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. Harms said.