Gamma Imaging: Adjunct to mammography
Manjula Puthenedam
Women with dense breast tissue have an increased risk of breast cancer. A recent study in Radiology has shown that the sensitivity of mammography alone was 27 percent, while the sensitivity of combined mammography and gamma imaging was 91 percent for breast cancer in women with dense breasts - making gamma imaging a potential adjunct to mammography.

Researchers from the Mayo Clinic
in Rochester, Minn., enrolled 936 at-risk women in the study, of which 11 had cancer. The researchers found that diagnostic yield was 3.2 per 1000 mammography, 9.6 per 1000 for gamma imaging, and 10.7 per 1000 for both. The specificity of gamma imaging and mammography were similar.

Although mammography added little increased diagnostic yield to gamma imaging in the study, the authors considered gamma imaging as an adjunct rather than as an alternative to screening mammography, given that mammography remains the only screening modality for which an associated reduction in breast cancer mortality has been demonstrated.

The effective dose of 20 mCi 99mTc-sestamibi used in the study was high relative to the radiation dose to the breast from a screening mammogram which translates to an effective dose of 0.7–1.0 mSv. But since the completion of the study, the Mayo researchers have improved the technical aspects of the system to reduce administered radiation dose to approximately 4 mCi, yielding an effective dose of less than 1.3 mSv.

An even larger study screening 2,500 general population women with dense breasts at a dose of 4 mCi is currently underway, according to the researchers.

These validation studies can tell us whether gamma imaging remains as an adjunct or could replace screening mammography in women in whom the sensitivity of mammography is limited. Stay tuned.

On these topics, or others, please feel free to contact me.

Manjula Puthenedam, PhD
Associate Editor, Molecular Imaging Insight