Proposal for a new prognostic score for linac-based radiosurgery in cerebral arteriovenous malformations.
OBJECTIVE
We evaluate patient-, angioma-, and treatment-specific factors for successful obliteration of cerebral arteriovenous malformations (AVM) to develop a new appropriate score to predict patient outcome after linac-based radiosurgery (RS).


METHODS
This analysis in based on 293 patients with cerebral AVM. Mean age at treatment was 38.8 years (4-73 years). AVM classification according Spetzler-Martin was 55 patients Grade I (20.5%), 114 Grade II (42.5%), 79 Grade III (29.5%), 19 Grade IV (7.1%), and 1 Grade V (0.4%). Median maximum AVM diameter was 3.0 cm (range, 0.3-10 cm). Median dose prescribed to the 80% isodose was 18 Gy (range, 12-22 Gy). Eighty-five patients (29.1%) had prior partial embolization; 141 patients (51.9%) experienced intracranial hemorrhage before RS. Median follow-up was 4.2 years.


RESULTS
Age at treatment, maximum diameter, nidus volume, and applied dose were significant factors for successful obliteration. Under presumption of proportional hazard in the dose range between 12 and 22 Gy/80% isodose, an increase of obliteration rate of approximately 25% per Gy was seen. On the basis of multivariate analysis, a prediction score was calculated including AVM maximum diameter and age at treatment. The prediction error up to the time point 8 years was 0.173 for the Heidelberg score compared with the Kaplan-Meier value of 0.192. An increase of the score of 1 point results in a decrease of obliteration chance by a factor of 0.447.


CONCLUSIONS
The proposed score is linac-based radiosurgery-specific and easy to handle to predict patient outcome. Further validation on an independent patient cohort is necessary.
Department of Radio-oncology and Radiotherapy, University of Heidelberg, Heidelberg, Germany. Stefanie_Milker-Zabel@med.uni-heidelberg.de
Stefanie
S
Milker-Zabel
Annette
A
Kopp-Schneider
Hannah
H
Wiesbauer
Wolfgang
W
Schlegel
Peter
P
Huber
Jürgen
J
Debus
Angelika
A
Zabel-du Bois
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000145:classification / Q000150:complications / Q000000981:diagnostic imaging / Q000601:surgery*; D020300:Intracranial Hemorrhages / Q000453:epidemiology / Q000209:etiology; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011379:Prognosis; D011859:Radiography; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods* / Q000592:standards; D011879:Radiotherapy Dosage; D012016:Reference Values; D016896:Treatment Outcome; D055815:Young Adult