Demographics of Feline Lymphoma in Australian Cat Populations: 1705 Cases

Lymphoma is the most common haematopoietic cancer in cats with few large studies evaluating breed and sex as risk factors for the disease. Australia's geographic isolation and quarantine rules have led to a potentially restricted genetic pool and, currently, there have not been any large local epidemiological studies reported. A total of 1705 lymphoma cases were identified from several sources and compared to a reference population of 85,741 cats, and represent cats that are presented to veterinary clinics. Odds ratios were calculated for each breed that included lymphoma cases, as well as sex, retroviral status, and immunophenotype. The distributions of age and weight in the lymphoma and control populations and proportions of lymphoma cases in anatomic locations were compared. Eight breeds were identified as displaying increased potential risk of lymphoma and three at decreased risk. Male cats were found to be at increased risk (OR 1.2, 95%CI: 1.1 to 1.3, <i>p</i> = 0.002). The lymphoma cases were older, with a median age of 11.7 years compared to 9.0 years (<i>p</i> < 0.0001), and weighed less, with a median weight of 3.7 kg compared to 4.0 kg (<i>p</i> = 0.010), than the control population. Several breeds were found to have significant variations in the proportions of anatomical presentations including the Siamese, Burmilla, Australian mist, ragdoll, British shorthair, and domestic cats. These findings require confirmation in future studies that address the limitations of this study, as outlined in the discussion.