Enhanced anti-tumor efficacy of Electrochemotherapy combined with marginal surgery in dogs with Mast Cell Tumors and Soft Tissue Sarcomas

Abstract Background and Objectives Electrochemotherapy (ECT) has emerged as an effective treatment modality for various tumor types in both preclinical and clinical settings within human and veterinary Oncology. We sought to evaluate the effect of electrochemotherapy (ECT) on survival of companion dogs with mast cell tumors and soft tissue sarcomas as an adjuvant to surgery. Materials and Methods A single-institution retrospective case series evaluation was used to identify dogs with mast cell tumors and soft tissue sarcomas undergoing surgical resection followed by electrochemotherapy from 2020–2024. Patients were selected based on having both therapies and categorized by histopathology. ECT was combined post-surgery with IV bleomycin and IL cisplatin in all cases. Overall response rate, survival and recurrence was analyzed. Results A total of 605 patients were identified as having surgery with incomplete margins followed by electrochemotherapy with either a diagnosis of mast cell tumor or soft tissue sarcoma. Grade was determined for all patients and recurrence free survival was stratified according to grade. Three hundred thirty-one dogs with mast cell tumor were retrospectively evaluated and two hundred and seventy-four dogs with soft tissue sarcoma were evaluated. This study obtained local control in both cutaneous and subcutaneous mast cell tumors as well as soft tissue sarcomas. The mean progression free interval in cutaneous mast cell tumors was 1825 days for grade I, 1803 days for low grade II, 902 days for high grade II and 817 days for grade III. Subcutaneous mast cell tumors were evaluated to be 1814 days for low grade and 1180 days for high grade. The mean progression free interval soft tissue sarcomas were 1432 days for grade I, 1000 days in grade II and 551 days in grade III respectively. Necrosis was observed at an average rate of 22% in mast cell tumors and in 18% of soft tissue sarcomas. Conclusion In this large study, electrochemotherapy decreased local recurrences after incomplete resection from surgery. The majority of publications are from European countries and this is the first evaluation of a large cohort of cases from the United States able to define overall progression free interval according to grade. Electrochemotherapy can offer a localized mechanism of control with minimal toxicity and continued use of this therapy is warranted in other tumor types.