Risk Analysis of LINAC Radiosurgery in Patients with Arteriovenous Malformation (AVM)
The purposes of this analysis were the evaluation of the toxicity of stereotactic single dose irradiation in patients with an arteriovenous malformation (AVM) and the comparison of the authors’ own results with already existing risk prediction models. Com
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Risk Analysis of LINAC Radiosurgery in Patients with Arteriovenous Malformation (AVM) J. Voges!, H. Treuer!, R. Lehrke!, M. Kocher 2 , S. Staar 2 , R.-P. Miiller 2 , and V. Sturm 1 1 Departments of Stereotactic and Functional Neurosurgery and 2Radiation Oncology, The University of Cologne, Federal Republic of Germany
Summary The purposes of this analysis were the evaluation of the toxicity of stereotactic single dose irradiation in patients with an arteriovenous malformation (AVM) and the comparison of the authors' own results with already existing risk prediction models. Computed-tomography (CT) or magnetic-resonance (MR) images, and clinical data of patients treated with linear accelerator radiosurgery for an A VM were analysed retrospectively. Using the Cox proportional hazards model (I), the relevance of treatment parameters and dose-volume relationships to the occurrence of radiation-induced tissue changes (oedema and localised blood-brain-barrier breakdown) were assessed. The 81 patients selected for analysis had a mean follow-up of 28.9 months (range: 9.0-65.7 months). Radiation-induced tissue changes (22 out of 81 i.e. 27.2%) were documented on CT or MR images 6.3-33.8 months after radiosurgery (median time: 12.8 months). The actuarial risk at 2 years was 32.1 % for the development of neuroradiological changes and 20.1% for the development of symptomatic tissue alteration. The coefficient of total volume receiving a minimum dose of 10 Gy (VTREATlO) reached statistical significance in a Cox proportional hazards model. These results demonstrate the particular vulnerability of normal brain tissue to single dose irradiation. Optimal conformation of the therapeutic isodose line to the 3D configuration of the target volume may help to reduce side effects. Keywords: Radiosurgery; LINAC; risk prediction; arteriovenous malformation.
However, little is known about the particular risks of single dose irradiation in patients suffering from an AVM. The main purpose of this analysis is the definition of risk factors and the comparison of the authors' results with already existing risk prediction models.
Patients
Eighty-one patients treated between June 1990 and August 1995 at the University of Cologne for an AVM with stereotactic single dose irradiation using a modified linear accelerator (UNAC) were selected for retrospective analysis of risk factors. The following selection criteria were applied: (a) Follow-up times of at least 9 months (end of follow-up; June 1996). (b) Availability of complete treatment data. (c) Follow-up information including the results of neurological and neuroradiological examinations (computed tomography (CT) and/or magnetic resonance imaging (MRI». Patients with perilesional oedema on preoperative CT or MR images were excluded.
Introduction
Radiosurgery performed either with a modified linear accelerator or with the gamma knife is an attractive tool in the treatment of cerebral arteriovenous malformations. In recent years, a growing number of neurosurgical and radiation oncology centres h
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