Lifetime Prevalence of Tumors in Companion Dogs Included in the Dog Aging Project Baseline Data

Abstract: Background: Cancer is a leading cause of morbidity and mortality in dogs in the United States, yet its frequency has not been robustly characterized. Most reports about cancer outcomes in dogs comes from populations seen at tertiary care centers. The Dog Aging Project (DAP), a longitudinal study of companion dogs in the US, provides an opportunity for cancer outcomes in dogs to be described more completely and associations between risk factors and outcomes to be investigated.

Objective: To estimate the lifetime prevalence of malignant and non-malignant tumors in companion dogs and investigate associations between dog characteristics and tumor outcomes.

Animals: 27,541 dogs enrolled in the DAP as of December 31, 2020.

Methods: Lifetime prevalence was calculated per 1,000 DAP participants. Crude associations were estimated in relation to the dog’s current age, breed, and size. Age-adjusted prevalence ratios (PRs) and corresponding 95% confidence intervals (CI) were estimated using Poisson regression models.

Results: 1,111 dogs were reported to have a history of malignant (819) or non-malignant (404) tumors. The lifetime prevalences of malignant and benign tumors were 29.7 and 14.7 per 1000 dogs, respectively. Dogs with a history of tumors (malignant or non-malignant) were more likely to be older and larger that the DAP population averages. Age-adjusted lifetime malignancy prevalence ratios increased with increasing dog size.

Conclusions: We observed the lifetime prevalence of malignant tumors to increase with increasing dog size. Ongoing prospective data collection for DAP will permit more nuanced studies of risk factors for canine tumor incidence.