The Power of Diffusion-Weighted Images and ADC Maps in Breast MRI.

Abstract

We thoroughly read a recent publication by Tezcan et al that discussed the role of combined Diffusion-Weighted Imaging (DWI) and dynamic contrast-enhanced MRI for differentiating malignant from benign breast lesions that demonstrate a washout kinetics curve. We would like to highlight several relevant points pertaining to the role of DWI sequences in both 1.5 and 3 T MRI in differentiating benign from malignant breast lesions, as well as the potential value of establishing an ADC cut-off value in the grading of invasive cancers. A study performed by Tan et al found statistically significant differences between benign and malignant breast lesions, for both b-values of 500 s/mm and 1000 s/mm (p < 0.010). The ADC cut-off values for benign and malignant lesions were determined to be 1.21 � 10�3 s/mm for a b-value of 500 s/mm and 1.22 � 10�3 s/mm for a b-value of 1000 s/mm, respectively. Another study by Partridge et al demonstrated that incorporating ADC values and the washout curve demonstrated statistically significant diagnostic results (p-value 1⁄4 0.008 at b-value of 1000) in the prediction of malignancy as opposed to the use of either of these techniques alone. The ADC value can also be a good discriminator between low and high-grade tumors in invasive ductal carcinoma (IDC), and hence a potential good predictor of response to chemotherapy. In a prospective study of 156 patients with IDC by Azzam et al the mean ADC values for grade I, grade II, and grade III IDC were 1.01 + 0.06 � 10� 3 s/mm, 0.74 + 0.12 � 10� 3 s/mm, and 0.70+ 0.09� 10� 3 s/mm, respectively. There was a significant difference between the mean ADC values of grade I and III tumors (p 1⁄4 0.001), as well as between grade I and II tumors (p 1⁄4 0.002). However, there was no significant difference between grade II and III tumors (p 1⁄4 0.979). We thank the authors for showing the potential value of utilizing ADC maps with specific cut-off values as an additional useful predictive marker for malignant breast lesions, as well as a potentially helpful tool for tumor grading. Declaration of Conflicting Interests