HGG

High-grade glioma (HGG) is a term used for malignant glial tumors of the central nervous system that grow rapidly and have a poor prognosis. In the modern WHO classification, HGG includes astrocytic or oligodendroglial tumors that are graded as 3 (for example, anaplastic astrocytoma or anaplastic oligodendroglioma) or 4 (glioblastoma). Most HGGs arise in the cerebral hemispheres, and glioblastoma (GBM) is the most common and aggressive form.

Clinical presentation and diagnosis often depend on tumor location but commonly include seizures, new or worsening neurological deficits, headaches, or cognitive changes. Magnetic resonance imaging (MRI) is the primary diagnostic tool, often showing a heterogeneous, enhancing lesion with surrounding edema. Definitive diagnosis requires biopsy or surgical resection with histopathology and molecular profiling. Key molecular markers increasingly guide classification and prognosis, including IDH mutation status, 1p/19q codeletion, and MGMT promoter methylation.

Treatment generally involves a combination of surgery, radiotherapy, and chemotherapy. Maximal safe surgical resection is pursued when feasible, followed by radiotherapy with concomitant and adjuvant temozolomide (the Stupp protocol) for GBM and many HGGs. Molecular features influence prognosis and therapy: IDH-mutant tumors and 1p/19q codeleted oligodendrogliomas tend to have better outcomes, while MGMT promoter methylation predicts greater benefit from alkylating chemotherapy. Median survival for GBM remains around one year or more with current treatments, though outcomes vary by molecular subtype and individual factors; recurrence is common.

Epidemiology and research emphasize that HGGs are the majority of malignant gliomas in adults, with peak incidence in middle to late adulthood. Risk factors are limited, though prior cranial irradiation increases risk. Ongoing research explores targeted therapies, immunotherapy, tumor-treating fields, and personalized regimens based on molecular profiling.