STEREOTACTIC VOLUME MODULATED ARC RADIOTHERAPY PROTOCOL FOR CANINE INTRACRANIAL MENINGIOMA.

Objective: to assess High Dose Hypofractionated Volume Modulated Arc Radiotherapy (HDH-VMAT) feasibility and clinical efficacy in canine meningiomas. Design: a prospective study was conducted on thirty-three patients with a presumptive diagnosis of encephalic meningiomas assumed from Magnetic Resonance Imaging (MRI) findings. Methods: all dogs, whose neurological status was scored through the use of an innovative evaluation scale (Romanengo Veterinary Neurological Scale ? RVNS), received HDH-VMAT by a Linear Accelerator (LINAC) equipped with an external beam modulator micro-multileaf collimator and an XVI Cone Beam Computed Tomography system (CBCT). The prescribed mean dose was 33 Gy delivered in 5 fractions. The treatment feasibility was tested through planned and delivered dose agreement checks. Regular clinical examinations were performed during and after irradiation time with regard to mentation, deambulation, cranial nerve dysfunction and seizures. Serial MRI exams were done 60 days after irradiation and after 4, 6, 12, 18, 24 months. Volumetric disease reduction criteria implemented with clinical neurological systematic evaluation were adopted to assess the course and to categorize patients? response. Results: complete and partial responses were observed on the whole in 65,5% of alive patients 24 months after irradiation. Two-year overall and disease-specific survival rates were 74.3% and 97.4%, respectively, and the putative radiotoxic effects were found to be few and slight. Conclusions: HDH-VMAT is a valid therapeutic option for encephalic canine meningioma. Volumetric MRI evaluation together with the hereby proposed RVNS should be considered for the evaluation of the post-treatment response