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Radiation therapy represents the most effective adjunctive treatment to surgery for the treatment of glioblastoma multiforme. In 1976, researchers from the Brain Tumor Study Group reported that whole brain radiation therapy increased median survival of patients with malignant gliomas from 14 weeks with surgery alone to 36 weeks with surgery plus adjunctive radiation therapy. Since that time, radiation therapy has been recognized as an effective adjunctive treatment for patients with glioblastoma multiforme.

Indications for radiation therapy for glioblastoma multiforme may include:

• After complete surgical removal of a glioblastoma to kill residual brain tumor cells to prevent or delay recurrence of the tumor.
• After partial resection of a glioblastoma that cannot be completely removed by surgery.
• In cases where surgery cannot be safely performed due to the location of the tumor (inoperable brain tumor).
• In cases where, either due to advanced age or poor general health, the patient is not considered a good candidate for brain surgery.

Conventional Radiation Therapy

Conventional radiation therapy uses radiation from an external source (external-beam radiation) to destroy cancer cells. The primary goal of radiation therapy after surgical removal of the brain tumor is to destroy residual cancer cells that cannot be removed by the surgery and, thereby, prevent or delay recurrence of the tumor. Because high doses of radiation can also damage normal brain tissue, the radiation treatments are divided (fractionated) into many smaller doses of radiation that are administered over a period of 5 to 7 weeks. The current recommendation if to administer a total of about 60 Gy (Gray; a unit of radiation) of conventional external-beam radiation in 1.8 to 2.0 Gy daily fractions five times a week for a period of 5 to 7 weeks. To minimize the extent of damage to normal brain tissue, external-beam radiation therapy is focused (targeted) at the area of the tumor.

In recent years, a technique called three-dimensional conformal radiation therapy has become available that uses computer technology to conform (match) the radiation beam that is delivered to the size and shape of the tumor. This technique enables doctors to focus and deliver high doses of radiation to the area of the tumor while minimizing the extent of damage to normal brain tissue. In some cases, depending upon the location and size of the brain tumor, the entire brain must be irradiated to destroy or slow-down the growth of the tumor. This type of conventional radiation therapy is know as whole brain radiation therapy (WBRT).

Stereotactic Radiosurgery

Stereotactic radiosurgery is a novel radiation therapy procedure that utilizes very accurately targeted high doses of radiation to destroy a tumor. Stereotactic radiosurgery is not actual "surgery" per se but is a form of radiation therapy. This treatment enables doctors to destroy a brain tumor by accurately administering a single, high-dose of radiation in a one-day treatment session. In most cases, stereotactic radiosurgery is used for the treatment of inoperable brain tumors, for the treatment of recurrent brain tumors, or for the treatment of secondary malignant brain tumors that have spread to the brain from cancer in another part of the body such as the lung.