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 WHY BREAST MRI? |
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 Normal mammograms use x-rays to generate images of the breast tissue to search for cancer. MRI, on the other hand, uses a magnetic field instead of x-rays. Therefore, it is not damaging to normal tissue. Also, with MRI, the contrast between soft tissues in the breast is 10 to 100 times greater than that obtained with x-rays. This is why MRI is used much more than, for example, CT (or CAT) scanning, which uses x-rays, for diagnosing tumors in the brain. This leads to greater sensitivity of breast MRI compared to mammogram and ultrasound. For example, breast MRI has a 90-95% sensitivity, which is the ability to tell you there is no cancer. Mammograms and ultrasounds on the other hand, provide anywhere from 30-65% sensitivity.
Besides improved detection, breast MRI is changing our
management of breast cancer. For instance, a mammogram or ultrasound (sonogram)
of the breast may reveal breast cancer in one area. An MRI provides excellent
visualization of both breasts, chest wall and axilla
(under the arms). The MRI of the breast may show that the cancer is in
fact multi-focal; small tumors are present in several areas of the breast.
Determining the extent of breast cancer with an MRI can help indicate treatment:
breast conserving surgery (lumpectomy) or breast removal (mastectomy). If the
cancer is multi-focal, a mastectomy may be indicated. There have been many cases
where mammogram or ultrasound discovered a cancer, a patient went for a
lumpectomy and later was discovered to have more cancer in the same or opposite
breast and needed additional surgery. In fact, some breast surgeons will not
even operate on a patient who has breast cancer unless an MRI is performed.
Another major benefit of MRI is that it plays a significant role in the visualization of breast implants. MRI can often show if an implant is leaking or ruptured. MRI can also image the breast tissue that is compressed by an implant. Implants can obscure some of the breast tissue on conventional mammogram images, making abnormalities or signs of cancer more difficult to see. This is because the x-rays used for mammography cannot penetrate silicone or saline implants well enough to image the overlying or underlying breast tissue. MRI imaging does not have this limitation. Recently, the FDA lifted the ban on silicone-gel implants, but recommended MRIs 3 years after the implant placement and then every 2 years after to evaluate for silent rupture.
 There are tremendous benefits with breast MRI over conventional screening techniques. Breast MRI does have its drawbacks however. First of all, it is 10-15x more expensive than a mammogram. If you have no known risk factors for breast cancer, your insurance may not cover the test.
If you do have risk factors
(family history, genetic BRCA1 and BRCA2 carrier, past history of breast cancer,
and/or dense breasts), you may be eligible for high-risk screening.
Women should still go for their annual screening mammograms. Breast MRI
is adjunct to conventional breast cancer screening, not a replacement. But it is
an invaluable and important piece of the breast cancer puzzle.
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