Published: May 04, 2010
Mayo Clinic Researcher Details Next-Era Advances in Use of Scopes for Cancer Detection
Just as cameras and televisions have been reinvented in the last decade
with improved optics, sharpness and brightness, so have the tiny imaging
scopes that physicians use to peer into the body's nooks and crannies --
its organs and digestive system.
VIDEO ALERT: Additional audio and video resources, including excerpts
from an interview with Dr. Michael Wallace describing the research, are
available on the Mayo
Clinic News Blog (http://newsblog.mayoclinic.org/2010/04/28/hd-medicine/).
These materials may be accessed in advance by journalists for
incorporation into stories. The password for this post is: wallaceddw.
And few places in the United States are testing the power of these new
endoscopic optics as thoroughly as are researchers at Mayo Clinic.
Gastroenterologists at Mayo are pitting multiple high-tech probes
against each other to see how well they detect the tiniest precancerous
polyp in the colon. They are testing other scopes to search lymph nodes
outside of the lung for evidence of micrometastatis -- the spread of
cancer cells that can't easily be seen. They are also finding new ways
to reduce laborious and painful screening in patients with Barrett's
esophagus.
"We can see detail that was unimagined 10 years ago," says Michael
Wallace, M.D. (http://www.mayoclinic.org/bio/14266458.html),
a gastroenterologist at Mayo Clinic's campus in Florida. "With the
newest systems, we can zoom in on a potential problem spot in the colon
or esophagus with 1,000-fold magnification, leading to a day when we can
perform virtual biopsies on patients -- meaning that we will be able to
tell if a lesion is precancerous by looking at it, and if it isn't, we
can leave it alone. Now we have to remove anything that looks even
slightly suspicious."
Dr. Wallace leads many clinical trials testing the newest scopes. At the Digestive
Disease Week (http://www.ddw.org/wmspage.cfm?parm1=679)
(DDW) 2010, an annual international meeting of physicians and
researchers in the fields of gastroenterology, hepatology, endoscopy,
and gastrointestinal surgery, he will discuss how these advanced scopes
can potentially help prevent or detect early colon
cancer (http://www.mayoclinic.org/colon-cancer/),
lung cancer metastasis and esophageal
cancer (http://www.mayoclinic.org/esophageal-cancer/).
Probe is most accurate to date in performing virtual biopsy of colon
polyps A Mayo Clinic research team, led by Dr. Wallace, has found that
an endoscopic imaging tool only one-sixteenth of an inch in diameter
shows the highest accuracy yet in detecting small precancerous polyps
inside the colon wall.
In the study, 84 patients were tested with three different technologies
while undergoing a colonoscopy. Two of these technologies -- use of
regular white light and a blue light that highlights blood circulation
-- are a standard feature on most high-definition scopes in use today.
They allow a physician to switch between light sources to pick up
additional detail in colon tissue. The third technology, the probe-based
confocal laser endomicroscopy (pCLE) system, is a state-of-the-art
technology that is being tested and used at Mayo and a few centers in
the U.S. This is a separate device that can magnify structures by
1,000-fold, to the point that it can detect precancerous changes in a
single cell -- a condition that could indicate development of a
precancerous polyp.
The researchers found that the pCLE system was the most accurate at
determining whether a small (6–9 millimeter) polyp was precancerous. Its
specificity was 100 percent, meaning that polyps it identified as
abnormal were, in fact, abnormal. All 145 polyps found in the patients
were examined with all three methods and then removed and examined by a
pathologist to see if they were benign or precancerous.
Dr. Wallace says that the sensitivity of the pCLE system was 91 percent.
"The benign small polyps were correctly determined to be benign 91
percent of the time by the pCLE system," he says. "Our goal is to bring
that figure up to as close to 100 percent as possible."
The researchers are working toward using an endoscopic probe to perform
virtual biopsies. As envisioned by Dr. Wallace, the endoscopic probe
will be able to determine if a polyp is benign, and if so, that polyp
can be left in the colon. Currently, all lesions are removed during a
colonoscopy and examined, but about half of all polyps are found to be
harmless. This adds time, expense, and a possible risk of side effects
to routine colonoscopies, Dr. Wallace says.
Use of three imaging techniques together identifies suspicious
lesions in patients with Barrett's esophagus
At Mayo Clinic, Dr. Wallace's research has also shown that the pCLE
system can reduce the number of biopsies necessary in Barrett's
esophagus (http://www.mayoclinic.org/barretts-esophagus/),
a condition where the tissue lining the esophagus is replaced by tissue
that is similar to the lining of the intestine -which can then morph
into cancer.
To rule out cancer development, physicians normally biopsy every four
inches of the esophagus in Barrett's esophagus patients to detect the
same kind of precancerous changes that occur in the colon. Usually only
one out of 100 biopsied samples of the esophagus has a lesion that is
precancerous when examined by a pathologist, Dr. Wallace says.
