Analysis of the obliteration rate after stereotactic radiotherapy using different radiation dose schedules in intracranial arteriovenous malformation

Stereotactic radiotherapy (SRT) is one of the treatment modalities for intracranial arteriovenous malformation (AVM). However, no standardized recommendation existed regarding the SRT dose schedule. The purpose of this research is to evaluate the outcomes of different SRT regimens implemented at our center. This retrospective study reviewed patient data from 2014 to 2021, comparing two SRT schedules: 36 Gy in 6 fractions on every other day (group 1) and 28 Gy in 4 consecutive daily fractions (group 2). Obliteration rates at 3 years were analyzed using the Mann–Whitney U test, while Fisher's exact test assessed incidence of radiation necrosis. Prognostic factors influencing obliteration were evaluated using Cox proportional hazards regression. A total of 60 patients were included in the analysis. Forty-three patients received treatment group 1 while the remaining 17 patients received treatment group 2. The 3-year complete obliteration rates were comparable between both treatment groups (51.16 % vs. 52.94 %, p = 0.736). The median time to complete obliteration was significantly shorter in treatment group 2 (28.7 months vs 13.7 months, p = 0.046). Age <18 years was a significant predictor of complete obliteration. Asymptomatic radiation necrosis occurred in 4 out of 17 patients in treatment group 2 without requiring steroid administration. The results of this analysis suggest that the median time to complete obliteration for SRT 28 Gy in 4 fractions was considerably shorter than that for 36 Gy in 6 fractions; however, the obliteration rate at 3 years did not differ significantly.