The aim of this population-based cohort study was to explore the impact of tumor location on OS based on statistical tumor maps constructed by segmentation of preoperative 3D MRI scans in patients with histopathologically verified WHO grade IV glioma (glioblastoma) and histopathologically verified IDH1 wild-type WHO grade II–III astrocytoma with radiological necrosis. The gene discussed is IDH1; the disease is astrocytoma (excluding glioblastoma).