A quantitative analysis of adverse radiation effects following Gamma Knife radiosurgery for arteriovenous malformations

Abstract

OBJECT The authors review outcomes following Gamma Knife radiosurgery (GKRS) of cerebral arteriovenous malformations (AVMs) and their correlation to postradiosurgery adverse radiation effects (AREs). METHODS From a prospective institutional review board–approved database, the authors identified patients with a minimum of 2 years of follow-up and thin-slice T2-weighted MRI sequences for volumetric analysis. A total of 105 AVM patients were included. The authors analyzed the incidence and quantitative changes in AREs as a function of time after GKRS. Statistical analysis was performed to identify factors related to ARE development and changes in the ARE index. RESULTS The median clinical follow-up was 53.8 months (range 24–212.4 months), and the median MRI follow-up was 36.8 months (range 24–212.4 months). 47.6% of patients had an AVM with a Spetzler-Martin grade ≥ III. The median administered margin and maximum doses were 22 and 40 Gy, respectively. The overall obliteration rate was 70.5%. Of patients who showed complete obliteration, 74.4% developed AREs within 4–6 months after GKRS. Late-onset AREs (i.e., > 12 months) correlated to a failure to obliterate the nidus. 58.1% of patients who developed appreciable AREs (defined as ARE index > 8) proceeded to have a complete nidus obliteration. Appreciable AREs were found to be influenced by AVM nidus volume > 3 ml, lobar location, number of draining veins and feeding arteries, prior embolization, and higher margin dose. On the other hand, a minimum ARE index > 8 predicted obliteration (p = 0.043). CONCLUSIONS ARE development after radiosurgery follows a temporal pattern peaking at 7–12 months after stereotactic radiosurgery. The ARE index serves as an important adjunct tool in patient follow-up and outcome prediction.

Early versus late arteriovenous malformation responders after stereotactic radiosurgery: an international multicenter study

“…Radiationinduced changes typically develop 12-18 months post-SRS and, unless symptomatic or permanent, bear little clinical significance except to herald future obliteration. 1 A higher margin dose was previously reported to be a key predictor of obliteration, 1,3,6,10,22,30,38 which was not demonstrated in this cohort. In the present report of AVM patients, all of whom had obliteration, we found that those who received a margin dose > 24 Gy responded sooner.…”

“…Arteriovenous malformations continue to represent a significant clinical challenge, and expert opinions differ regarding their optimal management. 1 Treatment goals can vary among patients: reducing seizure activity, ameliorating symptomatic chronic "vascular steal," or alleviating neurological deficits caused by associated cerebral edema. However, the main goal of any intervention for AVMs remains complete obliteration of the nidus, thereby eliminating subsequent risk of hemorrhage.…”

“…26,38 Obliteration rates are reported to vary between 70% and 80% 13,18 and are associated with a relatively low risk profile for adverse radiation effects. 1,20 An initial radiological response to SRS is often observed within the first 6-18 months. 15,21,35 Patients who demonstrated such a response may be called "early responders," whereas documented obliteration may not occur for up to 5 years (late responders) in other AVM patients.…”

Results of volume-staged fractionated Gamma Knife radiosurgery for large complex arteriovenous malformations: obliteration rates and clinical outcomes of an evolving treatment paradigm

“…Adverse radiation effects have been associated with a large nidus and a higher margin dose, among other factors. 5,14 Historically, the volume-staging strategy emerged to enable the administration of a higher global dose to a large volume while maintaining a low rate of adverse effects. 23 With the exception of Dalyai et al 6 , we administered a higher margin dose than the vast majority of reported series for volumestaged fractionation of large cerebral AVMs (20 Gy at the 50% isodose), and we used a longer time interval between stages.…”

A Methodology for Systematic Volumetric Analysis of Perioperative Cranial Imaging in Neurosurgical Patients

“…This poses a significant challenge in image registration for open craniotomies. However, once resolved, this methodology will provide an objective means of comparing parameters can affect how physicians utilize stereotactic radiosurgery in treatment of brain tumors, 87,88 arterio-venous malformations, 89 and cavernous malformations 90 by augmenting current understanding of treatment related MR changes.…”