DALLAS--RODEO breast MRI proved significantly more accurate than
mammography in determining the extent of lobular carcinoma and
in characterizing the morphology of the disease, Steven E. Harms,
MD, said at the American College of Radiology breast cancer symposium.
In the Baylor study of 20 breast cancer cases with pathology proven
infiltrating lobular carcinoma, RODEO MRI findings agreed with
pathology results concerning the extent of disease in 85% of cases
versus 31.8% for mammography.
Although lobular carcinoma accounts for less than 10% of breast
cancers, an estimated 30% of malpractice suits for failure to
diagnose on mammography involve the lobular carcinoma histology.
This is because the unique infiltrative pattern of lobular carcinoma
makes it difficult to palpate, and tumors may not show up on mammography
until the mass is very large, said Dr. Harms, director of magnetic
resonance imaging, Bay-lor University Medical Center, Dallas.
About one third of lobular cancers are bilateral and multifocal.
Although lum-pectomy is a treatment option, mastecto-mies are
more often performed because of the inability of mammography and
conventional MRI to correctly determine the extent of the disease
prior to surgery.
Conventional MRI is problematic in this setting because of volume
averaging, he said. "Low-contrast, low-resolution techniques
will average out the tumor with the surrounding tissue, so that
it is below the threshold for detection."
However, RODEO (rotating delivery of excitation
off-resonance) three-dimensional MRI provides 20 times higher
resolution and much better contrast than conventional MRI, Dr.