Tomo on par with diagnostic mammo for recall workup

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 - breast tomosynthesis
58-year-old woman with invasive ductal carcinoma (arrows) detected on screening mammography and digital breast tomosynthesis (DBT).
Source: American Journal of Roentgenology

Digital breast tomosynthesis (DBT) provided sensitivity and specificity on par with diagnostic mammography for the evaluation of noncalcified findings recalled from screening mammography, suggesting tomosynthesis can replace the conventional diagnostic approach. The study was published in the February issue of the American Journal of Roentgenology.

DBT is designed to minimize the effect of normal tissue overlap and improve lesion conspicuity. Previous studies have suggested DBT provides performance comparable with or superior to conventional mammography. However, earlier studies have not incorporated comprehensive screening data in the DBT assessment.

Kathleen R. Brandt, MD, from the department of radiology at Mayo Clinic in Rochester, Minn., and colleagues devised a study to mimic the clinical setting, evaluating DBT as an alternative to diagnostic mammography and providing readers with comparison mammograms and breast ultrasound results.

The study focused on 146 women with 158 screen-detected findings who were enrolled between March 2009 and April 2010. Patients underwent conventional diagnostic imaging and a two-view DBT exam.

At least six months later, three breast radiologists independently reviewed the tomosynthesis data, evaluating the data as if DBT were the primary diagnostic exam. Confidence scores were employed to determine if DBT sufficed for a final diagnostic exam or if additional imaging was needed.

BI-RADS results were grouped as follows: BI-RADS scores of 1 and 2 were grouped together because no additional follow-up is needed; BI-RADS scores of 4 and 5 were paired as both require biopsy and BI-RADS 3 was left as a separate category requiring short-term follow-up.

The diagnostic follow-up for the 158 abnormalities included additional mammographic views for 157 findings, and ultrasound in 78 of the abnormalities. A total of 136 findings were classified as BI-RADS 1 or 2, six were classified as BI-RADS 3, and the remaining 16 abnormalities were classified as BI-RADS 4 or 5 and underwent biopsy.

On DBT exam, readers 1, 2 and 3 showed concordance with the diagnostic mammography BI-RADS category in 97 percent, 95 percent and 90 percent of the lesions, respectively, according to Brandt and colleagues. “There was no significant difference between DBT and diagnostic mammography with respect to sensitivity for any of the readers,” the researchers continued. However, these estimates were not very precise, the researchers, wrote, due to the low number of positive cases.

Readers did not differ significantly from diagnostic mammography on specificity or accuracy, the researchers reported.

Confidence scores results indicated that DBT was considered adequate mammography evaluation for 99 percent of the findings for readers 1 and 2, and 93 percent for reader 3. Reader 1 would have ordered ultrasound for further evaluation in 44 percent of the cases, reader 2 in 28 percent and reader 3 in 48 percent.

The researchers noted no reader demonstrated improved sensitivity with DBT. In addition, they had anticipated a decline in cases requiring ultrasound with DBT but found radiologists continued to rely on diagnostic ultrasound with tomosynthesis. Brandt and colleagues partially attributed this result to the learning curve associated with DBT and predicted less frequent use of ultrasound as radiologists build experience with DBT.

Brandt and colleagues suggested DBT might improve technologist efficiency as DBT positioning is identical to routine mammography, while diagnostic positioning “can be challenging,” and required up to six extra views for some patients in this study.

“The results of this study showed that DBT has potential to replace conventional diagnostic mammography for evaluating noncalcified asymmetries, areas of distortion and masses recalled from screening mammography,” wrote Brandt et al.