Meningiomas are a common type of tumor originating in the membranes covering the brain and spinal cord, known as the meninges. While most meningiomas are benign, they can still cause significant health issues. Their growth can press on nearby brain tissue, nerves, or blood vessels. Radiation therapy is a well-established treatment option for meningiomas, often employed to control tumor growth or eliminate remaining cells after surgery.
Meningioma Basics and Radiation Therapy Overview
Meningiomas are the most common primary central nervous system tumor, accounting for approximately 38% of all primary intracranial tumors. These tumors arise from the arachnoid cap cells within the meninges. Most meningiomas are slow-growing and classified as Grade 1 by the World Health Organization (WHO). However, some can be more aggressive, with Grade 2 (atypical) and Grade 3 (malignant) meningiomas showing faster growth and a higher likelihood of recurrence.
Radiation therapy uses high-energy rays or particles to target and damage the DNA within tumor cells. This damage prevents tumor cells from dividing and can cause existing cells to self-destruct. The goal is to shrink the tumor or stop its growth, reducing pressure on surrounding brain structures and alleviating symptoms. Radiation delivery methods vary to maximize precision and minimize harm to healthy tissues.
Specific Radiation Therapy Methods
Radiation therapy for meningiomas employs several advanced techniques to deliver precise doses to the tumor. Stereotactic Radiosurgery (SRS) delivers a single high dose of radiation to a small, well-defined tumor. This non-surgical approach uses narrow beams focused on the tumor area, minimizing impact on healthy surrounding tissue. SRS is suited for smaller tumors, typically up to 3-3.5 cm, or those in difficult-to-reach locations like the skull base.
Fractionated Stereotactic Radiotherapy (FSRT) is similar to SRS in precision but delivers the radiation dose over multiple sessions, often daily for several days or weeks. This fractionation allows treatment of larger or irregularly shaped tumors, or those near sensitive structures where a single high dose might be too risky. Breaking the total dose into smaller fractions helps healthy tissues recover between treatments, reducing side effects.
External Beam Radiation Therapy (EBRT) is a broader term where radiation beams are generated by a machine outside the body and directed at the tumor. Intensity-Modulated Radiation Therapy (IMRT) is a type of EBRT that uses computer-controlled technology to shape and vary the intensity of multiple radiation beams. These beams are sculpted in three dimensions to conform closely to the tumor’s size and shape, sparing nearby healthy brain or spinal cord tissue. This method is often delivered once a day, five days a week, over several weeks.
Proton therapy is an advanced form of external beam radiation therapy that uses proton beams instead of traditional X-rays. Protons deposit most of their energy at a specific depth (the Bragg peak) and then stop, reducing the radiation dose to tissues beyond the tumor. This characteristic benefits tumors deep within the skull or near the skull base, potentially lowering radiation exposure to healthy surrounding structures.
Indications for Radiation Therapy
Radiation therapy is considered for meningiomas in several scenarios. One common indication is for small, asymptomatic tumors showing growth over time. This aims to control the tumor before it causes symptoms or becomes more challenging to manage.
Radiation therapy is also an option when surgical removal is not feasible. This occurs if the tumor is in an area difficult or too risky to access surgically, such as near critical nerves or blood vessels, or if a patient’s overall health precludes surgery. In such cases, radiation therapy may serve as the primary treatment.
For patients undergoing surgery, radiation therapy may treat any residual tumor that could not be completely removed. This adjuvant therapy helps destroy remaining tumor cells and reduces the likelihood of recurrence. Radiation is also recommended for recurrent meningiomas, especially if previous treatments have been exhausted or the tumor returns in a challenging location. Atypical (Grade 2) and malignant (Grade 3) meningiomas, due to their aggressive nature and higher recurrence rates, frequently receive radiation therapy after surgery, even if the entire tumor appears removed, to minimize regrowth.
Managing Treatment Side Effects
Patients undergoing radiation therapy for meningioma may experience side effects during or shortly after treatment. Fatigue is a common side effect, often becoming more noticeable in the latter half of treatment and potentially lasting for several weeks after completion. Localized skin reactions, such as redness or irritation in the treated area, can occur, particularly with external beam radiation.
Temporary hair loss may occur in the specific region where radiation beams are directed, with extent and permanence depending on the radiation dose. Swelling (edema) around the tumor is another potential side effect, which can lead to headaches, nausea, or a temporary worsening of pre-existing neurological symptoms. Medications, such as corticosteroids, are prescribed to manage this swelling. While the radiation treatment itself is not painful, any new or worsening symptoms should be discussed with the medical team. Most acute side effects are temporary and resolve within a few weeks to months after treatment concludes.
Long-Term Outlook and Follow-Up
The long-term outlook for many patients who undergo radiation therapy for meningioma is positive, with the primary goals being tumor control and prevention of further growth. Radiation therapy can effectively arrest tumor growth in a high percentage of cases. Studies report control rates of 80-90% or higher for Grade 2 meningiomas at 5 years. For WHO Grade 1 meningiomas, progression-free survival rates after radiotherapy range from 76% to 100%, with most studies showing rates between 90% and 95%.
Ongoing monitoring is a key part of long-term care after radiation therapy. Regular follow-up appointments, including neurological examinations and periodic imaging (typically MRI scans), are scheduled to track the tumor’s response and detect any potential recurrence. The frequency of these scans may vary but often begins with screenings every 6-12 months.
While rare, some patients may experience late-onset side effects years after treatment, such as cognitive changes affecting thinking, learning, or memory, or visual disturbances if optic nerves were near the treatment field. Very rare complications, like the development of a secondary radiation-induced tumor, are a possibility, but the incidence is low. Ongoing surveillance allows for early detection and management of any changes or new issues, contributing to favorable long-term outcomes for many individuals.