Screening breast ultrasound performed after mammography on women with greater than 50% breast density detects an additional 3.4 cancers or high risk lesions per one thousand woman screened, a detection rate just under that of screening mammography alone for women with less dense breasts, a new study shows. Screening mammography detects 4-5 cancers per thousand women screened.
The study, conducted in conjunction with seven Connecticut radiology practices, included 19,745 women who had dense breasts and "normal" mammograms. Sixty-seven cancers were found, said Dr. Sarah Steenbergen, lead author of the study, who is now at Yale University in New Haven, CT. "Out of the available surgical reports, only one case had nodal involvement at the time of diagnosis. This suggests that the cancers are detected early and therefore we anticipate a survival benefit," Dr. Steenbergen said.
The study has been conducted over two years, "and we've seen an improvement in the sensitivity of screening breast ultrasound from 96.6% to 100% and in specificity from 94.0% to 96% from the first to the second year," she said. This illustrates a learning curve, and "we anticipate that as the number of screening breast ultrasounds increase, physicians will be even better able to differentiate benign from malignant lesions," she said.
Recent legislation in Connecticut mandates reporting of breast density on mammograms and recommending follow up screening ultrasound for women with greater than 50% breast density, said Dr. Steenbergen. The study was conducted, in part, to measure the outcome of this legislation and what we can hope to achieve with screening breast ultrasound, she said.