International Journal of Radiation Oncology*Biology*Physics
Original ContributionsFive year results of linac radiosurgery for arteriovenous malformations: outcome for large AVMS
Introduction
Stereotactic radiosurgery is an effective and safe treatment for small intracranial arteriovenous malformations (AVMs). Most series in the radiosurgery literature have median AVM volumes between 1–4 cc (equivalent diameter 1–2 cm) with the majority of volumes treated being smaller than 14 cc (equivalent diameter < 3 cm). For these small AVMs, 2–3 year obliteration rates between 72–96% have been reported with associated complication rates between 1–10% 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20. There is only limited data for larger AVMs, and the results are conflicting with reported obliteration rates varying between 0–75% and complication rates varying between 3–50% 1, 3, 4, 7, 9, 10, 15, 18, 19, 20, 21, 22, 23, 24. For large AVMs, the optimal dose-volume relationship remains poorly defined as does the ideal integration of staged procedures, embolization, surgery, and re-irradiation 21, 23, 25, 26. The following report is a retrospective study of factors affecting the long-term outcome of LINAC radiosurgery for patients with AVMs larger than previously published in the literature. Over 50% of the AVMs were larger than 3 cm in diameter, and the median and mean treatment volumes were 8.4 cc and 15.3 cc, respectively.
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Patients
Between March 1988 and September 1991, 73 consecutive patients with intracranial AVMs underwent LINAC radiosurgery at the University of California at San Francisco (UCSF). Table 1 summarizes their clinical characteristics. Forty-six patients (63%) had a prior history of hemorrhage from their AVMs including 13 who had suffered multiple hemorrhages (range 0–4). Fifty-six patients (77%) had a history of focal neurologic symptoms, and 41 (56%) had a focal neurologic deficit at the time of
Follow-up
Six years after the last patient was treated, 46 patients (63%) reached one of the following endpoints (Fig. 1, Fig. 2 ) : 18 (25%) had AVM obliteration documented by angiography; 10 (14%) had AVM obliteration documented by MRI/MRA with angiographic confirmation either pending or refused; 7 (10%) were retreated with radiosurgery; 2 (3%) underwent surgery; 5 (7%) died of an intracranial hemorrhage; 1 (1%) died of treatment related complications; 3 (4%) died of intercurrent disease. The
Discussion
The AVMs treated in this study were significantly larger than those in other series in the literature. Over 50% were larger than 3 cm in diameter, and the median and mean treatment volumes were 8.4 cc and 15.3 cc, respectively. Furthermore, the volumes reported represent post-embolization volumes and do not reflect the large initial volumes prior to down-staging with embolization 21, 23, 36. Fifty-nine percent underwent prior embolization, a rate much higher than the 1–39% reported in other
Conclusions
With radiosurgery, successful outcomes are possible for patients with large AVMs otherwise not amenable to definitive therapy. However, effective and safe treatment requires the appropriate selection of patients, accurate imaging and definition of the AVM nidus, optimal planning and treatment techniques, proper selection of dose, and careful follow-up. As AVM size increases, the dose-volume range for optimal balance between successful obliteration and the risk of complications and
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