Gamma imaging picks up cancer unseen by mammograms

December 3, 2008

Out of every 10 women whose mammogram or physical exam reveals potentially cancerous cells in their breasts, approximately three of them will have additional dangerous clusters the examinations missed, according to a recent study presented at the RSNA conference Wednesday.

Out of every 10 women whose mammogram or physical exam reveals potentially cancerous cells in their breasts, approximately three of them will have additional dangerous clusters the examinations missed, according to a recent study presented at the RSNA conference Wednesday.

Breast-specific gamma imaging can detect cancer cells that escape the notice of mammograms and physical exams, said lead author Dr. Rachel Brem, a professor of radiology at The George Washington University Medical Center in Washington, DC.

The danger is even greater for women who have dense breasts that can mask the presence of cancer, a category that encompasses more than half of women under 50, Brem said.

Brem's team of researchers examined the records 159 women who underwent breast-specific gamma-imaging after their mammograms or clinical exams revealed one or more suspicious or cancerous lesions. Gamma imaging revealed at least one more suspicious lesion in 29% of them.

The technique uses a different approach from traditional mammograms.

"They're anatomic approaches to breast cancer detection. They ask, what does breast cancer look like?" Brem said. "But what if you could fundamentally look at breast cancer from a different perspective? What if you could say, ‘how does breast cancer function differently from the normal surrounding breast tissue?'"

To detect potentially dangerous cells using gamma imaging, the physician injects technetium-99m-sestamibi into the patient's arm. Cancer cells, due to their high metabolic activity, absorb much more of the substance than normal cells. This sends up a red flag for doctors looking for signs of danger.

At least half the occult cancers detected in this study were smaller than 1 cm, but Brem said gamma imaging can detect early lumps as small as 1 mm.

Although this radiotracer has been used for over 10 years, Brem said its ability to unearth additional cancers could affect how women receive treatment.

She also said it could be particularly helpful for patients with diabetes, a disease that can pose problems for the positron emission mammography (PEM). But she warned that gamma imaging should not be seen as a replacement for mammograms.

"This will not obviate the need for either mammography or tomosynthesis," she said, referring to an x-ray technique also used to detect breast cancer.

Brem estimated the equipment costs approximately $250,000, and the radiotracer roughly $75. More than 80,000 patients in the U.S. have used BSGI to date, according to Brem.