Glioblastoma
The most common and most aggressive primary malignant brain tumor in adults, now defined by molecular criteria and treated with coordinated surgery, radiation, chemotherapy, and device-based therapy.
Quick Answer
Glioblastoma (formerly glioblastoma multiforme, or GBM) is the most common and most aggressive primary malignant brain tumor in adults. Glioblastoma is defined under the 2021 WHO classification as an IDH-wildtype, grade 4 diffuse astrocytic glioma. Because its cells infiltrate surrounding brain tissue well beyond the area that lights up on MRI, treatment begins with maximal safe surgical removal and continues with radiation and chemotherapy. Care is coordinated by a multidisciplinary brain tumor team, with molecular findings such as MGMT promoter methylation helping guide drug therapy and clinical trials providing access to emerging treatments.
Key Takeaways
- Glioblastoma is the most common and most aggressive primary malignant brain tumor in adults, accounting for roughly half of all malignant primary brain tumors.
- Its cells infiltrate normal brain well beyond the tumor seen on MRI, which is why treatment combines multiple therapies in addition to surgery.
- Maximal safe resection aims to remove as much tumor as possible while protecting critical brain function; the completeness of removal is one of the few factors under the surgeon’s control that consistently affects outcome.
- MGMT promoter methylation predicts how well the tumor is likely to respond to temozolomide chemotherapy and influences treatment decisions, particularly in older patients.
- Glioblastoma can now be diagnosed on molecular grounds through TERT, EGFR, or chromosome 7 and 10 changes even when tissue does not show the classic microscopic features.
- The term “glioblastoma multiforme” has been retired; the current diagnosis is glioblastoma, IDH-wildtype, CNS WHO grade 4.
At a Glance
| What it is | Glioblastoma, IDH-wildtype, CNS WHO grade 4 — the most aggressive primary brain tumor |
|---|---|
| Who it affects | Most often diagnosed after age 55, with a median age around 65; less common in younger adults |
| Behavior | Infiltrates surrounding brain well beyond the area that enhances on MRI |
| Diagnostic criteria | IDH-wildtype and H3-wildtype, plus necrosis, microvascular proliferation, TERT promoter mutation, EGFR amplification, or gain of chromosome 7 with loss of chromosome 10 |
| Standard treatment | Maximal safe resection, then radiation with concurrent and adjuvant temozolomide |
| Key markers | MGMT promoter methylation predicts temozolomide benefit |
| Care model | Multidisciplinary tumor board |
| Additional options | Tumor treating fields, GammaTile brachytherapy, carmustine wafers, and clinical trials |
Symptoms
Symptoms of glioblastoma typically develop over weeks rather than months and reflect both the tumor’s location and the pressure created by the tumor and the swelling around it. Common features include headaches, seizures, nausea, and progressive neurological changes such as weakness, speech or language difficulty, vision changes, or changes in thinking, memory, and personality.
A substantial part of the early deficit often comes from that surrounding swelling rather than from the tumor itself, which is why symptoms frequently improve within a day or two of starting steroid medication — an improvement that is real but temporary, and not a sign that the tumor has been treated.
Common Warning Signs
- New or worsening headaches
- New seizures
- Progressive weakness or numbness
- Speech, language, or vision changes
- Changes in memory, thinking, or personality
When to Seek Care Promptly
- A first-time seizure
- Sudden severe headache
- Rapidly progressing weakness or speech difficulty
- New confusion or decline in alertness
- Any rapidly worsening neurological symptom
Diagnosis
Imaging
Diagnosis begins with a neurological examination and MRI of the brain with and without contrast. Glioblastoma has a characteristic appearance: an irregular rim of contrast enhancement surrounding a dark necrotic center, with a broad area of surrounding signal change that represents both swelling and infiltrating tumor cells. Advanced sequences add detail before surgery — perfusion imaging demonstrates the high blood volume typical of these tumors, and functional MRI with diffusion tensor tractography maps the language, motor, and visual pathways running near or through the tumor so the operation can be planned around them.
Tissue & Molecular Diagnosis
A definitive diagnosis requires tumor tissue, obtained at surgery or by biopsy, examined by a neuropathologist together with molecular testing. Under the current classification, glioblastoma is diagnosed in an adult diffuse astrocytic glioma that is IDH-wildtype and H3-wildtype and shows either the classic microscopic findings — necrosis or microvascular proliferation — or one of three molecular findings: TERT promoter mutation, EGFR amplification, or combined gain of chromosome 7 with loss of chromosome 10. Sometimes a tumor looks lower grade under the microscope but is still diagnosed and treated as glioblastoma if it carries those molecular changes, and next-generation sequencing is what finds them.
Testing also determines whether the MGMT gene promoter is methylated. MGMT methylation predicts how well the tumor is likely to respond to temozolomide and influences treatment planning, particularly in older patients.
