CLINICAL INVESTIGATION Central Nervous System VOLUMETRIC MODULATED ARC–BASED HYPOFRACTIONATED STEREOTACTIC RADIOTHERAPY FOR THE TREATMENT OF SELECTED INTRACRANIAL ARTERIOVENOUS MALFORMATIONS: DOSIMETRIC REPORTAND EARLY CLINICAL EXPERIENCE SAI SUBRAMANIAN, M.SC.,* CHILUKURI SRINIVAS, M.D.,* K. RAMALINGAM, M.SC.,* M. BABAIAH, M.D.,* S. THIRUMALAI SWAMY , M.SC.,* G. ARUN, M.SC.,* M. KATHIRVEL, M.SC.,* S. ASHOK, M.SC.,* ALESSANDRO CLIVIO, M.SC., y ANTONELLA FOGLIATA, M.SC., y GIORGIA NICOLINI, M.SC., y K. SRINIVASA RAO, M.D.,* T. PRATAP REDDY , M.D.,* JOTWANI AMIT , M.D.,* EUGENIO V ANETTI, M.SC., y AND LUCA COZZI,PH.D. y *Yashoda Super Specialty Hospital, Hyderabad, India; and y Oncology Institute of Southern Switzerland, Bellinzona, Switzerland Purpose: To evaluate, with a dosimetric and clinical feasibility study, RapidArc (a volumetric modulated arc tech- nique) for hypofractionated stereotactic radiotherapy treatment of large arteriovenous malformations (AVMs). Methods and Materials: Nine patients were subject to multimodality imaging (magnetic resonance, computed to- mography, and digital subtraction angiography) to determine nidus and target volumes, as well as involved organs at risk (optical structures, inner ear, brain stem). Plans for multiple intensity-modulated arcs with a single isocen- ter were optimized for a fractionation of 25 Gy in 5 fractions. All plans were optimized for 6-MV photon beams. Dose–volume histograms were analyzed to assess plan quality. Delivery parameters were reported to appraise technical features of RapidArc, and pretreatment quality assurance measurements were carried out to report on quality of delivery. Results: Average size of AVM nidus was 26.2 cm 3 , and RapidArc plans provided complete target coverage with minimal overdosage (V 100% = 100% and V 110% < 1%) and excellent homogeneity (<6%). Organs at risk were highly spared. The D 1% to chiasm, eyes, lenses, optic nerves, and brainstem (mean ± SD) was 6.4 ± 8.3, 1.9 ± 3.8, 2.3 ± 2.2, 0.7 ± 0.9, 4.4 ± 7.2, 12.2 ± 9.6 Gy, respectively. Conformity index (CI 95% ) was 2.2 ± 0.1. The number of monitor units per gray was 277 ± 45, total beam-on time was 2.5 ± 0.3 min. Planning vs. delivery g pass rate was 98.3% ± 0.9%. None of the patients developed acute toxicity. With a median follow-up of 9 months, 3 patients pre- sented with deterioration of symptoms and were found to have postradiation changes but responded symptomat- ically to steroids. These patients continue to do well on follow-up. One patient developed headache and seizures, which was attributed to intracranial bleed, confirmed on imaging. Conclusion: Hypofractionated stereotactic radiotherapy can be successfully delivered using the RapidArc form of volumetric arc technology for intracranial AVMs. The quality of delivery and calculated parameters are in agree- ment with each other and are in line with published reports for other sites. Ó 2012 Elsevier Inc. Arterovenous malformation, RapidArc, Volumetric modulated arc therapy, Stereotactic radiotherapy. INTRODUCTION Single-fraction stereotactic radiosurgery has been an accept- able treatment for intracranial arteriovenous malformations (AVMs) (1–8). The aim of treatment is to achieve complete obliteration while limiting postradiosurgery sequelae to a minimum. Success of the treatment depends on appropriate patient selection and the marginal dose delivered. However, in large AVMs and in AVMs located in eloquent areas like the sensorimotor cortex, visual cortex, internal capsule, deep cerebellar nuclei, brainstem, thalamus, and hypothalamus, the probability of long-term sequelae is high. Flickinger et al. (9) developed a model to predict postradiosurgery symptomatic sequelae on the basis of location and volume of brain receiving medium–high dose levels (9). Because in such AVMs surgery is not feasible and neuro- radiologic interventions are singularly not effective, Reprint requests to: Antonella Fogliata, M.Sc., Oncology Insti- tute of Southern Switzerland, Radiation Oncology Department, Medical Physics Unit, 6504 Bellinzona, Switzerland. Tel: (+41) 91-8119202; Fax: (+41) 91-8118678; E-mail: antonella.fogliata- cozzi@eoc.ch Conflict of interest: L.C. acts as Scientific Advisor to Varian Medical Systems and is Head of Research and Technological De- velopment at the Oncology Institute of Southern Switzerland, Bel- linzona. Received Oct 13, 2010, and in revised form Jan 26, 2011. Accepted for publication Feb 3, 2011. 1278 Int. J. Radiation Oncology Biol. Phys., Vol. 82, No. 3, pp. 1278–1284, 2012 Copyright Ó 2012 Elsevier Inc. Printed in the USA. All rights reserved 0360-3016/$ - see front matter doi:10.1016/j.ijrobp.2011.02.005