Breast-specific gamma imaging (BSGI) is effective in detecting cancers unfound on mammograms or by clinical exam, according to a study published Thursday at an annual academic meeting.

"BSGI can identify the most difficult to detect breast cancer -- invasive lobular carcinoma," said lead author Rachel Brem from George Washington University at the meeting of the Radiological Society of North America (RSNA).

"It also can help us detect additional lesions of all types of breast cancer in women whose mammograms show only one suspicious lesion," he added.

Breast cancer affects more women than any other non-skin cancer, accounting for more than 40,000 deaths annually in the United States. Most experts agree that the best way to cut breast cancer mortality is through early detection. However, some cancers are difficult to detect with mammography and by clinical exam, particularly in the earliest stage when treatment is most effective.

While mammography findings are characterized by differences in appearance between normal and suspicious breast tissues, BSGI findings are based on how cancerous cells function.

BSGI is an emerging molecular imaging technology using a high-resolution gamma camera that allows imaging with very mild compression of the breast, along with an injection of a low-dose nuclear material called a radiotracer, which is absorbed by the cells. Because cancerous cells have a higher rate of metabolic activity, the tracer is taken up by these cells at a higher level than by normal ones.

Brem and his colleagues reviewed records of 159 women, each with at least one suspicious or cancerous lesion found by mammography or physical exam, and had undergone BSGI to determine if additional lesions existed.

BSGI results showed an additional suspicious lesion was missed by mammography and physical exam for 46, or 29 percent of the women. Among them, for 14, or 36 percent of the 39 women who underwent biopsy, the newly discovered lesions were cancerous.

"The data suggest that BSGI allows for the diagnosis of more and earlier breast cancers," said Brem, who also pointed out that BSGI is not meant to replace mammography, but to be used as an adjunct to mammography.

"It is an excellent tool for locating difficult-to-detect cancers and for screening high-risk women who have normal mammograms and physical examination."