New guidelines from the American Cancer Society (ACS) recommend that women at very high risk for breast cancer receive magnetic resonance imaging (MRI) along with annual mammography, reports the October 2007 issue of Harvard Women's Health Watch.
In one recent study comparing MRI, mammography, and ultrasound in 171 women whose lifetime risk of breast cancer was very high (20% or more), MRI proved best at finding cancer. Of the six cancers diagnosed, MRI detected all six, mammography only two, and ultrasound only one. Only MRI detected the four cancers found in women with dense breast tissue.
Even so, the ACS and other groups don't recommend routine MRI screening for women at average risk, for reasons such as these: