Updated: Sep 8, 2009
Glioblastoma multiforme (GBM) is the most common and most aggressive of the primary brain tumors. The current World Health Organization (WHO) classification of primary brain tumors lists GBM as a grade IV astrocytoma. Astrocytoma is one of 3 distinct types of gliomas in the brain, although mixed cell types occur as well. GBMs are highly malignant, infiltrate the brain extensively, and at times may become enormous before turning symptomatic.
GBM is an anaplastic, highly cellular tumor with poorly differentiated, round, or pleomorphic cells, occasional multinucleated cells, nuclear atypia, and anaplasia. Under the modified WHO classification, GBM differs from anaplastic astrocytomas (AA) by the presence of necrosis under the microscope. Variants of the tumor include gliosarcoma, multifocal GBM, or gliomatosis cerebri (in which the entire brain may be infiltrated with tumor cells). These variants, however, do not alter the prognosis of the tumor. Multifocal metastasis of GBM is extremely rare but is increasing, including spinal drop metastasis, as patients live longer.1
Among primary brain tumors, malignant astrocytomas are the most common in all age groups. (However, among all brain tumors, metastases are the most common.) GBMs are the most common primary brain tumors in adults, accounting for 12-15% of intracranial tumors and 50-60% of primary brain tumors. Several authors have reported a true increase in the incidence of brain tumors, especially among the elderly, and many have attributed the observed changes to developments in diagnostic imaging or changes in the classification system.2
International incidence of GBM is similar to that of the United States.
Morbidity is from the tumor location, progression, and pressure effects. The overall prognosis for GBM has changed little in the past 2 decades, despite major improvements in neuroimaging, neurosurgery, radiation treatment techniques, adjuvant chemotherapy, and supportive care. Few patients with GBM survive longer than 3 years and only a handful survive 5 years. Previously reported long-term survivors of GBM may be patients diagnosed with GBM who actually harbor low-grade glioma, pleomorphic xanthoastrocytoma, ganglioglioma, or other lesions. Occasional patients with a single necrotic, demyelinating plaque of multiple sclerosis also may be misdiagnosed with GBM, especially if only CT scans are obtained.
High-grade astrocytomas (HGAs) are slightly more common in whites than in blacks, Latinos, and Asians.
GBM is slightly more common in men than in women; the male-to-female ratio is 3:2.
While GBM occurs in all age groups, its incidence is increasing in elderly patients. A true increase in incidence of primary brain tumors exists, which cannot be explained by the aging population, better imaging techniques, or earlier detection at surgery.
Glioblastoma multiforme (GBM), like other brain tumors, produces symptoms by a combination of focal neurologic deficits from compression and infiltration of the surrounding brain, vascular compromise, and raised intracranial pressure. Presenting features include the following:
Physical findings depend on the location, size, and rate of growth of the tumor, as with any other CNS tumor. Tumors in less critical areas (eg, anterior frontal or temporal lobe) may present with subtle personality changes and memory problems. Similarly, motor weakness and sensory hemineglect are the hallmarks of tumors arising in the frontal or parietal lobes and thalamic regions. Sensory neglect is more prominent in right hemispheric lesions.
The etiology of GBM is unknown. However, at least 2 genetic pathways have been delineated in its development: de novo (primary) glioblastomas and secondary glioblastomas. De novo glioblastomas are most common. De novo GBM develops in older patients and demonstrates a high rate of epidermal growth factor receptor (EGFR) overexpression, phosphatase and tensin homologue deleted on chromosome 10 (PTEN) mutations, and p16INK4A deletions. In contrast, secondary GBM develops in younger patients and develops from a malignant transformation of a previously diagnosed low-grade tumor. TP53 and retinoblastoma gene (RB) mutations are more common in the development of secondary glioblastomas.
Several genetic disorders are associated with increased incidence of gliomas (eg, tuberous sclerosis, neurofibromatosis type 1 and type 2, Turcot syndrome, Li-Fraumeni syndrome). An association exists between ionizing radiation and astrocytomas. Children who receive low-dose intracranial radiation have a 2.6-fold increase in prevalence of astrocytomas, and prophylactic whole-brain radiation therapy in patients with acute lymphocytic leukemia increased the incidence of astrocytomas 22-fold.
Other suspected risk factors, such as electromagnetic radiation and cellular telephone use, are yet to be substantiated by large epidemiologic studies. However, researchers reviewed 16 published studies that looked at cell phone use and the risk of brain cancers and concluded that using cell phones for more than 10 years gives a consistent pattern of increased risk of at least 2 types of brain cancer such as acoustic neuroma and gliomas. The risk is significantly higher for the ipsilateral exposure (tumor on the same side of the brain as cell phone exposure).3
| Arteriovenous Malformations | Meningioma |
| Brainstem Gliomas | Metastatic Disease to the Brain |
| CNS Melanoma | Multiple Sclerosis |
| Craniopharyngioma | Neurocysticercosis |
| Ependymoma | Neuroimaging in Neurocysticercosis |
| Frontal Lobe Syndromes | Oligodendroglioma |
| HIV-1 Associated Opportunistic Infections: CNS
Toxoplasmosis | Primary CNS Lymphoma |
| HIV-1 Associated Opportunistic Neoplasms: CNS
Lymphoma | Radiation Necrosis |
| Intracranial Epidural Abscess | |
| Low-Grade Astrocytoma |
Other brain tumors (eg, meningioma, metastasis, astrocytoma, oligodendroglioma)
Brain abscess
Large, single, necrotic multiple sclerosis plaque
CNS toxoplasmosis
Routine laboratory workup results often are negative, but excluding a metabolic or infective process is important in an otherwise healthy patient who presents with new-onset seizures or mental status changes for the first time.
High-grade astrocytomas (HGAs) are extremely heterogenous tumors characterized by varying degrees of increased cellularity, pleomorphism, mitoses, endothelial proliferation, and necrosis.
Many different grading systems exist for gliomas. The current WHO classification of gliomas is based on the presence or absence of 4 histologic criteria: (1) nuclear atypia, (2) mitoses, (3) endothelial proliferation, and (4) necrosis. Grade I tumors have none of the criteria, grade II have at least 1, grade III have at least 2, and grade IV (GBM) have at least 3 or 4 criteria present. Prominent microvascular proliferation and/or necrosis must be one of the criteria for GBM.
Although the prognosis of glioblastoma multiforme (GBM) is uniformly poor, treating patients in an attempt to improve the quality of life is worthwhile. Available definitive treatment options are surgery, radiotherapy, and chemotherapy. However, continuous supportive care is a major component of the medical treatment with primary brain tumors.
In GBM, surgery is always an incomplete debulking, since it is a highly infiltrating tumor and cannot be resected completely. The extent of surgical resection depends on location and eloquence of the brain areas. Whether surgery prolongs survival is debatable, but several studies suggest that survival correlates more closely with the amount of residual tumor observed on postoperative MRI scans.
Treatment of GBM is largely a multispecialty team approach. Therefore, neurology, neurosurgery, neuro-oncology, radiation oncology, psychiatry, and social service consultations should be obtained.
No special diet or limitations are required.
The goals of pharmacotherapy for glioblastoma multiforme (GBM) are to reduce morbidity and to prevent complications.
This oral alkylating agent has been approved for newly diagnosed GBM and recurrent anaplastic astrocytomas.
Oral alkylating agent converted to MTIC at physiologic pH; 100% bioavailable; approximately 35% crosses blood-brain barrier. Indicated for GBM combined with radiotherapy. Significant overall survival was demonstrated in patients treated with temozolomide and radiation compared with radiotherapy alone.
Adjust dose according to nadir neutrophil and platelet counts from previous cycle and at time of initiating next cycle
Concomitant phase: 75 mg/m2/d PO for 42-49 d with concomitant radiotherapy
Maintenance cycle 1: 150 mg/m2/d PO for 5 d followed by 23 d without treatment; initiated 4 wk following concomitant phase completion
Maintenance cycles 2-6: 200 mg/m2/d PO for 5 d; escalate dose from phase 1 only if blood count stable
Not established
None reported
Documented hypersensitivity to temozolomide or DTIC, since each drug is metabolized to MTIC
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Causes bone marrow suppression resulting in thrombocytopenia, anemia, and leukopenia (check blood counts weekly during concomitant phase, then at day 1 and 21 of each cycle); common adverse effects include nausea, vomiting, and alopecia; not known if drug is excreted in breast milk and because of potential serious adverse effects in infants, breastfeeding should be discontinued; PCP prophylaxis required during concomitant phase, continue if lymphocytopenia develops
Local chemotherapy with carmustine (BCNU) wafers (Gliadel wafers) significantly prolongs survival in patients with newly diagnosed primary malignant glioma.
