

Prior to the ACRIN study, most of her colonography patients were older and in fragile health, those on blood thinners, or those whose colonoscopies were incomplete.

Colonography is part of Johns Hopkins’ future. The radiology and gastroenterology departments are working together to firm up a business plan that will outline how colonography will be used, financed, and marketed.

Among the biggest cheerleaders of the new system is Horton, who is responsible for teaching the interns and radiology fellows how to perform the test. “Colonography is straightforward and not that difficult to do,” she said.

But even with the ease of it—she adds that most radiologists can become competent fairly quickly—it’s not for everyone. “I’m interested in the GI tract, and once you get the hang of the test, it’s like a little game [looking for the polyps],” she said. “But it’s not a test that’s for everybody.”

Obregon notes that not everyone who wanted to be a principal investigator were able to pass the test administered during the application process. “There certainly are a lot of challenges,” he said. “There’s a need and a demand for training. You need a certain number of cases under your belt, but how many—150, 100, 75? The more time you spend reading the colon, the more polyps you’ll find.” He noted that, as the scan becomes more accepted, the ACR will have to develop reading guidelines and tests.

These guidelines are necessary because of the additional level of skill that is needed. For instance, he said, with the fly-through features of most colonography software, the radiologist needs a higher level of attention and focus.

Colonography’s “game” of medical hide and seek is highly effective. According to Horton, about 90% of patients undergoing a colonography will not need a traditional colonoscopy.

Horton uses Siemens’ Syngo 16-slice CT with Siemens Colon software. She likes the flexibility of transitioning from the two-dimensional to three-dimensional views. According to her, Siemens has made a number of improvements to the software directly related to user feedback.

John Phelps, product manager, CT Oncology Solutions at Siemens Medical Solutions, adds that the software has a number of automated tools and can easily change views from endoscopic to panoramic. The Siemens Colon software also allows for virtual dissection and supports stool tagging.

The software has a high sensitivity for finding flat polyps. This is important since there have been some worries that because colonography has shown some inability to identify these less obvious polyps, it is less effective. Phelps notes that, while there has been a debate about these polyps, “the jury’s still out on how clinically relevant [they are].”

While Horton is a diehard Siemens user, the company isn’t the only kid on the colonography block. Philips and GE Healthcare both have CT colonography systems.

Philips and GE Healthcare

While CT colonography might be new to most, the technology has existed for more than 15 years, explains Charles Cassudakis, director of CT Oncology Therapy, Interventional and Screening for Philips, which is a good thing for radiologists and patients alike. “We have experience with this,” he said. “There’s such a low compliance [with colonoscopy screenings], and we’re taking away the fear and apprehension.”

The sites that had Philips scanners typically used the Brilliance line, which ranges from 16 to 64 slices. The company also has a 256-slice machine, the iCT. The company is currently working on another 16-slice scanner, the MX16.

The key tool, of course, is the software. The company’s Virtual Colonoscopy program is featured as part of its Extended Brilliance Workspace and Portal enterprise-wide solution. With this software, the colon can be placed in a filleted view that is “almost distortion free,” according to Cassudakis.

GE Healthcare’s Advantage CTC software is used in conjunction with its Lightspeed CT scanners. The software offers various viewing options, including virtual dissection, fly-through, and two-dimensional and three-dimensional renderings. According to Scott Schubert, general manager, Oncology Care Area, the primary thing holding up wholesale adoption of his and the other companies’ systems is the Centers for Medicare and Medicaid Services. “The technology is ready for prime time,” he said. “We just have to make sure that radiologists are trained and [facilities are] accredited correctly.”

The future is bright for CT colonography, but there are still issues to iron out and implications for the wholesale adoption of the study.

The New Gold Standard?

While the ACRIN study has caused a lot of excitement in the medical and patient communities, it still hasn’t dethroned colonoscopy as the gold standard for colon cancer screening. Clinicians Obregon and Horton have strong opinions about the two tests—and both side with the less invasive one. “Is colonoscopy a perfect test?” Obregon asked rhetorically. “No. It’s a good test, but not perfect.”

He admits that colonography has its downside. “Theoretically, the findings for small to medium polyps aren’t as good,” he said.

But the upside—its equivalence for detecting large polyps and cancers, no sedation risk, and lower pricing—makes it very attractive to clinicians and society in general.

So does this mean that colonography will become the new gold standard? Horton dismisses the idea of colonoscopy even being considered the standard. “Surgery is really the gold standard,” she said. “Before CT, you had exploratory surgery and you just cut everything out.”

Horton notes that most small polyps—those under 5 mm—are usually benign.

Obregon adds that with a test like colonography, clinicians can turn to other issues such as understanding what he calls “the natural history of small polyps.” “We remove everything, but many of these polyps under 5 mm resolve on their own and are normal mucosa. If we can follow small polyps, we can understand what the true mortality reduction rate is,” he said. “We now have a test.”

While CT colonography continues to gain acceptance and opens new avenues of study, manufacturers are looking at new vistas beyond this test.

New Vistas

Philips’ Cassudakis is keeping his eyes on the future of CT colonography, predicting that the technology will improve further to make prep—the one variable still affecting compliance—less onerous. This will mean that Philips and the other companies will need to develop electronic cleansing technology, which is still a work in progress. “The goal is to make [the scan] even easier,” he said.

One possibility for the future, he said, is in evaluating the bronchus noninvasively, noting that there’s some rudimentary fly-through software already available. “But for virtual bronchoscopy to catch on, it’ll again take scientific studies,” he said.

GE Healthcare’s Schubert echoes Phelps, and whatever form the next virtual test takes, “it’s [going to be] exciting and a continuation of what diagnostic imaging is already doing,” he said.


C.A. Wolski is a contributingwriter for Axis Imaging News. For more information, contact .