Glioma Treatment
The treatment of gliomas has evolved substantially over the past two decades, driven by landmark clinical trials and the integration of molecular biomarkers into therapeutic decision-making. Treatment strategies now vary significantly based on tumor type (as defined by WHO 2021 molecular classification), grade, MGMT promoter methylation status, and patient factors including age and performance status. This topic reviews the evidence-based management of adult-type diffuse gliomas, from glioblastoma through low-grade IDH-mutant tumors, with emphasis on landmark trials and practical treatment considerations for the neurologist.
Bottom Line
- Glioblastoma standard of care (Stupp protocol): Maximal safe resection → concurrent temozolomide + radiation (60 Gy/30 fractions) → adjuvant temozolomide (6 cycles, days 1–5 of 28-day cycles)
- MGMT methylation is the strongest predictor of TMZ benefit: Especially critical in elderly patients where it guides the choice between TMZ monotherapy vs. RT alone
- Low-grade gliomas: High-risk patients (age ≥40 or subtotal resection) benefit from RT + PCV chemotherapy (RTOG 9802 — OS benefit exceeding 5 years)
- Oligodendrogliomas are chemosensitive: PCV added to RT provides profound, durable survival benefit (RTOG 9402, EORTC 26951)
- Vorasidenib (IDH inhibitor): The INDIGO trial demonstrated significant PFS benefit for grade 2 IDH-mutant gliomas, heralding a new era of targeted therapy
- Bevacizumab improves PFS but not OS in recurrent GBM; useful for symptom palliation and steroid reduction
- Seizure management: Levetiracetam is preferred (no enzyme induction); prophylactic anticonvulsants are NOT recommended in seizure-free patients
Glioblastoma Treatment
Surgical Principles
Maximal safe resection is the first step in GBM management. Multiple studies have demonstrated that greater extent of resection (EOR) is associated with improved overall survival, with gross total resection (GTR) providing the most benefit. However, resection must be balanced against preservation of neurologic function, particularly in eloquent cortex locations.
Surgical Considerations
- Extent of resection goal: Gross total resection of enhancing tumor; studies suggest even “supratotal” resection (beyond enhancement into FLAIR abnormality) may further improve outcomes
- Awake craniotomy: Used for tumors near eloquent cortex (language areas, motor strip) to maximize resection while preserving function
- 5-ALA fluorescence: Oral 5-aminolevulinic acid causes tumor fluorescence under blue light, aiding identification of tumor margins; improves rates of complete resection
- Intraoperative MRI: Allows real-time assessment of residual tumor during surgery
- Biopsy: Stereotactic biopsy is appropriate for deep-seated, multifocal, or surgically inaccessible tumors to obtain tissue for molecular diagnosis
The Stupp Protocol (Standard of Care)
The landmark Stupp et al. 2005 NEJM trial established the current standard of care for newly diagnosed glioblastoma. This randomized phase III trial (n=573) demonstrated that adding temozolomide to radiotherapy significantly improved median overall survival from 12.1 months (RT alone) to 14.6 months (RT + TMZ), with 2-year survival increasing from 10.4% to 26.5%.
| Phase | Treatment | Details |
|---|---|---|
| Concurrent | RT + daily TMZ | 60 Gy in 30 fractions (6 weeks) + TMZ 75 mg/m²/day continuously during RT |
| Break | 4-week rest period | Between concurrent and adjuvant phases |
| Adjuvant | TMZ cycles | 150–200 mg/m²/day, days 1–5 of each 28-day cycle, for 6 cycles |
Temozolomide: Practical Points
- Mechanism: Oral alkylating agent; methylates DNA at O6-guanine, N7-guanine, and N3-adenine positions
- Bioavailability: Nearly 100% oral bioavailability; crosses the blood-brain barrier
- Key toxicity: Myelosuppression (lymphopenia, thrombocytopenia); monitor CBC weekly during concurrent phase, before each adjuvant cycle
- PCP prophylaxis: Trimethoprim-sulfamethoxazole required during concurrent phase due to lymphopenia-induced Pneumocystis risk; continue until lymphocyte recovery
- Dose modification: Adjuvant cycle 1 at 150 mg/m²; escalate to 200 mg/m² in cycle 2 if tolerated (ANC ≥1.5 × 10&sup9;/L, platelets ≥100 × 10&sup9;/L)
- Antiemetics: Ondansetron 30–60 minutes before TMZ; take TMZ on an empty stomach
MGMT Methylation and Treatment Decisions
The benefit of temozolomide is strongly modulated by MGMT promoter methylation status. In the Stupp trial, MGMT-methylated patients receiving RT + TMZ had a median survival of 21.7 months vs. 15.3 months for MGMT-unmethylated patients. While the standard Stupp protocol is still offered to most GBM patients regardless of MGMT status (given the modest but real benefit even in unmethylated tumors), MGMT status is especially critical in treatment decisions for elderly patients.
