Incidence and risk factors for feline lymphoma in UK primary-care practice

Objectives: The study aimed to estimate the incidence and prevalence of feline lymphoma in cats attending primary-care practices across the UK and to identify patient-based and environmental (radon and pesticide exposure) risk factors.

Materials and methods: Case records from the VetCompass programme from primary-care veterinary practices in the UK were searched for a diagnosis of lymphoma in cats in 2016. Cases were required to have had an external laboratory confirmed diagnosis based on cytology and/or histopathology. A nested case-control study design was used to identify risk factors for lymphoma using multivariable logistic regression.

Results: From a cohort of 562,446 cats under veterinary care at VetCompass participating practices in 2016, a total of 271 lymphoma cases were identified (prevalence: 48/100,000, 95% confidence interval (CI) 44 to 56/100,000; incidence 32/100,000, 95% CI 26 to 35/100,000). There were 180 incident lymphoma cases and 803 controls, all aged 2 years and older. Male (odds ratio (OR) 1.7, 95% CI 1.2 to 2.4), insured (OR 3.6, 95% CI 2.3 to 5.6) and older cats (compared to cats 2 to <5 years, OR 5.0, 95% CI 2.8 to 8.8) were associated with increased odds of lymphoma diagnosis. Vaccinated cats were associated with decreased odds (OR 0.7, 95% CI 0.5 to 1.0) compared to unvaccinated cats, although the type of vaccination received was not statistically significant. Breed and environmental factors studied were not associated with a diagnosis of lymphoma.

Clinical significance: This is the first study to estimate the frequency and report risk factors for lymphoma in cats attending UK primary-care practice.