Significance of monocyte-to-lymphocyte ratio as a prognostic factor in canine urothelial carcinoma: a retrospective study

Canine urothelial carcinoma (cUC) is an aggressive malignancy, yet clinically accessible and reliable prognostic markers remain limited. While systemic inflammatory responses are increasingly recognized as critical determinants of cancer progression in humans, the prognostic value of white blood cell fractions in cUC remains unexplored. This retrospective cohort study investigated the association between white blood cell fractions and survival in 86 dogs with urothelial carcinoma (cUC) diagnosed at a university-affiliated veterinary hospital between 2017 and 2024. Case assignment, presence of metastases, the extent of urinary tract involvement, treatment specifics, and complete blood count (CBC) data were extracted from electronic medical records. CBC analysis revealed neutropenia in 3 cases, monocytosis in 7 cases, eosinophilia in 4 cases, and lymphopenia in 19 cases. Due to limited case numbers, survival analyses focused on monocytosis and lymphopenia, with calculation of the monocyte-lymphocyte ratio (MLR). Log-rank tests demonstrated significant associations between shortened overall survival and monocytosis, lymphopenia, increased MLR, and metastasis (P=0.0050, P=0.0097, P