Gliadel is a small wafer that contains the chemotherapeutic drug carmustine, or BCNU. The wafer is designed to release the drug slowly over a period of 2-3 wk after placed in tumor bed. Up to 8 Gliadel wafers are implanted in the cavity, slowly delivering BCNU directly to tumor site.
8 Gliadel wafer implants placed in tumor bed
Not established
None reported
Documented hypersensitivity to BCNU or its content
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Adverse effects reported include seizures, intracranial infections, abnormal wound healing, and brain edema (swelling)
After the initial definitive treatment (surgical debulking) of glioblastoma multiforme (GBM), the patient may need further inpatient care during the ongoing radiation therapy. Chemotherapy usually is performed on an outpatient basis. Continuing outpatient follow-up care is necessary if the patient develops neurological deterioration such as acute motor weakness or depression of consciousness from the effects of therapy, increased intracranial pressure from vasogenic edema, or acute hydrocephalus from ventricular obstruction. Appropriate intervention depends on the nature of the problem (eg, steroid therapy for edema, shunting for hydrocephalus).
After the initial successful therapy, observe the patient regularly as an outpatient with neurologic examination and repeat MRI scans every 2 months with the chemotherapy cycles; continue every few months to follow tumor recurrence.
No specific medications are recommended for GBM. However, as mentioned previously, patients may need symptomatic therapy with steroids or anticonvulsants.
Transfer requirements depend on the tumor location and its response to treatment. If the tumor is in a noneloquent area and no neurological deficit is present after treatment, the patient remains fully ambulatory. However, other patients may require assistance, such as a 3-pronged cane or a wheelchair, depending on the residual neurological deficit.
No preventive measures exist for GBMs.
During continuing follow-up care, monitor the patient closely and treat appropriately any complications that may develop. These may be caused by ongoing treatment, such as radiation necrosis and chemotherapy-induced neuropathy, or by progression of the disease, such as recurrence or leptomeningeal spread.
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glioblastoma multiforme, GBM, malignant glioma, grade IV astrocytoma, grade IV glioma, high-grade astrocytoma, HGA, high-grade glioma, primary brain tumor, gliosarcoma, multifocal GBM, gliomatosis cerebri, intracranial tumor, MMAC1 mutations, CDKN2A deletions, MDM2 amplifications, tuberous sclerosis, neurofibromatosis type 1, neurofibromatosis type 2, Turcot syndrome, Li-Fraumeni syndrome, brain tumors, malignant astrocytoma, de novo glioblastomas, secondary glioblastomas, primary glioblastoma
ABM Salah Uddin, MD, Consulting Staff, Department of Internal Medicine, St Vincent's Hospital
ABM Salah Uddin, MD is a member of the following medical societies: American Academy of Neurology, American Epilepsy Society, and American Medical Association
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Tambi Jarmi, MD, Resident Physician, Department of Internal Medicine, Carraway Methodist Medical Center
Tambi Jarmi, MD is a member of the following medical societies: American College of Physicians and American Medical Association
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Amy A Pruitt, MD, Associate Professor of Neurology, University of Pennsylvania; Attending Neurologist, Hospital of the University of Pennsylvania
Amy A Pruitt, MD is a member of the following medical societies: American Academy of Neurology
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Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
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Jorge Kattah, MD, Head, Program Director, Professor, Department of Neurology, University of Illinois College of Medicine at Peoria
Jorge Kattah, MD is a member of the following medical societies: American Academy of Neurology, American Neurological Association, and New York Academy of Sciences
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Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital
Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association
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Stephen A Berman, MD, PhD, Professor, Department of Internal Medicine, Section of Neurology, Dartmouth Medical School; Chief, Neurology Service, White River Junction Veterans Medical Center
Stephen A Berman, MD, PhD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Neurology, and Phi Beta Kappa
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