ACR, SBI Statement on ACRIN Breast Ultrasound Trial Results and Role of Ultrasound in Breast Imaging Care
Early detection of breast cancer through annual screening mammography beginning at age 40 is a proven life-saving public health tool. The American Cancer Society has recommended that women at increased risk for breast cancer should consider beginning screening with mammography at a younger age and/or with supplemental methods. Validation of supplemental screening modalities has been sought. The results of the American College of Radiology Imaging Network National Breast Ultrasound Trial (ACRIN 6666) demonstrated that a single screening ultrasound examination, added to a screening mammogram, increased detection of breast cancer compared with mammography alone, among women at increased risk of breast cancer who also had dense breast tissue. As is the case for other screening modalities, the ultimate utility of screening ultrasound depends on many other factors in addition to cancer detection, including the number of false positive findings resulting in the need for additional evaluations and benign biopsies, the availability of equipment, staff, and other resources necessary to perform the test on an appropriate scale, and its cost effectiveness.
In ACRIN 6666, there was a substantial increase in the number of benign biopsies due to the addition of ultrasound compared to mammography alone, and the implications of this must be considered on both individual and societal scales. While the ACRIN study did demonstrate the utility of screening ultrasound at multiple centers, the examinations were performed by specially trained radiologists who had passed qualifying tests prior to participation in the study. Previously published studies comparing the use of mammography, ultrasound (US), and magnetic resonance imaging (MRI) in women at very high risk of breast cancer have demonstrated that MRI is a more sensitive and more specific examination, albeit at substantially higher cost. Neither MRI nor ultrasound should replace screening mammography, which is the only imaging modality that has proven to reduce mortality from breast cancer, although both US and MRI may have roles to play in some populations of women.
The American College of Radiology (ACR) and the Society of Breast Imaging (SBI) feel that the results of ACRIN 6666 increase the evidence base for the utility and limitations of screening ultrasound. ACRIN 6666 established standardized technique and interpretive criteria as well as experience requirements for physicians performing these examinations. At centers which follow similar practice, US may improve detection of early breast cancer in women at increased risk of breast cancer who are not currently recommended for MRI. These results do not justify the recommendation for screening ultrasound for the general public or in lieu of or in addition to MRI for very high-risk women.
