Low-Dose Digital Mammography May Be Accurate

Research by Chen et al suggests that low-dose techniques for digital mammography may be feasible, as results are not substantially affected by variations in radiation dose. Their study was published in Radiology.

The researchers analyzed retrospectively a cohort of women from the American College of Radiology Imaging Network Pennsylvania 4006 trial. All patients underwent breast screening with a combination of dose protocols, including standard full-field digital mammography, low-dose digital mammography, and digital breast tomosynthesis. A total of 5832 images from 486 women were analyzed with fully automated software for quantitative estimation of density.

Clinical Breast Imaging Reporting and Data System (BI-RADS) density assessment results were also available from the trial reports. The influence of image acquisition radiation dose on quantitative breast density estimation was investigated with analysis of variance and linear regression.

Radiation dose of image acquisition did not significantly affect quantitative density measurements, with percent density demonstrating a high overall correlation between protocols. However, differences in breast percent density were observed within high BI-RADS density categories, although they were significantly correlated across the different acquisition dose levels.

The authors concluded that reproducibility of automated breast density measurements with digital mammography are not affected by variations in radiation dose; thus, the use of low-dose techniques for the purpose of density estimation may be attainable.

Digital breast tomosynthesis may reduce recall rates

JAMA Oncology published McDonald et al research regarding the efficacy of digital breast tomosynthesis (DBT) on recall rates versus that of digital mammography (DM), and also its sustainability over the long term.

The study was a retrospective analysis of a total of 44468 screening events performed on 23958 women whose average age was 56 years and were followed over a period of 4 years.

Recall rates rose slightly for years 1 to 3 of DBT (88, 90, and 92 per 1000 screened, respectively) but remained significantly reduced compared with the DM zero rate of 104 per 1000 screened. The cancer cases per recalled patients continued to rise from DM zero rate of 4.4% to 6.2% for years 1 to 3 of DBT, respectively. Outcomes assessed for the most recent screening for individual women undergoing only 1, 2, or 3 DBT screenings during the study period demonstrated decreasing recall rates of 130, 78, and 59 per 1000 screened, respectively (P < .001). Interval cancer rates, determined using available follow-up data, decreased from 0.7 per 100 women screened with the use of DM to 0.5 per 1000 screened with the use of DBT.

Digital breast tomosynthesis screening outcomes are sustainable, with significant recall reduction, increasing cancer cases per recalled patients, and a decline in interval cancers.

No need to print mammograms on films; FDA

An FDA communiqué to mammography facilities “said that printing breast images to hard-copy film is no longer necessary and can be performed at the discretion of individual centers”. 

Over the past 20 years, there has been significant evolution in mammography, with the shift from screen-film to digital imaging being the most prominent change.

A total of 39 million procedures were performed in the 8,737 mammographic facilities that were accredited by the FDA as of Nov 1, 2015.   Today fewer than 350 screen-film units remain in use in the U.S. The nearly universal availability of computers for viewing of digital images diminishes the need for a facility to maintain a printer.

Today, with many mammograms shared on computer media such as compact discs or via online access, the provision of printed hard copies is becoming obsolete.

Computer-Aided Detection did not improve Digital Screening Mammography's Diagnostic Accuracy

Lehman et al in a paper published by JAMAInternal Medicine report on their findings that suggest that computer-assisted detection (CAD) used in most mammograms added no benefit to breast cancer screening while it substantially increased costs.

The authors compared the accuracy of digital screening mammography interpreted with (n = 495 818) versus without (n = 129 807) CAD from 2003 through 2009 in 323 973 women.  271 radiologists in 66 facilities interpreted the mammographic studies.  They found 3159 breast cancers within 1 year of the screening.

Screening performance was not improved with CAD on any metric assessed. Mammography sensitivity was 85.3% with and 87.3% without CAD. Specificity was 91.6% with and 91.4% without CAD. There was no difference in cancer detection rate (4.1 in 1000 women screened with and without CAD). Computer-aided detection did not improve intra-radiologist performance. Sensitivity was significantly lower for mammograms interpreted with versus without CAD in the subset of radiologists who interpreted both with and without CAD.

The authors concluded CAD does not improve diagnostic accuracy of mammography. These results suggest that while insurers pay an additional $400 million a year for CAD, its addition to standard mammography had no beneficial impact to women.

Benefits, Harms, and Costs of Screening with Digital Mammography

Stout et al in their article published by the JNCI, report on the economic impact digital mammography had as it has replaced film in the United States.

Their research compared digital screening strategies starting at age 40 or 50 years applied annually, biennially, or based on density with biennial film screening from ages 50 to 74 years and with no screening. Common data elements included cancer incidence and test performance, both modified by breast density. Lifetime outcomes included mortality, quality-adjusted life-years, and screening and treatment costs.

For every 1000 women screened biennially from age 50 to 74 years, switching to digital from film yielded a median improvement of 2 life-years, 0.27 additional deaths averted, 220 additional false-positive results, and $0.35 million more in costs. For an individual woman, this translates to a health gain of 0.73 days. Extending biennial digital screening to women ages 40 to 49 years was cost-effective, although results were sensitive to quality-of-life decrements related to screening and false positives. Targeting annual screening by density yielded similar outcomes to targeting by age. Annual screening approaches could increase costs to $5.26 million per 1000 women, in part because of higher numbers of screens and false positives, and were not efficient or cost-effective.

They concluded that transition to digital breast screening in the United States increased total costs for a small added health benefit.  While the value of digital mammography screening for breast cancer among women aged 40 to 49 years was cost effective the women should be cognizant of the high rate of false positives.