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Medulloblastoma: Pediatric Brain Tumor — Biology & Treatment

Epidemiology

  • Most common malignant pediatric brain tumor (20% of CNS tumors)
  • Peak: 3–8 years; rare in adults
  • Male predominance (1.5:1)

Molecular Subgroups (WHO CNS5)

  1. WNT-activated: Best prognosis (OS >90%); β-catenin nuclear
  2. SHH-activated: Infant/adult; TP53 status critical
  3. Group 3: Poor prognosis; MYC amplification, metastatic
  4. Group 4: Most common; intermediate prognosis

Clinical Features

  • Posterior fossa mass → obstructive hydrocephalus (headache, vomiting, ataxia)
  • Cranial nerve palsies (VI, VII)
  • Metastasis: leptomeningeal (drop mets to spine)

Treatment

  • Maximal safe resection
  • Craniospinal irradiation (CSI) + boost (age-adapted; avoid <3 yrs)
  • Chemotherapy: Cisplatin, vincristine, cyclophosphamide (Packer regimen)
  • Molecular risk stratification → de-escalation (WNT) or intensification (Group 3)

Late Effects

Neurocognitive decline, endocrine deficits, hearing loss, secondary malignancies — survivorship clinics essential.

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