MGMT-Guided Treatment in Elderly GBM
- Age ≥65–70 or poor performance status: Full Stupp protocol may not be tolerable; abbreviated regimens are preferred
- MGMT-methylated elderly: TMZ monotherapy (without RT) is a viable option (NOA-08 trial); alternatively, hypofractionated RT + TMZ
- MGMT-unmethylated elderly: Hypofractionated RT alone (40 Gy in 15 fractions) is preferred; TMZ monotherapy has limited benefit
- Nordic trial: Demonstrated that hypofractionated RT (34 Gy/10 fractions) was non-inferior to standard 60 Gy in elderly patients, and TMZ monotherapy benefited only MGMT-methylated patients
- Perry et al. (NEJM 2017): Hypofractionated RT (40 Gy/15 fractions) + TMZ improved OS vs. hypofractionated RT alone in elderly patients (median 9.3 vs. 7.6 months), with greater benefit in MGMT-methylated tumors
Tumor-Treating Fields (TTFields / Optune)
Tumor-treating fields deliver low-intensity, intermediate-frequency (200 kHz) alternating electric fields via transducer arrays placed on the shaved scalp. TTFields interfere with mitotic spindle assembly and cytokinesis, selectively affecting rapidly dividing cells.
TTFields: Evidence and Practical Considerations
- EF-14 trial: Adding TTFields to maintenance TMZ improved median OS from 16.0 to 20.9 months in newly diagnosed GBM; 5-year survival 13% vs. 5%
- FDA-approved: For newly diagnosed GBM (after completion of concurrent RT/TMZ) and recurrent GBM
- Compliance-dependent: Benefit correlates with usage ≥18 hours/day (≥75% compliance); average compliance in EF-14 was ~86%
- Controversies: Open-label trial design (no sham control), quality of life impact (scalp irritation, cosmetic concerns, device portability), high cost (~$21,000/month)
- Scalp toxicity: Contact dermatitis is the most common adverse effect; managed with topical corticosteroids and array repositioning
Low-Grade Glioma Treatment (IDH-Mutant, Grade 2)
Risk Stratification
Treatment intensity for low-grade gliomas is guided by risk stratification. The traditional risk factors from RTOG/EORTC trials include age ≥40 years, subtotal resection, tumor size ≥6 cm, tumor crossing midline, and astrocytoma (vs. oligodendroglioma) histology. In the molecular era, IDH mutation and 1p/19q codeletion status further refine prognosis.
| Risk Category | Features | Management |
|---|---|---|
| Low-risk | Age <40, gross total resection, IDH-mutant, favorable molecular profile | Observation with serial MRI; consider vorasidenib (per INDIGO) |
| High-risk | Age ≥40, subtotal resection/biopsy, large tumor, unfavorable features | RT + PCV chemotherapy (RTOG 9802); consider vorasidenib |
RTOG 9802: Landmark Trial for High-Risk Low-Grade Glioma
This pivotal randomized trial compared RT alone (54 Gy) vs. RT followed by 6 cycles of PCV chemotherapy in high-risk low-grade glioma patients (age ≥40 or subtotal resection). With long-term follow-up, RT + PCV demonstrated a dramatic improvement in median overall survival: 13.3 years vs. 7.8 years — a benefit of over 5 years. This established RT + PCV as the standard of care for high-risk low-grade gliomas.
