Radiation therapy and chemotherapy options vary according to histology and anatomic site of the brain tumor. For high-grade malignant gliomas—glioblastoma, anaplastic astrocytoma, anaplastic oligodendroglioma, and anaplastic oligoastrocytoma—combined modality therapy with resection, radiation, and chemotherapy is standard. Since anaplastic astrocytomas, anaplastic oligodendrogliomas, and anaplastic oligoastrocytomas represent only a small proportion of central nervous system (CNS) gliomas, phase III randomized trials restricted to them are not generally practical. However, since they are aggressive and are often included in studies along with glioblastomas, they are generally managed in a fashion similar to glioblastoma. Therapy involving surgically implanted carmustine-impregnated polymer wafers combined with postoperative external-beam radiation therapy (EBRT) has a role in the treatment of high-grade gliomas regardless of the extent of surgical resection. Specific treatment options for tumor types are listed below under the tumor types and locations. This section covers general treatment principles.
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Dexamethasone, mannitol, and furosemide are used to treat the peritumoral edema associated with brain tumors. Use of anticonvulsants is mandatory for patients with seizures.
Finally, active surveillance is appropriate in some circumstances. With the increasing use of sensitive neuroimaging tools, there has been increased detection of asymptomatic low-grade meningiomas. The majority appear to show minimal growth and can often be safely observed, with therapy deferred until the detection of tumor growth or the development of symptoms.[3,4]
For most types of brain tumors in most locations, an attempt at complete or near-complete surgical removal is generally recommended, if possible, within the constraints of preservation of neurologic function and underlying patient health. This recommendation is based on observational evidence that survival is better in patients who undergo tumor resection than in those who have closed biopsy alone.[5,6] However, the benefit of resection has not been tested in randomized trials. Selection bias can enter into observational studies despite attempts to adjust for patient differences that guide the decision to operate. Therefore, the actual difference in outcome between radical surgery and biopsy alone may not be as large as noted in the retrospective studies. An exception to the general recommendation for attempted resection is the case of deep-seated tumors such as pontine gliomas, which are diagnosed on clinical evidence and treated without initial surgery approximately 50% of the time. In most cases, however, diagnosis by biopsy is preferred. Stereotactic biopsy can be used for lesions that are difficult to reach and resect.
Reducing intracranial pressure by removing as much tumor as is safely possible to preserve neurological function.
However, total elimination of primary malignant intraparenchymal tumors by surgery alone is rarely achievable. Therefore, intraoperative techniques have been developed to reach a balance between removing as much tumor as is practical and the preservation of functional status. For example, craniotomies with stereotactic resections of primary gliomas can be done in cooperative patients while they are awake, with real-time assessment of neurologic function. Resection proceeds until either the magnetic resonance imaging (MRI) signal abnormality being used to monitor the extent of surgery is completely removed or subtle neurologic dysfunction appears (e.g., slight decrease in rapid alternating motor movement or anomia). Likewise, when the tumor is located in or near language centers in the cortex, intraoperative language mapping can be performed by electrode discharge-induced speech arrest while the patient is asked to count or read.