Molecular breast imaging: a review

Breast-specific imaging systems are by far the most sensitive and specific molecular modalities for the visualization of breast tumors, according to a review published Jan. 16 in the Journal of Nuclear Medicine.

Non-invasive molecular imaging of breast tumors presents opportunities for more personalized and predictive medicine and viable techniques for new drug therapies. Amy Fowler, MD, PhD, an assistant professor from the department of radiology at the University of Wisconsin–Madison, in Madison, Wis., broke down the sensitivity and specificities of all the major molecular imaging modalities for the breast and made recommendations for their clinical application.

Meta-analysis of scintimammography with Tc-99m sestamibi for the detection of breast cancer was gauged at 83 percent sensitive and 85 specific. There was no major difference in these numbers between SPECT and planar imaging.  FDG PET showed similar results, with 83 percent sensitivity and 89 percent specificity. PET/CT increased sensitivity slightly to 87 percent, but very small lesions—less than one centimeter—were imaged poorly with sometimes only 50 percent sensitivity.

“Thus, current recommendations do not support the routine use of F-18 FDG PET for primary breast cancer diagnosis because of its false-negative risk and have encouraged the development of dedicated breast PET scanners with improved spatial resolution for imaging small, clinically relevant, cancers,” wrote Fowler.

Another meta-analysis focusing on breast-specific gamma imaging (BSGI) as a supplement to mammography revealed a fine sensitivity of 95 percent and a specificity of 80 percent. Sensitivity dipped slightly for subcentimeter lesions (84 percent). A PET modality that places two flat detectors on either side of the breast, similar to mammography, has been developed and called positron-emission mammography (PEM). Another modality has the patient lying prone with the breasts placed into dual ring detectors. These modalities demonstrate 87 percent sensitivity and 85 percent specificity.

“Molecular imaging holds promise as an important adjunct modality for breast cancer detection and characterization,” noted Fowler. “As a diagnostic tool, however, it should be used only after a complete standard imaging evaluation and should not be used as an alternative to biopsy. It appears to be most useful when MR imaging is not an option.”

Fowler also mentioned that conventional nuclear medicine tests for the breast are tamped down when compared to mammography due to increased dose to the patient.