In terms of molecular markers, patients of the External Group harbored significantly more often IDH-mutant astrocytoma grade 4 and tumors with MGMT promoter methylation (7.8% vs. 3.3%, X2(2) = 99.028, p < 0.001 and 45.5% vs. 38.4%, X2(2) = 182.249, p < 0.001, resp). Here, MGMT is linked to astrocytoma (excluding glioblastoma).