- Design
- Multicentre, open-label, randomised superiority trial
- Population
- About 99,000 women aged 50–70 in German screening; 98,755 screen-negative
- Primary outcome
- Invasive interval cancer rate over 24 months
- Effect
- 14.2 vs 18.6 per 10,000; OR 0.76 (95% CI 0.55–1.06)
TOSYMA randomised about 99,000 women aged 50 to 70 in the German screening programme to digital breast tomosynthesis with synthesised two-dimensional images or standard digital mammography. Its first endpoint, already reported, showed higher detection with tomosynthesis. This second endpoint asked whether that translated into fewer cancers presenting between screens.
Over 24 months, invasive interval cancers occurred in 14.2 per 10,000 screen-negative women after tomosynthesis and 18.6 per 10,000 after mammography (OR 0.76), a difference that did not reach statistical significance. Within 12 months the difference was significant (4.5 versus 6.3 per 10,000; OR 0.71).
Fewer interval cancers is what would show that extra detection reflects meaningful cancers rather than overdiagnosis. The direction is encouraging, but the primary result is not conclusive. Tomosynthesis costs more and is less widely available, including in India, where coverage of any organised mammographic screening is limited.
- Regard tomosynthesis as a reasonable screening option where available, not yet as a proven reduction in interval cancer.
- Investigate new breast symptoms promptly regardless of a recent normal screen.
- Keep women in their screening programme whichever modality is offered locally.
- Expect further follow-up and pooled trial data before screening policies change.
Why it matters
Interval cancer is the test of whether extra detection in screening is worth having.
Don't overread it
The primary endpoint was not statistically significant.
The statistics, in plain English
An odds ratio of 0.76 points to fewer interval cancers, but the interval of 0.55 to 1.06 crosses 1.0, so the trial cannot exclude no difference. The significant 12-month result is a secondary outcome and carries less weight.
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