(Ultrasound Review) According to Australian researchers at the Sydney-Square Breast Clinic, sonography is more accurate than mammography in women 45 years or younger and should be the initial examination.
"We recognize that the evidence from this research is contrary to current thinking and clinical practice in breast imaging of symptomatic women, and we recommend further research that examines this issue using a prospective study," they wrote in the American Journal of Roentgenology.
Dr. Nehmat Houssami and colleagues studied 480 patients over a four-year period that included 240 patients with breast cancer, and 240 age-matched patients without breast cancer (25-55 years).
"Mammograms and sonograms were prospectively interpreted independently and without knowledge of age by two radiologists in a blinded manner, with a third radiologist arbitrating disagreements," they reported. Sensitivity and specificity for ultrasound and mammography were calculated in relation to patient age.
The breast cancer prevalence in the study population was 2% and the histologic types of cancer were invasive ductal (70%), ductal in situ (14%), invasive lobular (9%), tubular (4%), medullary (1%), and other types (1.2%). Results demonstrated that sensitivity for ultrasound (81.7%) and mammography (75.8%) were not significantly different in women above 50 years.
Ultrasound sensitivity for women 45 years or younger was 84.9% compared with 71.7% for mammography, which was a significant difference. In women 46-55 years old, the sensitivity of sonography and mammography were both 79.1%, and the specificity also was similar.
For the patients with cancer, "20% were correctly identified as cancer on sonography but not correctly identified as cancer on mammography, and 14% were correctly identified on mammography but not on sonography," they determined.
A combination of both sonography and mammography resulted in a high sensitivity of approximately 96%. Meaning 4% of cancers will be misdiagnosed in symptomatic women even when both examinations are performed.
"These data show that sonography is the more accurate imaging test in women 45 years old or younger who present with breast symptoms and may be an appropriate initial imaging examination," the authors concluded.
They suggested that future research should study the influence of hormonal status on diagnostic accuracy. They also suggested, "any change from current practice should be introduced initially in the context of dedicated breast services, in which systematic sonographic scanning and monitoring of accuracy are routine practice, before wider implementation."
Sydney breast imaging accuracy study: comparative sensitivity and sensitivity and specificity of mammography and sonography in young women with symptomsHoussami, N et al.
The Sydney-Square Breast Clinic, Sydney, Australia
AJR April 2003; 180:935-940
By Ultrasound Review
June 10, 2003
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