We were excited to apply propensity scoring as a statistical method in order to develop a matched
cohort of patients, which allowed comparison of screening metrics.
As more radiology practices begin incorporating digital breast tomosynthesis (DBT) technology, many are phasing in use of DBT over time while maintaining the use of stan-
dard 2D full-field digital mammography (FFDM), creating a “hy-
brid” screening environment in which both technologies are used.
Catherine S. Giess of Brigham & Women’s Hospital compares the
diagnostic performance of DBT and FFDM in such a hybrid
The retrospective observational study consisted of all female patients undergoing screening DBT or FFDM at an academic medical center and outpatient imaging facility between October 2012
and May 2015. Patient demographics and personal history of breast
cancer were collected from the electronic medical record. A natural language processing algorithm was used to extract patients’
breast density, current or prior imaging findings, and BI-RADS category from their most recent prior imaging examinations.
To control for differential selection of FFDM versus DBT, researchers applied propensity score matching based on patient age,
imaging site, and prior imaging findings. An institutional breast
cancer registry identified cancer diagnoses. Primary outcomes of
recall rate, cancer detection rate, and positive predictive value 1
(PPV1) were compared between matched FFDM and DBT groups.
The study found that DBT improves breast cancer detection at
screening mammography. Although the effects on overall recall
rate may be lower with DBT than previously reported, the improvement in PPV1 suggests a reduction in unnecessary recalls.
Catherine S. Giess
Chief, Division of Breast Imaging
Department of Radiology
Brigham & Women’s Hospital
As New Breast Cancer Screening
Technology Emerges, Which
Digital breast tomosynthesis has been termed “a better mammogram.” The primary objective of screening mammography is
to detect breast cancer, particularly invasive cancer, and DBT
detects more invasive breast cancers. Reported disadvantages of
DBT include cost of the equipment, increased storage for much
larger amounts of data, increased interpretation times, and increase in radiation dose when DB T is added to standard FFDM.
Future studies are needed to assess whether quality improvement interventions, such as focused interventions to lower individual and group recall rates, can enhance screening
performance with DBT. There is a continued need to objectively
evaluate both practice and radiologist parameters that may influence outcome metrics during adoption of any technology, without any proinnovation bias.
In an interview with InPractice, Giess offered some background on the research and advice for radiologists to stay on top
of the transitioning technology.
What prompted you to write the about this study?
It is important to evaluate any new technology before adoption, particularly when it is costly and increases radiation dose.
Our practice, like many, introduced it gradually, and apparent
differences in performance between FFDM and DBT could be
due to differential use in patient groups at different risk of developing breast cancer. That might affect your results and confound
a comparison of performance between the techniques.
We were excited to apply propensity scoring as a statistical
method in order to develop a matched cohort of patients, which
allowed comparison of screening metrics.
Many practices are phasing in DBT over time.
What advice would you give to practices regarding
managing the phase-in of DBT?
I would recommend that practices phasing in DBT over time
preferentially offer it to patients receiving baseline studies, because those patients have a higher recall rate than patients with
prior studies for comparison.
Breast Cancer Screening Technology continues on p. 16