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3-D mammography reduces recall, incident cancer rates over 3 years
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The addition of digital breast tomosynthesis to digital mammography appeared associated with sustained reductions in recall, increases in cancer cases per recalled patients and declines in interval cancers, according to results of a retrospective analysis.
“These findings reaffirm that 3-D mammography is a better mammogram for breast cancer screening … [and] are an important step toward informing policies so that all women can receive 3-D mammography for screening,” Emily F. Conant, MD, chief of breast imaging and professor of radiology at University of Pennsylvania’s Perelman School of Medicine, said in a press release.
Emily F. Conant, MD
The use of digital breast tomosynthesis (DBT, Hologic Inc.) in combination with digital mammography as a breast cancer screening tool has been shown to decrease false-positive examinations and increase cancer detection, according to study background.
However, the longitudinal performance of DBT had been unknown.
Thus, Conant and colleagues sought to determine whether the early improved outcomes associated with DBT persisted over time at the population level. Researchers also evaluated the effect of more than one DBT screening at the individual level.
The analysis included data from 23,958 unique women (mean age, 56.8 years) who received 44,468 screening mammograms at an urban academic hospital over the course of 4 years. Year 0 represented the year prior to conversion from digital mammography to DBT, and years 1 through 3 represented the years after conversion (year 0, n = 10,728; year 1, n = 11,007; year 2, n = 11,157; year 3, n = 11,576). Women who underwent screening years 1 through 3 received a DBT of two-view digital mammography and two-view DBT of each breast.
Researchers assessed screening differences between each DBT year and the digital mammography year, as well as differences based on number of screenings (1 vs. 2 vs. 3).
Key study endpoints included recall rates, cancer cases per recalled patients, biopsy rates and interval cancer rates.
Recall rates increased slightly between the first and third year of DBT — from 88 per 1,000 women in year 1 to 92 per 1,000 women in year 3 — but remained lower than digital mammography alone (n = 104 per 1,000).
Researchers calculated the odds of recall in analyses adjusted for age, race or ethnicity, breast density, and prior mammograms. Results showed women screened with DBT in year 1 (OR = 0.83; 95% CI, 0.76-0.91), year 2 (OR = 0.85; 95% CI, 0.78-0.93) and year 3 (OR = 0.87; 95% CI, 0.8-0.95) appeared less likely to be recalled than women who underwent digital mammography alone in year 0.
The incidence of cancer cases per recalled patients rose from 4.4% in year 0 to 6.2% in the first year of DBT. The percentage of cases reached statistical significance in year 2 (6.5%; P = .03) and year 3 (6.7%; P = .02).
Diana L. Miglioretti, PhD
Outcomes related to individual screening showed that the recall rate decreased as the number of DBT screenings a woman underwent increased (1 screening, n = 130 per 1,000; 2 screenings, n = 78; 3 screenings, n = 59; P < .001).
Interval cancer rates also decreased following the introduction of DBT, from 0.7 per 100 women screened to 0.5 per 1,000 women.
The researchers acknowledged limitations, including the lack of randomization and the lack of data regarding risk characteristics such as family history.
“Although DBT was initially implemented without knowledge of long-term performance, this is, to our knowledge, the first evidence that sustained and even improved performance is possible with consecutive DBT screenings,” Conant and colleagues wrote. “Despite limitations, we believe this represents the first longitudinal analysis of women recalled for further DBT screening and is an important initial step toward informing policies for possibly integrating this technology into population-screening programs.”
The results of this study may not be generalizable to the widespread use of DBT, Nehmat Houssami, MBBS, FAFPHM, MPH, PhD, professor of medicine and public health at The University of Sydney, and Diana L. Miglioretti, PhD, professor of biostatistics at University of California, Davis, wrote in an accompanying editorial.
“The majority of women in the U.S. receive screening from community-based radiology practices, and their mammograms are interpreted by general radiologists who do not specialize in breast imaging,” Houssami and Miglioretti wrote. “Many other countries, including Canada, Australia, and those in Europe, have population-based screening programs with mammograms double read by radiologists who specialize in screening mammography and who interpret large volumes of screens. The organized screening strategies used in these programs, including double reading, have generally lower recall rates than those in the U.S., with less scope of improvement from adjunct DBT. Thus, it will be important to determine whether the results from this academic medical center with breast imaging specialists can be replicated in other U.S. settings and other countries.” – by Cameron Kelsall
Disclosure: Conant reports paid advisory and lectureship positions with Hologic Inc. Conant and one other researcher report consultant roles with Siemen’s Healthcare. The other researchers, Houssami and Miglioretti report no relevant financial disclosures.
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