What is the role of radiation therapy in the treatment of glioblastoma multiforme (GBM)?

Updated: Jul 01, 2019
  • Author: Jeffrey N Bruce, MD; Chief Editor: Herbert H Engelhard, III, MD, PhD, FACS, FAANS  more...
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Radiation therapy   [62, 63, 64, 65]

Radiation therapy in addition to surgery or surgery combined with chemotherapy has been shown to prolong survival in patients with glioblastoma multiformes compared to surgery alone. The addition of radiotherapy to surgery has been shown to increase survival from 3-4 months to 7-12 months. [57, 66]

Dose response relationships for glioblastomas demonstrate that a radiation dose of less than 4500 cGy results in a median survival of 13 weeks compared with a median survival of 42 weeks with a dose of 6000 cGy. This is usually administered 5 days per week in doses of 1.8-2.0 Gy.

Jablonska et al reported that in patients with poor clinical factors other than advanced age, the combination of hypofractionated radiation therapy and temozolomide produced results comparable to those seen with standard fractionation. In the 17 patients in the study, poor clinical factors included postoperative neurological complications, high tumor burden, unresectable or multifocal lesions, and potential low treatment compliance due to social factors or rapidly progressive disease. Patients received 40, 45, and 50 Gy in 15 fractions to 95% of the planning target volume (PTV), clinical target volume (CTV), and gross tumor volume (GTV), respectively. Treatment was delivered using intensity-modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT). [67]

The responsiveness of glioblastoma multiformes to radiotherapy varies. In many instances, radiotherapy can induce a phase of remission, often marked with stability or regression of neurologic deficits as well as diminution in the size of the contrast-enhancing mass. Unfortunately, any period of response is short-lived because the tumor typically recurs within 1 year, resulting in further clinical deterioration and the appearance of an expansile region of contrast enhancement. [68, 69]

Two studies investigated tumor recurrence after whole-brain radiation therapy and found that the tumor recurred within 2 cm of the original site in 90% and 78% of patients, supporting the use of focal radiation therapy. Multifocal recurrence occurred in 6% of patients in one study and in 5% of patients in a second trial.

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