Combination of bleomycin and cisplatin as adjuvant electrochemotherapy protocol for the treatment of incompletely excised feline injection site sarcomas: A retrospective study

Background: Feline injection-site sarcomas (FISS) are mesenchymal tumors that can occur in cats after injections of different medical agents, and are easily prone to recurrence. Aim: The aims of this study were to report treatment outcomes for cats with feline injection site sarcomas (FISS) treated with both bleomycin and cisplatin, per adjuvant electrochemotherapy (ECT) protocol. Methods: Medical records of cats with a diagnosis of FISS that were treated with ECT using both bleomycin and cisplatin were retrospectively evaluated. Twenty-seven cats were available for statistical evaluation of their response. The cats received intravenous 20 mg/m2 bleomycin, and the tumor bed and margins were infiltrated with cisplatin at the dose of 0.5 mg/cm2. Then, trains of permeabilizing biphasic electric pulses lasting 50 + 50 µsec each, were delivered in bursts of 1,300 V/cm using caliper electrodes under sedation. A second session was performed 2 weeks later. Results: Side effects were limited to local inflammation in three cats. Three cats developed local tumor recurrence at days 180, 180 and 545, after surgery, two cats developed recurrence and metastases at 100 and 505 days after surgery and two cats experienced distant metastases. A median time to recurrence could not be calculated as over 80% of the study population remained disease-free or were censored due to death from other causes. Mean survival time was 985 days and median cumulative survival for all cases, was 1000 days. Conclusion: When compared to historical controls, the results of this study demonstrate superior rates of tumor-free survival and disease-free interval. This adjuvant therapy could be a useful addition to the current options for FISS in consideration of its efficacy, limited toxicity, and ease of administration