Comparative Effectiveness of Digital Breast Tomosynthesis and Mammography in Older Women.

Background: Digital breast tomosynthesis (DBT) has become a prevalent mode of breast cancer screening in recent years. Although older women are commonly screened for breast cancer, little is known about screening outcomes using DBT among older women.

Objective: To assess proximal screening outcomes with DBT compared to traditional two-dimensional(2-D) mammography among women 67-74 and women 75 and older.

Design: Cohort study.

Participants: Medicare fee-for-service beneficiaries aged 67 years and older with no history of prior cancer who received a screening mammogram in 2015.

Main Measures: Use of subsequent imaging (ultrasound and diagnostic mammography) as an indication of recall, breast cancer detection, and characteristics of breast cancer at the time of diagnosis. Analyses used weighted logistic regression to adjust for potential confounders.

Key Results: Our study included 26,406 women aged 67-74 and 17,001 women 75 and older who were screened for breast cancer. Among women 75 and older, the rate of subsequent imaging among women screened with DBT did not differ significantly from 2-D mammography (91.8 versus 97.0 per 1,000 screening mammograms, p=0.37). In this age group, DBT was associated with 2.1 additional cancers detected per 1,000 screening mammograms compared to 2D (11.5 versus 9.4, p=0.003), though these additional cancers were almost exclusively in situ and stage I invasive cancers. For women 67-74 years old, DBT was associated with a higher rate of subsequent imaging than 2-D mammography (113.9 versus 100.3, p=0.004) and a higher rate of stage I invasive cancer detection (4.7 versus 3.7, p=0.002), but not other stages.

Conclusions: Breast cancer screening with DBT was not associated with lower rates of subsequent imaging among older women. Most additional cancers detected with DBT were early stage. Whether detecting these additional early-stage cancers among older women improves health outcomes remains uncertain.