HGGs

High-grade gliomas (HGGs) are a group of malignant primary brain tumors arising from glial cells. They include WHO grade III and IV diffuse astrocytomas and oligodendrogliomas, with glioblastoma being the most common and aggressive form.

Classification and molecular features: The 2021 WHO CNS tumor classification emphasizes molecular characteristics alongside histology. Key markers include IDH mutation status, 1p/19q co-deletion, MGMT promoter methylation, and TERT promoter mutation. IDH-wildtype tumors generally have a worse prognosis than IDH-mutant tumors; 1p/19q co-deleted oligodendrogliomas with IDH mutation have relatively better outcomes.

Clinical presentation and imaging: Symptoms vary by location and include new-onset seizures, headaches, cognitive or focal neurological deficits. MRI typically shows a contrast-enhancing, infiltrative mass with surrounding edema; necrosis and microvascular proliferation are common in glioblastoma.

Treatment: The standard approach for eligible patients with GBM is maximal safe surgical resection followed by radiotherapy with concurrent and adjuvant temozolomide (the Stupp protocol). MGMT promoter methylation is associated with better temozolomide response. For IDH-mutant, 1p/19q co-deleted oligodendrogliomas, radiotherapy plus PCV chemotherapy is often used.

Prognosis and recurrence: HGGs have a poor prognosis, with median overall survival around 12–15 months for newly diagnosed GBM with standard treatment; IDH-mutant and/or 1p/19q co-deleted tumors have longer survival. Recurrence is common and treatment focuses on palliation and repeat therapies.

Epidemiology and research: HGGs are more common in adults, with a slight male predominance. Research areas include targeted therapies, tumor-treating fields, immunotherapy, and personalized vaccines, with growing emphasis on integrating molecular profiling into management.