To see if there is a better way to analyze the esophagus, Mayo Clinic
contributed the largest number of patients with Barrett's esophagus to
an international study testing pCLE imaging. The results are being
presented at DDW. Dr. Wallace is the senior author. The study findings
will be presented by the principal investigator, Prateek Sharma, M.D.,
from Kansas University Medical Center.
The 97 patients enrolled in the study were examined with a standard
endoscope that had both white and blue light, and then by pCLE. A total
of 718 random locations were biopsied and 138 suspicious lesions were
found. Researchers found that the three different technologies, when
used independently, detected 85 percent of precancerous changes, and
that a combination of white and blue lights identified 92 percent of
these lesions. When pCLE was added, 100 percent of precancerous lesions
were identified.
"We have now shown that adding pCLE to standard endoscopes gives us the
ability to identify all suspicious lesions in these patients," Dr.
Wallace says. "It is a simple matter to use them all in clinical
practice. The white and blue lights are part of one endoscope, and pCLE
device can be added to the scope. Our hope is that, in the future, we
will not need to remove so many samples from patients, and focus only on
those that have potential to become cancers. Our combination scope can
do that, and our hope is that this changes the kind of surveillance that
patients with Barrett's esophagus have to undergo."
Minimally invasive scope and molecular test can check lung cancer
patients for evidence of cancer spread to lymph nodes
Lung cancer is the most common cause of cancer death in the United
States. A patient's best hope is that the cancer is detected and treated
before it spreads from the lungs. Determining whether patients diagnosed
with lung cancer have malignant lymph nodes near their lungs -- the
first site the cancer usually spreads -- has always been difficult. Even
after these mediastinal lymph nodes have been removed, examined, and
determined to be cancer-free, cancer still returns in 30–50 percent of
patients. Whether the cancer has spread makes a difference in a
patient's treatment.
Researchers at Mayo Clinic, working with scientists at the Medical
University of South Carolina, had earlier found a panel of five markers
-- molecules only expressed in lung cancer cells -- that could identify
micrometastasis in these lymph nodes. Micrometastasis is the spread of
cancer that is too small to see with any current imaging or pathology
technology. They found in one of their first studies that
ultrasound-guided endoscopy used in a biopsy of the lymph nodes,
combined with real-time analysis of the markers in the nodes, detected
evidence of micrometastasis in about 20 percent of lymph nodes that had
been deemed to be cancer-free by pathological examination.
The examination is minimally invasive and is done before surgery, says
Dr. Wallace, who has led this research. The scope is threaded down the
esophagus and, with the assistance of ultrasound, guided to the
mediastinal nodes. There, a fine needle removes a tiny sample of the
tissue node. Dr. Wallace and a team of physicians and researchers have
shown that patients whose lymph nodes showed molecular evidence of
micrometastasis had significantly worse survival rates than patients
whose nodes did not express these molecules. The findings suggest that
this technology, dubbed EUS-FNA (endoscopic ultrasound–fine needle
aspiration), can help physicians decide which therapy to offer patients
whose lymph nodes show cancer spread.
"It may be better to give these patients chemotherapy and radiation
before surgery," says Dr. Wallace. "That will be our next study."
Short training session is enough to teach physicians how to interpret
pCLE images -- suggesting it could be widely used
No matter how accurate the pCLE probe (described above) is in mining the
colon for precancerous polyps, if most gastroenterologists find it too
difficult to use, the probe will sit on the shelf and not benefit
patients, according to Dr. Wallace. That is why he and his research team
decided to see what kind of learning curve physicians who have never
worked with the pCLE system need to undergo before they can use it.
In a small experiment, they taught a group of 11 physicians how to
interpret 20 video sequences taken by pCLE of benign and precancerous
polyps. "Since the pCLE is a high-definition imaging tool, we had to
know if these physicians could accurately interpret the images they were
given," Dr. Wallace says.
The physicians were then tested on 76 new video sequences, taken from 54
patients. After seeing 50 images, the group, on average, had an accuracy
level of 86 percent, which is similar to highly experienced users, Dr.
Wallace says. "The ability to interpret these images is rapidly learned,
and the technology could be fairly easily adopted into a general
practice," he says.
About Mayo Clinic
Mayo Clinic is the first and largest
integrated, not-for-profit group practice in the world. Doctors from
every medical specialty work together to care for patients, joined by
common systems and a philosophy of "the needs of the patient come
first." More than 3,700 physicians, scientists and researchers, and
50,100 allied health staff work at Mayo Clinic, which has campuses in
Rochester, Minn; Jacksonville, Fla; and Scottsdale/Phoenix, Ariz.; and
community-based providers in more than 70 locations in southern
Minnesota., western Wisconsin and northeast Iowa. These locations treat
more than half a million people each year. To obtain the latest news
releases from Mayo Clinic, go to www.mayoclinic.org/news.
For information about research and education, visit www.mayo.edu.
MayoClinic.com
(www.mayoclinic.com)
is available as a resource for your health stories.
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