Epidemiological analysis of brain tumours in dogs in Australia between 1994 and 2024

Brain tumours are a relatively rare but a clinically important cause of neurological diseases in dogs. This study aimed to estimate the incidence of canine brain tumours in Australia, assess spatio-temporal patterns, explore tumour type-dog breed relationships, evaluate post-diagnosis survival for selected brain tumours, and identify animal-level risk factors. A retrospective cross-sectional analysis was conducted using clinical records from 1994 to 2024 from veterinary clinics participating in the VetCompass Australia (VCA) registry. Records were retrieved using targeted keyword search terms, further processed using an AI-assisted extraction tool, and manually reviewed for accuracy. Of 926 identified cases, 109 (11.8%) were primary tumours, 33 (3.6%) secondary tumours, and 784 (84.7%) were classified as unconfirmed brain tumours. The overall incidence rate was 8.7 (95% CI: 8.2-9.3) cases per 100,000 dog-years at risk. Spatial analysis revealed geographic differences in the incidence rates of primary and secondary brain tumours across Australia, with the highest incidence observed in New South Wales (2.3 cases per 100,000 dog-years). A statistically significant spatial clusters of combined primary and secondary brain tumour cases (RR = 5.8, p = 0.001) was identified in New South Wales. Temporal trend analysis showed a steady increase in the incidence from 2008 to 2015, reaching 3.9 cases per 100,000 dog-years at risk. A hierarchical cluster analysis suggested a grouping of glioma and lymphosarcoma cases with breeds such as French bulldogs and boerboels overrepresented. The median survival time of dogs following diagnosis differed significantly between tumour types (log-rank test, p ≤ 0.001); it was 6.0 and 0.2 months for astrocytoma and glioma, respectively. Advancing age was strongly associated with brain tumour incidence (p ≤ 0.001), and utility breeds had a higher incidence rate than crossbreed dogs (IRR = 3.9; 95% CI: 2.3-6.6, p ≤ 0.001). This study provides the first nationwide description of canine brain tumour incidence, spatio-temporal patterns, risk factors, and survival outcomes in Australia. Future research using VCA data should focus on the development of prognostic models to the improve the understanding of canine brain tumour epidemiology in Australia.