Glioblastoma

A glioblastoma or glioblastoma multiforme (GBM) is a highly invasive tumor of the central nervous system, primarily of the brain, and, more specifically, the cerebral hemispheres, basal ganglia, and commissural pathways. It is not curable with present methods, although recent developments have improved median survival. Onset is most common in the fifth or sixth decade of life, but certainly can appear in any adult or adolescent stage.

It is termed "malignant", which usually refers to the propensity to metastasize, but, as typical of central nervous system neoplasms, does not metastasize beyond the blood-brain barrier but expands rapidly within the central nervous system. GBM is the most common and aggressive primary (i.e., not from metastasis) brain tumor.

There has been an overall increase in diagnoses of gliomas in the United States, but it is argued variously that there is a true increase, or that they are being diagnosed more often due to the revised classification or better medical imaging.

Diagnosis

History and physical

Symptoms are nonspecific, including headache, seizures, cognitive changes and focal neurologic signs.

Imaging

Magnetic resonance imaging is the preferred study. GBMs characteristically have low-signal intensity on T1-weighted images and high-signal intensity on T2-weighted images. With contrast, T1-weighted images typically have a central hypodensity surrounded by a thick enhancing rim of tumor.

Histopathology

It is a more pleomorphic and faster-growing form of astrocytoma, and is also called Grade IV astrocytoma. In addition to pleomorphism, the histopathology includes nuclear atypia, microhemorrhage, and necrosis. Margins are irregular and it is not encapsulated.

Treatment

While surgery has always been the core of treatment, prior to the use of adjuvant radiation and chemotherapy, it could only have a limited effect, as the irregular margins and infiltrating nature of the mass preclude complete removal, and indeed extensive debulking. The current standard of care begins with maximal feasible debulking, followed by radiation and chemotherapy. Excellent supportive therapy dealing with complications is essential.

Techniques of radiation therapy continue to evolve. The standard of care is fractionated electron beam radiotherapy, but methods being investigated include brachytherapy with implanted ₁₃₁iodine seeds,

While the preferred chemotherapeutic agent is temozolomide, ongoing studies also show a value for BCNU. One study with temozolomide and radiation showed median survival of 14.6 months with radiation therapy plus temozolomide and 12.1 months with radiation therapy alone. Some temozolomide-treated patients have survived for 5 years.