Definition
- Anaplastic oligodendroglioma (AO) is a WHO Grade III primary brain tumor arising from oligodendrocytes, the glial cells responsible for producing myelin.
- Considered malignant, faster-growing than low-grade oligodendrogliomas.
Key Molecular Features
- IDH mutation:
- Present in most oligodendrogliomas (better prognosis).
- 1p/19q co-deletion:
- Diagnostic hallmark of oligodendrogliomas.
- Predicts better response to chemotherapy, especially PCV.
- MGMT promoter methylation:
- Predicts response to temozolomide.
- TERT promoter mutation:
Clinical Presentation
- Seizures (most common)
- Headache
- Focal neurological deficits (depending on location)
- Cognitive changes
Imaging
- MRI: usually heterogeneously enhancing mass with calcifications (common in oligodendrogliomas).
- Often located in frontal lobes.
- High cellularity with atypical nuclei
- Increased mitotic activity
- Microvascular proliferation may be present
- Necrosis is rare (distinguishes from glioblastoma)
Treatment Overview
- Surgery
- Gross total resection if feasible.
- Extent of resection correlates with survival.
- Radiation Therapy (RT)
- Postoperative RT recommended for anaplastic tumors.
- Chemotherapy
- PCV (Procarbazine, CCNU/lomustine, Vincristine): traditional regimen, especially in 1p/19q co-deleted tumors.
- Temozolomide: alternative, used concurrently with RT in some cases.
- Molecular profile guides choice (e.g., MGMT unmethylated may favor RT + PCV).
Prognosis
- Better than anaplastic astrocytoma or glioblastoma, especially if IDH-mutant and 1p/19q co-deleted.
- Median survival: ~12–16 years for co-deleted AO vs. ~5–8 years for non-co-deleted.
Follow-up & Monitoring
- MRI every 3–6 months initially, then yearly if stable.
- Monitor for treatment toxicity: cytopenias (PCV), neuropathy (vincristine), liver function (lomustine), and radiation-related neurocognitive effects.