Adding tomosynthesis to digital mammography results in a decrease in recall rates and an increase in cancer detection rates, according to a study published online June 25 by JAMA.
Tomosynthesis may act a complementary partner to mammography, especially given the technology’s shortcomings, noted the researchers. “This combined mode (digital mammography + tomosynthesis) addresses the primary limitations of conventional screening mammography by increasing conspicuity of invasive cancers while concomitantly reducing false-positive results,” wrote the study’s lead author, Sarah M. Friedewald, MD, of the Advocate Lutheran General Hospital in Park Ridge, Ill., and colleagues.
The researchers conducted a multicenter analysis to compare the performance of digital mammography and tomosynthesis to that of digital mammography across a spectrum of radiology practices in the U.S. Analyzing the records from 13 American mammography centers before and after they added tomosynthesis, the researchers compared the cancer detection rate, how often women were called back for more scans and the proportion of the callbacks and biopsies to actually find cancer.
The study included 454,850 screenings: 281,187 were with digital mammography alone and 173,663 were with the combined technologies.
Results revealed an improvement in cancer detection thanks to tomosynthesis. Cancer was discovered in 4.2 of every 1,000 scans with mammography alone but in 5.4 when tomosynthesis was included. After further analyzing these results, it was discovered that performance for detection of invasive cancers was also improved with tomosynthesis. Combined testing found 4.1 invasive cancers per 1,000 scans while digital mammography found 2.9. In situ growths were discovered at the same rate of 1.4 per 1,000 for both variations of screening.
Recall rates were lowered with the addition of tomosynthesis. There were 91 callbacks for every 1,000 women among those who were screened with the combination, while mammography alone resulted in 107 callbacks for every 1,000 women.
Of the women who were screened with mammography and called back, 4.3 percent had cancer. When the tests were combined, 6.4 percent had cancer.
Although there were more biopsies with tomosynthesis (19.3 per 1,000 scans versus 18.1 with mammography), more were positive for cancer at 29.2 percent versus 24.2 percent with mammography alone.
These results were averages from the 13 detection centers and may not match an individual’s results, noted Friedewald and colleagues. The researchers suggested the need for further studies to assess the relationship of the study’s findings to clinical outcomes.
In an associated editorial, Etta D. Pisano, MD, of the Medical University of South Carolina in Charleston, and Martin J. Yaffe, PhD, of the University of Toronto, address the debate over whether tomosynthesis should replace digital mammography and assessed the study conducted by Friedewald et al.
“Although the findings of Friedewald et al are similar to those from prior studies, this report adds considerable evidence to the current knowledge of how tomosynthesis performs in everyday practice in a variety of academic and community settings,” wrote Pisano and Yaffe.
While the editorial’s authors believe that tomosynthesis is extremely promising, they contend that it is still unclear whether or not women should seek it or clinics should adopt it. Several issues exist with the current study, wrote Pisano and Yaffe, including its lack of a rigorous method to pick patients at random to compare the types of screening.
“The nonrandomized design of the study by Friedewald et al precludes drawing causal inferences about the results, and the lack of long-term follow-up information limits the ability to provide definitive estimates of false-negative result rates, diagnostic accuracy, interval cancer rates, or overdiagnosis,” they wrote.
The authors believe that while the current study adds to the case for tomosynthesis over digital mammography, those who are questioning the utility of screening mammography may not be convinced by the evidence.
“As Friedewald et al have indicated, tomosynthesis is likely an advance over digital mammography for breast cancer screening, but fundamental questions about screening remain, with all available technologies,” they wrote. “Only an appropriately powered multisite clinical trial of modern technology can answer the remaining questions definitively. The time is now for the National Institutes of Health to fund such a much-needed trial to address many of the remaining issues about breast cancer screening,” they concluded.