Meningioma (WHO Grade I)
Treatment is highly dependent on the site of disease but should be surgery if possible.
Observation
Asymptomatic lesions can be followed with serial MRI imaging. Surgery should occur if symptoms develop.
Surgery
Surgery is the main treatment for meningioma. It is usually possible unless:
- There is involvement of the posterior part of the superior sagittal sinus as brain infarction may occur if the sinus is compromised
- Base of skull lesions (particularly around the cavernous sinus) due to access and close proximity of critical structures
- Optic nerve (unless vision has been lost completely)
Debulking of unresectable tumours is desirable if possible.
Gross total resection leads to 90% progression free survival at 10 years. Subtotal resection is only 50% progression free survival.
Radiotherapy
Radiotherapy is used in several situations:
- For inoperable tumours. Radiotherapy can arrest the growth of meningioma but rarely causes resolution.
- When subtotal resection has occured. This is site dependent as observation is an alternative, particularly in non-critical areas or for older patients.
- When a meningioma has repeatedly recurred (ie. second recurrence), instead of further surgical intervention.
The total dose is 54 Gy in 30 fractions prescribed to the GTV with a 0.6 cm expansion to PTV (0.1 mm GTV->CTV, 0.5 mm CTV->PTV).
Stereotactic Radiotherapy
Stereotactic radiotherapy is increasingly popular. It is particularly useful for meningioma that is not adjacent to critical brain structures (eg. optic nerve, brainstem) which have poor tolerance. It may be less useful for higher grade meningiomas due to poor tolerance of adjacent structures. Marginal doses of between 12-16 Gy have been used, with lower doses appearing to provide equivalent control.
Atypical Meningioma (WHO Grade II)
A meningioma with increased mitotic activity (usually ~ 4 per ten high power fields) OR:
- Increased cellularity
- Small cells with high N/C ratio
- Sheet-like growth
- Small regions of necrosis.
These meningiomas have a much higher risk of recurrence following surgical excision (30-40%). Radiotherapy is usually indicated to improve local control.
- Gross total resection of Grade II meningioma is treated with 54 Gy in 30#.
- Subtotal resection should be treated to 59.4 Gy in 33#.
Anaplastic Meningioma (WHO Grade III)
A meningioma showing high grade features (20 mitoses per ten high power fields) or with features of carcinoma. Recurrence is frequent (70-80%) and 2 year survival is average (40-50%). Radiotherapy is almost always indicated adjuvantly, with doses the same as atypical meningioma (above).
