Exploring risk factors linked to canine lymphoma: a case-control study

Environmental factors, largely influenced by human behavior, account for approximately 80 % of malignant tumors. Risk factors associated with non-Hodgkin's lymphoma (NHL) have been identified in various countries among both humans and domestic animals. This study aimed to investigate potential risk factors for NHL in dogs residing in the district of Porto, Portugal. A comprehensive survey comprising 70 questions was undertaken and given to 113 dog owners, including 55 cases and 58 controls. Our findings revealed that dogs weighing over 10 kg (OR=9.1, p < 0.001), purebred dogs (OR=2.4, p = 0.037), those with consuming homemade food (OR=2.7, p = 0.03), and fruits and vegetables (OR=2.8, p = 0.022) exhibited higher odds of developing lymphoma. Notably, dogs with lymphoma were exposed to a significantly higher mean smoking index compared to the control group (13.7, SD=12.5 vs. 8.4, SD=9.3, p < 0.001). These findings suggest that lymphoma risk in dogs seems to be influenced by a combination of innate (genetic) factors and modifiable environmental factors linked to owner habits. Nevertheless, further large-scale epidemiological studies are warranted to validate these results.