Whole Body Diffusion-weighted MRI (WB-DWI) for Early Prediction and Evaluation of Therapy Response in Patients With Advanced Metastatic Gastrointestinal Stromal Tumors (GIST) Treated With Regorafenib.

Aim of the study

• To assess whole body diffusion-weighted magnetic resonance imaging (WB-DWI) for the assessment and early prediction of response of treatment with regorafenib or placebo in patients with advanced, metastatic gastro-intestinal stromal tumors (GIST)

1. Evaluation of pretreatment apparent diffusion coefficient (ADC) and b1000 signal intensity (SI) of GIST visualized on the WB-DWI as predictor of time to progression, determined by progression-free survival (PFS)
2. Evaluation of WB-DWI using changes of high b-value SI and ADC early during treatment (2weeks after start of therapy; allowed optimal window 10-14 days) as early predictor of time to progression or patient benefit according to RECIST (stable disease + partial response + complete response)
3. Evaluation of WB-DWI for treatment follow-up 3 months after initiation of treatment. Confirmation of prior published pilot study (Dunet V et al, J Nucl Med 2010)
4. Comparison of WB-DWI with conventional CT imaging for response assessment