Irreversible Electroporation of Spine Tumors in a Canine Model: Tumoricidal Effects and Neural Toxicity

Purpose: To evaluate the tumoricidal effects and neural toxicity of irreversible electroporation (IRE) in a canine spine tumor model. Materials and Methods: This preclinical large-animal study was approved by the Institutional Animal Care and Use Committee. Canine transmissible venereal tumors (cTVTs) were implanted in the thoracic and lumbar vertebrae of 3 immunosuppressed canines (4 tumors/canine). Magnetic resonance (MR) imaging monitored tumor growth. Computed tomography (CT)–guided IRE ablation was performed once tumors reached approximately 1.5 cm. One animal that developed paraplegia from epidural tumor extension before ablation was euthanized 24 hours after IRE and analyzed as an acute cohort for procedural feasibility and acute histopathologic response. Two animals survived 30 days with follow-up MR imaging and were analyzed for subacute neural toxicity and imaging response. Mathematical modeling estimated simulated electric field strength. Results: Tumors developed in 11 (92%) of 12 implanted vertebral levels, and bipolar IRE ablation was successfully performed in all tumors. Histological necrosis was observed at all ablated levels in the acute animal (mean tumor electric field, 526.1 V/cm [SD ± 53.8]). In survival animals, no postprocedural neurologic deficits occurred. Spinal cord findings were limited to Grade ≤2 histological changes, whereas 4 (22%) of 18 exiting nerve roots demonstrated Grade ≥3 changes. At 30 days, MR imaging showed imaging response in 6 (86%) of 7 tumors. Pathologic response was heterogeneous, with residual tumor in 1 survival animal and fibrosis without residual intraosseous tumor in the other. Conclusions: IRE ablation of spinal tumors in a canine model demonstrated tumoricidal effects, with Grade 3 Wallerian degeneration observed in 22% of exiting nerve roots in 30-day survival animals.