Gamma Imaging Bests Ultrasound for Dense Breasts

Nancy A. Melville

June 15, 2011

June 15, 2011 (San Antonio, Texas) — Breast-specific gamma imaging (BSGI) shows greater accuracy than ultrasound in detecting potentially cancerous tumors in complex breast imaging cases and should therefore improve the management of such cases, according to research presented here at the Society of Nuclear Medicine (SNM) 2011 Annual Meeting.

Conventional mammography often falls short in providing acceptable, clear images of malignancies in dense breast tissue. It typically detects about 85% of breast cancers in women with normal breast tissue, but only about 60% of cancers in women with dense breast tissue, according to the American Cancer Society.

In such cases, clinicians commonly turn to ultrasound to investigate unanswered diagnostic questions. However, BSGI is emerging as another valuable tool for imaging dense breast tissue, illuminating the metabolic activity of breast lesions, said lead author Douglas Kieper, BSNMT, professor and nuclear medicine research supervisor at Hampton University in Virginia.

"When other tests are needed [after mammography], ultrasound is the most frequently used," he explained. "However, since ultrasound and mammography are both anatomical imaging procedures, the things that make a mammogram hard to read can also affect ultrasound."

"BSGI is a metabolic imaging procedure that can detect cancers not seen with mammography or ultrasound, especially in women with dense breast tissue," noted Mr. Kieper, who is also vice president of science and technology for Dilon Technologies, which develops BSGI products.

In an effort to determine how BSGI can improve the management of such cases, Mr. Kieper and his colleagues evaluated 119 patients, from 4 medical centers, who were included in a patient registry and routinely scheduled for BSGI examination because of clinical or radiologic findings.

Biopsies were conducted as considered clinically necessary and were used as the gold standard.

The routine BSGI and ultrasound results were analyzed for their ability to provide additional information on the case and to alter the course of management.

Among the 119 patients, 102 benign, 15 malignant, and 2 high-risk breast lesions were discovered.

The use of BSGI resulted in a change in diagnosis in 109 of the 119 patients; the use of ultrasound resulted in a change in diagnosis in 71 patients.

BSGI offered greater sensitivity for detecting breast cancer than ultrasound (100% vs 77%) and greater specificity in identifying benign cases as negative (82% vs 52%).

"BSGI significantly improved the detection of breast cancer when mammography and ultrasound combined were not able to provide a confident diagnosis," Mr. Kieper said.

One concern about BSGI is its use of an injected nuclear radiotracer. The radiotracer is absorbed at a higher rate by cancerous cells, allowing for improved detection, but it also increases radiation exposure.

A recent report comparing imaging systems showed that a single BSGI exam involves a lifetime risk for fatal cancer that is as much as 20 to 30 times greater than that of digital mammography in women 40 years of age, according to the Radiological Society of North America.

In addition, whereas the risk for breast cancer is only slightly increased with the use of mammography, BSGI, along with positron emission mammography, might increase the risk for cancers in other organs of the body, including the intestines, kidneys, bladder, gallbladder, uterus, ovaries, and colon.

Researchers are working to adjust radiation doses, and some studies have shown encouraging signs of BSGI efficacy in imaging, even with much lower doses, noted Maroun Karam, MD, director of nuclear medicine and a professor of radiology at Albany Medical College in New York.

"The radiation level is a valid concern because the current guidelines from SNM [allow] a dose that is relatively high. However, recent studies from researchers at the Mayo Clinic and elsewhere have shown that this can be done with less radiation," he said.

Meanwhile, the technology represents an important addition to breast imaging tools, he added.

"I think this is a great breakthrough innovation in nuclear medicine and the diagnosis of breast cancer," Dr. Karam said. "There is a big gap for people with dense breasts, because the sensitivity of mammography in these women is quite low, so there is a need for imaging to resolve this issue."

The radiation levels are still a concern, but if the dose can be reduced to a relatively low level, BSGI could even be used as a screening method. At this point, it represents a valuable next step after mammogram for the imaging of dense breast tissue, and it's significantly less expensive than magnetic resonance imaging."

Mr. Kieper is vice president of science and technology for Dilon Technologies, which develops BSGI products. Dr. Karam has disclosed no relevant financial relationships.

Society of Nuclear Medicine (SNM) 2011 Annual Meeting: Abstract 246. Presented June 6, 2011.

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