Stereotactic radiosurgery in treating arteriovenous malformations of the brain

Findings by SBU Alert  

Version: 1

Technology and target group

Stereotactic radiosurgery (SRS) involves the very precise delivery of ionizing radiation to a well-defined target volume. One of several applications of SRS concerns the treatment of arteriovenous malformations (AVM) in the brain. AVM is a disorder characterized by a complex, tangled web of thin walled blood vessels. AVMs are present at birth and may vary in size and localization. Approximately 120 patients with AVM are treated annually in Sweden. If a sufficiently high dose of radiation is delivered to the entire web of vessels it affects the vessel walls to the extent that blood flow ceases, the vessels are obliterated, and the otherwise imminent risk for hemorrhaging can be avoided. In SRS planning and treatment, the patient is placed in a stereotactic frame and treatment is delivered using one of the following devices; (1) gamma knife (GK), (2) cyclotron, or (3) linear accelerator (LINAC). The GK is viewed as a practical method to achieve a safe treatment of smaller AVMs. With larger AVMs, a LINAC or a proton beam from a cyclotron may deliver a more even distribution of the radiation dose to the web of vessels.

Patient benefit

No randomized controlled trials have been performed. A Swedish followup of over 800 patients shows that the percentage of successful treatments with a GK ranges between 60% and 84%, depending on size and localization of the AVM and the dose delivered. The best results are achieved in small AVMs where it is usually possible to deliver a sufficient dose to the entire web of vessels without risk for damaging the surrounding normal brain tissue. The reported total obliteration frequency is somewhat less with proton and LINAC SRSs, which may be explained by the fact that these methods are applied in a higher percentage of larger AVMs which are more difficult to treat. Up to 10% of the patients experience temporary neurological problems after SRS. The rate of serious complications with permanent neurological loss is estimated to be about 4%.

Scientific evidence

There is poor* scientific documentation of the relative benefits, risks, and side effects concerning SRS treatment of AVMs. There is no* scientific documentation concerning the cost-effectiveness of the method. It is essential that the medical outcome and costs associated with treating AVM are followed up and assessed in a uniform manner. Furthermore, prospective treatment studies should be carried out in collaboration with centers in several countries to more quickly assemble a sufficiently large patient base.

*This assessment by SBU Alert uses a 4-point scale to grade the quality and evidence of the scientific documentation. The grades indicate: (1) good, (2) moderate, (3) poor, or (4) no scientific evidence on the subject.

This summary is based on a report prepared at SBU in collaboration with Assoc. Prof. Sten Graffman, MD PhD, Lund University Hospital and has been reviewed by Prof. Luigi Pellettieri, MD PhD, Sahlgrenska University Hospital.

The full report is available only in Swedish.

Alert is a joint effort by the Swedish Council on Technology Assessment in Health Care (SBU), the Medical Products Agency, the National Board of Health and Welfare, and the Federation of Swedish County Councils.

References

1. Engenhart R, Wowra B, Debus J, Kimmig B, Höver KH, Lorenz W, Wannenmacher M. The role of high dose, single-fraction irradiation in small and large intracranial arteriovenous malformations. Int J Rad Oncol Biol Phys 1994; 30:521-29.
2. Karlsson B, Lax I, Söderman M. Can the probability for obliteration after radiosurgery for arteriovenous malformations be accurately predicted? Int J Rad Oncol Biol Phys 1999; 43:313-19.
3. Kjellberg R, Hananmura T, Davis K, Lyons S, Butler W, Adamo R. Bragg-peak proton beam therapy for arteriovenous malformations of the brain. N Eng J Med 1983; 309:269-73.
4. Schneider W, Hailey D. Stereotactic radiosurgery: Options for Albertans. Alberta Heritage Foundation for Medical Research. Edmonton, March 1998.
5. Wigg D. A radiobiological basis for the treatment of arteriovenous malformations. Acta Radiol suppl 14, 1999; 38:3-29.
6. Wikholm G, Lundqvist C, Svendsen P. Transarterial embolization of cerebral arteriovenous malformations: Improvement with experience. Am J Neuroradiol 1995; 16:1811-17.