Screening with digital breast tomosynthesis plus synthesised mammography was associated with fewer invasive interval cancers than digital mammography in the 24-month follow-up of the TOSYMA trial. The primary outcome was not statistically significant, but the difference was in the first year.
What was known
Digital breast tomosynthesis reconstructs the breast in slices and detects more cancers than conventional digital mammography. It remained unclear, however, whether that higher detection translates into fewer tumours appearing between two screening rounds: interval cancers, a direct marker of how well a screening programme actually works.
What this work adds
TOSYMA is a randomised, controlled, multicentre trial conducted at 17 screening sites in two German federal states. Between 5 July 2018 and 30 December 2020, 99,689 women aged 50 to 70 were enrolled and randomly allocated (1:1) to digital breast tomosynthesis plus synthesised mammography or to digital mammography. The trial’s first objective, the invasive cancer detection rate, had already been reported; this paper presents the second: the invasive interval cancer rate in the 24 months after a negative screening result. Suspected cases were identified through data linkage to cancer registries.
Main results
Screening was negative in 99.1% of women in the tomosynthesis group (49,299 of 49,762) and in 99.3% of the digital mammography group (49,456 of 49,796). Over the following two years, invasive interval cancers were detected in 70 of those 49,299 women in the tomosynthesis group (14.2 cases per 10,000 women screened negative) and in 92 of the 49,456 in the digital mammography group (18.6 per 10,000), with an adjusted odds ratio of 0.76 (95% confidence interval 0.55-1.06; p=0.11). Within the first 12 months, cases numbered 22 versus 31 (4.5 versus 6.3 per 10,000; odds ratio 0.71; 95% CI 0.52-0.97).
What it means
The authors conclude that about a quarter of the invasive interval cancers seen with digital mammography over two years might be avoided with tomosynthesis plus synthesised mammography. Although the primary outcome did not reach statistical significance, the trial adds substantial evidence and supports the use of this technology in screening. The work is funded by the German Research Foundation.
Reading from the breast unit
For a breast unit the message is organisational: screening technology shapes how many tumours appear between rounds, a quality indicator for the programme. Moving to tomosynthesis involves changes in equipment, reading time and radiologist training, and these are best planned with each programme’s own data.
Reference: Weigel S, Hense HW, Weyer-Elberich V, Czwoydzinski J, Decker T, Kajüter H, et al. Invasive interval breast cancer rates after digital breast tomosynthesis plus synthesised mammography versus digital mammography screening (TOSYMA): 24-month follow-up of the multicentre, open-label, randomised, controlled, superiority trial. The Lancet Oncology, 2026. DOI
