Program Information
Early Assessment of Treatment Response in Sarcoma Utilizing MR Elastography (MRE) and Dynamic-Contrast Enhanced (DCE) MRI
K Pepin*, R Grimm , S Kargar , S James , M Howe , K Fritchie , M Frick , D Wenger , R Ehman , K McGee , N Laack , M Herman , D Pafundi , Mayo Clinic, Rochester, MN
Presentations
TU-D-601-3 (Tuesday, August 1, 2017) 11:00 AM - 12:15 PM Room: 601
Purpose: Conventional imaging (CT, MRI) provide anatomical-based information used to guide surgery, determine radiotherapy (RT) target volumes, and assess treatment response in sarcomas however, these techniques to assess early response have not been shown to predict outcome. To address the deficiencies of conventional imaging and leverage the advantages of biological-based techniques, we studied the use of magnetic resonance elastography (MRE) and DCE-MRI to quantify changes in mechanical properties and perfusion in sarcomas to serve as an early biomarker and as a surrogate of pathologic response.
Methods: Currently, 9 sarcoma patients are enrolled on this IRB approved study. Imaging was performed before, during, and after treatment. Tumor stiffness was evaluated using a 3D-GRE MRE sequence. Stiffness maps were reconstructed using a 3D local frequency estimation inversion and evaluated for manually drawn ROIs. Tissue perfusion was assessed using a T1-weighted 3D time-resolved DCE-MRI sequence, and quantitative parameters (Ktrans, kep) were computed. Surgical resection was performed in 5 of 9 patients for imagingď pathology correlations.
Results: Preliminary analysis shows MRE and DCE-MRI can quantitatively assess stiffness and perfusion in sarcomas during treatment. Complex and heterogeneous changes in stiffness and perfusion were observed, corresponding to pathologic findings of fibrosis, necrosis, and viable tumor. In one thigh sarcoma patient, total volumetric tumor stiffness decreased 30% (3.6 to 2.5 kPa) from baseline to completion of RT and histopathology confirmed 50% tumor necrosis. Within specimen sub-regions, areas of viable tumor had a stiffness of 2.78 kPa and Ktrans of 2.5 min-1, while necrotic areas were 1.08 kPa and 0.29 min-1, demonstrating a 60% difference in stiffness and 700% in permeability between viable tumor and necrosis.
Conclusion: MRE and DCE-MRI were sensitive to changes in tumor stiffness and perfusion following RT in sarcomas and may improve the ability to noninvasively determine response to therapy and efficiently evaluate novel therapies.
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