The goal of this interventional study is the development and validation of imaging markers, MRI and PET, plasma biomarkers, and/or cell markers that could support clinicians and researchers in differentiating pseudoprogression from true tumor progression in routine clinical activities and clinical trials in patients affected by glioblastoma. The endpoints of the study are: * the elaboration of predictive models using imaging advanced biomarkers, PET and MRI, biological serum markers, and cancer cell derived makers to differentiate tumor pseudoprogression or real progression in patients affected by glioblastoma who underwent therapeutical protocol as per treating physicians' indications (Stupp or hypofractionated RT) * to establish an in vivo murine model of pseudoprogression by orthotopic transplantation of glioblastoma stem cells derived from thirty-five patient subjected to subsequent treatment with irradiation and temozolomide administration. Participants will undergo: * baseline MRI and 18F-GE-180 PET imaging, and blood withdrawal * surgery * collection of glioblastoma stem cells (and hematopoietic stem cells from a sub-group of subjects) * standard treatment with radiotherapy and chemotherapy * MRI every 3 months * PET and blood withdrawal in case of MRI evidence of either suspected tumor progression or pseudoprogression * second surgery OR stereotactic biopsy OR clinico-radiological follow-up as for standard of care according to the Institutional Multidisciplinary Brain Tumor Board