Radiotherapy

Inoperable Meningioma

Summary

Radical treatment using 3D conformal radiotherapy alone.

Dose

54 Gy in 30 fractions

Pre-Simulation

Informed consent.
Ophthalmology review if optic nerves nearby or involved.

Simulation

CT simulation through region of interest.

Fusion

Fuse with pre-operative/diagnostic MRI

3D Conformal Technique

GTV = Visible tumour on MRI
CTV = 0.1 cm expansion (0.5 cm for WHO Grade II/III)
PTV = 0.5 cm expansion

Organs at Risk

Lens
Retina < 45 Gy
Optic Nerve < 54 Gy
Optic Chiasm < 54 Gy
Brainstem < 54 Gy

Long Term Outcomes

Surgery alone:

  • 90% 10 year progression free survival with gross total resection
  • 50% 10 year progression free survival with subtotal resection
    • Increases to 90% with adjuvant radiotherapy
  • 8 fold higher risk of recurrence if WHO Grade II; nearly always recurs if WHO Grade III

Late effects depend on site of disease and relationship to critical structures, but are uncommon.

Post-Operative Meningioma

Pre-Simulation

  • Informed consent
  • MDM/discussion with surgeons as to areas of residual disease

Simulation

  • Simulate supine in neutral position
  • Immobilisation with thermoplastic mask
  • No bolus required
  • CT scan to cervical spine

Planning

  • Fusion with pre-operative MRI (original extent of disease) and post-operative MRI (residual disease)
  • Volumes
    • GTV = Residual tumour if present, any abnormal bone adjacent to tumour site
    • CTV = Site of attachment to dura and GTV + 0.1 (Grade 1) or 0.5 (Grade 2-3) expansion
    • PTV = 0.3-0.5 mm expansion
  • Dose
    • 54 Gy (no residual disease)
    • 59.4 Gy (residual disease)
    • 51 Gy in 30# (adjacent to optic nerve/chiasm)
  • OAR
    • Brainstem < 54 Gy
    • Optic Nerve/Chiasm < 54 Gy
    • Retina < 45 Gy
    • Lens < 6 Gy
    • Brain < 60 Gy

Outcomes

  • Progression free survival: 50% without RT, 90% with RT (Grade 1); almost certain recurrence without RT, 50-80% with RT (Grade 2-3)
  • Early toxicity: Fatigue, ICP (headache, nausea, recurrence of symptoms), skin reaction, hair loss
  • Late toxicity: Brain necrosis (< 5%), cataract, optic pathway damage (< 1%), permanent alopecia, pituitary/endocrine disturbance (if sellar meningioma)

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