Primary brain tumors account for approximately 2 percent of all cancers diagnosed annually in the United States. These types of tumors form in the brain, meaning they are not metastases, and they rarely metastasize to other parts of the body. Primary malignant brain tumors include glioblastomas, most of the astrocytomas, and some oligodendrogliomas and ependymomas.
Tumors are graded from I to IV based on their microscopic appearances. Grade I tumors grow slowly and are the least life threatening. Grade II tumors grow slightly faster and may invade surrounding normal tissue. Grade III tumors are malignant, containing actively reproducing abnormal cells that invade surrounding normal tissue. Grade IV tumors are the most malignant and reproduce very rapidly. Glioblastoma multiforme (GBM) is the most common grade IV tumor and accounts for 52 percent of all primary brain tumor cases. Glioma is the general name for a tumor that arises from the glial tissue, which is the supportive tissue that binds brain cells together.
Treating primary brain tumors depends on the size of the tumor, its location, its growth rate, and the patient’s symptoms. If a patient has symptoms that are life threatening or significantly affect the quality of life, a craniotomy (open skull surgery) is usually performed. However, if the tumor is inaccessible, located too near critical structures, or if the patient is not well enough to tolerate surgery, other options must be considered.
Gamma knife radiosurgery precisely targets the primary brain tumor with 201 beams of radiation, and there is very little involvement with surrounding normal brain tissue. Typically, only one session is required. However, if the tumor has “tentacles”that have invaded the brain, more than one session may be required.
Gamma knife radiosurgery is frequently used in combination with conventional radiotherapy or as a secondary treatment after conventional surgery has reduced the size of the tumor.Tumors of 4 cm or smaller are best suited for this procedure.