Screening outcome for consecutive examinations with digital breast tomosynthesis versus standard digital mammography in a population-based screening program

Objectives To retrospectively investigate early performance measures of digital breast tomosynthesis (DBT) versus standard digital mammography (DM) for consecutive screening rounds. Methods We included information about 35,736 women screened in BreastScreen Norway, 2008-2016, with at least two consecutive screening examinations. The pair of two consecutive screening examinations was the unit of analysis, and results from the subsequent examination were the measure of interest. Screening technique changed during the study period, resulting in four study groups: DM after DM, DBT after DM, DM after DBT, and DBT after DBT. We compared selected early performance measures between the study groups. Results Recall for DM after DM was 3.6% and lower for all other study groups (p < 0.001). The rate of screen-detected breast cancer was 4.6/1000 for DM after DM; for DBT after DM and DBT after DBT, it was 9.9/1000 and 8.3/1000, respectively (p < 0.001 relative to DM after DM), and for DM after DBT 4.3/1000. The rate of tubular carcinoma was higher for DBT after DBT or after DM compared with DM after DM (p < 0.01). The rate of histologic grade 1 tumors was higher for DBT after DM compared with DM after DM (p < 0.001). We did not observe any statistical difference in the interval cancer rates. Conclusions Lower recall and higher cancer detection rates for screening with DBT were sustainable over two consecutive screening rounds. Positive predictive values were higher for DBT than DM. There were no differences in the interval cancer rates between the study groups. Key Points There is limited knowledge about early performance measures for screening with digital breast tomosynthesis beyond one screening round. A decline in recall rate and an incline in the rate of screen-detected breast cancer were observed for women screened with DBT compared with DM, irrespective of prior screening technique. The interval breast cancer rate did not differ statistically for women screened with DBT versus DM. Tumor characteristics tended to be prognostic favorable for DBT compared with DM with no differences in rates of more advanced cancers. The clinical significance of increased cancer detection and the potential for future mortality reduction remain unknown.