Endoscopic probe can detect whether polyp in colon is benign
2 June 2008
An endoscopic probe that can tell whether or not a cell living within
the human body is veering towards cancer development may revolutionize
how future colonoscopies are done, say researchers from the Mayo Clinic
in Jacksonville, Florida.
The researchers have found that technology known as a high resolution
confocal endomicroscopy probe system can determine whether a colon polyp
is benign (not precancerous), without having to remove it for
examination by a pathologist.
Their study, presented at Digestive Disease Week in San Diego last
week, shows that using the probe system was 89% accurate in identifying
whether polyps were either precancerous or benign. But more importantly,
it was correct 98% of the time in flagging polyps that were benign,
which would then not need to be removed for biopsy. The Mayo
researchers, who are the first in the US to comprehensively test the
system in the colon, believe they can push accuracy close to 100% with
more research.
What this means is that the probe system can be used during a
colonoscopy to rule out removal of polyps that are not harmful, says the
study’s senior author, Michael Wallace, MD, MPH., Professor of Medicine
at Mayo Clinic. “Today, half of all polyps surgically removed during
colonoscopy procedures are benign, and so this virtual biopsy will save
time and expense, and reduce complications that can occur,” he says.
The device is a tiny imaging tool, only 1/16th of an inch in
diameter, which can be attached to a variety of endoscopes that are
already being used during colonoscopies, Dr Wallace says. When a
suspicious polyp is seen during a colonoscopy, a physician can use the
probe to look closely at the lesion. To do this, a small amount of
fluorescent contrast is used to illuminate the area, and the probe
magnifies it by 1,000 times — enough to see a single red blood cell as
it moves through a blood vessel.
In this study, the researchers first tested 10 precancerous (adenomatous)
lesions as well as 10 benign (hyperplastic) lesions using the probe
system in order to understand the differences in appearance between the
two (the status of the polyps was later verified by pathologists). Among
other things, they looked at changes in cell colour and size, how nuclei
within the cells looked, and whether cells were crowed within tissue, or
fused.
They then, without knowledge of the pathologists’ diagnosis, used
their new grading system to determine the status of 37 polyps within 25
patients, which were then removed. The most important clinical result is
that the probe was 98% accurate in identifying lesions that were not
cancerous. “That is what you want in a device like this,” says the
project’s lead research fellow, Dr Anna M. Buchner, who will be
presenting the findings. “Removing a polyp that looks precancerous, but
turns out to be benign, is okay, but you don’t want to leave polyps
intact in the colon that are actually cancerous,” she says. “This probe
is almost perfectly reliable in that regard and with more experience I
am sure we can improve accuracy to nearly 100%.”
Wallace says the technology, which is also being tested in the
esophagus, has the capacity to fundamentally change how many different
endoscopy procedures are done. “This will shift our role from one of
going in and getting tissue for a pathologist to examine to one in which
we can do the pathology ourselves,” Dr Wallace says. “This is
instantaneous, real time pathology.”