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

Abstract

Electrochemotherapy (ECT), a medical treatment widely used in human tumor treatment, consists in the administration of bleomycin either systemically or locally followed by the application of an electric field. This procedure increases the toxicity of the bleomycin by 1000 fold in the treated area with an objective response rate of around 80%. Despite its success related to efficiency, low cost and minimum side effects, there is still a 20% of cases in which the ECT treatment is not responding. This could be ascribed to the fact that bleomycin, administered in the preferred way, that is, systemically for large tumors, is not properly reaching the whole tumor mass. The main cause is poor tumor vascularization, in which case local administration could cover areas unreachable with systemic administration. To address this problem here we propose the combined administration of bleomycin, systemic and locally, using companion animals as models for ECT tumor treating. Accordingly, we selected 7 canine and 2 feline patients with a single tumor with poor or no response to ECT, and then we repeat the treatment with ECT but now with a combined administration of bleomycin, systemic and local. The results show, according to an evaluation using the WHO criteria of tumor response, that from the 9 cases, 5 achieved a Complete Response, 3 a Partial Response, and 1 a Stable Disease after 30 days from the combined treatment date. In conclusion, the combined administration of bleomycin, systemic and local, in ECT could provide a good response in tumors that previously showed an unsatisfactory response. It is expected that these results could hopefully increase ECT efficiency.