Treatment results of radiosurgery for cerebral arteriovenous malformations in the modern APS era

Keywords: arteriovenous malformation, radiosurgery, gamma knife, robotics, outcome

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     AVM radiosurgery techniques have evolved over time.
The authors sought to assess the efficacy and safety of gamma knife radiosurgery (GKRS) with meticulously-planned conformal coverage using multiple small isocenters in 47 patients with cerebral arteriovenous malformations (AVMs) treated by GammaKnife Type C between 2005 and 2008.
     The mean volume of AVMs was 4.3 ml (range, 0.04-27.4). Eight patients had AVM nidus larger than 10ml. Dose planning was primarily based on MR angiography and was confirmed on digital subtraction angiography (DSA). The mean marginal dose was 21.3 Gy (range, 16.7-25). Total number of isocenters used in irradiation ranged from 2 to 76 (mean 27, median 27). In the follow-up period, MR images were taken every six months, and DSA was performed to confirm nidus obliteration at 3 years or earlier after GKRS.
      Outcomes such as the rates of obliteration, hemorrhage after treatment, and adverse radiation effects were analysed.
     All the 46 patients were followed up for longer than 3 years. Thirty-seven of them underwent DSA and thirty-five (94.6%) showed complete obliteration. In Kaplan-Meier analysis, the complete obliteration rate at 36 months was 97.8% for AVMs with a volume of less than 10 ml. The margin dose was the single factor associated with higher obliteration rate (p=0.022). Moderate to extensive radiation-induced edema was revealed on MR images in 21.3% (10 of 47). The number of total isocenters was the single significant factor associated with development of radiation-induced edema (p=0.03). Ten of 47 (21.3%) developed new or worsened neurologic symptom and three (6.4%) persisted. Six patients (12.8%) suffered hemorrhage from their AVMs after GKRS; two died of the hemorrhage and one became severely disabled. Among the eight patients with AVMs larger than 10 ml, five (62.5%) suffered hemorrhage.
     This was a retrospective study.
     Meticulous conformal coverage using multiple small isocenters contributed to higher obliteration rates at earlier stage after GKRS than previously reported, but does not lead to decrease in complication, and might be associated with higher bleeding rate with larger AVMs during the latency period.
     Modern gamma knife techniques may lead to better outcomes.


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