AJR June 2016

For women with dense breast tissue, the limitations of mammography combined with the increased risk of developing breast cancer suggest the need for additional imaging modalities to improve breast cancer detection.

In the June issue of AJR, a team of researchers and radiologists led by Maryellen L. Giger, Department of Radiology, University of Chicago, assess and compare radiologists’ performance in the detection of breast cancer using full-field digital mammography (FFDM) alone and using FFDM with 3D automated breast ultrasound (ABUS). Readers were evaluated in their ability to detect both mammography-negative breast cancers and mammography-positive breast cancers in women with dense breasts.

Are the results skewed because the study population was not limited to high-risk women?

The case set for the reader study came from the 13-site clinical registry study. Cases were selected to yield a cancer-enriched case set, which allowed a manageable number of cases for the reader study. All cases were obtained from asymptomatic women with breast density assessed as BI-RADS C or D by the registry clinical site radiologist during the initial mammographic screening interpretation.

A mammography-negative cancer case means that it was not detected on mammography at the clinical site and it was a biopsy-proven cancer.

All the women in the study had dense breasts, and thus based on breast density could be considered higher risk.

Was there anything about the outcome of the study that surprised you?

In this study, readers were evaluated on their ability to detect both mammography-negative breast cancers and mammography-positive breast cancers in women with dense breasts. While we expected improvement in the mammography-negative breast cancer cases, we also found improvement in the mammography-positive cases (in terms of AUC).

In addition, the readers became very adept with viewing the ABUS images and scrolling through the volume of breast in order to find the mammography-negative cancers.

Are there benefits to conducting a reader study versus a clinical trial? Are there disadvantages?

Since the study was a reader study and not a clinical trial, the radiologists’ performance may not match actual clinical performance. However, the performance of a reader study neutralizes the impact of a single radiologist’s interpretation because 17 radiologists interpreted the same examinations, albeit in different order. In addition, many studies are performed only in academic institutions that are not representative of varying clinical environments. Given the broad range of physicians from differing clinical settings included in this study, the possibility of similar real-world results is plausible.

Also, a preliminary study on reader concordance, which used a part of the reported dataset, focused on individual readers and showed acceptable inter-reader agreement with the use of ABUS. The inter-reader concordance shows the feasibility of implementing ABUS into routine clinical practice.

Please provide the study’s conclusion.

The addition of ABUS to screening mammography showed a significant increase in cancer detection with a nominal insignificant decrease in specificity.