CHICAGO – Adding tomosynthesis to full-field digital mammography improved cancer detection and reduced recall rates in women with dense breasts in a study of 293 patients.
"Both clinically and in trials, we’ve seen that tomosynthesis offers benefit for all women, but I think there is a particular benefit, the increased gains are more, for women with dense breast tissue," Dr. Elizabeth Rafferty said at the annual meeting of the Radiological Society of North America. "I think that underscores where we may start our triage efforts with limited resources."
Dr. Elizabeth Rafferty
She reported on an enriched case set of 69 biopsy-proven cancers, 74 benign biopsies, 50 recalled screening cases, and 100 negative screening cases, all with a BI-RADS (Breast Imaging Reporting and Data System) density score of 3 (heterogeneously dense) or 4 (extremely dense). Calcification was present in 25% and noncalcification in 75% of cases.
Eight radiologists read the cases in two separate sessions separated by 1 month, with half of the cases read in each mode for each reading session. Identification of the lesion location and type and initial BI-RADS score (0, 1, 2) were used to determine the recall rate. A probability of malignancy score from 0% to 100% was used to calculate the receiver operating area under the curve (AUC).
The difference in the AUC between standard full-field digital mammography (FFDM) plus tomosynthesis and FFDM alone was significantly higher at 8.3% for all cases (AUC 0.940 vs. 0.857, P value less than .0001), 4.1% for calcification cases (0.818 vs. 0.777, P = .048), and 11% for noncalcification cases (0.977 vs. 0.867, P = .0001), reported Dr. Rafferty, director of breast imaging at Massachusetts General Hospital in Boston.
The recall rate for all cancer cases was 9.7% higher for FFDM plus tomosynthesis vs. FFDM alone. Specifically, it was 3.8% higher for calcification cases and 14.3% higher for noncalcification cases.
Seven of the eight readers increased their cancer detection rate using FFDM plus tomosynthesis, while one reader had the same detection rate on the two modalities. For six of the seven readers, the improvement in cancer detection was statistically significant, she said.
For noncancer screening cases, the recall rate for FFDM plus tomosynthesis was 23.3% vs. 33.9% for FFDM alone, representing a 31% reduction in the noncancer recall rate.
Six of the eight readers had significant decreases in their screening recall rate using the combined imaging modality, while the other two readers had no significant change.
"In women with dense breast tissue, tomosynthesis, when added to FFDM, appears to offer particular value both in terms of sensitivity as well as specificity of the examination," Dr. Rafferty said.
She noted that the numbers were too small to identify a difference in performance with FFDM plus tomosynthesis between dense and extremely dense breasts.
"In women with dense breast tissue, tomosynthesis ... appears to offer particular value."
An attendee also asked whether she would recommend using tomosynthesis in lieu of screening ultrasound.
"In terms of the positive predictive value of screening ultrasound, I think that screening mammography, or some form of screening mammography, is going to remain the mainstay," she said. "But in terms of our diagnostic evaluation, I think ultrasound has become an incredibly important tool in the diagnostic evaluation.
"Basically, tomosynthesis examination plus ultrasound has become for me, and I think for many other people, kind of the go-to regimen instead of using additional views. The two are very complementary."
Dr. Rafferty reported no relevant financial disclosures. A coauthor reported serving as a patent holder and employee of Hologic.