April 24, 2019
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Digital breast tomosynthesis improves specificity of breast cancer detection

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Emily F. Conant, MD
Emily F. Conant

Screening with 3-D digital breast tomosynthesis appeared associated with increases in both specificity and proportion of breast cancers detected with better prognosis than two-dimensional digital mammography, according to results of a retrospective observational study published in JAMA Oncology.

The findings were especially true for a subgroup of women age 40 to 49.

“[Because of these findings], we believe that digital breast tomosynthesis screening has a very favorable risk-benefit ratio for all women, especially in the very controversial group of younger women, aged 40-49 years,” Emily F. Conant, MD, division chief of breast imaging, vice chair of faculty development in radiology and professor of radiology at Perelman School of Medicine at University of Pennsylvania, told HemOnc Today.

Conant and colleagues aimed to determine whether screening examinations with digital breast tomosynthesis detect breast cancers associated with an improved prognosis and to compare the detection rates by patient age and breast density.

Researchers analyzed data from 96,269 women aged 40 to 74 years (mean age, 55.9 years) with no known history of breast cancer who underwent a total of 180,340 breast cancer screening exams from January 2011 to September 2014.

Among these exams, 129,369 used digital mammography and 50,971 used digital breast tomosynthesis

Women who underwent digital breast tomosynthesis more often were younger (mean age, 54.6 years vs. 56.4 years), had dense breasts or were undergoing their first screening. Researchers adjusted for these factors when comparing the two screening methods.

Recall rate, cancer detection rate, positive predictive value, biopsy rate and distribution of invasive cancer subtypes served as primary outcome measures.

Results showed that exams with digital breast tomosynthesis detected a higher proportion of smaller (1 cm or less), more often node-negative, HER2-negative invasive cancers (73 of 99 women, 73.7%) than exams using digital mammography (276 of 422 women, 65.4%).

The use of digital breast tomosynthesis appeared associated with lower recall (OR = 0.64; 95% CI, 0.57-0.72) and higher cancer detection (OR = 1.41; 95% CI, 1.05-1.89) than digital mammography across all age groups and after stratification by breast density.

Women aged 40 to 49 years demonstrated the largest increase in cancer detection rate and the highest shift toward smaller, node-negative invasive cancers detected with digital breast tomosynthesis. Using this modality, the cancer detection rate for women in this age group with nondense breasts was 1.7 per 1,000 cases, and 2.27 per 1,000 for women with dense breasts.

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Screening exams with digital mammography detected cancers considered to have a poorer prognosis at a higher frequency than exams using digital breast tomosynthesis (OR = 2.28; 95% CI, 1.15-4.52).

Seven of 28 breast cancers detected using digital breast tomosynthesis were categorized as poor prognosis vs. 19 of 47 breast cancers identified using a digital mammography.

Study limitations included its nonrandomized design and underrepresentation of minority and Hispanic women.

“The biggest take away is that screening with digital breast tomosynthesis provides improved outcomes across all ages and breast densities compared to screening with 2D digital mammography alone,” Conant said. “We also found that the cancer detection rate increased for all ages and densities with DBT compare to DM screening and that the cancers detected by DBT tended to be smaller, node negative and have biologies associated with better prognoses compared to those found by DM screening.”

The findings in this study support reconsideration of guidelines for when to start routine breast cancer screening with digital breast tomosynthesis, Manisha Bahl, MD, MPH, and Constance D. Lehman, MD, PhD, both of the department of radiology at Massachusetts General Hospital, wrote in an accompanying editorial.

Currently, the Society of Breast Imaging and the American College of Radiology recommend that screening mammography begin at age 40 years, the American Cancer Society recommends starting at age 45 years, and the U.S. Preventative Services Task Force recommends age 50 years.

“Conant and colleagues suggest that the combined gains of increased cancer detection and reduced recall rates for women aged 40 to 49 years who undergo screening using [digital breast tomosynthesis] may lead to a shift in the balance of outcomes that are considered acceptable by the [USPSTF] for women aged 50 to 59 years who undergo screening with [digital mammography],” Bahl and Lehman wrote. “This finding lends support to the suggestion that guidelines for routine breast cancer screening with [digital breast tomosynthesis] be reconsidered in women aged 40 to 49 years.”– by John DeRosier

Disclosures: The NCI funded this study. Conant reports grants from the NCI during the conduct of the study and from iCAD Inc. and Hologic Inc. outside the submitted work. Please see the study for all other authors’ relevant financial disclosures. Bahl reports no relevant financial disclosures. Lehman reports research funding from and an advisory board role with GE Healthcare.