When looking at a 2-D and a 3-D image of a breast together, radiologists showed a 7 percent improvement in their ability to distinguish between cancerous and non-cancerous cases, according to two studies that the FDA considered during its approval process.
More accurate detection reduces the rate of false positives. In the United States, about 10 percent of women who have a screening mammogram will be called back for additional imaging, such as a sonogram or more mammography, according to the FDA. The vast majority of those women do not have breast cancer (about four cases of breast cancer are found for every 1,000 women who are screened, Greenberg says), but they have to cope with the fear and anxiety of having abnormal mammograms and perhaps undergoing more invasive testing.
"It's terrifying for a patient," Greenberg says. "It's anxiety-producing. It's inconvenient. It's additional radiation exposure. It's potential for a biopsy for something that really is benign."
Washington Radiology Associates began offering tomosynthesis in August 2011. Close to half of patients have been choosing to spend the extra $50, Greenberg says, which insurance does not cover. Aetna, for example, considers tomosynthesis "experimental and investigational because of insufficient evidence of its effectiveness."
Greenberg says that by using the combined 2-D and 3-D pictures, WRA has seen a 20 percent decrease in recall rates and a 31 percent increase in cancer detection over 2-D alone.
"It has been really helpful in detecting really small breast cancers and decreasing recall rates in all patients, whether they have dense breasts or fatty breasts or in between, whether they're 75 or 40 years old," Greenberg says.
In addition to a lack of information about whether 3-D alone would be as good as 2-D alone, there are no data yet to show which subgroups of women — stratified by age, breast size or density, cancer history — might benefit the most from tomosynthesis.