Re-Evaluation of the Size Limitation in Single-Session Stereotactic Radiosurgery for Brain Arteriovenous Malformations: Detailed Analyses on the Outcomes with Focusing on Radiosurgical Doses.

Abstract

Single-session stereotactic radiosurgery (SRS) for large arteriovenous malformations (AVMs) ≥10 mL remains controversial, which is considered as the current size limitation. To reconsider the size limitation of SRS for AVMs by profoundly analyzing dose-volume relationship. Data on 610 consecutive patients with AVM treated with SRS using regular (18-22 Gy) or low (<18 Gy) prescription doses were retrospectively analyzed. AVMs were classified into 4 groups: small (<5 mL), medium (≥5 and <10 mL), medium-large (≥10 and <15 mL), and large (≥15 mL). The maximum volumes were 22.5 mL (regular-dose group) and 23.5 mL (low-dose group). When treated with regular doses, the cumulative 6-yr obliteration rates for each of the 4 AVM groups were 86%, 80%, 87%, and 79%, respectively; the cumulative 10-yr significant neurological event (SNE) rates were 2.6%, 3.9%, 6.8%, and 5.3%, respectively. Regarding large AVMs, regular-dose SRS resulted in marginally better obliteration rate (6-yr cumulative rate, 79% vs 48%, P=.111) and significantly lower SNE (5-yr cumulative rate, 5% vs 31%, P=.038) and post-SRS hemorrhage rate (8-yr cumulative rate, 0% vs 54%, P=.002) compared to low-dose SRS. Multivariate analyses revealed that regular-dose SRS significantly contributed to increase in the obliteration rate and decrease in SNEs and hemorrhage. The outcomes for large AVMs were generally favorable when treated with ablative doses. Single-session SRS could be acceptable for AVMs up to ≈20 mL if treated with ablative doses.