Survival of dogs with melanoma from a referral veterinary hospital in Japan

Abstract

Canine melanoma is a malignant cancer affecting dogs, especially in the oral cavity, digits, and skin. This study investigated survival outcomes in 123 dogs diagnosed with melanoma at a veterinary teaching hospital in Japan between April 1, 2004, and March 31, 2023. Data were retrospectively obtained from electronic clinical records, with survival analysis performed using Kaplan-Meier curves, log-rank tests, and parametric survival models. The median survival time (MST) for all dogs was 244 days. Dogs that underwent surgical tumor removal had significantly longer survival (MST: 294 days) compared to those without surgery (MST: 93 days, P<0.001). The final parametric model with a log-logistic distribution identified tumor stage, location, and breed as key prognostic factors. Miniature Schnauzers and Toy Poodles had 3.36- and 4.80-fold longer survival times, respectively, compared to Golden Retrievers. Oral melanomas were associated with a 66% shorter survival time than non-oral melanomas (median survival times: 191 vs. 663 days; P=0.019). Advanced melanoma stages significantly decreased survival; time ratios for stage III and stage IV compared to stage I were 0.60 (95% confidence interval [CI]: 0.33–1.07; P-value: 0.084) and 0.42 (95% CI: 0.22–0.77; P-value: 0.006), respectively. These findings enhance understanding of canine melanoma in Japan and emphasize the need for multi-center studies to confirm these results.