Predictive factors of response to electrochemotherapy in canine oral malignant melanoma

Electrochemotherapy is a treatment modality which has been increasingly used in veterinary and human medicine for treating cutaneous and subcutaneous tumors. In this prospective work we evaluated the outcome of using electrochemotherapy as a first-line treatment for canine oral melanoma in different stages, with the aim of determining predictive factors of response to the treatment. Mucosal melanoma is the most common cause of oral cancer in dogs. Canine oral malignant melanoma is very similar to human oral melanoma in many aspects, being a very good translational model for studying response to this treatment. Sixty-seven canine patients were treated. Intravenous bleomycin was the preferred drug, and the standard operating procedures for electrochemotherapy were followed. The patients were followed-up for two years. According to WHO criteria, the objective response per stage was: stage I 100%, stage II 89.5%, stage III 57.7% and, stage IV 36.4%. The overall median survival was 7.5 months (2-30 months, mean 9.1 months). Median overall survival of patients in stage I was 16.5 months, in stage II was 9 months, in stage III 7.5 months, and in stage IV 4.5 months. The average number of electrochemotherapy sessions was 1.5 for every stage. The incidence of new metastases among treated patients was 28.4%. Patients in advanced stages, with bone involvement, and caudal location of the tumor had poorer response rates and shorter overall survival times. The treatment greatly improved the quality of life of the patients. Electrochemotherapy is an important technique in the oncological armamentarium against melanoma, and these results can be used to predict human response to this therapy in each stage.