FROM JOURNAL OF CLINICAL ONCOLOGY
Ultrasound was about 1.8 times more sensitive than tomosynthesis for the incremental detection of breast cancer in women with radiologically dense breasts and negative two-dimensional mammography screening, according to interim results from the first prospective trial to directly compare the two modalities.
“However, future application of adjunct screening should consider that tomosynthesis detected more than 50% of the additional breast cancers in these women, and could potentially be [a] primary screening modality,” wrote Dr. Alberto Tagliafico of the University of Genoa (Italy) and his associates. The study was published online March 9 in the Journal of Clinical Oncology and presented simultaneously at the European Breast Cancer Conference.
Radiologically dense breast tissue undermines the sensitivity of mammography and is itself an independent risk factor for breast cancer. Recently, many states began requiring that women be informed of their breast density and adjunct screening measures, such as ultrasound. But estimates of the sensitivity of ultrasound have ranged from about 1.9 to 4.2 cancers for every 1,000 screens, said the researchers. This variance, combined with costs and concerns about false-positive recalls, have fueled debates about the value of adjunct measures in breast cancer screening, they added. To help clarify these issues, the multicenter ASTOUND (Adjunct Screening With Tomosynthesis or Ultrasound in Women With Mammography-Negative Dense Breasts) study compared physician-performed ultrasound and tomosynthesis results for 3,231 asymptomatic women aged 44 to 71 years, whose median age was 51 years (J Clin Oncol. 2016 Mar 9. doi: 10.1200/JCO.2015.63.4147).
In all, the researchers detected 24 additional breast cancers, 23 of which were invasive. Thus, ultrasound detected about 7.1 additional cancers for every 1,000 screens (95% confidence interval, 4.2-10), compared with 4.0 additional cancers per 1,000 screens for tomosynthesis (95% CI, 1.8-6.2; P = .006). Only one cancer was detected by tomosynthesis alone. The rate of false-positive recalls was similar for the two modalities – 53 cases for tomosynthesis, versus 63 for ultrasound (P = .26). Rates of false-positive recalls leading to biopsy also were similar. Needle biopsies usually sufficed in recalled cases, but two women underwent surgical biopsies, both of which revealed radial scars.
If the final results of ASTOUND confirm these interim data, “it could be argued that breast tomosynthesis has little value in a setting where adjunct ultrasound is frequently used for screening women with mammography-dense breasts,” said the researchers. But tomosynthesis may have a role as a primary screening modality in other setting, especially because tomosynthesis acquisitions that also provide reconstructed 2D mammography are now available, lessening concerns about unjustified radiation exposure, they added.
The “modest” number of cancers in the interim report led to relatively wide confidence intervals, the investigators noted. Biomarker data were not available for all cancers, and both prevalent and incident ultrasound data were compared with prevalent tomosynthesis data, which might bias false-positive recall results in favor of ultrasound, they added.
