Adding Breast Tomosynthesis to Digital Mammography Increases Diagnostic Effectiveness

The multicenter study’s findings were published November 2012 in the journal Radiology. “This is the first major advance in breast imaging and breast cancer screening since the development of breast MRI magnetic resonance imaging],” said lead researcher Elizabeth A. Rafferty, MD, director of breast imaging at the Avon Comprehensive Breast Center at Massachusetts General Hospital (Boston, MA, USA). “The beauty of tomosynthesis is that it addresses two major concerns with screening mammography: missed cancers and false-positive rates.”

There is substantial evidence, according to the US National Cancer Institute, that screening mammography can slash breast cancer mortality in women between the ages of 40 and 74. However, as many as 30% of breast cancers are not identified by mammography and an additional 8% to 10% of women who undergo a screening mammogram are recalled for additional testing when no cancer is present (a false-positive result).

In contrast to a screening digital mammogram, which involves two X-ray images of each breast, breast tomosynthesis captures multiple, low-dose images from different angles around the breast. The images are then utilized to generate a 3D reconstruction of the breast. Both digital mammography and breast tomosynthesis, which was approved by the US Food and Drug Administration (FDA) in February of 2011, can be performed on the same mammography equipment, in rapid succession.

Dr. Rafferty’s study was comprised of 1,192 women recruited from five sites, of whom 997, including 780 screening cases and 217 women who required prebiopsy breast imaging, had complete data sets. Each of the women underwent a standard digital mammogram followed by breast tomosynthesis. The total radiation dose for the combined procedure was less than 3 milligray, which is the FDA threshold for one mammogram.

Drawing from the eligible cases, the researchers then conducted two reader studies
involving 312 and 310 cases, respectively. Twelve radiologists participated in the first reader study and 15 radiologists in the second. A total of 48 tumors were included in the first reader study and 51 tumors in the second. Compared to digital mammography alone, the use of both standard mammogram and tomosynthesis resulted in increased diagnostic accuracy for all 27 radiologists. Moreover, the diagnostic sensitivity of the combined exam--or the rate at which cancer present in the breast was correctly identified--increased by 10.7% for radiologists in reader study 1 and 16% for radiologists in reader study 2.

“Almost all of the gains in diagnostic sensitivity with the combined modality were attributable to the improved detection and characterization of invasive cancers, which are the cancers we are most concerned about because of their potential to metastasize,” Dr. Rafferty said.

By adding of breast tomosynthesis to traditional digital mammography, false-positive recall rates also substantially decreased for all 27 of the radiologists. Absolute recall rate reductions of 38.6% and 17.1% were seen in Reader Studies 1 and 2, respectively.

“In the clinical setting, we would expect that type of reduction in recall rate to translate into a substantial number of unnecessary diagnostic tests being avoided,” Dr. Rafferty said.

Related Links:
Comprehensive Breast Center at Massachusetts General Hospital