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, according to study results from the American College of Radiology Imaging Network National Breast Ultrasound Trial (ACRIN 6666).
Early detection of breast cancer through annual screening mammography beginning at age 40 is a proven life-saving public health tool, according to the ACR. 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.
The most recent findings, published in the May issue of the Journal of the American Medical Association, are from the first round of screening in the ACRIN-6666 trial. More than 2,800 women at high risk of developing breast cancer participated. The median age of the participants was 55 years and more than half had a personal history of breast cancer.
In ACRIN 6666, the researchers found that there was a substantial increase in the number of benign biopsies due to the addition of ultrasound compared to mammography alone and the implications must be considered on both individual and societal scales.
“The trial uncovered a significant trade-off with ultrasound screening,” said Jeffrey Blume, an associate professor in the Department of Community Health and the deputy director of the ACRIN Biostatistics and Data Management Center at Brown University. “While supplemental ultrasound screening uncovers more breast cancers, it also substantially increases the risk of a false positive cancer finding and unnecessary biopsy.”
“The medical community may well decide that the screening benefit is offset by the increase in risk to women from a false positive finding,” Blume said. “However this study also shows that supplemental ultrasound may be beneficial in women at high risk of breast cancer who could not, or would not, otherwise undergo a magnetic resonance imaging scan. Women should consult their doctor for more information.”
While the ACRIN study did demonstrate the utility of screening ultrasound at multiple centers, the examinations were performed by radiologists, who had passed qualifying tests prior to participation in the study, according to the ACR.
Previously published studies comparing the use of mammography, ultrasound and 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, the ACR said.
The ACR noted that 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 ultrasound and MRI may have roles to play in some populations of women.
The Society of Breast Imaging (SBI) and the ACR said that the results of ACRIN 6666 increase the evidence base for the utility and limitations of screening ultrasound.
W. Phil Evans, MD, a study author and professor of radiology at the UT Southwestern Center for Breast Care in Dallas, said ultrasound is attractive for supplemental screening because it is widely available, is well-tolerated by patients and involves no radiation. It’s also less costly than MRI, according to Evans.
“However, adding a single ultrasound to mammography does increase the number of false positives,” said Evans. “Whether or not the risk of false positives will diminish with subsequent rounds of the screening trial remains to be seen, but it’s something we’re tracking.”
ACRIN 6666 established standardized technique and interpretive criteria as well as experience requirements for physicians performing these examinations, according to the ACR. At centers which follow similar practice, ultrasound may improve detection of early breast cancer in women at increased risk of breast cancer who are not currently recommended for MRI.
The association noted that the 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.
The Avon Foundation and the National Cancer Institute funded the study.