"Adding screening ultrasonography to conventional breast mammography increases the diagnostic yield by about 50 per cent among women at high risk for breast cancer, according to study findings published in the
Journal of the American Medical Association for May 14. However, the combined strategy also substantially increases the number of false positives.
Although annual MRI is recommended in addition to mammography for women at very high risk, ultrasound may be an equivalent option that is less expensive, requires no contrast material, and is well tolerated and widely available, Dr. Wendie A. Berg, at American Radiology Services Inc., in Lutherville, Maryland, and her associates note.
In the American College of Radiology Imaging Network (ACRIN) 6666 trial, mammography and ultrasound were performed and read independently.
The trial included 2637 women, ages 25 to 91 years of age, of whom 53 per cent had a personal history of breast cancer. The remaining women were considered high risk on the basis of Gail or Claus model criteria, BRCA-mutation carrier status, prior chest/mediastinal radiation, or prior atypical biopsy result. All but 43 with no previous mammogram had heterogeneously or extremely dense parenchyma in at least one quadrant.
Cancer was diagnosed in 41 breasts of 40 subjects, including eight identified by both ultrasound and mammography, 12 observed on ultrasound alone, 12 on mammography alone, and nine on neither.
The diagnostic yield for mammography was 7.6 per 1000 women screened, which increased to 11.8 per 1000 for combined mammography plus ultrasound. Corresponding diagnostic accuracy was 0.78 and 0.91, respectively.
"Detection of asymptomatic, mammographically occult, node-negative invasive carcinomas with ultrasound should reduce mortality from breast cancer," the authors write, though they note that mortality was not an end point of the ACRIN 6666 trial.
Still, false-positive rates were higher with ultrasound alone and combined screening compared with mammography alone.
"Individualized screening schemes tailored to the individual risk and to the personal preferences of a woman may be the way to consider how to screen for breast cancer," Dr. Christiane K. Kuhl, at the University of Bonn in Germany, writes in a related editorial. "Whether in the long run ultrasound or breast MRI will be more appropriate for this purpose remains to be seen."
