Q: I recently heard in the news about a new breast cancer detection method that, according to the report, is really promising. Is this going to replace the mammogram?
A: The new technology is called molecular breast imaging. Although molecular breast imaging probably won’t replace mammography, it may be a useful screening tool for some, particularly women with dense breast tissue and those at high risk of breast cancer. The imaging technique isn’t widely available to the public yet because it still needs more research. But so far, the results look promising.
Mammography works very well for most women. However, for those who have dense breasts, a mammogram might not be sensitive enough to reveal the difference in appearance between normal breast tissue and a tumor. That’s a concern, because women who have dense breasts are four to six times more likely to develop breast cancer than other women. As a consequence, women who have dense breasts and other breast-cancer risk factors often need more advanced breast-cancer screening than just mammography.
For molecular breast imaging, patients are injected with a short-lived radioactive agent (radio tracer) that is absorbed by breast tissue. This agent is tracked with a special camera that can distinguish healthy tissue from breast cancer tumors because cancer cells absorb more of the radioactive agent than do the healthy cells. As a result, molecular breast imaging generates an image of how a tumor behaves, compared with normal tissue. These differences between a tumor and normal tissue are much clearer with molecular breast imaging than with other techniques.
A recent Mayo Clinic study involving 940 women compared molecular breast imaging with mammography as a breast-cancer screening tool. All 940 had dense breast tissue plus an increased risk of breast cancer because of personal or family history, a genetic mutation related to breast cancer, a previous precancerous condition or history of chest radiation therapy.
In study participants, molecular breast imaging detected three times as many cancers as mammography. Also, the new imaging technique did not increase the number of false-positive results, compared with mammography. This indicates that molecular breast imaging could be an important tool. More work is needed, however, before it can be used routinely.
One issue is determining how to lower the radiation dose to the level of radiation from a mammogram and maintain imaging accuracy. Currently, the radiation used in molecular breast imaging is safe, if a woman has the test just several times during her lifetime. But the radiation dose is too high for annual screening. Current research is looking at ways to maintain the accuracy of molecular breast imaging with lower levels of radiation.
Other studies are comparing molecular breast imaging with breast magnetic resonance imaging (MRI). Although very effective in detecting breast cancer, MRI is significantly more expensive than mammography. Molecular breast imaging also is more expensive than mammography but only about one-fifth the cost of breast MRIs.
Larger studies are needed to further validate Mayo’s original research findings. Molecular breast imaging’s ability to detect cancers that are not easily visible on screening mammography is encouraging.Write to medicaledge@mayo.edu, or Medical Edge from Mayo Clinic, c/o TMS, 2225 Kenmore Ave., Suite 114, Buffalo, N.Y., 14207; or visit
Dr. Carrie Hruska, Radiology, Mayo Clinic, Rochester, Minn.
