Screening mammography: Is 3D better?

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Research on 3D mammography to date suggests that it improves breast cancer detection and reduces recall for false-positive results compared with 2D technology. A new study suggests that it also may be better at finding smaller, node-negative cancers-particularly in women aged 40 to 49. 

The findings, published in JAMA, are from a retrospective analysis of prospective data from three US research centers. Data in the PROSPR (Population-based Research Optimizing Screening Through Personalized Regimens) consortium reflected outcomes in women aged 40 to 74 who underwent screening with 2D and 3D mammography from January 1, 2011 through September 30, 2014. 

The authors looked at recall rate, cancer detection rate, positive predictive value, biopsy rate, and distribution of invasive cancer subtypes in nearly 100,000 women, 71.7% of whom had 2D digital mammograms and 28.3% of whom had 3D mammograms (digital breast tomosynthesis). 

A higher proportion of screening-detected node-negative invasive breast cancers ≤ 1 cm was associated with use of 3D technology (73.7%) versus 2D technology (65.4%). The cancers found with 2D screening also were more likely to have a poor prognosis than those found with 3D screening (P= .02). (Poor prognosis was defined as metastases, positive nodes and/or invasive tumor size ≥ 2 cm and/or estrogen receptor-negative and progesterone receptor-negative and/or HER2-positive tissue ≥ 1 cm.) Likelihood of recall also was lower with 3D screening (odds ratio [OR], 0.64; 95% CI, 0.57-0.72; P< .001) and rates of cancer detection were higher (OR, 1.41; 95% CI, 1.05-1.89; P= .02) for all age groups, even when stratified by breast density. 

“We also found that the cancer detection rate increased for all ages and densities and that the cancers detected by 3D mammography tended to be smaller, node-negative and have biologies associated with better prognoses compared to those found by 2D-alone screening,” principal investigator Emily F. Conant, MD, Professor and Chief, Division of Breast Imaging and Vice Chair of Faculty Development, Department of Radiology, University of Pennsylvania, told Contemporary OB/GYN.

“This finding, she said, “was especially true for women aged 40 to 49 years where the largest shift toward better prognosis cancers were found.” In that age group, the rate of cancer detection for screening with 3D mammography, in women with non-dense breasts, was 4.41 per 1000, versus 2.71 per 1000 for 2D screening. Rates of detection women aged 40 to 49 with dense breasts were 5.20 per 1000 for 3D versus 2.93 for 2D screening. For these younger women, 3D screening was associated with only 25% of breast cancers categorized as poor prognosis versus 40.4% for 2D screening. 

“Controversy over breast cancer screening guidelines continues to center around the risk-benefit balance – minimizing false positives while maintaining or even increasing the detection of clinically significant cancers,“ Dr. Conant said. “We believe that 3D screening has a very favorable risk-benefit ratio for all women, but especially in the very controversial group of younger women, aged 40 to 49 years.” More research is needed, however, to confirm these findings in other populations, particularly to see if the increased cancer detection rate holds true during multiple rounds of screening