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SHAPED BEAM RADIOSURGERY (SRS) FOR INTRACRANIAL AVMS - REPORT OF EXPERIENCE IN A SINGLE CENTRE

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SHAPED BEAM RADIOSURGERY (SRS) FOR INTRACRANIAL AVMS - REPORT OF EXPERIENCE IN A SINGLE CENTRE
Narayanamurthy H, Whitfield P.
South West Stereotactic Radiosurgery Unit, Plymouth, UK.

Context:

•UK tertiary neurosurgical unit (population of over 1.2 million)
•Radiosurgery service managed by 2 neurosurgeons, 2 oncologists, 1 neuroradiologist, 1 physicist and specialist radiographers.

AVM treatment protocol:

•SRS Treatment in Plymouth started in 2005, LINAC + M3 collimator used initially, Novalis Tx used since January 2014.
•Flowchart used for treatment:

Statistics:

•Total number of patients treated at Plymouth SRS centre: 744
•Total number of AVM patients treated: 49 (+ 4 to be treated yet)
•Females: 25  Males: 28, Mean age: 46.6yrs
•Patients presenting with:
•Bleed: 56.6% (n = 30)
•Seizures: 22.6% (n = 12)
•AVM as an incidental finding/ with non-specific symptoms: 20.7% (n = 11)
•Spetzler-Martin Grades and mean Pollock-Flickinger scores:
•1 – 11.3% (n = 6) with mean PF score 1.266
•2 – 54.7% (n = 29) with mean PF score 1.295
•3 – 28.3% (n = 15) with mean PF score 1.621
•4 – 5.7% (n = 3) with mean PF score 2.596
•Mean volume of AVM treated – 3.71c.c.
•Predominantly in eloquent cortex (42) and had mainly superficial venous drainage (37)
•7 patients had associated aneurysms (5 ipsilateral and 1 contralateral, 1 possible).
•4 patients had pre – SRS embolisation of their aneurysms.
 

Treatment:

•46 patients received radiosurgery (SRS)
•3 were given hypofractionated radiotherapy (SRT) (volumes were 10.41c.c, 12.86c.c and 37.71c.c)
•Frame based (n = 43) and frameless (n = 6) localisation
•Isocentre dose ranged from 20.51Gy to 25Gy for SRS
•Dose to encompassing isodose was 18 – 20Gy
•During SRT, encompassing isodoses were 4.5 – 5.4 Gy in 8 – 11 fractions

Results:

•Of the 36 angiograms performed, 89% (32 ) showed complete obliteration in 24 – 48months (mean of 31.3 months).
•5.5% (2) showed complete obliteration on a DSA performed at 66 and 67 months.
•This includes 1 patient who needed re-treatment and 4 who showed a persistent draining vein but no early venous filling.
•5.5% (2) have shown a persistent nidus and are planned for re-treatment
•The persistent nidus, in both cases, is smaller compared to the lesion before the first treatment.
 

Complications:

•42 patients have been reviewed, 7 are awaiting clinical review.
•9.5% (4) patients developed motor deficits – hemiparesis. 1 was transient, 1 was steroid responsive. 1 patient had mild hemiparesis. 1 had a permanent right hemiparesis which did improve from its initial status.
•4.75% (2) patients had seizures, 1 early onset, 1 at 3 months post-treatment.
•No patients had a re-bleed
•35% (15) patients showed a high signal (oedema) on check MRIs
•23.8% (10) patients needed steroid treatment for their symptoms – 3 motor deficits, 2 seizures, 1 brief quadrantanopia and 4 headaches + lethargy
 

Conclusions:

•LINAC-delivered SRS is an effective treatment for intracranial AVMs.
•Hypofractionated SRT is an effective treatment option in the management of large AVMs. 
•Continued follow-up with MRI and angiography will provide confidence in treatment efficacy and high quality data for analysis.
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