TOSYMA-2: tomosynthesis screening did not significantly cut 24-month interval cancers

Design

Multicentre, open-label randomised superiority trial (TOSYMA-2 analysis), 24-month registry follow-up

Population

About 98,755 screen-negative women aged 50 to 70 in Germany

Primary outcome

Invasive interval cancer rate in 24 months after negative screen

Effect

14.2 vs 18.6 per 10,000; adjusted OR 0.76 (95% CI 0.55 to 1.06), P=0.11

TOSYMA is a multicentre, open-label randomised trial at 17 screening sites in two German states. Women aged 50 to 70 were randomised 1:1 to digital breast tomosynthesis plus synthesised 2D mammography or digital mammography. The first primary endpoint, cancer detection, was reported earlier. This second primary endpoint is the rate of invasive interval cancers in the 24 months after a negative screen. Cancers were found by linkage to registries.

Of 99,689 women enrolled, 49,299 in the tomosynthesis group and 49,456 in the mammography group screened negative. There were 70 invasive interval cancers (14.2 per 10,000) with tomosynthesis and 92 (18.6 per 10,000) with mammography: adjusted OR 0.76 (95% CI 0.55 to 1.06; P=0.11). Within 12 months, there were 22 vs 31 (OR 0.71, 0.52 to 0.97), a prespecified secondary outcome.

The authors suggest about a quarter of interval cancers over two years might be avoided, but the primary endpoint did not reach statistical significance. Interval cancers are a proxy for screening sensitivity; mortality is not yet known, and follow-up continues.

• Tomosynthesis lowered interval cancer rates numerically (14.2 vs 18.6 per 10,000) but not significantly.
• The 12-month secondary result was significant (OR 0.71), but it is secondary.
• Interval cancer is a proxy; effects on breast cancer deaths are not yet known.
• Availability and cost determine whether tomosynthesis is feasible in screening programmes in India.

Why it matters

It tests whether more cancers found at screening translates into fewer cancers appearing between screens.

Don't overread it

The primary endpoint was not significant, and interval cancer rates are not a measure of lives saved.

The statistics, in plain English

An odds ratio of 0.76 with an interval of 0.55 to 1.06 means the data are consistent with up to a 45% reduction and also with a 6% increase. The 12-month result had a narrower interval that excludes 1, but secondary results carry less weight when the primary result is not significant.

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