An important factor in predicting a woman’s risk for breast cancer is breast density. The method most commonly used to measure density is 2D mammography in which a radiologist or a mathematical algorithm allocates one of four categories according to the Breast Imaging-Reporting and Data System (BI-RADS): (a) fatty; (b) scattered fibro-glandular tissue; (c) heterogeneously dense; and (d) extremely dense. The problem with mammographic percent density (MPD) is that the woman is exposed to ionizing radiation – not ideal for women younger than 40 – and MPD only provides modest improvements in risk prediction.
A recent paper in the Journal of Clinical Medicine (JCM) has compared the use of automated breast ultrasound (ABUS) and MPD to assess breast cancer risk (since JCM is an open assess journal, a PDF copy of the paper may be downloaded by clicking here). The ABUS system is known as SoftVue and the manufacturer, Delphinus, was featured in last week’s blog as the recipient of investments of $67M. One of the parameters measured by SoftVue is the speed of the ultrasound waves as they pass through breast tissue, and the authors hypothesized that sound speed would be a better predictor of cancer risk than MPD.
This was a case-control study that included 61 women with a recent diagnosis of breast cancer, and a comparison group of 165 women with a recent negative mammogram and no personal history of breast cancer. Seen at left (© JCM) are sound speed images for four different women, showing the BI-RADS categories a, b, c and d. Note the grey scale where sound speed ranges from 1.48 to 1.62 km/s.
The findings, which were statistically significant, demonstrated that whole breast volume-averaged sound speed was more strongly associated with increasing breast cancer risk than MPD. With SoftVue the woman lies on a bed (seen below right) and the ultrasound waves are transmitted through her breast, thus enabling sound speed to be measured. While other ABUS systems – including CapeRay’s Aceso – are based on measuring reflected waves, a Swiss group has recently demonstrated this modality can also measure sound speed.
First author Neb Duric, who was one of the original developers of SoftVue, commented: “This study expands the potential application of our platform technology beyond diagnostic imaging and breast cancer screening to cancer risk stratification for women at virtually any age.” Co-author Rachel Brem was also upbeat: “We are encouraged by our results that indicate the potential use of whole breast ultrasound to improve the accuracy of breast cancer risk assessment with a non-ionizing breast imaging modality.”