Stereotactic radiosurgery for arteriovenous malformations, Part 6: multistaged volumetric management of large arteriovenous malformations

Abstract

Object The object of this study was to define the long-term outcomes and risks of arteriovenous malformation (AVM) management using 2 or more stages of stereotactic radiosurgery (SRS) for symptomatic large-volume lesions unsuitable for surgery. Methods In 1992, the authors prospectively began to stage the treatment of anatomical components to deliver higher single doses to AVMs with a volume of more than 10 cm3. Forty-seven patients with such AVMs underwent volume-staged SRS. In this series, 18 patients (38%) had a prior hemorrhage and 21 patients (45%) underwent prior embolization. The median interval between the first-stage SRS and the second-stage SRS was 4.9 months (range 2.8–13.8 months). The median target volume was 11.5 cm3 (range 4.0–26 cm3) in the first-stage SRS and 9.5 cm3 in the second-stage SRS. The median margin dose was 16 Gy (range 13–18 Gy) for both stages. Results In 17 patients, AVM obliteration was confirmed after 2–4 SRS procedures at a median follow-up of 87 months (range 0.4–209 months). Five patients had near-total obliteration (volume reduction > 75% but residual AVM). The actuarial rates of total obliteration after 2-stage SRS were 7%, 20%, 28%, and 36% at 3, 4, 5, and 10 years, respectively. The 5-year total obliteration rate after the initial staged volumetric SRS with a margin dose of 17 Gy or more was 62% (p = 0.001). Sixteen patients underwent additional SRS at a median interval of 61 months (range 33–113 months) after the initial 2-stage SRS. The overall rates of total obliteration after staged and repeat SRS were 18%, 45%, and 56% at 5, 7, and 10 years, respectively. Ten patients sustained hemorrhage after staged SRS, and 5 of these patients died. Three of 16 patients who underwent repeat SRS sustained hemorrhage after the procedure and died. Based on Kaplan-Meier analysis (excluding the second hemorrhage in the patient who had 2 hemorrhages), the cumulative rates of AVM hemorrhage after SRS were 4.3%, 8.6%, 13.5%, and 36.0% at 1, 2, 5, and 10 years, respectively. This corresponded to annual hemorrhage risks of 4.3%, 2.3%, and 5.6% for Years 0–1, 1–5, and 5–10 after SRS. Multiple hemorrhages before SRS correlated with a significantly higher risk of hemorrhage after SRS. Symptomatic adverse radiation effects were detected in 13% of patients, but no patient died as a result of an adverse radiation effect. Delayed cyst formation did not occur in any patient after SRS. Conclusions Prospective volume-staged SRS for large AVMs unsuitable for surgery has potential benefit but often requires more than 2 procedures to complete the obliteration process. To have a reasonable chance of benefit, the minimum margin dose should be 17 Gy or greater, depending on the AVM location. In the future, prospective volume-staged SRS followed by embolization (to reduce flow, obliterate fistulas, and occlude associated aneurysms) may improve obliteration results and further reduce the risk of hemorrhage after SRS.

Volume-staged radiosurgery for large arteriovenous malformations: an evolving paradigm

“…13 The overall obliteration rate in their study was 23% for initial VS-SRS with 7% and 28% probabilities of obliteration at 3 and 5 years. Among patients treated with ≥ 17 Gy, however, the rate of obliteration including salvage therapy improved to 62% at 5 years.…”

“…In 2004 we prospectively changed the overall treatment paradigm, as a dose-response relationship and predictors of complications became established. 5,6,13 We shifted to using smaller treatment volumes per stage, shorter intervals between stages, and higher radiation doses per stage. The current review includes all 69 patients with large AVMs who planned to undergo VS-SRS in the period from 1992 to 2008 and compares the outcomes from 2 treatment eras.…”

Stereotactic radiosurgery of intracranial arteriovenous malformations and the use of the K index in determining treatment dose

“…[7][8][9][10][11][12] It is characterized by high obliteration rates, especially in small lesions, and low risk of adverse effects and complications. In the present retrospective study, we were not able to demonstrate an association of the optimal K index dose with improved obliteration rates, in comparison with smaller doses.…”

“…Stereotactic radiosurgery has gained popularity in recent years. 1,2,4,5,[7][8][9][10][11][12]21 Its effect on the obliteration of AVMs is gradual, with patients remaining at risk for hemorrhage during this latency period. Complete obliteration, after a single session, has been reported to vary between 60% and 80% over 5 years.…”

Editorial

“…In this 6-part series, the group from the University of Pittsburgh provides us with an update of their experience with radiosurgical treatment of AVMs in different situations. [1][2][3][4][5][6] How can we incorporate the information provided into our management of these challenging lesions?…”