Use of Diffusion-Weighted, Intravoxel Incoherent Motion, and Dynamic Contrast-Enhanced MR Imaging in the Assessment of Response to Radiotherapy of Lytic Bone Metastases from Breast Cancer

Rationale and Objectives: To investigate the value of diffusion-weighted (DW), perfusion-sensitive, and dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) techniques in assessing the response of bone metastases from breast cancer to radiotherapy, with particular emphasis on the role of intravoxel incoherent motion (IVIM)-DW parameters as a potential valuable imaging marker of tumor response. Materials and Methods: Fifteen women having breast cancer and bone metastases underwent MRI before and after radiotherapy (3weeks [time 1], 2 months [time 2], and 4months [time 3]), consisting of DW, perfusion-sensitive (IVIM), and DCE acquisitions. MR-based DW and perfusion parameters, including water diffusivity ( D), perfusion fraction ( f), pseudodiffusion ( D*), total apparent diffusion coefficient (ADC-total), fractionated ADCs (ADC-high and ADC-low), and initial area under the gadolinium concentration curve after the first 60seconds (IAUGC60), were determined. The morphologic MRI findings were also recorded. A one-way repeated measures analysis of variance was used to compare the value of MR-based parameters at the different time points. Results: A significant variation between pretreatment (time 0) and post-treatment (times 1, 2, and 3) was found for ADC-total and D parameters ( P<.001). A statistically significant reduction was also found for IAUGC60 values between times 0 and 3 ( P<.001). A significant change across the different time points was observed for D* and IAUGC60 parameters ( P<.001). On the contrary, there was no statistically significant change over time for parameters ADC-total, D, f, and IAUGC60 comparing response between each metastasis, that is, the response to therapy was similar for each metastasis. Conclusions: DW, IVIM, and DCE-MRI techniques show effectiveness in assessing the response to radiotherapy in bone metastases from breast cancer