Conventional radiation therapy of intracranial arteriovenous malformations: long-term results.

Conventional radiation therapy has been used in the treatment of arteriovenous malformations (AVM's) for many years, but there are limited data pertaining to specific treatment parameters, long-term results, and complications. Between 1955 and 1985, 15 patients with AVM's deemed inoperable or incompletely obliterated using surgical or endovascular techniques were treated at the University of Western Ontario. There were nine males and six females, aged 15 to 48 years (mean 29 years). Presenting symptoms included hemorrhage in nine patients, seizures in four, and focal neurological deficits in two. There were three infratentorial and 12 supratentorial AVM's, ranging in size from 1.5 to 6.5 cm. Therapy prior to irradiation consisted of incomplete surgical removal in four cases and subtotal embolization in four. One patient received 2000 cGy of irradiation, while 4000 to 5000 cGy were delivered in the remaining patients to fields ranging in size from 4 x 4 to 14 x 14 cm in 15 to 28 fractions. The 15 patients have been followed for 1 1/2 to 21 years since undergoing radiotherapy (mean 8.1 years). Angiography in 12 patients at 1 to 21 years following irradiation demonstrated no significant change in seven patients, a slight reduction in AVM size in two, near-complete obliteration in one, and complete obliteration in two. One patient with an AVM measuring 6.5 cm refused angiography but underwent magnetic resonance imaging at 5 years which showed no evidence of residual AVM. There were four hemorrhages in 122 patient-years of follow-up study, indicating a hemorrhage rate of 3.3% per year. The authors conclude that conventional irradiation is successful in obliterating AVM's in only about 20% of cases.