Epidemiology of Four Major Canine Tumours in the <scp>UK</scp> : Insights From a National Pathology Registry With Comparative Oncology Perspectives

Pet dogs with naturally occurring cancers provide valuable models for comparative oncology and pathology tumour registries offer a powerful resource for onco-epidemiological research. Here, we analysed the Small Animal Veterinary Surveillance Network (SAVSNET) pathology-based tumour registry (PTR), one of the largest veterinary tumour registries to date, focusing on four major canine tumours: mast cell tumour (MCT), osteosarcoma (OSA), haemangiosarcoma (HSA), and melanoma (MEL). A case-control study was conducted using a subset of 130 998 histologically confirmed tumours drawn from the pathology tumour registry containing over 1.1 million canine tumour records from 1.02 million dogs collected in the UK between 2010 and 2023. Case-control analyses were performed for melanoma, haemangiosarcoma, OSA and MCT using a denominator population of dogs attending first-opinion veterinary practices. Additionally for MCT, comparisons were made against dogs diagnosed with other tumour types ('tumour denominator' approach). Breed-specific risks were identified, including high odds ratios (OR) for Bulldog-related breeds and Retrievers with mast cell tumours (MCTs) (OR up to 6.8, 95% CI 6.0, 7.6), Rottweilers, Shar Pei and Giant-Schnauzer with melanoma (OR up to 50.3, 95% CI 24.7, 102.5), and German Shepherd Dogs, Mastiffs, and Bullmastiffs with haemangiosarcoma (OR up to 28.0, 95% CI 10.6, 40.9). Higher-grade MCT were diagnosed at older ages and certain breeds were more predisposed to higher-grade MCT (Shar Pei, Rottweiler) while others were more prone to low-grade MCTs (Boxer, Boston Terrier). Neutered dogs generally had higher tumour odds than entire dogs; for example, in MCTs, female-neutered vs. female-entire showed OR 1.81 (95% CI 1.6, 2.0) in ages 3-6, with similar patterns across older age bands. In general, the difference in OR values between entire and neutered dogs was consistently more pronounced in females than in males. These findings demonstrate the value of the SAVSNET PTR as a comprehensive resource for canine tumour surveillance, with potential to support health initiatives and cancer research by identifying breed-specific and demographic risk factors as well as a foundational tool for comparative cancer epidemiology.