Advanced diffusion-weighted imaging for evaluating neoadjuvant chemotherapy in breast cancer.

Neoadjuvant chemotherapy (NAC) is widely used for locally advanced breast cancer. Imaging monitoring during NAC facilitates timely treatment adjustments and leads to improved patient outcomes. Dynamic contrast-enhanced MRI plays a key role in assessing NAC response; however, early during treatment, tumor volume changes lag behind intracellular microstructural and functional alterations. Diffusion-weighted imaging (DWI) provides average tissue diffusion information based on Gaussian water motion but fails to capture intratumoral heterogeneity. Advanced DWI techniques, including intravoxel incoherent motion (IVIM), stretched exponential modeling (SEM), diffusion kurtosis imaging (DKI), diffusion tensor imaging (DTI), and DWI-based virtual magnetic resonance elastography (vMRE), have attracted growing interest in evaluating breast cancer during NAC. These techniques require no gadolinium-based contrast agents and can provide valuable information on tumor microstructure, heterogeneity, and microcirculation. However, a notable gap persists between the potential benefits of advanced DWI and their actual clinical utility. This review assesses the current applications and limitations of advanced DWI techniques in NAC for breast cancer.