MRI under exploration for
new ways to detect and treat breast cancer
BY RUTHANN RICHTER
Magnetic resonance imaging
(MRI) has the potential to become a powerful tool for
screening women at high risk for developing breast
cancer, a visiting lecturer from the University of
Toronto told a Stanford audience from engineering,
radiology and surgery during a presentation April 13.
In recent years, MRI has
become an increasingly useful device in the diagnosis and
treatment of breast cancer patients, said Stefanie
Jeffrey, MD, assistant professor of surgery and chief of
breast surgery at Stanford. For instance, Stanford
physicians now use MRI to help evaluate the impact of
preoperative chemotherapy in women with large cancers of
the breast and to look for multiple tumors in some women
before breast conservation surgery, Jeffrey said.
Stanford doctors also use MRI to help find hidden tumors
that could not be detected through other means,
particularly in women with dense breast tissue or in
women at risk for cancer in both breasts, Jeffrey told
more than 50 faculty and students at the presentation in
the Packard Engineering Building.
"There are patients
behind the work that you do, and it really has helped
many of them," Jeffrey told the group, which
included a number of Stanford scientists who have made
major contributions to the imaging field. She said
Stanford remains in the forefront of breast MRI research,
which is being conducted at about a dozen academic
medical centers across North America.
Donald Plewes, PhD, a
professor of medical biophysics and a senior scientist at
the University of Toronto, described his experience using
MRI to screen women considered at high risk for the
disease. Plewes directs an ongoing multicenter trial that
so far has compared MRI with other traditional imaging
methods, including mammography and ultrasound, to screen
some 176 high-risk women. The women, whose mean age was
43, were either carriers of one of the breast cancer
genes -- known as BRCA1 and BRCA2 -- or had several close
female relatives with breast cancer.
Using MRI, the researchers
were able to identify eight out of nine cases of early
breast cancer in the asymptomatic women -- the most
effective method available, Plewes reported. By
comparison, mammography detected only four of the nine
cases, while ultrasound identified five of the nine
cases. A clinical exam, in which a doctor examines the
breast for possible lumps, detected only two of the nine
tumors, he said.
"It certainly is
encouraging in that we see cancers [with MRI] that we
don't see through other imaging methods," Plewes
said. "I think MRI has a very compelling role in
this arena."
One of the drawbacks of
the imaging technique is its high cost -- roughly $1,000
to $2,000, compared to $100 to $200 for a mammogram,
Plewes said. But MRI becomes much more cost-effective
when applied in a group known to be at high risk, he
said.
He said some 26 percent of
the women in the study indicated that they found the exam
uncomfortable, largely because of the need for an
intravenous line. The 45-minute test is done while the
woman lies still, face down in the MRI scanner. The
patient is given an injection of a contrast solution,
which tends to accumulate in cancerous tissues, showing
up as a bright spot on the image. The solution is
harmless, and MRI generally is considered entirely safe,
Plewes said.
While MRI may be useful as
an initial screening tool, doctors still must perform a
biopsy to confirm whether a tumor is malignant or benign,
noted Bruce Daniel, MD, an assistant professor of
radiology at Stanford.
"A key issue is when
you find something, what do you do about it?" Daniel
said after Plewes' talk.
Daniel said Stanford has
eased the biopsy process through a technique that uses MR
guidance to channel a wire directly to the site of a
tumor. When Jeffrey and her fellow surgeons then go in to
retrieve a tumor sample for biopsy, they know precisely
where the lesion is located, he said. Stanford is one of
a few medical centers in the country using the wire
localization technique, he said. Daniel and his
colleagues are also working on newer, minimally invasive
methods for biopsy that would not require an open
incision and a trip to the operating room, he said.
In addition, Stanford
scientists are working on some technical aspects of MRI
to help improve its specificity -- currently one of the
major shortcomings of the imaging method. Because of its
lack of specificity, MRI tends to produce more false
positive test results than other imaging methods, Daniel
said, forcing some women to undergo testing of tissue
that turns out to be noncancerous. He said Stanford
researchers already have made major technical strides
that have significantly increased the resolution and
speed of MRI, as well as the ability to analyze test
results.
Finally, Daniel, Jeffrey
and colleagues are planning to investigate the use of MR
guidance in an experimental treatment for breast cancer
known as radiofrequency ablation. The technique involves
insertion of a needle electrode through the skin into a
breast tumor. A low level of radiofrequency energy then
is applied to heat and kill the tumor cells.
"You'd like to try to
destroy a tumor without doing an open surgery, but it's a
tricky business," Daniel said. He said clinicians
want to be assured that they have not left cancerous
cells behind.
The Stanford team was
among the first in the world to apply the radiofrequency
ablation technique in breast cancer patients, publishing
results on the first five patients last October in the
Archives of Surgery. In all five women, there was
evidence of cancer cell death, the researchers reported.
In the next phase, the
researchers plan to test whether MRI can help define the
boundaries of the ablated zone with respect to the tumor.
Their ultimate goal is to produce even better clinical
results. SR
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