Introduction

The aim of this study was to demonstrate the feasibility of treating canine osteosarcoma (OS) with histotripsy, a novel non-thermal focused ultrasound tumor ablation technique. This study evaluated the ablative effect of histotripsy on canine OS cells and on the immune profile of peripheral blood mononuclear cells. Evaluation of the ablative and immune effects of histotripsy in OS informs development of histotripsy as a non-invasive limb salvage and immunotherapeutic for OS.

Methods

Five canine OS patients were enrolled in a clinical trial. The primary tumor was treated with histotripsy and a standard-of-care limb amputation was performed 1 day after histotripsy treatment. Histotripsy treatment was performed using a 500 kHz transducer with an ultrasound imaging probe coaxially aligned for real-time image guidance and monitoring of cavitation bubble cloud formation. A 2-cm spherical portion of the tumor was treated with histotripsy at a pulse repetition frequency of 500 Hz and a dose of 500 pulses/point. Treated tumors were evaluated grossly and histologically after surgical excision. Pre- and post-histotripsy treatment peripheral blood samples were collected from 3 dogs for immune cell phenotyping via flow cytometry.

Results

Tumor ablation zones were successfully identified grossly and microscopically, ablated tumor volumes corresponded with planned treatment volumes and effective ablation of tumor cells was noted microscopically. Immune cell phenotyping identified an increase in peripheral CD4+ T lymphocytes post-histotripsy treatment.

Conclusion

Histotripsy successfully ablated the targeted area within the primary tumor, demonstrating its potential to serve as a novel treatment modality for OS.

Funding Information

1. American Kennel Club Canine Health Foundation