PCV Chemotherapy Regimen
- P: Procarbazine 60 mg/m² PO days 8–21
- C: CCNU (lomustine) 110 mg/m² PO day 1
- V: Vincristine 1.4 mg/m² IV (max 2 mg) days 8 and 29
- Cycle length: 6 weeks; total 6 cycles
- Toxicity: Significant — myelosuppression, nausea, peripheral neuropathy (vincristine), allergic reactions (procarbazine); many patients cannot complete all 6 cycles
- TMZ substitution: Many centers substitute TMZ for PCV due to better tolerability; however, the evidence base for this substitution is weaker (CATNON supports TMZ for grade 3 IDH-mutant astrocytoma but grade 2 data is less robust)
Vorasidenib and the INDIGO Trial
The INDIGO trial (Mellinghoff et al., NEJM 2023) represents a landmark advance in targeted therapy for IDH-mutant gliomas. This phase III randomized trial enrolled 331 patients with residual or recurrent grade 2 IDH-mutant gliomas (astrocytoma or oligodendroglioma) who had not received prior treatment beyond surgery.
INDIGO Trial Key Results
- Drug: Vorasidenib 40 mg daily — a brain-penetrant dual IDH1/IDH2 inhibitor
- Primary endpoint: Progression-free survival: 27.7 months (vorasidenib) vs. 11.1 months (placebo); HR 0.39 (p < 0.001)
- Time to next intervention: Significantly delayed with vorasidenib
- Tolerability: Generally well tolerated; key adverse effects include elevated ALT/AST (≤grade 3 in ~9%), which was reversible with dose modification
- Clinical significance: First targeted therapy to show benefit in low-grade gliomas; may delay or replace the need for RT/chemotherapy in some patients
- FDA approval: Granted in 2024 for grade 2 IDH-mutant astrocytoma and oligodendroglioma following surgery
Oligodendroglioma Treatment
Oligodendrogliomas (IDH-mutant, 1p/19q-codeleted) are among the most chemosensitive adult brain tumors. Two landmark trials established the benefit of adding PCV to radiotherapy:
| Trial | Design | Key Result |
|---|---|---|
| RTOG 9402 | PCV → RT vs. RT alone (anaplastic oligodendroglioma) | 1p/19q-codeleted: median OS 14.7 years (PCV + RT) vs. 7.3 years (RT); non-codeleted: no benefit |
| EORTC 26951 | RT → PCV vs. RT alone (anaplastic oligodendroglioma) | 1p/19q-codeleted: median OS not reached at 11.7 years vs. 9.3 years (RT); significant OS benefit |
These trials confirmed that the survival benefit of PCV is specific to 1p/19q-codeleted tumors. For grade 3 oligodendroglioma, RT + PCV is now the standard of care. For grade 2 oligodendroglioma, observation after surgery is reasonable for low-risk patients, with RT + PCV for high-risk patients (per RTOG 9802). Vorasidenib is also an option for grade 2 oligodendroglioma given the INDIGO results.
IDH-Mutant Astrocytoma, Grade 3–4
CATNON Trial
The CATNON trial evaluated the role of temozolomide in non-1p/19q-codeleted anaplastic glioma (predominantly IDH-mutant astrocytoma grade 3). Results showed that adjuvant TMZ (12 cycles after RT) significantly improved overall survival in IDH-mutant tumors. Concurrent TMZ (during RT) did not add significant benefit in IDH-mutant tumors. This supports RT followed by adjuvant TMZ as the standard for IDH-mutant astrocytoma grade 3.
