Metabolic imaging of brain tumor responses to radio-chemotherapy can give an early indication of treatment outcome. We show here that Deuterium Metabolic Imaging (DMI) with 2H-labeled fumarate can be used to detect early evidence of cell death following radio-chemotherapy in an orthotopic patient-derived glioblastoma model. 2H spectra were acquired from tumors, following an injection of 2H-labeled fumarate. Within one week of treatment the rate of tumor malate production increased significantly. Increased levels of labeled malate were also evident in spectroscopic images of the tumors. These measurements were compared with 13C MRSI measurements of [1,4-13C2]malate production from hyperpolarized [1,4-13C2]fumarate1.