Dutch Study Casts Some Doubt on New Technology

Digital tomosynthesis detects more breast masses, better categorizes those masses, and produces lower callback rates than conventional mammography. In a study of symptomatic patients, tomosynthesis was not superior to mammography, but a combination of the two techniques detected more carcinomas than either alone.

Citing results gathered from 30 consecutive subjects in an ongoing study, Dr. Mark A. Helvie, director of breast imaging at the University of Michigan Health System, reported that experienced readers detected 36% more masses with digital tomosynthesis than with mammography. Tomosynthesis provided 48% better margin assessment and detected 100% of cancers (6/6) compared with mammography's 83% (5/6). Malignant cases were rated as 48% more likely to be malignant on digital tomosynthesis compared with mammography.

Digital tomosynthesis can also reduce callback rates, according to research presented by Dr. Richard Moore, director of breast imaging research at Massachusetts General Hospital. In a screening setting of more than 2000 scans for each modality, patients who had prior studies and were then imaged using digital tomosynthesis had a callback rate of 5.1%, compared with a baseline radiologist rate of 6.8% and the average mammography rate of 8%.

Among patients with no prior studies, the callback rate was 12.9% for mammography and 11.6% for tomosynthesis. For patients with prior studies, rates were 8.1% and 5.1%, respectively. Both types of studies were read in batch mode.

The research also suggested that the tomosynthesis callback rate improves with experience. In the first eight months the system was in use, the callback rate was 6.3% for patients who had received prior studies. In the third eight-month period, that rate dropped to 4.5%.

Moore warned that the appearance of previous surgery on digital tomosynthesis can be jarring when radiologists first begin using the system, as a surgical scar can mimic a new lesion.

A final study threw some cold water on the digital tomosynthesis lovefest, however. Dr. Hendrik Teertstra of the Netherlands Cancer Institute in Amsterdam presented research suggesting that the ability to detect malignant lesions was not significantly different for digital tomosynthesis and mammography and that the role of tomosynthesis has yet to be established in symptomatic patients. A combination of the two techniques did detect more carcinomas than either technique alone.

The study of 113 carcinomas in 933 symptomatic breasts determined that the rate of false negatives produced using digital tomosynthesis was 6.2%, while that using mammography was 7%. When a combination of the two techniques was used, false negatives dropped to 2.65%.
-By Sarah Jersild