Digital breast tomosynthesis may reduce interval cancer rates vs. traditional screening
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Digital breast tomosynthesis appeared associated with reductions in interval breast cancer rates compared with traditional digital mammography among a large cohort of women in Sweden, according to study results published in Radiology.
Interval cancers detected after screening with either modality generally had similar non-favorable characteristics, researchers noted.
“Our results indicate that 3D mammography, or digital breast tomosynthesis, possibly detects cancers that would otherwise have been diagnosed later at a more advanced stage,” Kristin Johnson, MD, a doctoral student at Lund University and radiology resident at Skåne University Hospital in Sweden, said in a press release.
In the prospective screening study, Johnson and colleagues compared interval breast cancers — those detected between screenings — using conditional logistic regression among 13,369 women (mean age, 56 years) included in the Malmö Breast Tomosynthesis Screening Trial and 26,738 controls (mean age, 56 years), matched 2-to-1 by age and screening date, who underwent traditional digital mammography.
Researchers also compared the types of breast cancer involved, as well as breast cancer invasiveness.
Results showed women in the digital breast tomosynthesis group had 40% lower odds of interval cancer than women in the matched control group (age-adjusted OR = 0.6; 95% CI, 0.3-0.9). Researchers reported interval cancer rates of 1.6 (95% CI, 1-2.4) per 1,000 women screened with digital breast tomosynthesis (n = 21 of 13,369) and 2.8 (95% CI, 2.2-3.6) per 1,000 women screened in the control group (n = 76 of 26,738).
Interval cancer rates appeared numerically lower with digital breast tomosynthesis both among women aged younger than 55 years at screening (1.3 per 1,000 vs. 2.6 per 1,000; conditional OR = 0.5; 95% CI, 0.2-1.1) and those aged 55 years and older at screening (1.8 per 1,000 vs. 3 per 1,000; conditional OR = 0.6; 95% CI, 0.3-1.1).
In addition, 90% of the 21 interval cancers in the digital breast tomosynthesis cohort were deemed invasive, compared with 95% of the 76 interval cancers in the control group. Invasive interval cancers among women in both groups typically had a high Ki-67 status (63% vs. 75%), whereas researchers observed low proportions of luminal A-like subtype (26% vs. 17%).
“Screening with digital breast tomosynthesis shows potential in reducing interval cancers,” Johnson said. “However, we need to see more studies pointing in the same direction.”
Perspective
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Andrea M. Abbott, MD
We are happy to see any research that provides data to help us detect breast cancers earlier. We are particularly excited to see more research on the benefits of tomosynthesis as it becomes more routine for breast cancer screening in the United States. However, this study is of limited benefit due to the differences in screening in the U.S. vs. Sweden, most significantly the screening interval — in the U.S., we screen every 12 months, whereas the screening intervals in the study varied between 18 and 24 months.
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