Is DBT ready to replace digital mammography for screening?

By Kate Madden Yee, staff writer
March 2, 2017

VIENNA - Enthusiasm for digital breast tomosynthesis (DBT) continues to grow, with adherents lauding its increased cancer detection and reduced false-positive rates. Thus far, the technology has been used as an adjunct to digital mammography. But could it replace that modality? Two presentations given during a Wednesday session at ECR 2017 addressed the question.

It's clear that DBT's sensitivity is superior to that of mammography, said session moderator Dr. Sylvia Heywang-Köbrunner of Breast Diagnostics Munich. However, finding more cancers doesn't necessarily translate into reduced mortality rates, since increased detection could be caused by overdetection of "harmless" malignancies, she said.

"We need further data to estimate the technology's effectiveness and its potential for overdiagnosis," she told session attendees. "And there are logistical problems such as longer reading time and how to optimize hanging protocols and comparison with both digital mammography and DBT priors."

In addition, more evidence is needed regarding how tomosynthesis does with interval cancers.

"Several trials show that tomosynthesis has excellent sensitivity and good specificity, but we still don't know how it performs with interval cancers," Heywang-Köbrunner said. "So although tomosynthesis is promising, we need more interval cancer data."

More from Malmö

The need for more interval cancer data for tomosynthesis was on the list of "lessons learned" from the Swedish Malmö Breast Tomosynthesis Screening Trial, which Dr. Kristina Lång, PhD, of Lund University presented during the session.

Lång outlined key takeaways from the study, which recruited 15,000 women between 2010 and 2015. The women were between the ages of 40 and 74 and underwent one-view DBT and two-view digital mammography. Lång and colleagues have published preliminary results that include data from 7,500 women; they are in the process of analyzing data for the total study cohort.

These preliminary results have shown the following:

  • Tomosynthesis increased breast cancer detection in screening by 43%, from mammography's 6.3 per 1,000 cases to DBT's 8.9 per 1,000. "Tomosynthesis as a standalone modality found all these additional cancers," Lång said.
  • The additional cancers identified are mainly small and invasive. "Of the 21 additional cancers tomosynthesis found, 17 were invasive, and they were approximately 13 mm," she said. "Forty-eight percent of them were grade 1, and 90% were node-negative, which suggests that there's a trend toward downstaging."
  • Tomosynthesis increases the recall rate, from mammography's 2.6% to 3.8%, but this increase is commensurate with the increase in cancer detection, according to Lång.
  • False-positive rates initially increase with tomosynthesis, but they stabilize over time as readers become accustomed to the technology. "There was a clear learning curve," she said. "The tomosynthesis false-positive rate decreased by 50% during the first one and a half years of the trial, to stabilize at a rate of 1.5%."
  • Tomosynthesis is "one size fits all" when it comes to breast tissue density. "The additional detected cancers tomosynthesis found were across all density categories," she said.
  • Breast compression can be reduced with DBT. "We found that there was no significant difference in image quality when breast compression was reduced by 50%," Lång said.
  • One-view tomosynthesis is sufficient with a wide-angle system.
  • The technology brings workflow challenges, including longer exam times, the need for more data storage, and the logistics of tomosynthesis-guided biopsy -- not to mention reading times that are two to four times longer than with digital mammography, according to Lång. Artificial intelligence technology will probably help with this last issue, she said.

Investigating intervals

All of these findings suggest that tomosynthesis could indeed replace digital mammography for screening. But like Heywang-Köbrunner, Lång emphasized that more data on DBT and interval cancers are needed. Her team plans to work with researchers from the Screening With Tomosynthesis or Standard Mammography (STORM) trial and the Oslo Tomosynthesis Screening Trial (OTST) to tackle the issue.

"We're planning a joint effort with [researchers from the] other prospective, population-based trials to do an individual participant data meta-analysis and evaluate whether tomosynthesis reduces the interval cancer rate," Lång said. "When we have analyzed interval cancer rates, let's use tomosynthesis in screening -- with the aid of artificial intelligence."

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Last Updated np 3/14/2017 9:51:57 AM

2 comments so far ...
3/2/2017 7:35:28 PM
The ONLY reason for using DBT is for screening. You cannot increase cancer detection rates by using it only for diagnosis, and you cannot reduce callback rates unless it is used for screening. It may have some advantages for analyzing lesions in a diagnostic setting, but it is an expensive way to do what can be done with additional conventional imaging.
At some point the nonsense needs to stop. DBT is a replacement for 2D mammography. It is simply a better mammogram. Digital mammography did not actually improve our ability to detect cancers (the analysis of DMIST was contrived to show a slight edge for DM). Digital replaced conventional Film/Screen mammography because the World was changing to digital and the logistics were facilitated - no more film libraries, handling folders, and losing images. Digital was not adopted because it found more cancers and it did not reduce recalls.
Digital did allow me to apply tomosynthesis to breast evaluation and it allowed my group to develop and test DBT. Our early results showed what we had hoped – increased sensitivity AND improved specificity that have been repeatedly confirmed.. DBT is the next advance in screening and a replacement for conventional 2D mammography.
It is not clear whether DBT is finding cancers that would be found next year or the year after, earlier, or whether it is finding "interval cancers". Remember, 2D screening does not result in saving everyone, so that finding the same cancers earlier is still a major benefit.
I am surprised that anyone has bought into the false claim that there are many (if any) "overdiagnosed" invasive cancers. All of the papers that have made this claim have been shown to be scientifically flawed. These are all "real" cancers. At this point in time we need to try to find as many invasive cancers as early as possible to continue to drive down the death rates. If we could screen everyone with MRI we might reduce deaths by 80% or 90%, but this is not practical. DBT will help further reduce deaths but we should stop debating its merits and work to find even better ways to find more curable breast cancers.

3/30/2017 1:33:16 AM
Is This Post by dr Daniel Kpoans from MGH?