Prognostic Value of Magnetic Resonance Imaging Defined Extent of Surgical Resection in Dogs With Intracranial Meningiomas.

Surgery is a common treatment for intracranial meningiomas in dogs, although the prognostic impact of the extent of resection (EOR) has not been systematically evaluated. This retrospective study identified prognostic factors associated with clinical outcomes in dogs that underwent surgery and early post-operative magnetic resonance imaging (epoMRI) to evaluate meningioma EOR. We hypothesised that gross total tumour resection (GTR) would result in longer progression free (PFS) and overall survival (OS), and superior post-operative seizure control and resolution of neurological dysfunction than subtotal resection (STR). Multivariable logistic regression was used to identify prognostic factors, and Kaplan-Meier analyses to compare survival outcomes. Forty-one dogs were included of which 24 (59%) had GTR and 17 (41%) had STR. GTR was associated with decreased rates of tumour progression (HR = 0.21; 95% CI, 0.09-0.42; p < 0.0001) and death (HR = 0.49; 95% CI, 0.14-0.69; p < 0.0001), and longer PFS (618 vs. 189 days, p < 0.0001) and OS (694 vs. 349 days, p < 0.0001) compared to STR. Higher tumour grade and increasing age negatively impacted PFS and OS, respectively. Seizure freedom was attained in a larger proportion of dogs with GTR (18/20 [90%]) than STR (4/13 [31%]; p < 0.001), but rates of improvement of neurological deficits were not different between groups. GTR resulted in durable clinical improvements and survivals in the absence of adjuvant treatments. EpoMRI to assess EOR should be routinely incorporated into management of canine meningiomas to inform outcome expectations, and to identify STR cases in which adjuvant therapies should be considered.