Treatment by Glioma Subtype — Summary
- GBM, IDH-wildtype: Stupp protocol (RT 60 Gy + concurrent/adjuvant TMZ) ± TTFields
- Astrocytoma, IDH-mutant, grade 4: RT + TMZ (extrapolated from Stupp; CATNON supports adjuvant TMZ)
- Astrocytoma, IDH-mutant, grade 3: RT + adjuvant TMZ (CATNON trial)
- Astrocytoma, IDH-mutant, grade 2 (high-risk): RT + PCV (RTOG 9802) or vorasidenib (INDIGO)
- Astrocytoma, IDH-mutant, grade 2 (low-risk): Observation; consider vorasidenib
- Oligodendroglioma, grade 3: RT + PCV (RTOG 9402, EORTC 26951)
- Oligodendroglioma, grade 2 (high-risk): RT + PCV (RTOG 9802) or vorasidenib
- Oligodendroglioma, grade 2 (low-risk): Observation; consider vorasidenib
Bevacizumab in Glioblastoma
Bevacizumab, a monoclonal antibody targeting vascular endothelial growth factor (VEGF), is FDA-approved for recurrent glioblastoma based on response rates and PFS improvement. However, its impact on overall survival has been disappointing.
| Trial | Setting | PFS Benefit | OS Benefit |
|---|---|---|---|
| AVAglio (NEJM 2014) | Newly diagnosed GBM (added to Stupp) | Yes (10.6 vs. 6.2 months) | No (16.8 vs. 16.7 months) |
| RTOG 0825 (NEJM 2014) | Newly diagnosed GBM (added to Stupp) | Yes (10.7 vs. 7.3 months) | No (15.7 vs. 16.1 months) |
| EORTC 26101 | Recurrent GBM (bev + lomustine vs. lomustine) | Yes (4.2 vs. 1.5 months) | No (9.1 vs. 8.6 months) |
Bevacizumab: Practical Role
- Steroid-sparing effect: Bevacizumab reduces vasogenic edema, allowing dexamethasone taper — particularly valuable for steroid-dependent patients
- Symptom palliation: Improves neurologic function and quality of life in many patients despite lack of OS benefit
- Pseudoresponse: Bevacizumab normalizes blood-brain barrier permeability, reducing enhancement on MRI without necessarily killing tumor cells; non-enhancing tumor progression on FLAIR must be monitored
- Dose: 10 mg/kg IV every 2 weeks (most common); some use 7.5 mg/kg or 15 mg/kg
- Key toxicities: Hypertension, proteinuria, wound healing impairment (hold 4–6 weeks before surgery), venous thromboembolism, rare intracranial hemorrhage
Supportive Care in Glioma
Seizure Management
Seizures occur in 20–90% of glioma patients depending on tumor grade and location, with higher rates in low-grade gliomas and cortical tumors.
Anticonvulsant Principles in Glioma
- Levetiracetam is the preferred first-line agent: no hepatic enzyme induction (important with chemotherapy), no drug interactions, IV formulation available, rapid titration possible
- No prophylactic anticonvulsants in seizure-free patients: AAN practice parameter recommends against prophylaxis; no evidence of benefit, and older AEDs interact with chemotherapy
- Avoid enzyme-inducing AEDs: Phenytoin, carbamazepine, phenobarbital reduce efficacy of temozolomide, corticosteroids, and many chemotherapies via CYP450 induction
- Alternatives to levetiracetam: Lacosamide, lamotrigine, valproic acid (valproate has theoretical benefit via HDAC inhibition, but clinical evidence is mixed and thrombocytopenia risk limits use with TMZ)
- Perioperative seizures: 7-day postoperative anticonvulsant prophylaxis is common practice, followed by taper if seizure-free
Corticosteroid Management
Dexamethasone is the standard corticosteroid for peritumoral vasogenic edema in glioma, owing to its minimal mineralocorticoid activity and long half-life.
