Molecular Breast Imaging Has Promise

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An MRI (magnetic resonance imaging) scan of the breast is a good screening method for:

  • women with a high risk of breast cancer
  • women with dense breast tissue (less fat than average)
  • evaluating a suspicious mammogram result

Unfortunately, interpreting MRI images is more complex than interpreting mammogram images. MRI results are best read by a doctor very experienced in breast MRI interpretation. Breast MRI is also expensive. So doctors have been looking for other breast imaging techniques that are as reliable and more affordable than MRI.

A small study found that molecular breast imaging was similar to breast MRI in detecting breast cancer. Molecular breast imaging costs much less than breast MRI and is easier to interpret than breast MRI.

In molecular breast imaging (also known as a Miraluma test, sestamibi, or scintimammography), a small amount of the molecule sestamibi that has been tagged with a radioactive substance (technetium 99) is injected intravenously. Breast cancer cells tend to take up the tagged sestamibi molecule much more than normal cells. A nuclear medicine scanner then scans the breast and looks for any areas where the radioactive substance is concentrated, suggesting breast cancer.

This study looked at the records of 48 women who had BOTH breast MRI and molecular breast imaging within 30 days:

  • 42 women had the tests to evaluate an area of concern after a mammogram or to determine how much an already-diagnosed breast cancer had spread
  • 6 women were at high risk of breast cancer and had the tests to screen for breast cancer

The researchers looked at the biopsy results of women who had a biopsy or looked at the medical records of women who didn't have a biopsy to see whether breast cancer was diagnosed over the next 15 months.

The records showed that 32 of the 48 women were diagnosed with breast cancer. MRI and molecular breast imaging were both good at finding breast cancers. MRI found breast cancer 98% of the time. Molecular breast imaging found breast cancer 94% of the time. Molecular breast imaging missed two breast cancers in one woman, while MRI did find these cancers.

Both molecular breast imaging and breast MRI have rather high false positive rates. A false positive is an area identified as cancer that turns out to be normal. In this study, about 25% of both the MRI and molecular breast imaging findings were false positives. Besides the fear of being diagnosed with breast cancer, a false positive also means more tests (including biopsies) and follow-up doctor visits. The process can be very stressful and upsetting.

Molecular breast imaging has been used for some time now. Some doctors feel molecular breast imaging isn't good for detecting small, early breast cancers. While the results reviewed here suggest that molecular breast imaging may be a reliable and less expensive alternative to breast MRI, this study is very small and more research is needed.

Visit the Screening and Testing section to learn more about the tests used to diagnose breast cancer.

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