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Table of Contents    
NI FEATURE: THE EDITORIAL DEBATE I-- PROS AND CONS
Year : 2017  |  Volume : 65  |  Issue : 4  |  Page : 699-700

Dose fractionated gamma knife radiosurgery for large arteriovenous malformations: A word of caution


Department of Neurological Surgery, Center of Image-Guided Neurosurgery, The University of Pittsburgh, Pittsburgh PA, USA

Date of Web Publication5-Jul-2017

Correspondence Address:
L Dade Lunsford
Department of Neurological Surgery, The University of Pittsburgh, Pittsburgh PA
USA
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/neuroindia.NI_525_17

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How to cite this article:
Lunsford L D. Dose fractionated gamma knife radiosurgery for large arteriovenous malformations: A word of caution. Neurol India 2017;65:699-700

How to cite this URL:
Lunsford L D. Dose fractionated gamma knife radiosurgery for large arteriovenous malformations: A word of caution. Neurol India [serial online] 2017 [cited 2019 May 24];65:699-700. Available from: http://www.neurologyindia.com/text.asp?2017/65/4/699/209526




The optimal management for large volume symptomatic arteriovenous malformations (AVMs) continues to be a challenging issue for both surgeons and patients. Radiosurgery has proven to be an often successful and cost effective method to obliterate AVMs, thereby reducing the subsequent bleed risk as well as providing symptomatic improvement in patients with seizures and headache.[1],[2] In a single stereotactic radiosurgery (SRS) session, AVMs treated with a single marginal dose of 20-22 Gy, feasible for AVMs generally smaller than 7 cc and those without angiopathic perinidal vascular changes (in short, a discrete nidus), can expect obliteration rates in 3-5 years approaching 90%. However, targeting with high conformality and selectivity are also important to reduce the risks of adverse radiation events (well demonstrated by the volume of brain plus lesion that receives 12 Gy). Standard fractionated radiation therapy for AVMS (e.g., 1.8 -2Gy for 30 or so fractions) has had no benefit in terms of obliteration and has had significant delayed adverse risks We have reported volume staging of larger AVMs (>10 cc as we prefer in Pittsburgh). Others have preferred dose staging, currently the in-vogue term being hypofractionation. The present report adds experience in 14 patients, of whom 7 had a follow-up, and of those, 3 had angiographic obliteration. The protocol varied over the course of time between 2 and 3 fractions with various inter- fraction intervals. Much is made of trying to define a method of dose selection using formulae derived from the Linear Quadratic method. As the authors point out, this approach is basically “a shot in the dark,” as the numbers to put into the calculation are basically unverified and untestable.[3]

AVMS are basically a constituent of the normal tissue of the brain. The concept of alpha beta ratios, variations of which can lead to remarkably different suggestions of biologically equivalent doses, is largely 'pseudoscience'. The authors describe a number of patients with temporary adverse radiation effects and the frequent need for weeks of corticosteroid use for headache. The evolution of these reactive early treatment complications requires additional experience and a longer follow-up.

It is surprising that the authors discontinued further staged SRS procedures in patients without a prior hemorrhage. The ARUBA (a randomized trial of unruptured brain arteriovenous malformations) study has been largely discredited because of major center selection bias and the primary use of invasive management options such as embolization and surgery, both of which have high initial complication rates. The ARUBA follow-up was less than 3 years in patients with a life -long complication risk from AVMs left untreated. We recently reported that gamma knife radiosurgery has a much more favorable result with the same outcome variable as was used in the ARUBA trial: Stroke or death of the patient during the observation interval.[4],[5]

We hope that the authors will proceed cautiously and stick to a single treatment paradigm as they evaluate the risks and benefits of dose staging for large volume AVMS.



 
  References Top

1.
Lunsford LD, Kondziolka D, Flickinger JC, Bissonette DJ, Jungreis CA, Maitz AH, et al. Stereotactic radiosurgery for arteriovenous malformations of the brain. J Neurosurg 1991; 75:512-4.  Back to cited text no. 1
[PUBMED]    
2.
Moorthy RK, Rajshekhar V. Stereotactic radiosurgery for intracranial arteriovenous malformations: A review. Neurol India 2015;63:841-51.  Back to cited text no. 2
[PUBMED]  [Full text]  
3.
Mukherjee KK, Kumar N, Tripathi M, Oinam AS, Ahuja CK, Dhandapani S, et al. Dose fractionated gamma knife radiosurgery for large arteriovenous malformations on daily or alternate day schedule outside the linear quadratic model: Proof of concept and early results. A substitute to volume fractionation. Neurol India 2017;65:826-35.  Back to cited text no. 3
  [Full text]  
4.
Starke RM, Kano H, Ding D, Lee JY, Mathieu D, Whitesell J, et al. Stereotactic radiosurgery for cerebral arteriovenous malformations: Evaluation of long-term outcomes in a multicenter cohort. J Neurosurg 2017;126:36-44.  Back to cited text no. 4
[PUBMED]    
5.
Ding D, Starke RM, Kano H, Lee JY, Mathieu D, Pierce J, et al. Stereotactic radiosurgery for Spetzler-Martin Grade III arteriovenous malformations: An international multicenter study. J Neurosurg 2017;126:859-71.  Back to cited text no. 5
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