Molecular breast imaging (MBI) is a method for detecting breast cancer. The technique is also known as a Miraluma test, sestamibi, scintimammography, or breast specific gamma imaging.
MBI uses a radioactive tracer that “lights up” any areas of cancer inside the breast. This tracer is injected into the body through a vein in the arm. Breast cancer cells tend to take up the radioactive substance much more than normal cells do. A special camera called a nuclear medicine scanner then scans the breast, looking for any areas where the radioactive substance is concentrated. The process takes about half an hour, and unlike mammography, it yields images of cancerous tissue regardless of the tissue’s density.
MBI continues to be tested, but it appears to hold promise for detecting breast cancer in women who are at higher-than-average risk for the disease and have dense breasts. When women have a lot of dense breast tissue, tumors become hard to spot on mammograms. On mammograms, fatty breast tissue looks dark, but dense tissue is light, like tumors, so it can hide any cancerous areas that may be present.
In a recent study published in the August 2016 issue of the American Journal of Roentgenology, Molecular breast imaging was shown to be effective as a supplementary screening tool to mammography for women with dense breasts. Researchers from Ohio, California, and New Hampshire performed a retrospective study to assess the utility of MBI as a supplementary screening tool for 1,696 women with dense breast tissue. The results showed that 13 mammographically occult malignancies were detected among the study group. Eleven were invasive, one was node positive, and one had unknown node positivity. Other findings showed:
- Lesion size ranged from 0.6 to 2.4 cm, mean 1.1 cm
- Incremental cancer detection rate was 7.7%
- Recall rate was 8.4%
- Biopsy rate was 3.7%
When incorporated into a community-based clinical practice environment, molecular breast imaging yielded a high incremental cancer detection rate of 7.7 cases of breast cancer for every 1,000 women at an acceptable radiation dose. However, one drawback of MBI is that it involves a much greater dose of radiation than mammograms.
MRI (magnetic resonance imaging), is often the preferred tool for evaluating women who are considered high-risk and have dense breasts. However, MRI has no radiation, but is more expensive than MBI and can return false positive results, leading to unnecessary biopsies. If a mammogram shows that you have dense breast tissue, MBI may be an alternative to ask about.
Bottom line: If you are at average risk for breast cancer and do not have dense breasts, mammography remains the screening tool of choice for you. Many doctors believe that, for most women, mammography is better than MBI at detecting breast tumors when they are small and generally easier to treat.
About the author: Raja P. Reddy, MD is a board certified diagnostic radiologist specializing in breast imaging. He is also a contributing editor for Digital Mammography Specialists, a leading provider of outpatient women’s imaging services in the greater Atlanta, GA area.