What is the role of Stereotactic Radiosurgery (SRS) in the treatment of meningioma?

From the Guidelines

Stereotactic radiosurgery (SRS) is a recommended treatment option for meningiomas, particularly for small WHO grade 1 meningiomas, with a typical radiation dose of 12-15 Gy in a single fraction. This treatment approach is supported by the evidence from 1, which suggests that SRS can be an effective treatment for small WHO grade 1 meningiomas. The use of SRS for meningiomas is also discussed in 1, which provides guidance on the treatment of meningiomas based on tumor size and WHO grade.

Key Considerations

• SRS is typically used for small to medium-sized tumors (typically less than 3-4 cm) that are surgically inaccessible, residual, or recurrent after surgery, or in patients who are poor surgical candidates.
• The typical radiation dose for SRS in meningiomas ranges from 12-16 Gy for benign meningiomas (WHO grade I), with lower doses used for larger tumors or those near critical structures.
• SRS provides excellent local tumor control rates of 90-95% for benign meningiomas at 5-10 years, with lower rates for higher-grade tumors.
• Potential side effects of SRS include temporary fatigue, headache, and rarely radiation necrosis or edema.

Treatment Planning

• Patients typically undergo MRI with contrast for treatment planning, and the procedure is performed as an outpatient treatment with minimal recovery time.
• Follow-up imaging is typically performed every 6-12 months to monitor tumor response, as SRS works by damaging tumor cell DNA, preventing further growth rather than immediately shrinking the tumor.
• The evidence from 1 suggests that SRS can be an effective treatment option for brain metastases, and this may also be applicable to meningiomas, although the specific evidence for meningiomas is limited to 1 and 1.

From the Research

Stereotactic Radiosurgery (SRS) in Meningioma

• SRS is an established treatment option for patients with intracranial meningiomas, particularly for those with smaller tumors that are considered inoperable or for patients who prefer not to undergo surgery 2, 3.
• The efficacy and safety of SRS in treating meningiomas have been evaluated in several studies, with reported local control rates ranging from 71% to 100% at 10 years 4.
• The prescription dose for SRS in meningioma typically ranges between 12 and 15 Gy, delivered in a single fraction 4.
• Toxicity rates associated with SRS for meningioma are generally low, with reported rates of treatment-related complications ranging from 8% to 14.4% 2, 3.

Indications and Results of SRS in Meningioma

• SRS is often used as an alternative or adjuvant therapy to surgery for meningiomas in locations where operative manipulation may be difficult, such as the skull base 3, 5.
• The technique is also useful for larger meningiomas or those closely approximating critical structures, such as the optic chiasm and brainstem 5.
• Reported rates of imaging-documented regression are higher for SRS, but neurological recovery is relatively good with both SRS and fractionated stereotactic radiotherapy (SRT) 5.

Radiobiological Considerations of SRS in Meningioma

• The alpha/beta value for meningioma has been estimated to be around 3.28 Gy, which is used to calculate the expected efficacy of hypofractionation compared to single-dose SRS 6.
• The estimated optic nerve tolerance to single doses of radiation is around 8-10 Gy, which is lower than the optimal dose required to treat benign meningioma 6.
• The use of small numbers of fractions to treat patients with meningioma may result in undertreatment of the tumor and/or exceeding optic nerve tolerance, and standard fractionation is recommended in such cases 6.