3D May Be the 'Most Exciting Improvement' to Mammography

Roxanne Nelson

June 25, 2014

3D mammography, or digital breast tomosynthesis, can locate significantly more invasive cancers than conventional digital mammography, reducing unnecessary follow-up exams, according to a retrospective study published in the June 25 issue of JAMA.

In fact, the rate of invasive cancer detection increased by 41% after the implementation of tomosynthesis.

The rate of ductal carcinoma in situ (DCIS) detection remained the same after the implementation.

The use of tomosynthesis also reduced the number of women who were called back for unnecessary screenings because of false alarms by 15%.

"It's the most exciting improvement to mammography that I have seen in my career, even more important for women than the conversion from film-screen mammography to digital mammography," said senior author Emily F. Conant, MD, chief of breast imaging in the Department of Radiology at the Perelman School of Medicine, University of Pennsylvania, in Philadelphia, in a statement.

"3D mammography finds more clinically significant breast cancers earlier, which is the key, so that women have more treatment options and ultimately better health outcomes," she noted.

However, the fact that the trial had a nonrandomized design "precludes drawing causal inferences about the results," write Etta D. Pisano, MD, from the Medical University of South Carolina in Charleston, and Martin J. Yaffe, PhD, from the University of Toronto, in an accompanying editorial.

In addition, the lack of any 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 note.

Previous Data Show Efficacy

Previous studies have demonstrated that tomosynthesis significantly increases the detection of invasive breast cancers and lowers the rate of false-positive readings.

A study published last year demonstrated a 40% increase in the detection of invasive cancers and a 15% decrease in the false-positive rate.

Another study found that tomosynthesis "offers the dual benefit of significantly increased diagnostic accuracy and significantly reduced recall rates for noncancer cases," as reported by Medscape Medical News.

Tomosynthesis was approved by the US Food and Drug Administration in 2011 for use in combination with standard digital mammography for breast cancer screening.

Theoretically, the combination of digital mammography and tomosynthesis addresses the primary limitations of conventional screening mammography by increasing the conspicuity of invasive cancers and lowering the incidence of false-positive results.

Lower False-Positive Rate

In their multicenter retrospective analysis, Dr. Conant and colleagues compared the performance of digital mammography plus tomosynthesis with digital mammography alone in radiology practices across the United States. This is the largest study reported to date measuring the effectiveness of the technology, according to the authors.

The data come from a range of breast cancer screening programs at 13 geographically diverse community practices and academic centers.

The researchers evaluated 281,187 digital mammography examinations and 173,663 examinations using both tomosynthesis and digital mammography from 2010 to 2012 in the United States.

Table 1. Outcomes With the 2 Techniques

Outcome Mammography and Tomosynthesis, n Mammography, n
Recalled patients 15,541 29,726
Biopsies conducted 3285 5056
Cancer diagnoses 950 1207
   Invasive 707 815
   DCIS 243 392

 

The authors used a statistical model to estimate rates per 1000 screens.

Overall, the recall rate was lower with the tomosynthesis combination than with mammography alone at 11 of the 13 centers, and the rate of cancer detection was better with the combination at 12 centers.

Table 2. Outcomes at the 13 Centers

Outcome Mammography and Tomosynthesis Mammography P Value
Per 1000 screens      
   Recalls 91 107 <.001
   Cancer detection 5.4 4.2 <.001
   DCIS cancer detection 4.1 2.9 <.001
Positive predictive value      
   For recall 6.4% 4.3% <.001
   For biopsy 29.2% 24.2% <.001

 

"This study confirms what we already know — 3D mammography finds more of the invasive, harmful cancers we want found and saves women the anxiety and cost of having additional exams for what turns out to be a false alarm," said study coauthor Donna Plecha, MD, director of breast imaging at University Hospitals Case Medical Center in Cleveland, in a statement.

What About Outcomes?

Will this have any impact on overall outcomes? The authors note that this study did not assess clinical outcomes, so whether the increase in cancer detection rates is of benefit is not known. "Further studies are needed to assess the relationship to clinical outcomes," they conclude.

These concerns are echoed by Drs. Pisano and Yaffe: "Tomosynthesis is likely an advance over digital mammography for breast cancer screening, but fundamental questions about screening remain, with all available technologies." They report that breast cancer remains a major public health problem, with about 40,000 women dying annually of the disease in the United States.

"The continuing controversy surrounding the most effective strategy for deploying the various available technologies continues unabated, and clear consensus is lacking on when to screen, how often, and with what tools, or even which screen-detected cancers could be managed more conservatively," Drs. Pisano and Yaffe explain. "Only an appropriately powered multisite controlled clinical trial of modern technology can answer the remaining questions definitively."

They emphasize that "the time is now" for the National Institutes of Health to step up to the plate and fund "a much-needed trial to address many of the remaining issues about breast cancer screening."

The study was funded by Hologic, the manufacturer of 3D mammography, and the National Cancer Institute. Dr. Conant reports a financial relationship with Hologic. Some of her coauthors report various financial relationships, some with Hologic, as detailed in the publication. Dr. Pisano and Dr. Yaffe are involved in a project funded by the Canadian Breast Cancer Foundation. Dr. Pisano's laboratory is partially funded through contracts with FujiFilm and Koning Corp., supporting research on tomosynthesis and cone-beam breast computed tomography, and he is a shareholder in Mammographic Physics.

JAMA. 2014;311:2499-2507, 2488-2489. Abstract, Editorial

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