Hypofractionated conformal stereotactic radiotherapy for arteriovenous malformations

Arteriovenous malformations (AVMs) are congenital vascular lesions that are associated with high morbidity and mortality if left untreated. There are several options for treatment, including radiotherapy. Safe and effective single-fraction radiotherapy for patients with large AVMs has been considered difficult. Between December 1986 and June 2001, 36 patients with cerebral AVMs were treated with hypofractionated conformal stereotactic radiotherapy at Umeå University Hospital. Twenty-nine patients have been followed angiographically to date and are reported in this study. Twenty-four (83%) of 29 patients (mean AVM volume, 11.5 cm(3)) underwent complete obliteration of their AVMs. The rates of angiographically verified total obliteration at 2 years after treatment were 56% for AVMs 4 to 10 cm(3) and 50% for AVMs larger than 10 cm(3). The obliteration rate increased considerably with extended follow-up. Five years after treatment, the obliteration rates were 81% for AVMs 4 to 10 cm(3) and 70% for AVMs larger than 10 cm(3). Hypofractionated conformal stereotactic radiotherapy may be an important alternative to single-fraction radiotherapy in patients with large AVMs or AVMs located in eloquent areas, because it allows the administration of a higher radiation dose than is possible to deliver in single-fraction radiosurgery. With our technique of hypofractionated conformal stereotactic radiotherapy, the rate of obliterating AVMs was comparable to that of single-dose radiosurgery, although the volumes of the irradiated AVMs in our study were larger than those reported previously.