Ultrasound edges out mammography in younger women

When it comes to diagnosing breast cancer in symptomatic women, age counts, according to researchers in Australia. For women under 45, sonography is more accurate than mammography. It could be the best initial imaging test in this patient group.

The Sydney Breast Imaging Accuracy Study included 240 women from 25 to 55 years of age with breast cancer, and 240 control subjects of matching ages. They underwent both sonography and mammography.

Researchers gauged sensitivity and specificity for both tests in symptomatic women separated by age. Overall sensitivity for ultrasound was 81.7% compared with 75.8% for mammography for women younger than 45. Specificity for both modalities was approximately 88%. The findings were published in the April issue of the American Journal of Roentgenology.

"The evidence provided through our study is contrary to current thinking and clinical practice," said principal investigator Dr. Nehmat Houssami, director of the Sydney-Square Breast Clinic at the time the study was conducted.

The study validated other recent research, however, suggesting that age is a determining factor in the sensitivity of both mammography and ultrasound in women with breast cancer symptoms. It included pre- and perimenopausal women, and both mammograms and sonograms were prospectively, blindly, and independently reviewed by two radiologists.

The implications of the study for diagnosis suggest that both modalities could complement rather than exclude each other. Sonography could be the best preliminary imaging assessment for symptomatic women 45 years and younger with palpable findings on clinical examination. Based on the Sydney study's evidence, it would be inappropriate to reassure symptomatic women in this age group on the basis of a negative mammogram alone, Houssami said.

"We know that neither mammography nor sonography will correctly diagnose all breast cancers," she said. "We also know - and this is well demonstrated in the Sydney study - that each imaging test will accurately diagnose a proportion of breast cancers that will not be accurately identified by the other test. So in combining both tests, we would expect an increase in the number of breast cancers that are correctly diagnosed."

This approach may lead to a large number of false-positive results among women who are cancer free, however. Whether mammography is indicated in addition to sonography in women 45 years and younger will depend on the clinical and sonographic findings. It may also depend on whether a given patient is under a specific risk of developing breast cancer, Houssami said.

Ultrasound is generally cheaper, safer, more readily available, and comfortable than mammography. Ultrasound machines are getting smaller and more affordable, which is not only good for the young woman, but also for the country that cannot afford population-based mammography, said Dr. Cary S. Kaufman, medical director of the Bellingham Breast Center in Bellingham, WA.

But ultrasound, compared with mammography, is still very operator-dependent and time-consuming. And despite the density effect on their breasts, many young women's mammograms can be easily read.

On the other hand, mammograms cannot tell a solid lump from a liquid one, while ultrasound is very good at this distinction. Ultrasound also has an edge over mammography at identifying cysts, Kaufman said.

"A 14% advantage in sensitivity with no specificity advantage may not be high enough to choose only an ultrasound, but it might sway you to pick the ultrasound first sometimes," he said.

For more from the archives of Diagnostic Imaging:

Breast tumors in younger, symptomatic patients may show up better on ultrasound
http://www.dimag.com/db_area/onlinenews/2002/2002061401.shtml