Hypofractionated stereotactic radiosurgery for treatment of cerebral arteriovenous malformations: outcome analysis with use of the modified arteriovenous malformation scoring system

• Variations in dose, staging and fractionation have been attempted to improve outcome in arteriovenous malformation (AVM) radiosurgery.
• A retrospectively acquired series of patients undergoing hypofractionated radiosurgery is presented.
• The modified radiosurgery based AVM scoring system was employed to stratify this cohort.
• Hypofractionated radiosurgery for AVM employing adequate doses can result in high overall obliteration rates with acceptable complication profile.

Radiosurgery has long been an accepted modality for definitive treatment of cerebral arteriovenous malformations (AVM). Efforts to improve the therapeutic ratio for this indication include use of staged volume procedures and hypofractionation. This study reviews our experience with a cohort of patients treated with hypofractionated radiosurgery. Over a 3 year period, 38 patients harboring 39 cerebral AVM were treated with hypofractionated stereotactic radiotherapy. Seventeen of these patients presented due to hemorrhage, four were asymptomatic unruptured lesions and the remainder were symptomatic unruptured lesions. The median AVM volume was 11.43 cc and median modified Radiosurgery-Based Arteriovenous Malformation Score (mRBAS) was 2.02. The median follow-up was 7.32 years. Four patients harboring four AVM were lost to follow-up before a result could be ascertained leaving 35 AVM for analysis. Excellent outcomes (AVM obliteration without new deficits) occurred in 17 of 34 (50%) patients and in 18 of 35 (51%) AVM treated. AVM obliteration was seen in 26 of 35 (74%) lesions treated. Two patients died during the follow-up period (6%). A poor result (major deficit without obliteration) was seen in one patient. Of 19 patients harboring AVM with mRBAS >2.0, an excellent outcome was achieved in eight (42%). Hypofractionation for cerebral AVM can result in satisfactory obliteration rates, but with risk of significant complications commensurate with mRBAS. Further study of this technique will be needed to ascertain the degree of incremental improvement, if any, over other radiosurgery treatment methods.