MBI - Latest Screening Technology: A Better Tool For Dense Breasts?

Patient Expert

Coming soon to a hospital near you: the MBI, a great new screening tool that might someday replace the mammogram.

Wait a minute hasn't MBI, or molecular breast imaging, been around for awhile? Isn't it known mainly for its slew of false positives, its inconvenience, and its expense?

Have We Already Heard about MRI for Cancer Detection -- and Its Flaws?

No, you're thinking of the MRI magnetic resonance imaging. This breast cancer screening tool has indeed been available for awhile now. And despite an initial flurry of hope that it might prove even more accurate and effective than our faithful old mammogram, it has yet to live up to its early promise, basically due to those false positives. Way too many women end up having needless biopsies when an area of breast tissue identified as "suspicious" in an MRI turns out to be nothing more than a benign shadow.

But MBI that's a different (new) story. Molecular breast imaging, an emerging technology, was the focus of a study presented Tuesday at the American Society of Clinical Oncology's 2008 Breast Cancer Symposium, being held this week in Washington, D.C. While mammography uses conventional X-rays to differentiate tumors from breast tissue, the MBI relies on identifying cancer cells through the use of an injected radioactive agent, which is absorbed by breast tissue. Cancer cells in the breast absorb more of this agent than healthy cells; and these killer cells are then identified with a special camera, which detects the increased degree of gamma rays they emit.

In a study of nearly 1,000 women identified as being at high risk for breast cancer due to genetics or family history, the MBI identified 10 tumors, while mammography picked up just three. And just as importantly, the MBI didn't result in any more false positives than did mammograms.

Statistically, mammograms "miss" up to 15% of cancerous tumors. And often, it's due to the inability of the mammogram's X-rays to distinguish tumor from breast tissue, a serious issue for women identified as having dense breasts. The MBI could be an important breakthrough for these women, who represent about 25% of the female population.

Not only do dense breasts place a woman at greater risk of breast cancer; they often "hide" tumors from X-rays. In an X-ray, fat tissue shows up clear, while breast tissue and tumors both show up opaque. Thus a woman with more breast tissue than fat runs the risk of tumors being camouflaged within her breast tissue. This isn't the case with the MBI, which marks cancer cells in a very different way than healthy cells, whether in fat tissue or breast tissue.

There's still work to be done. At about $500 per use, the MBI is more expensive than a mammogram (though less expensive than an MRI). And at its current levels, the radioactive injection presents an unacceptable health risk if used on a regular basis (i.e., every year or two). Realistically, the MBI may someday be a great adjunct to mammography, rather than a complete replacement. But keep your ears open; MBI is a coming technology. And, especially if you have dense breasts, it might someday help save your life.