Adding three-dimensional breast imaging—tomosynthesis—to standard digital mammography significantly increases the diagnostic accuracy of radiologists while reducing the rate of false positive recalls.
Screening mammography reduces cancer mortality in women aged 40 to 74 years, according to the National Cancer Institute (NCI). However, as many as 30% of breast cancers are not detected by mammography, and an additional 8% to 10% of women who undergo a screening mammogram are recalled for further testing when no cancer is present, which is a false positive result.
While a digital screening mammogram involves two radiographic images of each breast, breast tomosynthesis captures multiple, low-dose images from different angles around the breast. The images are then used to produce a three-dimensional reconstruction of the breast. Both digital mammography and breast tomosynthesis, which was approved by the FDA in February 2011, can be performed on the same mammography equipment in rapid succession.
This study involved 1,192 women recruited from five sites. Among these women, complete data sets were available for 997, including 780 screening cases and 217 women who needed prebiopsy breast imaging. Each enrolled woman underwent standard digital mammography followed by breast tomosynthesis. The combined procedure had a total radiation dose of less than 3 milligray, which is the FDA limit for a single mammogram.
The research team conducted two reader studies. The first reader study of 312 cases included 12 radiologists and 48 cases of cancer, while the second reader study of 310 cases included 15 radiologists and 51 cancers.
Compared with digital mammography alone, using both standard mammography and tomosynthesis increased the diagnostic accuracy for all 27 radiologists. In additional, the diagnostic sensitivity of the combined exam increased by 10.7% for radiologists in Reader Study 1 and by 16% for radiologists in Reader Study 2. The false positive recall rates were significantly lower for all 27 radiologists involved with the combined imaging. The absolute recall rate reductions were 38.6% and 17.1% in Reader Studies 1 and 2, respectively.
“This is the first major advance in breast imaging and breast cancer screening since the development of breast MRI,” said lead researcher Elizabeth A. Rafferty, MD, director of Breast Imaging at the Avon Comprehensive Breast Center at Massachusetts General Hospital in Boston. “The beauty of tomosynthesis is that it addresses two major concerns with screening mammography: missed cancers and false positive rates.”
“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.
This study was published in Radiology (2012; doi:10.1148/radiol.12120674).