There has been a great deal of debate regarding the use of magnetic resonance imaging (MRI) to detect breast cancer. Unlike mammography, which uses low dose x-rays, MRI's do not expose the patient to ionizing radiation. Additionally, the false-negative (missed cancer) rate for mammography is around 10%. However, MRIs have high rate of false positives which, like a false alarm, can lead to unnecessary biopsies.

Although some studies indicate that MRI may be better able to detect certain breast cancers compared with mammography, the cost, high rate of false-positives, and inconsistent standards for performing MRIs have made broad use impractical. This year, new guidelines and findings from several studies provided additional guidance about how MRI should be used for breast imaging:

1. The American Cancer Society released guidelines stating for the first time that evidence supported routine MRI screening for patients at high risk of developing the disease - those with a 20% or greater risk of developing breast cancer over their lifetime, including individuals with strong family histories of breast cancer, certain genetic mutations, and other known risk factors.

2. A study suggested that patients recently diagnosed with cancer in one breast may benefit from MRI of the other breast to increase the chance of detecting additional cancers that may have been missed by mammography or clinical examination, since individuals who have had cancer in one breast are at increased risk for developing cancer in the other.

3. A second study found that MRI is significantly more sensitive than mammography for detecting ductal carcinoma in situ (a non-invasive, precancerous condition in which abnormal cells are found in the lining of a breast duct). MRI was particularly effective at finding those tumors that are more likely to be biologically aggressive and have the potential to turn into invasive breast cancer.

It is important to note that despite the benefits of breast MRIs for individuals in high-risk groups, MRI is not yet recommended for the majority of individuals as a screening tool for breast cancer because of the cost, lack of standards, and high rate of false positives, which can lead to unnecessary biopsies.

Mammograms are still considered the best screening tool for people who are at normal risk for breast cancer.

Updated by Medical Writers Group, LLC, New York, for John W. Nick Foundation, Inc. - January, 2008. (Made possible through a grant provided by Cancer Research and Prevention Foundation.)