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MRIs for Breast Cancer Screening—Who Needs Them?

Many experts believe that mammograms save lives. Since the widespread introduction of mammography to screen for breast cancer in the mid-1980s, the number of women ages 50 and older getting mammograms has more than doubled. Pair that figure with steady drops in breast cancer deaths since the 1990s.

But some health care professionals argue that mammograms are not enough for some women at high risk for breast cancer. New studies suggest that MRIs (magnetic resonance imaging) may improve the early detection of cancer in women at high risk.

Current Screening Guidelines for Women at High Risk

According to the American Cancer Society, you are considered at high risk for breast cancer if you answer yes to any of these questions:

  • Do you have a first-degree relative (parent, brother, sister, or child) with a known BRCA1 or BRCA2 gene mutation, but have not had genetic testing done yourself?

  • Have you tested positive for genetic changes that increase the risk for breast cancer—BRCA1 or BRCA2 mutations?

  • Has your doctor estimated that you have a lifetime risk of breast cancer of 20 to 25 percent or greater, according to risk assessment tools that are based mainly on family history?

  • Did you get radiation therapy to the chest when you were between the ages of 10 and 30?

  • Do you have Li-Fraumeni syndrome, Cowden syndrome, or Bannayan-Riley-Ruvalcaba syndrome, or have one of these syndromes in first-degree relatives?

If you're a woman at high risk for breast cancer, you should ask your doctor if you should have more frequent screenings, with a variety of tests, starting at a younger age. For women at high risk, some experts recommend monthly breast self-exams starting between ages 18 to 21, clinical breast exams one to two times a year, and yearly mammography starting at about age 30. The American Cancer Society recommends that women known to be at high risk get an MRI along with a mammogram every year, starting at age 30.

How MRIs Work

Instead of the X-rays used in mammography, an MRI uses magnets and radio waves connected to a computer to make many detailed pictures of the breast. A woman receives an injection of a contrast dye, called gadolinium-DTPA, to better outline the breast tissue and possible tumors.

Researchers have found that MRIs given to women with a high risk of hereditary breast cancer detected tumors that mammography or clinical breast exams had missed.

One reason MRIs may find these tumors is because high-risk women tend to be younger and have denser breasts. This means that the breast has less fat and more fiber-like connective tissue, which can block X-rays during a mammogram. An MRI is not affected by dense, fibrous breast tissue.

Drawbacks of MRIs

It's also important to weigh the pros and cons of MRIs for defined groups of high-risk women. Here are some of their drawbacks.

  • MRIs may have a high rate of false positives. A false positive means it looks like cancer but is not. MRIs are more sensitive, which means they are more likely to find changes that turn out to not be cancer. This leads to further testing to determine if the suspicious lump is actually cancer. Those tests may include another MRI, other tests, or biopsies.

  • MRIs are costly. They require special breast MRI equipment and a radiologist trained in breast imaging to interpret the images. Possible follow-up tests or biopsies add to the costs.

  • Women may have an allergic reaction to the contrast dye. The dye gadolinium-DTPA is injected before an MRI. Very rarely, this may cause an allergic reaction, but even the thought of receiving an injection can increase anxiety in some patients.

  • The MRI machine makes some people uncomfortable. The narrow tunnel-like opening of the MRI--a machine that a patient is placed in during the exam--may cause anxiety and discomfort, especially in those who are claustrophobic.



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