Demographic risk factors for lymphoma in Australian dogs: 6201 cases

Abstract

BackgroundLymphoma is common in the dog. Studies of population risk factors primarily have been derived from referral institution or insurance data.ObjectiveTo identify and quantify the host risk factors for lymphoma in a broad population of Australian dogs.AnimalsData on 6201 client owned dogs were retrieved from a commercial veterinary laboratory, a general practice group and 2 referral hospitals.MethodsData collected included breed, sex, and neuter status. A reference population of 640 105 dogs was generated from the referral hospitals and from council registration data. The risk of lymphoma by sex and neuter status was calculated as odds ratios (OR).ResultsThe study identified 30 breeds at increased risk of lymphoma, 15 that have not been reported previously, and 26 breeds at decreased risk, 18 that have not been reported previously. Males were over represented compared to females with an OR of 1.1 (95% CI, 1.1–1.2; P < .001). Neutered animals were at higher risk compared to intact animals with an OR of 3.2 (95% CI, 2.9–3.5) which was found in both males (OR, 2.8; 95% CI; 2.5–3.2) and females (OR, 4.4; 95% CI, 3.5–5.1).Conclusions and Clinical ImportanceBreed, sex, and neuter status alter the risk of lymphoma in dogs. These 3 factors must be considered when evaluating lymphoma risk as potential markers of underlying differences in disease etiology. Comparison of breeds at increased and decreased risk could be advantageous when evaluating specific etiological factors.

Lymphoma in Australian Border Collies: survey results and pedigree analyses

“…Female dogs had twice the odds of being reported as affected by lymphoma than male dogs in this study, which was in contrast to previous findings across multiple breeds that females, 25 and particularly intact females, had a decreased risk 21 , although there may be some breed variation for sex predisposition. 25 Furthermore, the common practice of desexing in Australia most likely explains the small number of entire dogs in this study, making interpretation of this information difficult. In people, being female and the use of hormone therapy with oestrogen and/or progestin have been associated with a decreased risk of non-Hodgkin's lymphoma, 45,46 although another study did not show the same relationship.…”

“…The analyses performed provided evidence that there is familial clustering in affected ABCs, consistent with conclusions from epidemiological studies that a genetic predisposition for canine lymphoma is present in ABCs. 22,25 The mean age of diagnosis in this study was 9 years and was comparable to that of previous non-breed-specific studies, which reported a mean range of diagnosis from 6.7 to 8.3 years. 13,19,20,40,41 The peak age for developing lymphoma in this study was 7-11 years, which is consistent with previous reports.…”

“…The survey identified the largest group of lymphoma‐affected ABCs with accompanying pedigree data that has been reported to date. The analyses performed provided evidence that there is familial clustering in affected ABCs, consistent with conclusions from epidemiological studies that a genetic predisposition for canine lymphoma is present in ABCs …”

“…Our recent study of the demographics of more than 6000 dogs with lymphoma in Australia demonstrated an increased breed risk (odds ratio (OR) = 1.8; 95% confidence interval (CI) 1.6-2.0) in Border Collies compared with the general population. 25 However, in that study pedigree information was not available for individually affected dogs, preventing a more detailed investigation of any potential genetic aetiology. Collection and analysis of pedigree data has the potential to identify modes of inheritance and carriers of disease in a population.…”

“…Previous studies have identified breeds with a consistent increased risk of lymphoma despite different geographic locations, 13,[19][20][21][22][23][24] but reported at-risk breeds may also vary between geographic regions. 19,21,25 Although this may be explained by breed popularity or environmental factors in different regions, selective breeding based on genetically restricted subpopulations will also contribute.…”