[Radiosurgery of cerebral arteriovenous malformations: a prescription algorithm].
OBJECTIVE
To study prognostic factors of obliteration and risk factors of brain radiation necrosis in order to propose an algorithm for radiosurgery prescription for cerebral arteriovenous malformations (cAVM).


METHODS
One hundred and seventy-nine patients were analysed. Radiosurgery delivered 6 or 10 MV X-rays by arc therapy in 84% of cases, or by fixed field in 16% of cases using two different micro-multileaf collimators (micro-MLC). Follow-up consisted of screening radiation necrosis by MRI every 6 months, and assessing local control by arteriography every 2 years. Obliteration was defined as at least 95% reduction of cAVM volume. Cox proportional hazard model was used to evaluate the local control and the appearance of radiation necrosis over time.


RESULTS
Local control rate was 82.7% with the mean follow-up of 3.1 years (0.5-11). Significant prognostic factors were: simple nidus (RR=2.8, p<0.0001), number of embolizations before radiosurgery below 4 (RR=2.9, p<0.0001), prescribed dose to the periphery of at least 18 Gy (RR=2, p=0.0002), nidus volume below8cm(3) (RR=1.9, p=0.0002), and number of table positions below six (RR=1.4, p=0.05). Radiation necrosis rate was 11.2% with a mean time to onset of 18 months. Significant predictive factors were: fixed field versus arc therapy (according to MLC RR=9.1, p<0.0001, and RR=15.1, p=0.01), age below 30 years (RR=2.5, p=0.04), depth of cAVM greater than or equal to 7 cm (RR=7.6, p=0.008), and volume of brain tissue covered by the 12 Gy isodose (V12 Gy) of at least 11 cm(3) (RR=7.8, p=0.05).


CONCLUSIONS
A radiosurgery prescription algorithm taking into account the prescribed dose to the periphery (> or = 18 Gy) and reduction of V12 Gy was elaborated from these data.
Blanchard
N
N
Département de radiothérapie, centre Alexis-Vautrin, 6, avenue de Bourgogne, 54511 Vandoeuvre-lès-Nancy, France. nblanchard@dijon.fnclcc.fr
Bernier
V
V
Anxionnat
R
R
Picard
L
L
Marchal
C
C
Buchheit
I
I
Metayer
C
C
Desandes
E
E
Peiffert
D
D
D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D000704:Analysis of Variance; D001927:Brain Diseases / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology; D002533:Cerebral Angiography; D016009:Chi-Square Distribution; D002648:Child; D003663:Decision Trees; D019583:Dose Fractionation, Radiation; D005260:Female; D005500:Follow-Up Studies; D005602:France / Q000453:epidemiology; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000150:complications / Q000601:surgery*; D053208:Kaplan-Meier Estimate; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009336:Necrosis; D011237:Predictive Value of Tests; D055656:Prescriptions; D011379:Prognosis; D016016:Proportional Hazards Models; D011832:Radiation Injuries / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D016896:Treatment Outcome