The administration of steroids, most commonly dexamethasone (DEX), has established as standard of care during treatment of glioblastoma (GBM) and is widely used during the entire course of the disease including pre- and postoperative management, chemo- and radiotherapy. The primary purpose is to reduce tumor-associated vasogenic edema and to prevent or treat increased intracranial pressure. However, steroids are also linked to a multitude of adverse side effects that may affect survival of GBM patients such as major immunosuppression. The use of steroids during radiotherapy is associated with reduced overall- and progression-free survival and has been identified as an independent poor prognostic factor. Despite these findings, the suspicion of GBM often triggers the administration of DEX in routine clinical practice, regardless of neurological symptoms, tumor size, or extension of cerebral edema. The purpose of this study is to assess whether selected GBM patients can be treated safely with a restrictive DEX regimen from referral to the neurosurgical center until discharge. The primary objective is to determine the failure rate of a restrictive DEX regimen defined as edema or mass effect leading to any of the following: GCS deterioration ≥ 2 points, NIHSS increase ≥ 3 points, increase of midline Shift ≥ 2mm, or any surgical rescue procedure for increasing mass effect.