RSNA 2008: New Breast Imaging Modalities Reveal Cancers as Small as a Single Millimeter

Martha Kerr

December 04, 2008

December 4, 2008 (Chicago, Illinois) — Two imaging modalities that look at breast cancer activity on a cellular level can pick up occult tumors that are only 1 to 3 mm in size in women with a history of breast cancer, radiologists reported here at the 94th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA 2008).

Results with positron-emission mammography (PEM) were announced by Kathy Schilling, MD, medical director of the Center for Breast Cancer, in Boca Raton, Florida. Results with breast-specific gamma imaging (BSGI) were announced by Rachel F. Brem, MD, professor of radiology and director of the Breast Imaging and Interventional Center at the George Washington University Medical Center, in Washington, DC.

Mammography and ultrasound analyze the anatomic structures of the breast. PEM and BSGI assess cellular activity. PEM measures uptake of fluorodeoxyglucose by breast cancer cells and BSGI uses sestamibi (technicium 99m) uptake to assess cellular activity.

Dr. Schilling presented findings from PEM in 208 patients with breast cancer. The investigators found 189 malignant lesions, of which 176 were visible on PEM, for a sensitivity of 93%.

PEM was able to detect malignancies in 100% of fatty breasts, 93% of dense breasts, and 85% of extremely dense breasts, and in 90% of premenopausal women and 94% of postmenopausal women with breast cancers, whether or not they were taking hormone-replacement therapy.

"There is no hormonal influence on PEM. There is no change it its accuracy," Dr. Schilling said, "and there is no effect of breast density on PEM accuracy."

"PEM can identify 2 mm ductal cancer in situ lesions. These are not visible on conventional mammography," she added. One caution is that PEM is performed while the patient is fasting. That and the glucose-based radiotracer that is used make it unsuitable for diabetic patients, Dr. Schilling cautioned.

PEM is done with the patient seated. "It is a very comfortable procedure," Dr. Schilling commented. The same is true for BSGI, Dr. Brem added.

Dr. Brem presented findings from BSGI in 159 women with at least 1 suspicious or cancerous lesion found on mammography or physical examination. The objective was to determine how often unsuspected occult cancers could be detected in a population already known to have breast cancer.

An additional suspicious lesion was found in 46 women (29%). Lesions were malignant in 14 of 39 (36%) cases biopsied. Nine lesions were in the same breast and 5 were in the contralateral breast. Dr. Brem reported that 73% of women had dense breasts.

The mean size of the occult lesions was 1.16 mm, and the smallest was only 1 mm in size. Half of the occult lesions were smaller than 1 cm.

BSGI is an effective approach for the detection of unsuspected cancers," Dr. Brem said. "It is complementary to ultrasound and uses a lower dose of radiation than PEM."

"PEM delivers the equivalent to approximately 3 mammograms. BSGI is at least half that dose," she said. There are few or no contraindications with BSGI. It can be used in diabetics and in patients with compromised renal function, and there are no weight restrictions or other limitations, Dr. Bream said.

In an interview with Medscape Radiology during RSNA 2008, Society spokesperson Lillian Stern, MD, assistant professor of radiology at Thomas Jefferson University School of Medicine, in Philadelphia, Pennsylvania, commented that PEM and BSGI "are novel ways of looking at breast cancers, looking at cellular activity rather than anatomically or physiologically."

"It's effective in tumors with 'single-file cells' that have no round masses or calcifications that would be visible with conventional imaging," she noted.

"I use BSGI in asymmetrical breasts, where there is less fat in 1 breast.... Most of the time, the results are clearly positive or clearly negative, and we can give the results to the patient immediately."

It will not replace mammography or magnetic resonance imaging (MRI), but I am using MRI less often now," Dr, Stern commented.

Dr. Schilling is a consultant with Johnson and Johnson and Naviscan PET Systems, Inc. Dr. Brem is a board member with Dilon Technologies LLC, manufacturers of a BSGI system. Dr. Stern has disclosed no relevant financial relationships.

RSNA 2008: 94th Scientific Assembly and Annual Meeting of the Radiological Society of North America: Scientific Session VB31-04: Presented December 3, 2008.

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