Effect of implementing digital breast tomosynthesis (DBT) instead of mammography on population screening outcomes including interval cancer rates: Results of the Trento DBT pilot evaluation

Abstract

Background/aim The Trento screening program transitioned to digital breast tomosynthesis (DBT) screening based on evidence that DBT improves breast cancer (BC) detection compared to mammography; an evaluation of the transition to DBT is reported in this pilot study. Methods Prospective implementation of DBT screening included women aged ≥50 years who attended the Trento program for biennial screening. DBT screening included DBT acquisitions with synthesized 2D-images. A historical cohort of women who attended the program (January 2013–October 2014) and received digital mammography (DM) provided a comparison group. Independent double-reading (with a third arbitrating read for discordance) was used for DBT and DM screening. Screening outcomes included cancer detection rate (CDR/1000 screens), percentage of screens recalled to assessment (recall%), interval cancer rate (ICR/1000 screens) at 2-year follow-up, and screening sensitivity. Rate ratios (RR) and 95% confidence interval (95%CI) examined outcomes for DBT versus DM screening. Results From women aged 50–69 years who accepted an invitation to screening (October 2014–October 2016) 46,343 comprised the DBT-screened group: amongst these 402 BCs (includes 50 ductal carcinoma in-situ (DCIS)) were detected (CDR 8.67/1000), whereas 205 BCs (includes 33 DCIS) were detected amongst 37,436 DM screens (CDR 5.48/1000) [RR for CDR:1.58 (1.34–1.87)]. Recall% was lower for DBT (2.55%) than DM (3.21%) [RR:0.79 (0.73–0.86)]. Compared to DM, DBT screening increased CDR for stage I-II BC, for all tumour size and grade categories, and for node-negative BC, but did not increase CDR for DCIS. Estimated ICR for DBT was 1.1/1000 whereas ICR for DM was 1.36/1000 [RR:0.81 (0.55–1.19)]. Screening sensitivity was 88.74% for DBT versus 80.08% for DM [RR:1.11 (0.94–1.31)]. Conclusion DBT significantly improved early-detection measures but did not significantly reduce ICR (relative to DM screening), suggesting that it could add benefit as well as adding over-detection in population BC screening.

Comparison of interval breast cancers with 2D digital mammography versus 3D digital breast tomosynthesis in a large community‐based practice

“…As expected, the implementation of DBT was associated with a statistically significant increase in cancer detection rates and a decrease in recall rates when compared to DM (5.9 per 1000 screens with DBT versus 3.5 per 1000 screens among DM groups; P < .0001). These findings are congruent with what is reported in the literature 2‐4,6,9,16 …”

“…Several studies investigating differences in interval cancer rates in the current literature found no statistically significant differences in rates of interval cancer rates between the two screening modalities 9,10,12 . While these studies occurred at academic institutions, our study evaluated a large community‐based practice and a greater total number of mammograms (236 845) were included in our study.…”

“…A study of large population tumor registry data from 2003 to 2011 with 2D mammography found that false‐negative screening mammograms are uncommon with a reported rate of 1.0 to 1.5 per 1000 women 8 . In more recent years, most studies evaluating interval cancers before and after the implementation of tomosynthesis have occured in European biennial screening mammography programs for women aged 50‐69 3,9‐11 . A prospective population‐based evaluation of DBT screening of women enrolled in the Trento program found the rate of interval cancers did not significantly differ with DM (1.36 per 1000 screens) when compared with DBT (1.1 per 1000 screens with DBT) 9 .…”

“…In more recent years, most studies evaluating interval cancers before and after the implementation of tomosynthesis have occured in European biennial screening mammography programs for women aged 50‐69 3,9‐11 . A prospective population‐based evaluation of DBT screening of women enrolled in the Trento program found the rate of interval cancers did not significantly differ with DM (1.36 per 1000 screens) when compared with DBT (1.1 per 1000 screens with DBT) 9 . Similarly, a prospective cohort study of the BreastScreen Norway program found similar interval cancer rates of 1.5 per 1000 screens in the DM control group and 2.0 per 1000 screens in the DBT study group with ( P = .12) 10 .…”

Do we still need breast cancer screening in the era of targeted therapies and precision medicine?

“…Despite the widespread use of screening mammography, the introduction of digital techniques represents the most important technical advancement: of note, tomosynthesis has become the technique of choice for symptomatic women and those who are recalled for further assessment after a screening mammogram [13]. Conversely, the evidence in favour of its use as a firstlevel screening tool is still not sufficient in terms of reduction of interval cancer rate (possibly due to an underlying rate of overdiagnosis [70][71][72][73]) and European guidelines [13] have advised against its use for population-based screening programs. On the other hand, increasingly effective novel systemic treatment options are being introduced as a standard of care and gene expression profiling is progressively enabling better decision-making.…”