Epidemiology and risk factors for mammary tumours in female cats.

Objectives: This study aimed to estimate the incidence and risk factors for mammary tumours in female cats attending UK primary-care practices. The study hypothesised that middle-aged, intact and certain breeds are associated with increased mammary tumour risk.

Materials And Methods: A case-control study design identified mammary tumour cases by assessment of electronic patient records, nested within a denominator population of 259,869 female cats attending 886 primary-care VetCompass participating veterinary practices in the UK in 2016.

Results: From 2858 potential mammary tumour cases identified within the denominator, 270 cats met the case definition, giving an incidence risk of 104 per 100,000 (0.104%, 95% confidence interval 0.092 to 0.117%) during 2016. In the risk factor analysis increasing age, purebred compared to crossbred and veterinary group were associated with increased odds of mammary tumour. Median survival after the diagnosis of mammary tumour cats was 18.7 months.

Clinical Significance: The current study provides an updated estimate of the incidence of mammary cancer in cats seen in primary care veterinary practice in the UK with increasing risk seen in older cats and with purebred status. This study can aid veterinary surgeons to identify cats at greater risk of mammary tumour and advise on survival after diagnosis.