Electrochemotherapy in non-satisfactory responding tumors in vet patients: combined administration of bleomycin, systemic and local

Introduction : Electrochemotherapy (ECT) a medical treatment widely used in human patients for tumor treatment, increases the toxicity of the bleomycin by 1000 folds in the treated area with an objective response rate of around 80%.  Despite its high response rate, there is still a 20% of cases in which the treatment is not responding. This could be ascribed to the fact that bleomycin, administered systemically is not reaching properly the whole tumor mass because of the poor tumor vascularization, in which case local administration could cover areas that are unreachable by systemic administration. Materials and methods: We propose the combined administration of bleomycin, systemic and local, using companion animals as models. We selected 11 canine and 2 feline patients according with selection criteria:  1. Single tumor previously treated with ECT with poor response, 2. Schwanomas that according to our previous experience, have no objective response with the ECT treatment, or 3. Tumors that because of their size, an objective response was not expected.  We repeated the treatment with ECT with a combined administration of bleomycin, systemic and local. Results: According to the WHO criteria of tumor response, from the 13 cases, 6 achieved a Complete Response, 6 a Partial Response, and 1 a Stable Disease. 92% of the cases showed an improved response of ECT with the combined administration of bleomycin as compared to ECT with systemic bleomycin alone. Conclusion: The combined administration of bleomycin in ECT could provide a good response in tumors that previously showed an unsatisfactory response.