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1. Linear accelerator-based radiosurgery alone resulted in the durable obliteration of AVMs smaller than 4cm3.
2. The rates of post-treatment bleeding and radiation injury were low and comparable or superior to other modalities of treating AVMs in the literature.
Evidence rating: 2 (Good)
Study Rundown: Intracranial arteriovenous malformations (AVMs) are vascular dyscrasias that may rupture and bleed. Some AVMs that are located in eloquent cerebral territories, or are embedded in deep regions of the brain, are not amenable to conventional neurosurgical approaches. It has been previously shown that stereotactic radiosurgery (SRS) in these instances provide an effective alternative. However, because the natural time course of effect for SRS is long, little is known about the long term efficacy and safety of this modality of treating AVMs. In this study, 51 patients with AVMs were treated with linear accelerator-based SRS and followed closely for a median of more than 15 years—longer than any other study available. Overall, obliteration of the AVM nidus occurred in 72% of cases. 19 patients had incomplete obliteration after 3 years, of which 8 underwent re-irradiation. Post treatment bleeding occurred in 7 cases (13.7%), 5 of whom had bleeding prior to SRS. Radiation injury occurred in 9 patients, 6 of which was successfully reversed with therapy. 3 patients whose AVMs were in the basal ganglia experienced some persistent symptoms of radiation injury. In multivariate analysis, positive outcomes for SRS only was associated with lesions <4cm3, modified AVM scores <1.5, and ability to deliver >12 Gy irradiation. This study is limited in its observational nature.
Click to read the study in International Journal of Radiation Oncology
Relevant reading: Stereotactic radiosurgery for intracranial arteriovenous malformations using a standard linear accelerator
In Depth [observational study]: In this long term observational study, 51 patients with AVMs that were not amenable to conventional surgical intervention were treated with LINAC-based SRS. The median nidus volume was 4.57cm3, with 35 lesions occurring in cereberal hemispheres. Patients were followed up every 4 months with contrast MRI and MR angiography to confirm AVM obliteration and detect adverse sequelae of therapy. Median follow up was 15.6 years (range 12.5-20.5yrs). Obliteration was achieved after single SRS treatment in 72% of cases overall, and 46.9%, 54.0%, 64.4%, and 68% of patients after 3, 5, 10, and 15 years, respectively. Posttreatment bleeding occurred in 5 cases within 1 year, 1 case after 5 years, and 1 case after 11 years. 6 patients developed symptomatic radiation injury within 2 years of treatment and 3 patients developed symptoms after 10 years. Factors that were positively correlated with obliteration was target volume >4cm3 (p=0.001), treatment dose >12Gy (P=0.041), and modified AVM score >1.5 (P=0.006). Correlations were made using univariate and multivariate logistic regressions.
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