Phase II study to examine efficacy prediction of Regorafenib with FDG-PET/CT in patients with treatment-refractory metastatic colorectal cancer

Interventions: Regorafenib:160 mg orally, once daily for 3 weeks and one week rest in each cycle.
Primary outcome(s): Response rate in change of SUVmax in primary target lesion (the highest value in SUVmax at baseline) at 4 weeks after treatment by Regorafenib.
Study Design: Single arm Non-randomized