How to improve obliteration rates during volume-staged stereotactic radiosurgery for large arteriovenous malformations

Abstract

OBJECTIVE The management of large-volume arteriovenous malformations (AVMs) with stereotactic radiosurgery (SRS) remains challenging. The authors retrospectively tested the hypothesis that AVM obliteration rates can be improved by increasing the percentage volume of an AVM that receives a minimal threshold dose of radiation. METHODS In 1992, the authors prospectively began to stage anatomical components in order to deliver higher single doses to AVMs > 15 cm in volume. Since that time 60 patients with large AVMs have undergone volume-staged SRS (VS-SRS). The median interval between the first stage and the second stage was 4.5 months (2.8-13.8 months). The median target volume was 11.6 cm (range 4.3-26 cm) in the first-stage SRS and 10.6 cm (range 2.8-33.7 cm) in the second-stage SRS. The median margin dose was 16 Gy (range 13-18 Gy) for both SRS stages. RESULTS AVM obliteration after the initial two staged volumetric SRS treatments was confirmed by MRI alone in 4 patients and by angiography in 11 patients at a median follow-up of 82 months (range 0.4-206 months) after VS-SRS. The post-VS-SRS obliteration rates on angiography were 4% at 3 years, 13% at 4 years, 23% at 5 years, and 27% at 10 years. In multivariate analysis, only ≥ 20-Gy volume coverage was significantly associated with higher total obliteration rates confirmed by angiography. When the margin dose is ≥ 17 Gy and the 20-Gy SRS volume included ≥ 63% of the total target volume, the angiographically confirmed obliteration rates increased to 61% at 5 years and 70% at 10 years. CONCLUSIONS The outcomes of prospective VS-SRS for large AVMs can be improved by prescribing an AVM margin dose of ≥ 17 Gy and adding additional isocenters so that ≥ 63% of the internal AVM dose receives more than 20 Gy.

Optimizing stereotactic radiosurgery in patients with recurrent or residual craniopharyngiomas

“…This nding parallels the report of Kano et al who demonstrated that AVM obliteration results can be improved signi cantly when at least 63% of the AVM receives a dose >20 Gy; this also con rmed that margin dose critical predictor of successful obliteration. (23) Using the Gamma knife, we can increase the percent volume receiving higher dose by adding low weighted isocenters within the target volume while not changing the prescription margin dose or conformity. (23) Adverse radiation effect In a previous large SRS craniopharyngioma series, the rate of visual eld deterioration without tumor progression was 0-2.2% (4,5,7).…”

“…(23) Using the Gamma knife, we can increase the percent volume receiving higher dose by adding low weighted isocenters within the target volume while not changing the prescription margin dose or conformity. (23) Adverse radiation effect In a previous large SRS craniopharyngioma series, the rate of visual eld deterioration without tumor progression was 0-2.2% (4,5,7). In the present study, a single patient had visual eld deterioration unrelated to tumor progression.…”

Chinese Cerebrovascular Neurosurgery Society and Chinese Interventional & Hybrid Operation Society, of Chinese Stroke Association Clinical Practice Guidelines for Management of Brain Arteriovenous Malformations in Eloquent Areas

“…Optimization of radiosurgical planning is important to improve the total obliteration rate while maintaining reasonable safety. For example, A recent study proposed that in addition to keeping a minimal margin dose of 17 Gy, increasing the percentage of the bAVM volume that receives at least 20 Gy treated in two stages could improve the outcome for large-volume bAVMs ( 302 ). What is more, a novel deep learning-based method to automatically segment the bAVM volume may be helpful for radiosurgical planning ( 303 ).…”

One-Day Two-Fraction Radiosurgery for Brain Metastases Using Gamma Knife

“…Some reports noted a correlation between post-treatment brain radiation injury and the volume that received a specific dose, including surrounding structures other than the treated volume. Kano et al reported a correlation of 12 Gy-volume (the volume of tissue, including target, receiving >12 Gy) during GKRS for brain arteriovenous malformation (AVM) [24]. Korytko et al also reported a correlation of 12 Gy Volume and post-radiosurgical radionecrosis on imaging during GKRS for non-AVM intracranial tumors, including brain metastasis cases (53.5%= 92 / 198 cases) [25].…”