RESEARCH COMMUNICATIONS OF THE 28th ECVIM-CA CONGRESS

This is a retrospective study of the efficacy of electrochemotherapy (ECT) in 60 dogs with tumours of the head including the oral cavity. Patients were privately owned pets. Tumours treated were mast cell tumours (19, 18 of which Paitnik grade 2, one grade 1) squamous cell carcinomas (15), spindle cell tumours (11), malignant melanomas (5), ameloblastomas (2), histiocytomas (2), basal cell tumour (1), carcinoma (1), epulis (3), plasmacytoma (1). Cases were treated using Bleomycin (15000 iu/sq m) intravenously with electroporation using either a Cytopulse PA 2000 or Cytopulse Oncovet signal generator, 8 pulses of 1000 V/cm at either 1 Hz or 5MHz applied starting 8 minutes after drug administration. Treatments were applied under general anaesthesia. ECT was applied either as sole therapy (n=42), to tumour margins during surgery (intra‐operative, n=8) or to surgical scars roughly 2 weeks after surgery (adjuvant, n=9) whilst one case was initially treated by sole therapy with repeat during surgery. Two patients received second treatments whilst 58 received only a single treatment. All treatments were applied using Gehl array electrodes, two rows of needles 6 mm apart. Intra‐operative treatment was applied after cytoreduction with no attempt to excise margins: in some cases some macroscopic tumour was present in the treated volume. Mast cell tumour cases receiving sole therapy ECT showed 10/12 (83.3%) enduring CR and those receiving intra‐operative or adjuvant ECT showed 6/7 (85.7%) disease‐free at censoring. Response to ECT of squamous cell carcinoma showed dependency on site. Those in the premaxilla or external nares (n=3) showing no responses. In other (all oral) lesions (n=12), 7 CR (58.3%), PR 3 (25%) and 2 surgically removed before ECT. Of these, 1 CR recurred and was treated for a second time leading to disease‐free state at censorship, 3 PR recurred. Results for spindle cell tumours were disappointing: one small fibrosarcoma showing CR after sole therapy and overall response (CR and disease control) 5/12 (41.6%). Ameloblastomas and epulides showed 100% CR after sole therapy (n=5). Melanomas gave relatively poor results (25% CR to sole therapy – n=4). ECT showed good results in mast cell tumours and fair results in oral squamous cell carcinomas not involving the rostral portion of the mouth. Cosmetic and functional results were excellent with some scarring apparent in cases where skin was treated. Healing of oral lesions, even where bone was exposed, was rapid and complete.