The procedure is nearly identical to a routine mammogram, except that in mammography the machine is stationary, while in tomosynthesis it moves around the breast. Sometimes called 3-D mammography, the test takes many X-rays at different angles to create a three-dimensional image of the breast.
The study analysed the records from 13 American mammography centres before and after they added tomosynthesis. The researchers compared the cancer detection rate, how often women had to be called back for more scans to check on suspicious findings, and what proportion of the callbacks and biopsies actually found cancer. The project involved 454,850 screenings: 281,187 with digital mammography alone and 173,663 that combined it with tomosynthesis. The exams were done from March 2010 through December 2012.
Tomosynthesis improved cancer detection. Cancer was found in 4.2 of every 1,000 scans with digital mammography alone, but in 5.4 when tomosynthesis was added.
Dr Etta D Pisano, a mammography expert and dean of the College of Medicine at the Medical University of South Carolina, called tomosynthesis extremely promising. But in an editorial with the journal article, Dr Pisano, who was not involved in the study, said it was still not clear whether women should seek it or clinics should adopt it. She said more research was needed. One concern she raised about the study was that it simply looked back at records instead of using the more rigorous method of picking patients at random to compare types of screening.
Even so, more and more mammography centres are buying the equipment, which is far more costly than a standard mammography unit, and marketing the test to patients as a more sensitive and accurate type of screening.
It is very much taking hold in the breast-imaging world, said Dr Sarah M Friedewald, the section chief of breast imaging at Advocate Lutheran General Hospital in Park Ridge, Illinois, and the first author of the new study.