The major goal of radiation treatment is to kill meningioma tumor cells while minimizing damage to surrounding normal brain tissue. Radiation therapy for meningiomas involves externally beaming from a machine high energy X-rays at the tumor site (known as external beam radiation). There are variations of radiation therapy and the type chosen is based on factors used for determining treatment options discussed at the beginning of this section (size, location, symptoms, age and health of patient), as well as the extent of tumor removal and the WHO grade of the meningioma.
Radiation therapy is often prescribed following surgery where there has been incomplete tumor removal, regardless of the tumor grade. When used as such, the treatment is called adjuvant radiotherapy, meaning it is used in addition to the primary treatment option of surgery in order to increase the chances of a more positive outcome. In the case of benign meningiomas that were incompletely removed, its use has been effective in decreasing the recurrence rates.
If there has been complete tumor resection, radiation is not recommended for benign tumors. In some cases, however, radiation may be recommended as follow-up treatment with atypical and malignant tumors despite complete removal. While some studies have indicated that this type of follow-up radiation therapy does have a positive effect in reducing atypical and malignant meningioma recurrence rates, more rigorous research is needed to obtain a more accurate assessment of its efficacy under these circumstances.
With recurrent tumors, some form of radiation therapy and/or surgery may be recommended.
The most common adjuvant radiation is conventional external beam radiation, which typically involves treatment given five days a week for 5 to 7 weeks. Intensity-modulated radiation therapy (IMRT) is a specialized variation of this type and allows the radiation to conform more closely to the shape of the tumor and allows greater control of the amount of radiation being received by the tumor cells versus the surrounding healthy tissue. A linear accelerator (LINAC) is used to beam the radiation.
Radiation therapy is also used as a treatment option when tumors are inoperable, in locations where the risk of surgery is considered too high, or the patient is not a good surgical risk. Two variations of external beam radiation often employed in these cases are stereotactic radiosurgery and stereotactic radiotherapy. Stereotactic radiosurgery is not actually surgery, but rather a delivery of a very intense dose of radiation, much higher than the daily dose received with conventional radiation. It is given in a single dose that is delivered by either a Gamma Knife machine or a linear accelerator. This radiation methodology is only appropriate for small tumors. Stereotactic radiotherapy is similar to stereotactic radiosurgery, except that instead of one high dose of radiation, the dose is broken down into smaller amounts of radiation and administered over several sessions to achieve the desired total dose of radiation (also known as fractionated stereotactic radiotherapy). This can help reduce damage to healthy brain tissue, while still allowing the appropriate radiation dose to reach the tumor.
More recently, stereotactic radiosurgery has been employed as the first treatment option to destroy smaller meningiomas, even though surgery was possible. While some studies have indicated that this approach may be just as effective as surgery as a primary treatment, there is not yet a consensus regarding this approach, and surgery, if possible, is still the preferred initial treatment option (unless the wait-and-monitor approach is a reasonable alternative).