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.