Thus, non-invasive repetitive PET/CT/(MRI) with [18F]TFAHA may facilitate future clinical studies aimed to elucidate the roles of HDAC class IIa enzymes in gliomagenesis and progression and to optimize therapeutic doses of novel HDACs class IIa inhibitors in combined chemo-radiotherapy of GBM. This evidence concerns the gene HDAC9 and glioblastoma.