Soft tissue sarcoma in dogs: a treatment review and a novel approach using electrochemotherapy in a case series Soft tissue sarcoma

Canine soft tissue sarcomas (STSs) are locally invasive mesenchymal neoplasms. Electrochemotherapy (ECT) is an antitumour local ablative treatment that uses electric pulses to enhance the intracellular delivery of cytotoxic drugs. The aim of this retrospective study was to review the current treatment for STSs and to evaluate the efficacy and safety of ECT with bleomycin in canine STSs. Fifty-two dogs with 54 STSs were included. Three groups were arranged: (1) ECT alone, (2) intra-operative ECT, and (3) adjuvant ECT. Signalment, tumour size, location, histological grade and margins, and ECT parameters were collected. Recurrence rate (RR), and disease-free interval (DFI) were calculated. Treatment toxicity was assessed using a 6-point scale. STSs were mostly located on limbs (77.8%). Median tumour size was 4.3 cm (range 0.4-17.0 cm). Most STSs were grade I (47.7%) and II (50.0%) and histological margins were incomplete in 94.5% of cases. Two complete remissions, one partial remission and one stable disease were recorded in group 1. Group 2 and 3 were similar for tumour location, size and grade, histological margins, treatment toxicity, pulse frequency and voltage. Moreover, RR and DFI were similar between group 2 and 3 (23% and 25%, 81.5 and 243 days, respectively). Local toxicity post ECT was mild (score ≤2) in 66.7% of cases. Higher toxicity score was associated with higher pulse voltage (1200 V/cm vs. 1000 V/cm) (p=0.0473). ECT coupled with bleomycin resulted safe and efficient in tumour local control and should be considered as an option for treatment of canine STSs.