Introduction

Histotripsy is a non-thermal and non-invasive high-intensity focused ultrasound ablative technique that causes mechanical fragmentation of tissue resulting in liquefied cellular debris with histologically clear demarcated boundaries between treated tissue and non-treated tissue. Histotripsy has never been evaluated in a spontaneous cancer model. Our objective was to evaluate the safety and feasibility of histotripsy to achieve tumor ablation in dogs with soft tissue sarcoma (STS).

Methods

Dogs diagnosed with STS were recruited. CT of the chest, abdomen, and the tumor was performed for staging and treatment-planning, and pretreatment biopsy was obtained. Safety was monitored with exams, owner reports, and CBC/serum biochemistry. Partial tumor ablation was performed using a prototype Histotripsy system. Anatomical ablation characteristics were evaluated with contrast CT at 1- and 4-days post-treatment, with tumor resection 4-days post-treatment. Tumor ablation effectiveness was evaluated with H&E.

Results

Ten dogs were recruited and treated. Tumor histologies included 3 grade III STS, 4 grade II STS, 2 grade I STS, and 1 malignant mesenchymoma. Currently, 7 dogs are alive, 2 dogs were euthanized from recurrence or suspected metastasis, and 1 dog was lost to follow up. There were no changes in bloodwork values. The mean planned ablated volume was 8.41±5.01 cm3. The mean duration of treatment was 30.43±12.67 min. Histotripsy-related complications were generally self-limiting and included various degrees of cutaneous injury. Post-treatment histopathology indicated complete ablation of targeted tumor with no intact cells identified.

Conclusion

Histotripsy can achieve safe, rapid, and effective tumor ablation in dogs diagnosed with STS.

Funding Information

Focused Ultrasound Foundation.