MRI
Helps Find Breast Cancer In High-Risk Women
More Evidence
Points To MRI Usefulness
For a small group
of women with a genetic or family history for breast cancer,
regular magnetic resonance imaging (MRI) breast screening may be the
best way to spot tumors early, according to a report in the New
England Journal of Medicine.
While mammography is mostly
effective in spotting tumors, a small percentage of women - such as
those carrying the BRCA1 or BRCA2 breast cancer genes - may need screening
technologies with even greater powers of detection.
Magnetic resonance imaging
(MRI) is a diagnostic procedure that uses a combination of a large
magnet, radiofrequencies, and a computer to produce detailed images
of organs and structures within the body.
Breast cancer remains the
second leading cause of cancer death among US women. The American
Cancer Society estimates that 215,990 new cases of invasive
breast cancer will be diagosed in the US in 2004.
For women at high risk
for breast cancer, "In their lifetime, 50 to 85 percent of these women
will develop breast cancer," explains Dr. Laura Liberman, a radiologist at
the Breast Imaging Section at Memorial Sloan-Kettering Cancer Center
in New York City.
MRI Spots
Cancer More Often
In the new study, breast
MRIs conducted annually were nearly 80 percent effective in picking
up invasive cancers in high-risk women, compared to the 33 percent
effectiveness rating of annual mammograms, researchers report.
However, experts agree
that MRI's high rate of false positive results - findings that could
be malignant tumors, but turn out to be benign - make the technology
much less desirable for women at normal breast cancer risk.
While regular MRI breast
scans may be of benefit to women at high risk, "women at normal risk
should not be encouraged to undergo regular MRI screening," said study
author Dr. Jan G. M. Klijn, a medical oncologist at the Netherlands'
Rotterdam Family Cancer Clinic.
Dr. Liberman, who wrote
an editorial accompanying the Dutch study, said that for these women,
an annual mammogram is not enough. "So, people are now studying
supplementary techniques, such as MRI," she says.
In their study, Dr. Klijn's
team selected 1,909 adult women who were either carriers of the BRCA1
or BRCA2 genes, or who had a strong family history of breast cancer
- defined as close relatives diagnosed with breast tumors before age
30.
All of the women received
clinical breast exams every six months, plus mammography and MRI screening
annually, over the course of three years.
Fifty-two breast cancers
were detected among the group during the study period, the researchers
report.
In terms of early detection,
MRI far outperformed mammography or clinical breast exams. MRI was
also much better at detecting very small tumors (10 millimeters or
less in diameter) at a very early stage.
Based on the findings,
Dr. Klijn says, "Our recommendations are to use MRI as a screening
method in specialized facilities, for women with a BRCA [1 or
2]mutation or a really high risk of breast cancer."
Save MRI
for High-Risk Women
Both Drs. Klijn and Liberman
are careful to not extend this recommendation to women at average
risk, however.
Dr. Liberman explains that,
besides the scarcity and high cost of MRI, the technology's strength
- its ability to spot very tiny abnormalities in tissue - is also
a weakness.
"This is a very sensitive
test," she says. "If there's a cancer hiding in the breast, it's likely
to show up. But as a tool it's also not very specific, meaning that
a lot of normal stuff will light up, too."
That may be acceptable
for the anywhere from 1 percent to 10 percent of women at very high
risk for breast cancer, she says. For these women, "If you have a
positive result, the likelihood that it's [a tumor] is so much higher"
that it may be worth going to the next step, which is biopsy, Dr.
Liberman explains.
On the other hand, MRI's
high false-positive rate "would simply cause a lot of anxiety and
then lead to a lot of unnecessary, benign biopsies if we started to
apply it as a screening test in the general population," she says.
"There's just no evidence that it's a helpful screening test in women
at normal risk."
Always consult your physician
for more information.
|
September 2004
MRI
Helps Find Breast Cancer In High-Risk Women
MRI
Spots Cancer More Often
Save
MRI for High-Risk Women
What
Is Magnetic Resonance Imaging (MRI)?
Online
Resources
Other
Resources:
St.
John's Mercy Cancer Services
Find
a St. John's Mercy Physician
Breast
Health Information
Women's
Health Information
St.
John's Mercy Classes and Programs
What
Is Magnetic Resonance Imaging (MRI)?
Magnetic resonance imaging
(MRI) is a diagnostic procedure that uses a combination of a large
magnet, radiofrequencies, and a computer to produce detailed images
of organs and structures within the body.
The MRI machine is a large,
cylindrical (tube-shaped) machine that creates a strong magnetic field
around the patient.
The magnetic field, along
with a radiofrequency, alters the hydrogen atoms' natural alignment
in the body.
Computers are then used
to form a two-dimensional (2D) image of a body structure or organ
based on the activity of the hydrogen atoms.
Cross-sectional views can
be obtained to reveal further details. MRI does not use radiation,
as do x-rays or computed tomography (CT scans).
A magnetic field is created
and pulses of radio waves are sent from a scanner. The radio waves
knock the nuclei of the atoms in your body out of their normal position.
As the nuclei realign back
into proper position, they send out radio signals. These signals are
received by a computer that analyzes and converts them into an image
of the part of the body being examined.
This image appears on a
viewing monitor. Some MRI machines look like narrow tunnels, while
others are more open.
MRI may be used instead
of computed tomography (CT) in situations where organs or soft tissue
are being studied, because with MRI scanning bones do not obscure
the images of organs and soft tissues, as does CT scanning.
Always consult your physician
for more information.
Online Resources
American
Cancer Society
American
Society for Clinical Oncology
Centers
for Disease Control and Prevention (CDC)
National
Cancer Institute
National
Institutes of Health (NIH)
National
Women's Health Information Center
Susan
G. Komen Breast Cancer Foundation
|
