Intravoxel incoherent motion diffusion-weighted MRI for predicting response to neoadjuvant chemotherapy in breast cancer

Purpose To determine the diagnostic performance of intravoxel incoherent motion (IVIM) diffusion-weighted (DW) magnetic resonance imaging (MRI) parameters in predicting response to neoadjuvant chemotherapy (NAC) in breast cancer patients. Materials and methods Forty-six patients with stage II or III breast cancer underwent MRI including DW imaging with 10 b values before and after 2 cycles of NAC. Apparent diffusion coefficient (ADC) and IVIM parameters (D, D* and f) were obtained using histogram analysis derived from whole-tumor volumes. After surgery, imaging parameters were compared with histopathologic responses using the Miller-Payne grading system. Results Before NAC, D_mean, D₅₀, and D₇₅ were higher in good responders than in minor responders (P ≤ 0.043). After NAC, ADC_mean, ADC₅₀, ADC₇₅, D_mean, D₂₅, D₅₀, and D₇₅ were higher in good responders (P ≤ 0.037). Skewness of ADC and D were lower in good responders after NAC (P ≤ 0.005). Most histogram metrics of posttreatment ADC and D had similar AUC values with reasonable accuracy for prediction of good response (AUC ≥ 0.7, P < 0.05). Conclusion D and ADC are useful for the prediction of response to NAC in breast cancer patients. Additional information is obtained by application of the IVIM model in DW imaging analysis and histogram analysis using whole-tumor volume data.