Available online 9 February 2013
Publication year: 2013
Source:World Neurosurgery
Object Gamma Knife radiosurgery (GKRS) is a minimally invasive technique employed in the treatment of intracranial arteriovenous malformations (AVM's). Patients experience a low incidence of complications following treatment. As the long-term follow-up data became available, some late adverse effects have been reported. However, the exact incidence of radiosurgically induced neoplasia is not known. Methods At UVA, imaging and clinical outcomes of 1309 patients with intracranial AVM's treated with GKRS have been reviewed. AVM patients underwent magnetic resonance imaging (MRI's) every 6 months for 2 years and then annually following GKRS. When the nidi were no longer visible on MRI, angiography was performed to verify the obliteration of AVM's. Patients were thereafter recommended to continue MRI's every 3-5 years to detect any long-term complications. A subset of 812, 358, and 78 patients had neuro-imaging and clinical follow-up of at least 3, 10, and 15 years respectively. Results The authors report the occurrence of 3 cases of radiosurgically induced neoplasia. More than 10 years after GKRS, 2 patients were found to have an incidental, uniformly enhancing, dural based mass lesion near the site of the AVM with radiological characteristics of a meningioma. As the lesions have shown no evidence of mass effect, they are being followed with serial neuro-imaging. A third patient was found to have neurological decline from a tumor in immediate proximity to an AVM previously treated with proton beam radiosurgery and GKRS. The patient underwent resection demonstrating a high grade glioma. The 3, 10, and 15-year incidence of a radiation-induced tumor is 0% (0/812), 0.3% (1/358), and 2.6% (2/78) respectively. The cumulative rate of radiosurgically induced tumors in those with a minimum of 10 year follow up is 3 in 4692 person-years or 64 in 100,000 person-years. Thus, patients had a 0.64% chance of developing a radiation induced tumor within 10 or more years following GKRS. If we calculate rates based on a subset of 78 patients with neuro-imaging and clinical follow-up of at least 15 years, the cumulative rate was 3.4%. These are the 2nd, 3rd, and 5th reported cases of radiation induced tumors following GKRS for an AVM. Conclusions Although radiosurgery is generally considered a safe modality in the treatment of AVM's, radiation induced neoplasia is a rare but serious adverse event. The possibility of GKRS induced tumors underscores the necessity of long-term follow-up in AVM patients receiving radiosurgery.
Júlio Leonardo B. Pereira
Phone: (+1) 424-2301706
Linkedin:http://www.linkedin.com/in/juliommais
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