For the study, 2,662 participants from 21 sites in the U.S., Canada, and Argentina completed three annual rounds of screening (a total of 7,473 exams) with mammography and whole-breast ultrasound performed and interpreted by physicians. In the fourth year, each participant had either biopsy or a 12-month clinical follow-up.
The cohort included 110 women who were diagnosed with 111 breast cancer events, 80% of which were invasive. The total number of cancers detected by ultrasound or mammography was comparable, at 58 out of 111 (53%) versus 59 out of 111 (53%). Berg's group also found that the vast majority of the cancers detected by ultrasound were invasive (53 out of 58, or 91%), compared with 41 out of 59 (69%) by mammography.
Cancer detection with ultrasound alone compares favorably to mammography alone, and ultrasound offers greater detection of node-negative invasive cancer than mammography, according to the researchers.