Glioblastoma Multiforme (GBM)

Glioblastoma multiforme (GBM) is a high-grade (WHO grade 4) primary brain tumor arising from astrocytic glial cells. It accounts for nearly half of all gliomas, with an annual incidence of 3-5 per 100,000. Most patients are diagnosed between 55-70 years of age, with a slight male predominance. Despite modern therapy, median overall survival remains 15-18 months due to its aggressive biology.

Histopathology demonstrates dense cellularity, nuclear atypia, mitotic activity, microvascular proliferation, and necrosis. Molecular classification distinguishes IDH-wildtype GBM from IDH-mutant astrocytoma grade 4 with prognostic significance. MGMT promoter methylation predicts temozolomide response. EGFR amplification, TERT promoter mutations, and chromosome 7 gain/10 loss are characteristic. The infiltrative growth pattern usually precludes complete surgical resection.

Standard treatment is the Stupp protocol: maximal safe resection followed by concurrent radiotherapy (60 Gy in 30 fractions) plus temozolomide, then 6 cycles of adjuvant temozolomide. Tumor treating fields (TTFields/Optune) added to maintenance therapy improves survival in selected patients. At recurrence, bevacizumab, lomustine, re-irradiation, or clinical trial enrollment are considered. Favorable prognostic factors include younger age, good performance status, MGMT methylation, gross total resection, and IDH mutation.