medwireNews: Women with extremely dense breasts and a high breast cancer risk have a lower risk for advanced cancer when screened by digital breast tomosynthesis (DBT) than digital mammography, US study findings indicate.
Writing in JAMA, Karla Kerlikowske (San Francisco Veterans Affairs Medical Center, California) and co-authors say their results suggest that “for facilities with both DBT and digital mammography available, triaging women with extremely dense breasts and at high risk to undergo DBT may be clinically indicated.”
They add: “For other women, there were no significant differences between DBT and digital mammography in the ability to detect interval and advanced cancers.”
The study included data for 504,427 women aged 40 to 79 years (median 58 years) with no history of breast cancer who underwent 374,002 DBT screenings and 1,003,900 digital mammography screenings between 2011 and 2018.
Overall, the rate of interval invasive cancer within 12 months of screening was not significantly different between the women who received DBT and those who received digital mammography, at 0.57 versus 0.61 cases per 1000 examinations.
There was also no significant difference in interval cancer rates between the two techniques for women who had a low to average (<1.67%) US Breast Cancer Surveillance Consortium (BCSC) 5-year breast cancer risk or among those with a high (≥1.67%) BCSC 5-year risk, regardless of breast density.
However, for advanced cancers (≥stage II) diagnosed within 12 months of screening, the rate was significantly lower with DBT than with digital mammography, at 0.36 versus 0.45 cases per 1000 examinations, and the team found that breast density and BCSC risk affected the outcome.
Specifically, the rates of advanced cancer were significantly lower with DBT than digital mammography for the 3.6% of women with extremely dense breasts and a high BCSC 5-year risk, at 0.27 versus 0.80 cases per 1000 examinations.
By contrast, there was no significant difference between the two methods for women with extremely dense breasts but low to average BCSC 5-year risk, at a respective 0.54 and 0.42 cases per 1000 examinations.
Similarly, advanced cancer rates did not differ significantly between DBT and digital mammography among women at either low to average or high risk and almost entirely fatty, scattered fibroglandular densities, or heterogeneously dense breasts.
Kerlikowske and team say that “[f]uture studies will need to examine early-stage and advanced-stage rates with DBT by screening round, breast density, and risk to determine in which groups early-stage cancer rates increase as advanced stage cancer rates decrease indicating that more aggressive tumors are being diagnosed earlier.”
In an accompanying editorial, Sarah Friedewald (Northwestern University, Chicago, Illinois, USA) and Lars Grimm (Duke University, Durham, North Carolina, USA) comment that the findings “expand the current understanding of the potential utility of DBT” but say that low incidence of clinically relevant outcomes in some groups means that “evidence that the choice of digital mammography [versus] DBT influences mortality or interval cancers is lacking” for those individuals.
The editorialists also point out that there were “[n]otable decreases in false-positive recalls, short-interval follow-up, and biopsy recommendations” with DBT versus digital mammography, which may influence screening choice.
They conclude: “Given that DBT is now available at 83% of mammography facilities in the US and is not associated with higher burdens for women (unless there are higher co-pays), ensuring that women at high risk with dense breasts are screened with DBT should be feasible.”
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