Electroporation-enhanced targeted bleomycin delivery for the treatment of canine perianal tumors

Introduction: Perianal tumors are common in middle-aged to older male dogs. Treatment of these tumors remains a clinical challenge due to the complex anatomy of the region and limited surgical margins, which increase the risk of local recurrence. In this context, electrochemotherapy (ECT) emerges as a promising non-surgical alternative that combines chemotherapeutic agents, such as bleomycin, with high-intensity and short-duration electric pulses, enhancing cell membrane permeability and potentiating the antitumor effect. The objective of this study was to evaluate the efficacy and safety of ECT as a non-surgical treatment for perianal tumors. Materials and methods: Medical records of dogs of various breeds diagnosed with perianal neoplasms confirmed by histopathology were reviewed. Both benign and malignant lesions of variable size and number were included, excluding apocrine gland anal sac carcinomas. For each patient, the number of treatment sessions, type of clinical response, and recurrence were recorded. All animals underwent ECT consisting of eight monophasic pulses at 5 kHz and an electric field strength of 1,000 V/cm using a long needle electrode. The first pulse was delivered 8 minutes after the administration of intravenous bleomycin (15,000 IU/m2). Results and discussion: Thirty-three dogs with perianal tumors were treated with ECT. The most frequent diagnoses were adenocarcinoma (57.6%), adenoma (36.4%), and hemangiosarcoma (6.1%). Most lesions were solitary (75.8%) and varied in size: <1cm (30.3%), 1-3 cm (48.5%), and >3cm (30.3%). A single ECT session was sufficient in 87.9% of cases, while 12.1% required two sessions. A complete response (CR) was achieved in 87.9% of patients, and a partial response (PR) was 12.1%. No cases of progressive or stable disease were reported in this study. Regarding tumor type, adenomas showed a 90.9% complete response rate, adenocaricnomas 84.2%, and hemangiosarcomas 100%. The recurrence rate was low (9.1%) with an overall treatment efficacy of 90.9%. Adverse effects were mild and self-limiting, consisting mainly of local inflammation (100%) and transient pain. However, one case presented with mild post-procedural constriction and constipation. Conclusions: Electrochemotherapy represents an effective option for managing canine perianal tumors, particularly when complete surgical excision is not feasible or when preservation of anal function is desired.