For a study, researchers sought to determine if digital breast tomosynthesis (DBT) screening was related to a decreased incidence of interval invasive carcinoma and advanced breast cancer compared to digital mammography in terms of breast density and risk of breast cancer.
A cohort study of 504,427 women aged 40 to 79 years who had 1,003,900 digital screening mammography and 375,189 screening DBT examinations from 2011 to 2018 at 44 US Breast Cancer Surveillance Consortium (BCSC) facilities, with cancer diagnoses, followed up on through 2019 via linkage to state or regional cancer registries. Rates per 1,000 exams of interval invasive carcinoma and advanced breast cancer (prognostic pathologic stage II or above) within 12 months of screening mammography, both determined using inverse probability weighting.
The median age at the time of mammography was 58 years among the 504,427 women in the study population (IQR, 50-65 years). Interval invasive cancer rates per 1,000 examinations were not significantly different for DBT vs. digital mammography (overall, 0.57 vs. 0.61, respectively; difference, 0.04; 95% CI, 0.14 to 0.06; P=.43) or among all 836,250 examinations with a BCSC 5-year risk of less than 1.67% (low to average risk) or all 413,061 examinations with a BCSC 5-year risk of 1.67% or higher (high risk) DBT versus digital mammography advanced cancer rates were not substantially different in women at low to moderate risk or at high risk with virtually completely fatty, dispersed fibroglandular densities, or heterogeneously dense breasts. For the 3.6% of women with extremely dense breasts and a high risk of breast cancer (13,291 examinations in the DBT group and 31 300 in the digital mammography group; 0.27 vs. 0.80 per 1,000 examinations; difference, 0.53; 95% CI, 0.97 to 0.10), advanced cancer rates were significantly lower for DBT compared to digital mammography, but not for women at low to average risk (10,611 examinations in the DBT group and 37,796 in the digital mammography group; 0.54 vs. 0.42 per 1,000 examinations; difference, 0.12; 95% CI, −0.09 to 0.32).
Screening with DBT versus digital mammography was not linked with a meaningful difference in risk of interval invasive cancer, but it was associated with a considerably decreased risk of advanced breast cancer in the 3.6% of women with highly thick breasts and a high risk of breast cancer. There was no significant difference in the 96.4% of women with nondense breasts, heterogeneously dense breasts, or highly dense breasts who were not at high risk.