Interpreting MRI After Treatment
Imaging after treatment requires careful interpretation. In the first three months after radiation and temozolomide, roughly one in five patients develops new or larger enhancement on MRI that represents treatment effect rather than tumor growth — a phenomenon called pseudoprogression. Mistaking it for true progression can lead to stopping treatment that is in fact working. Distinguishing the two relies on timing relative to radiation, perfusion imaging, the pattern of change across serial scans, and occasionally repeat tissue sampling. This is one of the most important reasons for treatment with a multidisciplinary team that includes neuroradiologists who see these tumors regularly and review them in a tumor board setting.
Treatment
Maximal Safe Surgery
Treatment for glioblastoma usually begins with maximal safe resection — removing as much of the tumor as possible while protecting areas of the brain responsible for movement, speech, language, and thinking.
The goal is to remove all of the tumor that can be safely seen and reached and, when possible, tumor cells extending into nearby abnormal tissue. Removing more of the tumor can help keep the disease controlled longer, but protecting brain function always comes first. Surgery also provides tissue needed to confirm the diagnosis and perform molecular testing that helps guide the next steps in treatment.
At Atlantic Brain and Spine, tumors near critical areas of the brain are approached using a combination of advanced surgical technologies and brain-mapping techniques. The specific tools used are tailored to the tumor’s location and each patient’s individual needs.
Radiation & Chemotherapy
Because glioblastoma cells infiltrate surrounding brain tissue beyond what can safely be removed surgically, surgery is generally followed by radiation therapy and chemotherapy. Molecular findings, particularly MGMT promoter methylation, help the treatment team understand how likely the tumor is to respond to temozolomide and may influence treatment decisions.
One Diagnosis. Multiple Perspectives.
Every patient is reviewed at our multidisciplinary brain tumor board, bringing together:
Together, the team examines the complete integrated diagnosis and agrees on a coordinated treatment plan.
The Diagnosis-to-Treatment Pathway
1. Neurological evaluation
The pattern and pace of symptoms help guide the initial evaluation.
2. Advanced imaging
MRI with and without contrast defines the tumor, while perfusion and functional mapping help characterize it and plan surgery.
3. Surgery and tissue diagnosis
Maximal safe resection removes as much tumor as possible while preserving function and provides tissue for diagnosis.
4. Integrated molecular diagnosis
IDH and H3 status help establish the diagnosis, while MGMT methylation predicts likely benefit from temozolomide.
5. Multidisciplinary tumor board
Neurosurgery, neuro-oncology, radiation oncology, neuropathology, and neuroradiology review the complete diagnosis together.
6. Radiation and chemotherapy
Treatment continues after surgery with radiation and temozolomide, tailored to the tumor’s molecular findings and the individual patient.
7. Additional options and surveillance
Device-based therapy, local treatments, clinical trials, and ongoing MRI surveillance are considered as appropriate.
Frequently Asked Questions
Glioblastoma multiforme is a Grade IV glioma and the most common and most aggressive primary malignant brain tumor in adults. Its cells infiltrate surrounding brain tissue, which is why treatment combines surgery with radiation and chemotherapy rather than surgery alone.
Surgery is a critical first step and removing as much tumor as safely possible improves outcomes, but because glioblastoma infiltrates surrounding brain, microscopic tumor cells remain after even the most complete removal. This is why radiation and chemotherapy follow surgery. Treatment aims to control the tumor and extend and improve life.
These molecular markers refine the diagnosis and predict response to treatment. MGMT promoter methylation can indicate better response to certain chemotherapy, and IDH status affects classification and prognosis. Testing them helps the tumor board personalize therapy.
You take a fluorescent agent before surgery that is taken up by tumor cells, making them glow under specialized light in the operating room. This helps the surgeon distinguish tumor from normal brain and remove more of the infiltrating tumor, which can be nearly invisible under ordinary light.
Yes. Trials are open for both newly diagnosed and recurrent glioblastoma, testing therapies such as immunotherapy and targeted agents that have shown promise. Trials provide access to treatments not otherwise available and are overseen under rigorous regulation. Your team will tell you if a trial fits your situation.
Yes, and it is encouraged. Glioblastoma treatment involves consequential decisions, and reviewing them with a multidisciplinary team is reasonable. Send us your imaging and pathology and our tumor board will review your case and clearly explain your options.
Glioblastoma can recur even after surgery, radiation and chemotherapy because tumor cells may remain within surrounding brain tissue. If the tumor returns, treatment options depend on its location, previous treatments, molecular characteristics and the patient’s overall health. Options may include additional surgery, radiation, systemic therapy, tumor treating fields or a clinical trial. A multidisciplinary review can help determine the most appropriate next step.
Specialists Who Treat Glioblastomas
Glioblastoma care at Atlantic Brain and Spine is led by neurosurgeons with specialized expertise in complex brain tumor surgery, working as part of a multidisciplinary brain tumor team.
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