It's unlikely that pathology will become an extinct practice, but those who study human tissues under a microscope may lose at least one job assignment if a relatively new microscopy technology continues to prove cost efficient and accurate.
Adding a miniature microscope to the end of an endoscope – called confocal laser endomicroscopy (pCLE) – is an approach to disease detection that's been around for about four years. As with any new med tech, it takes time and studies to validate. Physicians at Mayo Clinic (Jacksonville, Florida) have now demonstrated that it might soon be possible to use such a device to determine whether or not a colon polyp is benign without removal for biopsy.
“By removing polyps during colonoscopy, you incur some risks of bleeding or perforation of intestines. We do about 14 million colonoscopies a year in the U.S., so even the smallest risks get multiplied into a big number of people who have bleeding or severe complications. So if we can avoid taking polyps out that have no malignant potential, that's desirable,“ Michael Wallace, MD, MPH, professor of medicine at the College of Medicine, Mayo Clinic, told Medical Device Daily. “The other issue is cost. Pathology is an additional cost above and beyond colonoscopy. Once you start doing two to three biopsies, that cost becomes the most expensive part of the procedure, more than the colonoscopy.“
Currently all polyps are extracted during colonoscopies and sent to a pathologist for examination. The use of pCLE would be a practice-changing paradigm shift.
Wallace and his colleagues have, in several studies, looked at the use of pCLE to reduce or even eliminate the need for pathologists in the detection of colon cancer. The latest study, reported in the March issue of Gastroenterology, found that pCLE, is much more accurate than another type of new tech probe imaging called virtual chromoendoscopy, also known as narrow-band imaging. The pCLE — an imaging tool only one-sixteenth of an inch in diameter — can magnify a polyp by a factor of 1,000 to detect potentially dangerous changes in even single cells, such as enlargement of the nuclei. Narrow-band imaging uses blue light to enhance an image.
Wallace and team found that pCLE was 91% accurate in detecting precancerous polyps and narrow-band imaging was 77%, when compared to biopsy findings.
The gastroenterologist said that 91% is pretty good, but not quite ready for everyday use.
“It's a tough question to say if it's good enough to stop doing biopsies or polyp removals,“ he said. “We have asked many different doctors how good we need to be in using optical diagnosis compared with pathology. Most think we should be in the 95% to 98% range. From that perspective, we're not quite ready to abandon pathology. But we're a significant step closer.“
Wallace believes that someday this type of probe could be used to virtually biopsy most polyps, removing only those that are precancerous. And because half of all polyps now removed during a colonoscopy are benign, the healthcare savings and patient safety improvements are potentially huge.
For his study, Wallace used the Cellvizio, a pCLE system first launched by Mauna Kea Technologies (Paris) and its U.S. subsidiary CellVizio (Fort Washington, Pennsylvania) in 2007.
The device is an endoscopic accessory which, when placed against mucosal tissue, provides microscopic visualization of the tissue. The images obtained have a resolution 500 to 1,000 times greater than a regular endoscope. Cellvizio delivers up to 12 images per second and is designed to be used with almost any endoscope. It has 510(k) clearance and the CE mark for use in the gastrointestinal and pulmonary tracts (MDD, Dec. 23, 2009).
More than 5,000 Cellvizio procedures have been completed worldwide to date (MDD, Jan. 20, 2010), but Wallace points out that these are at research institutions and large academic referral centers. It is not yet being used as a regular protocol.
“We evaluated this extremely high magnification device,“ Wallace said. “This is a true microscope, similar to what a pathologist uses. What's different is that instead of being a large microscope on desk, it's 2 mm that can go inside a colonoscope. So when you see a polyp, instead of taking it out, you can bring the microscope inside the colon and look at the polyp. The confocal part is unique. It means the you use pinhole cameras to look at thin slice of tissue without getting blurring from light. We can look down deep into the polyp and filter out images we would get above and below.“
In this study, funded by the American Society of Gastrointestinal Endoscopy Research (Oak Brook, Illinois), researchers administered a standard colonoscopy to 75 patients, and during the procedure used narrow-band imaging as well as pCLE to determine cancer risk in the polyps. In all, 119 polyps were removed from the patients and sent to pathologists for analysis. Eighty-one polyps were precancerous and 38 were benign. Both methods were equally specific, meaning that they had the same ability to detect benign polyps, but the pCLE system was much more sensitive in detecting precancerous polyps.
Wallace has already completed a yet-to-be published follow-up study. Preliminary analysis finds that pCLE is best used on smaller polyps.
“The most accurate diagnoses are in polyps that are 6 mm to 9 mm,“ he said, adding that these study findings will be presented next month at the Digestive Disease Week meeting in New Orleans. “We've realized that the polyps we need to focus on that are most relevant are very small polyps. We know that all larger polyps need to be removed regardless of whether it's benign or malignant because they cause other problems. In focusing now on smaller polyps, we're getting even higher accuracy.“
pCLE use won't be limited to the diagnosis of colon caner. Wallace's data already shows that the probe system could reduce biopsies in Barrett's esophagus, among other potential applications.
Lynn Yoffee; 770-361-4789