Glioblastoma multiforme after stereotactic radiotherapy for acoustic neuroma: case report and review of the literature

Abstract

Indications for the use of radiotherapy in the management of a variety of benign intracranial neoplastic and nonneoplastic pathologies are increasing. Although the short-term risks are minimal, the long-term risks of radiation-induced de novo secondary neoplasms or malignant progression of the primary benign tumor need to be considered. There are currently 19 reported cases of tumors linked with stereotactic radiotherapy/radiosurgery, to which we add our second institutional experience of a patient who succumbed to a glioblastoma multiforme (GBM) after stereotactic radiotherapy for an acoustic neuroma (AN). Review of these 20 cases revealed 10 de novo secondary tumors, of which eight were malignant, with six being malignant gliomas. The majority of the cases (14 of 20) involved AN, with most being in patients with neurofibromatosis-2 (NF2; 8 of 14), reflecting the large numbers and long-term use of radiotherapy for AN. Accelerated growth of the primary benign AN, some 2 to 6 years after focused radiotherapy, was found in six of eight NF2 patients, with pathological verification of a malignant nerve sheath tumor documented in most. The exact carcinogenic risk after radiotherapy is unknown but likely extremely low. However, the risk is not zero and requires discussion with the patient, with specific consideration in young patients and those with a cancer predisposition.

Figures

Fig. 1

(A) Hematoxylin and eosin (H/E) and S100 immunohistochemistry demonstrated classical features of benign schwannoma at initial translabyrinthine resection. A small amount of tumor was left carpeted on the seventh cranial nerve. (B) Two years after translabyrinthine resection: axial T2- and fluid-attenuated inversion recovery–weighted images demonstrated an approximately 1.8-cm recurrent right acoustic neuroma (white arrow). There were no T2 or T1 abnormalities in the adjacent right temporal lobe.

Fig. 2

(A) Nine years after translabyrinthine resection (5 years after stereotactic radiotherapy [SRT]): T2 and T1 gadolinium-enhanced axial MR images demonstrated the unchanged recurrent, approximately 1.8-cm acoustic neuroma (white arrowhead). However, there was a new right temporal ring-enhancing lesion (*) with perilesional edema (T1 plus gadolinium [gad] and fluid-attenuated inversion recovery (Flair)–weighted axial and coronal MR images). (B) Hematoxylin and eosin and glial fibrillary acidic protein (GFAP) immunohistochemistry of right temporal lesion, demonstrating features of a glioblastoma multiforme (GBM). (C) Fusion of SRT isodose curves to T1 gadolinium-enhanced coronal MR image of the de novo GBM, approximately 5 years after SRT. GBM volume, 4.82 cm3; minimum dose, 145 cGy; maximum dose, 694 cGy; mean dose, 446 cGy.