Treatment of Recurrent Malignant Gliomas With Stereotactic Intensity Modulated Radiation Therapy

Abstract

Malignant gliomas are usually refractory to aggressive combined-modality therapy, and the incidence of recurrence and death after treatment is very high. State-of-the-art techniques such as stereotactic intensity-modulated radiation therapy (IMRT) are now available to deliver a high dose of radiation to the tumor with relative preservation of surrounding tissues to achieve optimal tumor coverage with minimal toxicity. We report 10 patients (median age 48 years) with recurrent malignant gliomas that were treated with stereotactic directed IMRT. Initial tumor histologies included one low grade glioma (upgraded to anaplastic astrocytoma at recurrence), four anaplastic astrocytomas, and four glioblastomas multiforme. One patient was originally presumed to have a brain metastasis secondary to renal cell carcinoma but was pathologically confirmed as having glioblastoma multiforme at the time of recurrence. Before recurrence, all patients had been treated with external beam radiation therapy (median 59.7 Gy). All recurrences were confirmed by a subtotal resection (5/10) or by imaging (5/10). The median Karnofsky performance score at the time of IMRT was 80. The median tumor volume was 34.69 cm. Treatment was delivered on a 10-MV linear accelerator with a mini-multileaf collimator, MIMiC, and planned with Peacock/Corvus software. Radiation was delivered in daily fractions of 5 Gy, to a total median dose of 30 Gy at the 71% to 93% median isodose line. Median overall survival time was 10.1 months from the date of stereotactic treatment, with 1- and 2-year survival rates of 50% and 33.3%, respectively. Fractionated stereotactic intensity modulated radiation therapy is a novel technique used in the treatment of recurrent malignant gliomas, which produces results comparable to other currently used stereotactic techniques.

Hypofractionated reirradiation for recurrent malignant glioma

“…Conventionally fractionated total doses of 36 Gy up to 46 Gy were resulting in overall survival rates of 8 and 6.1 months, respectively [8,41]. Two groups report on an overall survival of 8-10 months with a total dose of 30 Gy using a hypofractionated schedule with a single dose of 5 Gy [42,43]. An association of longer overall survival times with prior reresection as described before [4] was not seen in our series.…”

“…Comparison of overall survival and toxicity of the chosen treatment with results of different approaches using external-beam radiotherapy for reirradiation reported over the last years [1,4,8,9,11,22,25,35,36,[41][42][43] certainly remains difficult because of the variation in target definition, treatment technique, tumor volume, concomitant chemotherapy, and initial patient characteristics. However, considering the large median PTV of 50 ml and the high number of glioblastoma included, this is comparable to the earlier results.…”

Prolonged survival when temozolomide is added to accelerated radiotherapy for glioblastoma multiforme

“…Re-irradiation was performed with a total dose of 30 Gy in six fractions, and we previously reported overall survival of 7.9 months after re-irradiation with this fractionation schedule [28]. Similar favorable results of fractionated stereotactic re-irradiation are documented in the literature [3,4,8,29]. More recent studies reported the integration of modern targeted chemotherapy into stereotactic re-irradiation and preliminary results are encouraging [10,17,25].…”

Chemoradiotherapy: Radiation Total Dose and Fractionation

“…Therefore, IMRT has been investigated in small series of patients [ 131 ], and no dose limiting toxicity was observed at 35 Gy in 10 fractions after previous 60 Gy [ 109 ] and a good tolerance has been reported with 6 × 5 Gy [ 131 ].…”