Treatment of MRI‐Diagnosed Trigeminal Peripheral Nerve Sheath Tumors by Stereotactic Radiotherapy in Dogs

Abstract

BackgroundStereotactic radiotherapy (SRT) is an emerging technique for treating tumors in animals.ObjectivesTo assess the outcome of dogs with suspected intracranial trigeminal nerve peripheral nerve sheath tumors (PNST) treated with SRT.AnimalsEight dogs with presumptive PNST.MethodsThis was a retrospective study of dogs identified by searching UC Davis Veterinary Medical Teaching Hospital medical records for dogs treated with SRT for a presumed PNST. Presumptive diagnosis was based on magnetic resonance imaging. SRT was delivered in 3 dose fractions of 8 Gray (Gy) on consecutive days or every other day to a total dose of 24 Gy.ResultsMedian disease‐specific survival was 745 days (range: 99–1375 days, n = 6). No signs of acute adverse effects of radiation treatment were recorded. Late radiation effects versus tumor progression could not be confirmed histopathologically because of few animals undergoing necropsy.Conclusions and Clinical ImportanceThis study provides preliminary evidence that dogs with PNST benefit from SRT in terms of long‐term survival. The treatment appears to be well tolerated and requires fewer anesthetic events for animals compared to full‐course radiation.

Clinical and imaging findings, treatments, and outcomes in 27 dogs with imaging diagnosed trigeminal nerve sheath tumors: A multi‐center study

“…In this study, all dogs with trigeminal nerve sheath tumors had intracranial extension of bulky tumor at the level of the trigeminal ganglion and the most commonly affected portion of the fifth cranial nerve was the mandibular branch, with up to 81% of dogs having more than one branch affected. Clinical signs in this population were similar to a previous report and survival times were within the range of previous reports (324–881 days) . In this study, stereotactic radiation therapy appeared to have benefitted most of the dogs presenting with intracranial signs referable to trigeminal nerve sheath tumor, but did not yield improved ocular health or contribute to resolution of masticatory muscle atrophy in the majority of affected dogs.…”

“…Magnetic resonance imaging (MRI) is an established imaging modality upon which a presumptive diagnosis of trigeminal nerve sheath tumor can be made . Previously reported are outcomes of dogs with no treatment, surgical removal, and more recently, stereotactic radiotherapy or radiosurgery . Untreated dogs with presumptively diagnosed trigeminal nerve sheath tumors have been reported to have a median survival time of 12 months; whereas two dogs treated with surgery survived 4 and 27 months, respectively .…”

“…Untreated dogs with presumptively diagnosed trigeminal nerve sheath tumors have been reported to have a median survival time of 12 months; whereas two dogs treated with surgery survived 4 and 27 months, respectively . The published median survival time after stereotactic radiation therapy has been reported to range from 324 to 881 days . However, the clinical behavior of trigeminal nerve sheath tumors and comparative benefits provided by these various treatments remain incompletely defined.…”

High dose hypofractionated frameless volumetric modulated arc radiotherapy is a feasible method for treating canine trigeminal nerve sheath tumors

“…This finding is consistent with those reported by Hansen et al. where one dog had bulla effusion before treatment, and two more dogs developed it after treatment . The absence of clinical symptoms related to the middle and inner ear suggests that this condition could be an incidental finding, as well as being features of subclinical ear inflammation, possibly correlating either with the tumor or radiation exposure.…”

“…The planning target volume was obtained with an isotropic expansion of 2 mm margin around the clinical target volume to account for uncertainties of positioning . Relevant organs at risk were contoured including the brain, brainstem, cerebellum, eyes, inner ears, and laryngopharynx . The prescribed dose to the planning target volume was 37 Gy delivered in five fractions on alternate days.…”