Women's Health Specialists of St. Louis
Obstetrics and Gynecology

Articles - Breast MRI

Even with no family history of breast cancer, approximately 1 out of 8 women will develop breast cancer in their lifetime. The majority of these breast cancers will occur in post-menopausal women. Annual mammograms are still the best screening tool for breast cancer. Though the majority of women who get breast cancer will have no family history, 5% of women who get breast cancer will have an inherited increased risk for breast cancer. Women who have inherited risk factors will often develop breast cancer at an earlier age. Women are considered at high risk if they carry the BRCA gene mutation, have first degree relatives with pre-menopausal breast cancer, or have multiple family members with breast, ovarian, colon, and uterine cancer. Women who are at increased risk for developing breast cancer ideally should begin screening at as early as 25 years of age. Unfortunately, mammograms are not generally recommended prior to age 35 because the density of the breast tissue reduces the sensitivity of the mammogram. Mammography may miss as much as a third of early breast cancers. Healthcare providers have been working diligently to try to develop better screening tools for breast cancer. Breast MRI is the most promising new screening modality for patients at increased risk of developing breast cancer. MRI is an abbreviation for Magnetic Resonance Imaging. During an MRI a giant magnet rather than x-rays are used. The magnet is so powerful that it is able to generate a magnetic field 10,000-30,000 times the Earths magnetic field. The response of the tissues within the magnetic field is then recorded and interpreted by computer to reveal a very precise picture. Breast MRI is 86-100% sensitive for the detection of breast cancer. The sensitivity of the test is not affected by the density of the breast. There of course are some drawbacks. First and foremost, it is a very sensitive tool but not very specific. In other words, if a mass is present it will be seen by MRI but the MRI can not differentiate masses that represent cancer from those that may be non-cancerous breast changes. This translates to need for further testing twice as often as those women screened by mammography and to a biopsy rate almost 5 times higher than those screened by mammography. This would be acceptable if we knew that the outcome of the follow-up exams and biopsies actually caught breast cancer earlier and saved lives. Unfortunately, studies have not yet shown that MRI saves lives over traditional mammography. MRI also takes about 45 minutes for the procedure and costs about ten times as much as mammography. Currently, MRI may be an addition to screening for women who are at high risk for the development of breast cancer. In the future, MRI may also be a very powerful tool for the detection of breast cancer in the general population. Many studies are underway to help develop protocols to use this sensitive tool for both women at high risk and also for the general population. At this time, all women are advised to have a baseline mammogram at age 35 and regular screening with mammogram beginning at age 40. Women who believe that they may be at increased risk for the development of breast cancer should discuss their options with their physician.