Treatment outcome of single or hypofractionated single-isocentric stereotactic irradiation (STI) using a linear accelerator for intracranial arteriovenous malformation

Background and purpose: We investigated the use of hypofractionated stereotactic radiotherapy (HFSR) to reduce adverse radiation effects in comparison to single-fraction stereotactic radiosurgery (SRS) for intracranial arteriovenous malformations (AVMs). Materials and methods: This study includes 53 intracranial AVMs treated between 1991-1998. HFSR was selected for 26 AVMs with a maximum diameter greater than or equal to2.5 cm or at eloquent area. Twenty-seven patients were treated with SRS (18 AVMs <2.5 cm at non-eloquent area, nine patients who were unlit for prolonged ring-wearing). The most frequent minimum dose (Dmin) was 20 Gy for SRS and 28 Gy for HFSR in four fractions. The mean follow-up duration was 34.6 months for SRS and 35.4 months for HFSR. Results: As a whole, the 3 and 5-year actuarial obliteration rates were 64 and 92%. Age <20 years old (P = 0.02) and a maximum diameter <2 cm were favorable factors (P = 0.05). A difference in the distribution of patients was observed in size (<greater than or equal to>2.5 cm or not) (P < 0.001) and location (eloquent or not) (P < 0.001) between SRS and HFSR due to the treatment selection. However, no significant differences were observed in the actuarial rates or obliteration and transient increased signals with T2-weighted MR images between SRS and HFSR. Radiation necrosis occurred in two patients treated with SRS and in none with HFSR. Intracranial hemorrhage after treatment happened in two treated with SRS and three with HFSR. Conclusions: HFSR appears to be at least us effective as SRS in achieving complete obliteration of intracranial AVM, although its definitive role remains to be investigated. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.