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Senior Citizen Health & Medicine
Women Found with Cancer in One Breast Should Use MRI
to Screen the Other
Other testing missed cancers found by magnetic
resonance imaging
 March 28, 2007 - Women with a recent diagnosis of
cancer in one breast should have MRI screening of the opposite breast,
concludes a multi-center study involving University of North Carolina at
Chapel Hill researchers.
The international research team found that MRI, or
magnetic resonance imaging, detected cancer in the opposite breast in 30
of 969 women (3.1 percent) that had been recently diagnosed with cancer
in just one breast. The cancers in the opposite breast were missed by
previous mammography and clinical exam.
The authors recommend MRI screening for women at
high risk for breast cancer those who already have the disease, have
been recently diagnosed or have a family history of breast cancer. The
results appear in the March 29, 2007, issue of The New England Journal
of Medicine.
"This study is pretty definitive evidence that the
opposite breast needs to be evaluated with MRI," said study co-author
Dr. Etta Pisano, a principal investigator and Kenan professor of
radiology and biomedical engineering at the UNC School of Medicine.
"But no one is recommending that we give up
mammography. MRI screening is a very expensive tool that should be used
judiciously for high risk populations. The last thing we would want is
for every woman to think she should get an MRI," Pisano said.
In addition, MRI does not detect calcifications,
one of the earliest signs of breast cancer. Mammography is the only way
to detect calcifications.
The study was conducted by the American College of
Radiology Imaging Network (ACRIN) at 25 test sites in the U.S. and
Canada. The National Cancer Institute funded the research.
Despite negative clinical breast exams and
mammography of the opposite breast, up to ten percent of women are later
diagnosed with cancer in the opposite breast after having begun
treatment for breast cancer, the study said.
This means patients must undergo two rounds of
cancer therapy (surgery and possibly radiation and/or chemotherapy)
rather than one, as would be the case if cancer in the other breast was
found at the time of initial diagnosis.
Sixty percent of the cancers uncovered by MRI were
invasive, with potential to spread beyond the breast. Such breast tumors
"are the most important ones to find," Pisano said. The average tumor
size was nearly 11 millimeters.
Pisano, director of the UNC Biomedical Research
Imaging Center and a member of the UNC Lineberger Comprehensive Cancer
Center, said the percentage of cancers found in the opposite breast was
huge.
"If you were to screen the opposite breast with
mammography in the general population, you would expect to find four to
seven cancers per 1,000 patients. This study found three per 100, nearly
ten times higher."
Smaller, less rigorous studies at a single center
had suggested that MRI would detect otherwise hidden cancers in roughly
5 percent of women with a recent breast cancer diagnosis. But the
percentages of additional cancers ranged widely, as did the ability of
these studies to correctly identify the absence of cancer. Nor did these
studies include a one-year follow-up to determine the breast cancer
status of the women in whom MRI did not detect disease.
The ACRIN authors note that the additional cancers
detected in their study was not influenced by the patients breast
density, menopausal status or primary tumor history.
"The reason why dense breasts are a problem is that
tissue lies between the tumor and the detector. The beam has to go
though a lot of normal tissue, which can hide the tumor. But if you take
slices, as MRI does, you get images in focus every few millimeters and
the tumor cant hide," Pisano said.
Editor's Notes:
Pisano was the lead investigator of the Digital
Mammographic Imaging Screening Trial (DMIST), an international study
which assessed the diagnostic accuracy of film and digital mammography
in screening women for breast cancer.
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