Assessing radiologist performance using combined digital mammography and breast tomosynthesis compared with digital mammography alone: results of a multicenter, multireader trial

Abstract

Purpose: To compare radiologists' diagnostic accuracy and recall rates for breast tomosynthesis combined with digital mammography versus digital mammography alone.

Materials and methods: Institutional review board approval was obtained at each accruing institution. Participating women gave written informed consent. Mediolateral oblique and craniocaudal digital mammographic and tomosynthesis images of both breasts were obtained from 1192 subjects. Two enriched reader studies were performed to compare digital mammography with tomosynthesis against digital mammography alone. Study 1 comprised 312 cases (48 cancer cases) with images read by 12 radiologists; study 2, 312 cases (51 cancer cases) with 15 radiologists. Study 1 readers recorded only that an abnormality requiring recall was present; study 2 readers had additional training and recorded both lesion type and location. Diagnostic accuracy was compared with receiver operating characteristic analysis. Recall rates of noncancer cases, sensitivity, specificity, and positive and negative predictive values determined by analyzing Breast Imaging Reporting and Data System scores were compared for the two methods.

Results: Diagnostic accuracy for combined tomosynthesis and digital mammography was superior to that of digital mammography alone. Average difference in area under the curve in study 1 was 7.2% (95% confidence interval [CI]: 3.7%, 10.8%; P < .001) and in study 2 was 6.8% (95% CI: 4.1%, 9.5%; P < .001). All 27 radiologists increased diagnostic accuracy with addition of tomosynthesis. Recall rates for noncancer cases for all readers significantly decreased with addition of tomosynthesis (range, 6%-67%; P < .001 for 25 readers, P < .03 for all readers). Increased sensitivity was largest for invasive cancers: 15% and 22% in studies 1 and 2 versus 3% for in situ cancers in both studies.

Conclusion: Addition of tomosynthesis to digital mammography offers the dual benefit of significantly increased diagnostic accuracy and significantly reduced recall rates for noncancer cases.

Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120674/-/DC1.

RSNA, 2012

Figures

Figure 1:

Subject imaging and case selection for breast tomosynthesis with digital mammography (DM). Women were excluded if they had a history of breast cancer, previous surgical biopsy, or an implanted tissue marker within the breast. Also excluded were women with breast implants and those who were pregnant or lactating.

Figure 2:

Pooled ROC curves for reader studies 1 and 2 using probability of malignancy scores; curves represent average ROC performance for 12 readers in study 1 and 15 in study 2. ROC curves and AUC differences were nearly equal for the reader studies. At 13 and 15 months after imaging, two cases initially characterized as noncancer cases in study 1 were diagnosed as ductal carcinoma in situ. These cancers were detected after the 365-day follow-up window and not treated as cancers in this analysis; if ROC analysis is repeated with these cases classified as malignant, the AUC difference is unchanged. DM = digital mammography, Tomo = tomosynthesis.

Figure 3:

Recall rates for, A, noncancer and, B, cancer cases for individual readers. DM = digital mammography, SD = standard deviation, Tomo = tomosynthesis.

Figure 4:

Pooled ROC curves for reader studies 1 and 2: A, calcification and, B, noncalcification cases. ROC curves were calculated from probability of malignancy scores except for calcification curves for study 1; forced BI-RADS scores were used for these curves because data were available for all 12 readers. The ROC program failed to produce an ROC curve using probability of malignancy scores for this subanalysis. For all other analyses, BI-RADS and POM ROC curves provided nearly equal results. There were 83 and 79 cases classified as calcification in studies 1 and 2, respectively; the remainder were classified as noncalcification. DM = digital tomography, Tomo = tomosynthesis.

Figure 5a:

(a) Digital mammography and (b) tomosynthesis images of an invasive ductal carcinoma.

Figure 5b:

(a) Digital mammography and (b) tomosynthesis images of an invasive ductal carcinoma.