Diffusion-weighted magnetic resonance imaging for assessment after neoadjuvant chemotherapy in breast cancer, based on morphological concepts.

The study aimed to evaluate the utility of diffusion-weighted imaging (DWI) and to assess the response of breast cancer patients to neoadjuvant chemotherapy (NAC), based on morphological concepts. This retrospective study included 35 breast cancer patients (36 lesions) who had conventional magnetic resonance imaging (MRI), with DWI acquired before and after NAC. The morphological pattern of delayed enhancement on MRI before NAC was classified into two types: focal mass (FM), and multiple masses and/or non-mass like (MM/NM), based on Breast Imaging Reporting and Data System (BI-RADS). Of the 36 tumors, 26 were classified as FM and 10 as MM/NM. Tumors were clearly visualized on the initial DWI although one case of suspected MM/NM was not observed on DWI following NAC. A correlation was found between changes in the apparent diffusion coefficient and response rates to NAC in FM tumors (r=0.608, p<0.001), but not in MM/NM tumors (r=0.141, p=0.717). There was agreement between MRI findings after NAC and pathological findings in 30 of the 36 tumors (83.3%). Thus, we concluded that DWI is potentially useful in assessing the response to NAC for breast cancer for tumors diagnosed as FM on the initial conventional MRI.