Corticosteroid Considerations
- Starting dose: Dexamethasone 4–16 mg/day in divided doses for symptomatic edema; lower doses (2–4 mg/day) for mild symptoms
- Taper as able: Use the lowest effective dose; prolonged use causes significant morbidity (myopathy, hyperglycemia, immunosuppression, osteoporosis, insomnia, psychiatric effects)
- PPI prophylaxis: Recommended during concurrent dexamethasone + temozolomide or dexamethasone + anticoagulation
- PCP prophylaxis: Consider TMP-SMX if on dexamethasone ≥4 mg/day for ≥4 weeks, or during concurrent TMZ regardless of steroid dose
- Steroid myopathy: Proximal weakness, especially hip flexors; can mimic tumor progression; reversible with dose reduction
- Immunotherapy interaction: Corticosteroids may diminish efficacy of checkpoint inhibitors; minimize steroid use in patients enrolled in immunotherapy trials
Recurrent Glioblastoma
Despite optimal initial treatment, glioblastoma inevitably recurs, typically within 6–9 months. Management of recurrence is challenging, with no established standard of care and limited survival benefit from available therapies.
Treatment Options at Recurrence
- Re-resection: Consider if symptomatic, accessible, and adequate time since prior surgery; may improve survival in selected patients
- Re-irradiation: Increasingly used with stereotactic radiosurgery (SRS) or hypofractionated stereotactic RT (HFSRT) for focal recurrences; must consider cumulative dose to normal brain
- Bevacizumab: FDA-approved; improves PFS and symptoms but not OS; useful for steroid-sparing
- Lomustine (CCNU): Standard chemotherapy agent for recurrent GBM in many countries; modest response rates
- Temozolomide rechallenge: Can be considered, especially in MGMT-methylated tumors with prolonged initial response; alternative dosing schedules (e.g., metronomic, dose-dense) have been explored without clear superiority
- Clinical trials: Strongly encouraged at recurrence; novel agents include targeted therapies, immunotherapies, and combination approaches
Distinguishing Progression from Pseudoprogression
Pseudoprogression vs. True Progression
- Pseudoprogression: Occurs in 20–30% of GBM patients within 3–6 months of completing chemoradiation; represents treatment-induced inflammation and blood-brain barrier disruption mimicking tumor growth on MRI
- More common in MGMT-methylated tumors (~30%) than unmethylated (~10%), and is actually a favorable prognostic sign
- RANO criteria: Response Assessment in Neuro-Oncology criteria recommend not declaring progression within 12 weeks of completing radiation unless there is new enhancement outside the radiation field or histologic confirmation
- Advanced imaging: Perfusion MRI (rCBV), MR spectroscopy (choline/NAA ratio), PET (FET-PET or amino acid PET) can help differentiate but are imperfect
- Clinical correlation: If the patient is clinically stable or improving, pseudoprogression is more likely; continue treatment and repeat imaging in 4–8 weeks
- Pseudoresponse: Distinct phenomenon with bevacizumab — rapid decrease in enhancement due to vascular normalization rather than tumor reduction; monitor FLAIR for non-enhancing progression
Venous Thromboembolism Prophylaxis
Glioma patients are at substantially increased risk for venous thromboembolism (VTE), with an incidence of 20–30% during the disease course. This is driven by tumor procoagulant factors, immobility, surgery, and corticosteroid use.
VTE Management Principles
- Prophylaxis: Mechanical prophylaxis (sequential compression devices) perioperatively; pharmacologic prophylaxis with LMWH can be started 24–48 hours after craniotomy once hemostasis is confirmed
- Treatment of established DVT/PE: Therapeutic anticoagulation with LMWH is preferred over warfarin or DOACs in glioma patients; risk of intracranial hemorrhage is approximately 3–5% and is generally outweighed by VTE recurrence risk
- Inferior vena cava (IVC) filters: Reserved for patients with absolute contraindications to anticoagulation (e.g., recent intracranial hemorrhage); should be retrievable when possible
- Duration: At least 3–6 months for acute VTE; many neuro-oncologists continue indefinitely given the persistent prothrombotic state
- Bevacizumab consideration: Bevacizumab may paradoxically reduce VTE risk through vascular normalization, but also increases wound healing complications and arterial thrombotic events
Cognitive and Quality-of-Life Considerations
Neurocognitive impairment affects the majority of glioma patients at some point during their disease course, resulting from the tumor itself, treatment effects (surgery, radiation, chemotherapy), seizures, and medications (corticosteroids, anticonvulsants).
