Biotech Values

[DewDiligence]

Software Improves Accuracy of Virtual Colonoscopy

[This is a topic much discussed on this board in years past. The key question: just how likely are small polyps to turn into cancer?]

http://health.yahoo.com/news/141903

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Standards for Equipment, Process Still Needed

December 8, 2005

Summary: Using computer software to look for polyps makes virtual colonoscopy about as accurate as traditional colonoscopy, researchers from the National Institutes of Health report in the December issue of Gastroenterology. In their study, the two methods performed equally well at finding large colon polyps, although traditional colonoscopy was better at finding smaller ones.

Why it's important: Colon cancer is the second leading cause of cancer deaths in the US (lung cancer is first), yet many cases could be caught early and even prevented by regular screening. Screening -- with colonoscopy or other methods -- can find colon growths called polyps before they turn into cancer. Although the American Cancer Society recommends regular screening for all people beginning at age 50, many who should get screened don't.

Traditional optical colonoscopy is considered the gold standard for colon cancer screening. However, this procedure is invasive and requires sedation. Because virtual colonoscopy is less invasive, some people might prefer it over standard colonoscopy.

"It is important for the scientific and medical community to explore and perfect methods that may encourage more people to get checked," said Ronald M. Summers, MD, lead author of the new study and a senior investigator and staff radiologist at the NIH Clinical Center.

What's already known: Virtual colonoscopy uses computed tomography (CT) scans to take hundreds of images, which are combined by a computer to create 2-dimensional or 3-dimensional images of the colon. A radiologist then reviews the images, looking for polyps or cancers. Computer-aided detection (CAD) uses a computer program that acts as a second set of "eyes" to help the radiologist locate suspicious areas on the images.

Previous studies comparing virtual colonoscopy to regular colonoscopy have had mixed results. Some found it performed equally well, while others showed it was much less accurate. Moreover, there are questions about how much training radiologists need to be able to interpret the images properly, and about which types of CT equipment should be used.

How this study was done: The researchers gave more than 1,200 adults with no symptoms of colon cancer both traditional and CAD-assisted virtual colonoscopy on the same day. They compared how many polyps and cancers were found by each method.

What was found: Virtual colonoscopy with CAD performed similarly to traditional colonoscopy for large polyps. It found nearly 90% of polyps 10mm or larger and more than 85% of those 8mm or larger. It was about as effective as traditional colonoscopy, which found 86% of 10mm polyps and 90% of 8mm polyps.

However, virtual colonoscopy with CAD was significantly worse than traditional colonoscopy at finding polyps between 6mm and 8mm -- and that raises some concerns, said Durado Brooks, MD, director of prostate and colorectal cancer for the American Cancer Society.

Although there is debate about how dangerous polyps of this size are, they do have some potential for growing into cancer. Most doctors would remove a 6mm or 7mm polyp found during regular colonoscopy, Brooks said, but polyps of that size might not be found with virtual colonoscopy.

"So we're talking about potentially not detecting and therefore leaving unchecked a significant number of smaller lesions," he said.

But Brooks emphasized that no screening method -- not even optical colonoscopy -- can find every problem. In this study, for instance, both types of colonoscopy missed some large polyps. And CAD-assisted virtual colonoscopy found 2 cancers among the people screened, while regular colonoscopy found only 1 of those cancers.

The bottom line: The study is promising, Brooks said, because it shows there are ways to improve the accuracy of virtual colonoscopy. But researchers have to do more studies to find out just which methods -- there are various types of CT scanners and CAD software available -- will work best. So for now, virtual colonoscopy remains an investigational tool, not a recommended screening method.

Citation: "Computed Tomographic Virtual Colonoscopy Computer-Aided Polyp Detection in a Screening Population." Published in the December, 2005, issue of Gastroenterology (Vol. 129, No. 6). First author: Ronald M. Summers, MD, PhD, Diagnostic Radiology Department, National Institutes of Health.
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