Meningiomas are the most common type of tumor that develops within the head, originating from the meninges surrounding the brain and spinal cord. While the majority are classified by the World Health Organization (WHO) as Grade I (benign and slow-growing), their location can still cause significant neurological symptoms by compressing adjacent structures. When surgical removal is not feasible or complete, or when the tumor is more aggressive, radiation therapy is a highly effective, non-invasive method to control tumor growth and prevent recurrence. This treatment uses high-energy beams to damage the DNA of the abnormal cells, stopping them from growing or dividing.
The Clinical Application of Radiation Therapy
Radiation treatment is selected based on the tumor’s characteristics, location, and the success of any prior surgical intervention. For tumors that are only partially removed during surgery—a procedure known as subtotal resection (STR)—radiation is frequently used as an adjuvant therapy. This post-operative treatment targets residual tumor cells, significantly improving local control. Adding external beam radiation after an STR can improve the five-year progression-free survival rate from 38–60% to as high as 80–100%.
Radiation also serves as the primary treatment option when a tumor is deemed inoperable due to its location near sensitive areas, such as the skull base, optic nerves, or major blood vessels. For these inaccessible meningiomas, primary radiation aims to stabilize the tumor size, or even cause it to shrink, without the risks associated with complex neurosurgery. The aggressiveness of the tumor, determined by its WHO grade, heavily influences the decision to use radiation.
While Grade I meningiomas may be observed after complete removal, higher-grade tumors (atypical Grade II and malignant Grade III) are likely to require immediate post-operative radiation. This is necessary due to their high recurrence rates. Radiation is also a standard intervention for managing recurrence. For recurrent or high-grade tumors, a minimum radiation dose of approximately 59.4 Gy is often necessary to achieve adequate local control, preserving neurological function and improving long-term outcome.
Specific Delivery Methods and Technologies
The effectiveness of modern radiation therapy lies in its ability to precisely target the tumor while minimizing exposure to surrounding healthy brain tissue.
Specific Delivery Methods
One highly focused approach is Stereotactic Radiosurgery (SRS), which delivers a single, high dose of radiation in one session. SRS is effective for smaller, well-defined meningiomas, typically those measuring 3 centimeters or less. Precision is achieved using specialized machines, such as the Gamma Knife or linear accelerators, which focus numerous beams onto the target area.
For larger tumors, or those located adjacent to sensitive structures like the optic chiasm or brainstem, Fractionated Stereotactic Radiotherapy (FSRT) is preferred. FSRT divides the total dose into multiple smaller doses, often given over 5 to 30 treatment days. This fractionation allows healthy tissues to repair themselves between sessions, reducing the risk of damage while delivering a high cumulative dose to the tumor. A common FSRT regimen involves delivering 1.8 to 2 Gy per fraction, totaling 50.4 to 54 Gy.
Planning and Technology
The process begins with an intensive planning phase to ensure maximum accuracy. Patients undergo high-resolution imaging, typically a combination of MRI and CT scans, to create a detailed, three-dimensional map of the tumor and all nearby structures. Specialized software then uses this information in dosimetry to calculate the exact angle, shape, and intensity of the radiation beams.
During treatment, immobilization devices, such as custom-fitted thermoplastic head masks or rigid frames, ensure the patient’s head remains perfectly still. While older techniques like conventional radiotherapy are less common, advanced methods like Intensity-Modulated Radiation Therapy (IMRT) further refine delivery by sculpting the radiation dose across the target area, allowing for highly conformal treatment volumes that match the tumor’s irregular shape.
Managing Expected Treatment Effects and Recovery
Patients undergoing radiation therapy may experience several temporary acute side effects. Fatigue is common, often beginning a few weeks into therapy and persisting for weeks to months after the final session. Localized effects include mild skin irritation in the treatment area, resembling a sunburn, or localized hair loss, which may be temporary or permanent depending on the dose delivered.
Temporary swelling of the brain tissue around the tumor, called edema, can sometimes occur, causing symptoms like headache or nausea. This swelling is usually managed effectively with a short course of corticosteroid medication. Although most acute side effects are mild and manageable, long-term or delayed effects can occasionally occur months or even years after treatment has concluded. These delayed effects are rare but can include subtle cognitive changes, such as difficulty with short-term memory or concentration.
Radiation Necrosis (RN), a rare complication where treated tissue dies off, is another delayed effect that can sometimes be difficult to distinguish from a tumor recurrence on standard follow-up imaging. There is also a small, long-term risk of developing a secondary tumor due to the radiation exposure, which is weighed against the benefits of treatment. Following therapy, lifelong monitoring is required, typically involving regular follow-up MRI scans, often scheduled annually for the first five years for Grade I meningiomas. The treatment’s primary goal is stabilization, meaning the tumor stops growing, though slow shrinkage may be observed over many months or years.