Combining b2500 diffusion-weighted imaging with BI-RADS improves the specificity of breast MRI

The purpose of this study was to evaluate the diagnostic performance of visual assessment of diffusion-weighted images (DWI) obtained with a b value of 2500 s/mm² in addition to a conventional magnetic resonance imaging (MRI) protocol to characterize breast lesions.

This single-institution retrospective study included participants who underwent clinically indicated breast MRI and breast biopsy from May 2017 to February 2020. The examination included a conventional MRI protocol including DWI obtained with a b value of 50 s/mm² (b₅₀DWI) and a b value of 800 s/mm² (b₈₀₀DWI) and DWI obtained with a b value of 2500 s/mm² (b₂₅₀₀DWI). Lesions were classified using Breast Imaging Reporting and Data Systems (BI-RADS) categories. Three independent radiologists assessed qualitatively the signal intensity within the breast lesions relative to breast parenchyma on b₂₅₀₀DW and b₈₀₀DWI and measured the b₅₀-b₈₀₀-derived apparent diffusion coefficient (ADC) value. The diagnostic performances of BI-RADS, b₂₅₀₀DWI, b₈₀₀DWI, ADC and of a model combining b₂₅₀₀DWI and BI-RADS were evaluated using receiver operating characteristic (ROC) curves analysis.

A total of 260 patients with 212 malignant and 100 benign breast lesions were included. There were 259 women and one man with a median age of 53 years (Q1, Q3: 48, 66 years). b₂₅₀₀DWI was assessable in 97% of the lesions. Interobserver agreement for b₂₅₀₀DWI was substantial (Fleiss kappa = 0.77). b₂₅₀₀DWI yielded larger area under the ROC curve (AUC, 0.81) than ADC with a 1 × 10^-3 mm²/s threshold (AUC, 0.58; P = 0.005) and than b₈₀₀DWI (AUC, 0.57; P = 0.02). The AUC of the model combining b₂₅₀₀DWI and BI-RADS was 0.84 (95% CI: 0.79-0.88). Adding b₂₅₀₀DWI to BI-RADS resulted in a significant increase in specificity from 25% (95% CI: 17-35) to 73% (95% CI: 63-81) (P < 0.001) with a decrease in sensitivity from 100% (95% CI: 97-100) to 94% (95% CI: 90-97), (P < 0.001).

Visual assessment of b₂₅₀₀DWI has substantial interobserver agreement. Visual assessment of b₂₅₀₀DWI offers better diagnostic performance than ADC and b₈₀₀DWI. Adding visual assessment of b₂₅₀₀DWI to BI-RADS improves the specificity of breast MRI and could avoid unnecessary biopsies.