Breast MRI – Using MRI for Breast Cancer Diagnosis and Screening

Diagnostic Imaging to Aid Breast Cancer Treatment Decisions

Doctors examining x-ray
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Eva was initially diagnosed with a 3cm invasive breast cancer tumor. As part of her diagnostic workup, she had two breast MRIs done to help her surgeon see if any cancer cells had scattered from the main tumor (they had) so he could be sure to get clean surgical margins (he did). Her MRI created a three-dimensional picture of the tumor, revealing that it was not 3cm, as her mammogram showed, but was indeed 5cm, which changed her treatment plans -– and her life.

In order to help you understand more about the use of MRIs and treatment decisions, I looked up what the experts say in UpToDate -- a trusted electronic reference that is used by many of the oncologists who treat breast cancer patients.

You may or may not need a breast MRI. But you will need to know the size, extent, and location of your cancer. Start by reading this excerpt to see why a breast MRI may be important for you.

Diagnosing Breast Cancer: A Discussion of Breast MRI From UpToDate

"Magnetic resonance imaging (MRI) uses a strong magnet to create a detailed image of a part of the body. It does not use x-rays or radiation. Breast MRI may be recommended to aid in the diagnosis of breast cancer in selected situations. MRI is not recommended to detect breast cancer in all women because it is not as good as a mammogram for certain breast conditions, such as ductal carcinoma in situ (a type of noninvasive or early breast cancer).

The role of breast MRI for the diagnosis and management of breast cancer is evolving, and there is disagreement as to which women should undergo breast MRI in addition to mammography."

What is a Breast MRI?
Magnetic resonance imaging (MRI) is a noninvasive imaging technique that uses no compression, x-rays, or radiation. An MRI creates a detailed picture of the internal architecture of your breast tissue. Most MRI machines produce a digital image, which a radiologist can examine on a computer, or print out for study. This type of image can be done with or without the use of contrast agent.

Why Are Breast MRIs Used As Part of a Diagnostic Workup?
You've already had a mammogram, and perhaps an ultrasound and a biopsy. A breast MRI might also be done for some patients, to get more information about your cancer, or to see if tumors are responding to treatment. Mammograms are much less expensive than MRIs, and are good at detecting DCIS as well as calcifications. Breast MRI can image both breasts at once, and works well even with dense breast tissue. It is good at finding invasive breast cancer, imaging around breast implants, and detecting possible spread of cancer beyond the primary tumor. A breast MRI is also effective at finding unsuspected cancer in the other breast, which would allow for early treatment of both tumor sites at once. For women at high risk of breast cancer, an MRI would be a good way to fully screen the breasts and axilla.

Who Might Need a Breast MRI?
Mammograms are still the primary screening method used for breast cancer, and breast MRI is used primarily as a supplement to a mammogram. For young women with mutated BRCA genes, MRI may be used as screening for breast cancer, to see within dense breast tissue that might otherwise conceal masses. In diagnostic use, breast MRI might be used in these circumstances:

  • If a woman has swollen underarm lymph nodes, but no discernable breast mass on a mammogram, then an MRI may be used to carefully examine her breast to see if a small tumor is present, and may have shed cells to the axillary nodes.
  • For a newly diagnosed woman with dense breasts, a mammogram may not give enough guidance for the surgeon. So an MRI may be done to get more architectural information.
  • When biopsy results indicate a larger tumor than a mammogram reveals, an MRI can help map out the size and location of the tumor. This affects your decision regarding much tissue needs to be removed –- lumpectomy or mastectomy.
  • If it appears that there is more than one tumor in the same breast, an MRI can help image the size and spatial relationship of multiple tumors, and aid in planning the right surgery to remove those lesions.

Take-Home Message
Before making your decision on which surgery to have, you and your surgeon need as much accurate information about your cancer as possible. If you have a clear diagnosis of DCIS, and your mammogram gives a good image of your tumor, then your surgeon most likely has all the information needed to remove the cancer. But if your mammogram does not provide enough detail, or if your surgeon or radiologist has more concerns about the size and location of the cancer, then you may benefit from a breast MRI.

As for Eva, she chose to join a clinical trial, and took a new drug that shrunk her tumor greatly, before having breast surgery. She also had an MRI-guided biopsy, which detected satellite lesions. Fortunately, those other lesions disappeared during chemotherapy. Her MRI was a critical part of her treatment decisions.

Want to learn more? See UpToDate’s topic, "Diagnosing Breast Cancer: A Discussion of Breast MRI," for additional in-depth, current and unbiased medical information on breast cancer, including expert physician recommendations.

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