Early assessment of glioblastoma (GBM) response to standard 6-week chemo-radiation enables changing or adjusting therapy in patients with progressive tumors. Chemical Exchange Saturation Transfer (CEST) probes the concentration and exchange of labile proteins and peptides in ht tumor and is more sensitive to treatment-induced effects. CEST was capable of differentiating progressors from non-progressors as early as two weeks into the treatment. Moreover, certain CEST metrics (i.e. MTRNOE, MTRAmide, CESTNOE) were capable of characterizing GBM aggressiveness even before the start of the treatment.