Abstract: Background – Radiotherapy and surgery are both options for treating intracranial meningioma but their comparative effectiveness is unknown. A randomized controlled trial for this question is not currently practical. Hypothesis/Objectives – To compare survival following treatment of suspected intracranial meningioma by surgery or radiotherapy. Animals – 285 companion dogs with suspected intracranial meningiomas presenting to 9 specialty clinics in 3 different countries. Methods – Parallel cohort comparison study on retrospective data. Dogs diagnosed with intracranial meningioma by board-certified veterinary neurologists or radiologists and treated by radiotherapy or surgery were identified through medical record searches and presenting and survival data extracted. Lesion site was classified as rostro- or caudotentorial and size was measured on contrast MR images. Outcome was determined by all-cause death. Analysis of survival by Cox proportional hazards, including selection for optimal multivariable model using lasso, and counterfactual modelling including variables associated with treatment allocation and survival. Results – 168 dogs received radiotherapy and 117 dogs received surgery. All analyses indicated reduced survival associated with surgery compared to radiotherapy. Surgery was associated with univariable hazard ratio of 1.802 (95%CI:1.357–2.394), multivariable hazard ratio 1.755 (95%CI: 1.315-2.343) compared with radiotherapy. Counterfactual modeling estimated a mean survival with radiotherapy of 673 days, and reduction of this survival by a mean of 194 days associated with surgery, representing a decrease in survival of 29%. Location and size of the suspected meningioma were not associated with survival duration. Conclusions and clinical importance – Dogs with suspected intracranial meningioma have substantially superior survival after radiotherapy compared to surgery.
