What is ABUS (Automated Breast Ultrasound) Imaging?
ABUS is an automated ultrasound technique that standardizes breast imaging by separating image acquisition from interpretation, designed specifically as supplemental screening for women with dense breasts where mammography sensitivity drops to as low as 30%. 1
Technical Overview
ABUS differs fundamentally from traditional handheld ultrasound (HHUS) in several key ways:
- Image acquisition can be performed by a technician rather than requiring a radiologist to be present during scanning, significantly reducing physician time requirements 2
- Standardized imaging protocol reduces operator dependence and increases reproducibility compared to HHUS 2, 3
- Multiplanar reconstructions provide unique coronal plane views that are not available with conventional handheld ultrasound, introducing new diagnostic information 2, 3
- Interpretation occurs separately from acquisition, allowing radiologists to review images at a different time and location 2
Clinical Performance in Screening
The cancer detection rates with ABUS demonstrate meaningful supplemental benefit:
- ABUS detects an additional 12.3 per 1,000 cancers in women with greater than 50% breast density when added to mammography, compared to 4.6 per 1,000 by mammography alone 4
- Mean tumor size detected is 14.3 mm, indicating clinically significant cancers are being identified 4
- Combined ABUS and mammography interpretation improves diagnostic performance compared to either modality alone, with statistically significant improvements in area under the curve (AUC) values 5
Current Guideline Recommendations
The American College of Radiology and European guidelines suggest NOT routinely implementing ABUS for supplemental screening, despite its detection capabilities 1:
- Low biopsy positive predictive values and high false-positive rates are major concerns, including high rates of short-term follow-up recommendations 1
- No mortality benefit has been demonstrated - the link between higher detection rates and reduced breast cancer deaths remains unproven 1
- Resource requirements are substantial given the need for additional equipment, technician time, and radiologist interpretation time 1
Practical Interpretation Considerations
Radiologists using ABUS must understand its unique characteristics:
- Interpretation time averages 9 minutes for a bilateral normal examination 5
- Shadowing from dense parenchyma is the most common cause of false-positive interpretations 5
- Considerable inter-observer variability exists, with kappa values ranging from 0.07-0.44 depending on reader experience 5
- Combined reading with mammography should be standard if ABUS is implemented, as all readers improve performance with combined interpretation 5
Clinical Context and Alternatives
When considering supplemental screening for dense breasts, ABUS competes with other modalities:
- MRI demonstrates superior cancer detection with rates of 15.2 per 1,000 compared to ABUS performance, and is the preferred supplemental modality for high-risk women 6
- Handheld ultrasound (HHUS) detected 4.9 per 1,000 additional cancers in the ASTOUND-2 trial, though with more false-positives than digital breast tomosynthesis 1
- Digital breast tomosynthesis (DBT) is recommended for all women regardless of density as the primary supplemental approach 1
Key Limitations
The primary barriers preventing widespread ABUS adoption include:
- Lack of mortality data - no studies demonstrate that ABUS screening reduces breast cancer deaths or improves quality of life 1, 6
- High false-positive burden increases patient anxiety, additional imaging, and unnecessary biopsies 1
- Cost-effectiveness remains unproven with incremental costs potentially exceeding $238,550 per quality-adjusted life-year gained based on indirect evidence 1