Tomosynthesis showed an earlier-detection advantage
Digital breast tomosynthesis detected invasive breast cancer more often than conventional digital mammography in the TOSYMA screening study, and a follow-up analysis found fewer invasive cancers diagnosed in the first year after a normal screening result.
The research, led by teams at the University of Münster and University Hospital Münster with other partners, examined whether the higher detection rate previously reported for tomosynthesis translated into a clinically meaningful difference after screening. Its latest findings were published in The Lancet Oncology.
Breast cancer is the most common cancer among women in Germany, with about 75,000 new cases annually, according to the researchers. Screening aims to identify tumors before symptoms develop, but a normal result does not eliminate the possibility that a cancer will be diagnosed before the next scheduled examination.
Those diagnoses are known as interval cancers. Because they emerge between routine screening appointments, they are an important measure for evaluating how well a screening method finds disease early enough to reduce missed or rapidly emerging invasive tumors.
What the TOSYMA analyses found
The first TOSYMA analysis, published in 2022, reported that tomosynthesis identified 7.1 invasive breast cancers per 1,000 women screened, compared with 4.8 per 1,000 among women screened with digital mammography.
That result established that tomosynthesis found more invasive cancers during the screening visit. It did not, by itself, settle whether the technology improved subsequent screening outcomes. Finding more cancers can reflect earlier detection, but follow-up data are needed to assess whether cancers are less likely to appear after an apparently normal exam.
The new TOSYMA-2 analysis addressed that question by comparing invasive interval cancers in the two groups. In the first year following a normal screening result, the invasive breast-cancer diagnosis rate was 29% lower in the tomosynthesis group than in the mammography group.
The researchers reported that 4.5 of every 10,000 women in the tomosynthesis group were diagnosed with invasive cancer during that first year after a normal result. They estimate that using digital breast tomosynthesis in the screening program could prevent roughly one quarter of invasive interval cancers that occur within two years of a digital mammogram.
Why the imaging method may make a difference
Digital breast tomosynthesis uses multiple low-dose X-ray images taken from different angles. Those images can be reconstructed into cross-sectional views of the breast as thin as one millimeter.
The central practical difference is that tomosynthesis can reduce the problem of overlapping tissue. In a two-dimensional image, structures can lie over one another and obscure signs that might otherwise prompt closer examination. Cross-sectional reconstruction can make structural abnormalities around an early-stage tumor easier to distinguish.
The study’s reported results are consistent with that rationale: more invasive cancers were detected at the time of screening, while fewer invasive cancers were diagnosed during the first year after a normal result. The findings do not mean that tomosynthesis eliminates interval cancers, nor do they establish that every additional cancer identified at screening produces the same outcome for every patient. They do, however, provide follow-up evidence beyond a simple comparison of detection rates.
Why interval cancers matter
Interval cancers are especially important in breast-screening research because they tend to be more aggressive and to have a poorer prognosis than cancers found through screening, the researchers said. A lower interval-cancer rate after a normal examination can therefore indicate that a method is better at detecting tumors that would otherwise have been missed at that visit.
For screening programs, the question is not merely whether one technique produces more findings. It is whether a different imaging approach changes the pattern of cancers diagnosed after participants have been told their examination was normal. TOSYMA-2 was designed to examine precisely that issue.
The study adds to the case for considering tomosynthesis in organized breast-cancer screening, particularly because its comparison is described by the researchers as the largest of the two diagnostic approaches conducted worldwide to date. Any change in a national screening program would still require evaluation of implementation, capacity, follow-up pathways and the balance of benefits and possible harms.
What comes next
The new analysis provides a clearer measure of clinical effectiveness than the earlier detection comparison alone. It links tomosynthesis screening with a lower first-year rate of invasive interval cancers after a normal result.
Its two headline figures describe the potential value: 7.1 versus 4.8 invasive cancers detected per 1,000 women screened in the earlier analysis, and a 29% lower first-year invasive diagnosis rate after a normal screen in the tomosynthesis group. Together, those results suggest that the additional views available through tomosynthesis can reveal cancers that might otherwise remain hidden by overlying tissue.
For now, the findings are evidence from the TOSYMA study rather than a universal guarantee about individual screening outcomes. But they give health systems a more complete basis for judging whether digital breast tomosynthesis should play a larger role in routine breast-cancer screening.
This article is based on reporting by Medical Xpress. Read the original article.
Originally published on medicalxpress.com
