Diagnostic Performance of Fused Diffusion-Weighted Imaging Using T1-Weighted Imaging for Axillary Nodal Staging in Patients With Early Breast Cancer.

PURPOSE: To evaluate the diagnostic performance of fused diffusion-weighted imaging (DWI) using T1-weighted imaging (T1WI) for axillary nodal staging in patients with early breast cancer (stage I or II).

MATERIALS AND METHODS: We enrolled 149 axillae in 147 consecutive patients who performed preoperative breast magnetic resonance imaging (MRI) and definitive surgery. All patients underwent T2-weighted imaging (T2WI), fused DWI using T1WI, and non-fat-suppressed (non-FS) T1WI. Two radiologists scored each axillary nodal status by using a 5-point scale and independently measured the apparent diffusion coefficient (ADC) values of the most suspicious lymph node and an index tumor. Diagnostic performance was calculated on a patient-by-patient basis.

RESULTS: Macrometastasis was present in 26.2%, micrometastasis in 7.4%, and benign lymph nodes in 66.4%. Area under the receiver operating characteristic curves (AUCs) of both readers for predicting axillary lymph node metastasis were 0.676 and 0.603 for non-FS T1WI, 0.749 and 0.727 for T2WI, 0.838 and 0.790 for fused DWI, and 0.868 and 0.837 for the combined reading using ADC. AUCs of tumor ADC were 0.709 and 0.737, whereas those of lymph node ADC were 0.818 and 0.781 for both readers. With stepwise addition of tumor ADC, lymph node ADC, and lymphovascular invasion status to the fused DWI, the AUCs gradually increased from 0.838, 0.892, and 0.908 to 0.924 for reader 1 and from 0.790, 0.863, and 0.901 to 0.908 for reader 2.

CONCLUSION: Fused DWI using T1WI showed better diagnostic performance than conventional T2WI and non-FS T1WI for the prediction of lymph node metastasis.