Cognitive Management Strategies
- Baseline neurocognitive assessment: Recommended before treatment initiation, especially in low-grade glioma patients where cognitive preservation is a key treatment goal
- Radiation-related cognitive decline: Late delayed effect (months to years post-RT); hippocampal-sparing techniques may mitigate memory decline; whole-brain RT should be avoided when possible
- Pharmacologic interventions: Methylphenidate and modafinil have shown modest benefit for cancer-related fatigue and cognitive slowing in small studies; memantine during whole-brain RT may be neuroprotective
- Rehabilitation: Cognitive rehabilitation, occupational therapy, and speech therapy should be offered as part of comprehensive neuro-oncologic care
- Driving: Patients with seizures, visual field deficits, or significant cognitive impairment should be counseled regarding driving safety; state-specific reporting requirements apply
Emerging Therapies
IDH Inhibitors
Beyond vorasidenib, several IDH inhibitors are in clinical development. Ivosidenib (IDH1-selective) has shown activity in recurrent IDH-mutant gliomas. The success of the INDIGO trial has catalyzed multiple ongoing trials evaluating IDH inhibitors in combination with other therapies and in higher-grade IDH-mutant gliomas.
Immunotherapy
Despite transformative success in other solid tumors, immunotherapy has largely failed in glioblastoma to date. CheckMate 143 (nivolumab vs. bevacizumab in recurrent GBM) was negative for OS. Challenges include the immunosuppressive tumor microenvironment, low mutational burden, blood-brain barrier, and obligate corticosteroid use. Ongoing investigations include combination checkpoint inhibitors, vaccine approaches (including neoantigen vaccines), CAR-T cell therapy, and oncolytic viruses.
Novel Targeted Approaches
- BRAF inhibitors: Dabrafenib + trametinib for BRAF V600E-mutant gliomas (FDA breakthrough designation)
- FGFR inhibitors: For FGFR-altered gliomas, particularly in recurrent IDH-mutant tumors with FGFR-TACC fusions
- CDK4/6 inhibitors: Being explored for CDKN2A/B-deleted tumors
- Convection-enhanced delivery: Bypasses blood-brain barrier by directly infusing therapeutic agents into tumor via catheter
- ONC201/dordaviprone: Showing promise in H3K27-altered diffuse midline gliomas
Landmark Trials Summary
| Trial | Population | Intervention | Key Finding |
|---|---|---|---|
| Stupp 2005 | Newly diagnosed GBM | RT + TMZ vs. RT alone | OS 14.6 vs. 12.1 months; established standard of care |
| EF-14 (2017) | Newly diagnosed GBM | TTFields + TMZ vs. TMZ | OS 20.9 vs. 16.0 months |
| RTOG 9802 (2016) | High-risk LGG | RT + PCV vs. RT alone | OS 13.3 vs. 7.8 years |
| RTOG 9402 (2013) | Anaplastic oligodendroglioma | PCV → RT vs. RT | OS 14.7 vs. 7.3 years (1p/19q-codeleted) |
| EORTC 26951 (2013) | Anaplastic oligodendroglioma | RT → PCV vs. RT | Significant OS benefit in 1p/19q-codeleted |
| CATNON (2021) | Non-codeleted anaplastic glioma | RT ± concurrent/adjuvant TMZ | Adjuvant TMZ benefits IDH-mutant tumors |
| INDIGO (2023) | Grade 2 IDH-mutant glioma | Vorasidenib vs. placebo | PFS 27.7 vs. 11.1 months; HR 0.39 |
| Perry 2017 | Elderly GBM | Hypo-RT + TMZ vs. hypo-RT | OS 9.3 vs. 7.6 months |
| NOA-08 (2012) | Elderly GBM | TMZ vs. RT | MGMT-methylated: TMZ non-inferior; unmethylated: RT better |
| AVAglio (2014) | Newly diagnosed GBM | Stupp + bevacizumab vs. Stupp | PFS improved; OS not improved |
| CheckMate 143 (2020) | Recurrent GBM | Nivolumab vs. bevacizumab | No OS benefit for immunotherapy |
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