We have heard about other tests besides mammograms, and many women come in with questions about these tests. Some of this is due to the limitations of mammograms and others are looking for more comfortable testing because mammograms can be painful for some women. The most common questions I get are about breast MRI.
Breast Magnetic Resonance Imaging (MRI) is a 3-dimensional test to evaluate the breasts. You are placed on your belly on a table that is surrounded by a tubular structure and requires you to lie still for about 20 minutes. A material called gadolinium is used for contrast and is injected prior to going in the tube. There is no radiation exposure. The test looks at the blood flow in your breasts and areas will “light up” if there is increased blood flow. It is important to note that certain conditions may prevent you from having this test. These include any metal in your body, any previous allergic reaction to gadolinium contrast material, claustrophobia and too much weight. The MRI is a magnet so any metal will be attracted to the machine. There is a maximum weight limit so being too heavy may also prevent testing. Breast MRI seems to be a good tool for women who have very dense breasts, where mammograms may be limited in viewing the breasts well.
Breast MRI is a very sensitive test but is not very specific. In other words, it can pick up a lot of things, but these things are not necessarily abnormal. It can highlight cysts, fibroadenomas, and other benign conditions. Breast MRI has a 13% false positive rate which means that it can find things that are not cancer. This may result in more testing, and possibly, an unnecessary breast biopsy. This is one limitation of breast MRI. The other is cost. Breast MRI can cost thousands of dollars. Because of this, insurance companies have been reluctant to cover this unless strict criteria are met. Breast MRI is usually indicated in the following situations:
- Newly diagnosed breast cancer-to look for more cancer in the same breast or the other breast.
- Unknown primary cancer-lymph nodes may show breast cancer but the primary tumor is not found on mammograms.
- Evaluation for implant leaks.
These are considered diagnostic MRIs. Screening MRIs are different because they are performed when the woman has no breast issue or problem. The American Cancer Society came out with some guidelines about when MRI should be used. It should be considered in women who have a 20-25% lifetime risk of developing breast cancer. In other words, a woman who is at high-risk should consider having this test. If you are at high-risk and your insurance will cover the test, it may be reasonable to have a breast MRI. Since every woman is different, I would recommend that you discuss this with your doctor. Next week: What does weight have to do with breast cancer?
Katherine Lee, MD