TOPLINE

Digital breast tomosynthesis (DBT) plus synthesised mammography lowered the 24-month invasive interval cancer rate by 24% compared with digital mammography among women aged 50-70 years in a randomised screening trial, but the difference was not statistically significant.

METHODOLOGY

• Researchers enrolled 99,689 women at 17 German screening sites and randomly assigned them to receive one round of screening with DBT plus synthesised two-dimensional (s2D) mammography or digital mammography in the TOSYMA trial.
• The analysis included 98,755 women with negative screening results, of whom 49,299 were screened with DBT plus s2D mammography and 49,456 with digital mammography. Participants had a median age of 57 years (IQR, 53-62), and 17.3% of the participants were attending their first screening.
• DBT plus s2D mammography involved synthesised 2D images reconstructed from tomosynthesis scans. The comparator was full-field digital mammography, and both groups underwent independent double reading.
• The first primary endpoint was invasive cancer detection at screening, and the detection rate was higher with DBT, as reported earlier; this analysis covers the second primary endpoint, the number of invasive interval cancers (cancers diagnosed after a negative screen) per 10,000 women within 24 months.
• The 12-month occurrence of invasive interval cancers was a prespecified secondary outcome, and cases were identified through linkage to regional cancer registries.

TAKEAWAY

• Over 24 months, invasive interval cancers occurred at rates of 14.2 per 10,000 women with DBT plus s2D mammography and 18.6 per 10,000 women with digital mammography, a 24% relative reduction that was not statistically significant (adjusted odds ratio [aOR], 0.76; P = .11).
• In the first 12 months, rates were 4.5 per 10,000 women with DBT plus s2D mammography vs 6.3 per 10,000 women with digital mammography (aOR, 0.71; 95% CI, 0.52-0.97), a 29% relative reduction.
• The 24-month rate was similar among women attending their first screening but lower among those returning for subsequent screening (13.5 vs 18.8 per 10,000 women; aOR, 0.72; 95% CI, 0.51-1.01).
• Programme sensitivity, which represents the share of invasive cancers detected at screening rather than as interval cancers, was 83.5% vs 72.3%, and specificity was similar between the two methods. The difference in interval cancer rates was mainly attributable to T1 tumours (6.5 vs 10.1 per 10,000 women).

IN PRACTICE

"[D]igital breast tomosynthesis plus s2D mammography screening has a favourable impact on lowering the rate of invasive interval breast cancers. The effect after 24 months appears particularly pronounced in women attending subsequent rounds of screening," the authors wrote.

SOURCE

The study was led by Stefanie Weigel, MD, University Hospital Münster, Münster, Germany. It was published online on October 9 in The Lancet Oncology. 

LIMITATIONS

The study was limited by statistical power of about 70% after COVID-19 disrupted recruitment and by an analysis restricted to women with negative screening results, which meant that the groups were no longer structurally equivalent. Interval cancers are a surrogate outcome, post hoc analyses were uncorrected for multiple testing, and the number of cases was too small to allow meaningful comparisons by stage or grade, with advanced-stage rates to be evaluated in the next screening round.

DISCLOSURES

The study was funded by the German Research Foundation, which was not involved in the trial's design, analysis, or reporting. Three authors reported being employees of the National Reference Center Mammography Münster and receiving payments for lectures from the centre. One author reported honoraria from several organisations, including QUIRIS Healthcare and Roche. Full disclosures are reported in the original source article.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.