Treatment Outcomes and Tolerability of Postoperative Radiotherapy in 10 Dogs with Spinal Meningiomas

Canine meningioma is the most common intradural extramedullary and primary spinal cord tumor. Previous studies suggest that postoperative radiation therapy can be effective for spinal meningiomas. Information on radiation-induced complications and prognosis remains limited. This case series evaluated treatment outcomes of surgical and radiation therapy in dogs with spinal meningiomas. Ten dogs were included. All underwent surgery, and histopathological examination confirmed meningioma. Among the four cases where surgical margins were assessed, three had incomplete resections. Postoperative radiation therapy was administered as an adjuvant treatment in nine dogs. One dog that did not receive postoperative radiation underwent radiation upon recurrence, observed at 99 days postsurgery. The radiation protocol consisted of fractionated irradiation (32-55 Gy/12-21 fractions) delivered five times per week. During the observation period, nine of 10 dogs died, with a median survival time of 568 days (range: 165-1823 days). Local recurrence occurred in six dogs at 95, 99, 153, 367, 433, and 1086 days postoperatively, confirmed by magnetic resonance imaging. Among 10 dogs receiving radiation, one experienced worsening limb paralysis on day 1679, suspected as a radiation-induced complication. No clinically evident acute or late radiation-induced side effects were noted in the medical records of the remaining cases.