Benign intracranial tumors occur about as often as primary malignant brain tumors. Most benign tumors are noninvasive, well defined and well visualized on MRI, and have a slow rate of progression. Each of these features makes them good candidates for radiosurgery.
Radiosurgery can deliver a destructive dose of radiation to the target with little or no radiation effects on adjacent structures. Proper patient selection for this procedure is critical.
With 2 decades of experience performing radiosurgery, Mayo Clinic neurosurgeons have accumulated a depth of expertise and a vast database that includes patient characteristics, radiosurgical dosimetry, and outcomes.
After reviewing more than 1,400 cases of meningiomas, vestibular schwannomas, and pituitary adenomas, Mayo clinicians observe that radiosurgery is an excellent choice when these types of benign tumors are small, occur in critical locations, or have recurred following previous surgery.
Radiosurgery is also well tolerated and of particular utility in elderly patients with medical conditions that put them at risk for an open procedure. Additionally, radiosurgery does not preclude an open procedure, should that be necessary at a later time.
The rate of recurrence for a surgically removed meningioma is about 18% to 25% at 10 years. For this reason, Mayo neurosurgeons recommend maintaining extended surveillance of meningiomas. In contrast, radiosurgery has been found to reduce the risk of recurrence or progression.
Tumor progression outside the field of radiation and tumor histology can affect both long- and short-term outcomes. Tumors that can be clearly imaged and those that are benign and without atypical histology have a far greater rate of 5-year progression-free survival.
Radiosurgery is also an effective therapy for cavernous sinus meningiomas, except when there is symptomatic mass effect, an unusual clinical presentation, or nontypical features on imaging.
Radiosurgery is typically not recommended for convexity and parasagittal meningiomas.
Several studies report that radiosurgery for small to moderate-sized vestibular schwannomas is associated with higher rates of hearing preservation and improved facial nerve outcomes when compared to surgical removal. This conclusion was supported by a Mayo Clinic study comparing surgical resection and radiosurgery for vestibular schwannomas with an average diameter of less than 3 cm. These Mayo investigators also found that the radiosurgical patients experienced less postprocedure dizziness.
Radiosurgery is considered safe and effective for hormone-secreting pituitary adenomas. When compared with radiotherapy, radiosurgery appears to shorten by more than half the time required to achieve biochemical remission and normal hormone levels.
Controversy remains over whether pituitary-suppressive medications at the time of surgery have a negative impact on tumor control. Several studies, however, including a series of 46 acromegaly cases at Mayo Clinic, found that patients were more than 4 times as likely to reach normal hormone levels if they were taken off such medications before surgery.
At Mayo Clinic, patients with oversecretion of growth hormone or adrenocorticotropic hormone and patients who experience new or progressing visual field deficits are referred for surgical resection. Patients with tumors that extend into the cavernous sinuses and patients with recurrent tumors after prior surgery, however, are generally treated with radiosurgery if the tumor does not directly involve the optic nerves and chiasm.
Across Mayo Clinic's 3 sites in Arizona, Florida, and Minnesota, patients are seen by neurosurgeons with expertise in both open procedures and radiosurgery. When used as an alternative to or in conjunction with traditional neurosurgery, radiosurgery is an effective, noninvasive option for treating benign intracranial tumors.