Pilot Study of Partial Tumor Ablation Using Thermal High-Intensity Focused Ultrasound (HIFU) in Feline Soft Tissue Sarcomas.

Soft tissue sarcomas (STS) are locally invasive and aggressive tumors that occur spontaneously in humans, dogs, and cats. High-intensity focused ultrasound (HIFU) is a non-invasive ablation technology that has been explored in canine but not feline STS. The objective of this pilot study was to determine the in vivo safety and feasibility of HIFU ablation for feline STS and to investigate the impact of HIFU on the acute immunological response. Client-owned cats diagnosed with spontaneous STS were recruited. Computed tomography (CT) scans of the chest, abdomen, and tumor were performed prior to treatment for staging and treatment planning. A commercially available HIFU unit (Echopulse, Theraclion, Malakoff, France) was used to target portions of solid tumors before standard-of-care surgical resection. Ablation efficacy and local immunological response were characterized using histopathological and immunohistochemical assessments. Acute safety was monitored with physical examinations, owner reports, and CBC/serum biochemistry. Multiplex serum cytokine levels were used to evaluate the systemic immune response. A total of three cats diagnosed with STS were recruited and treated. No significant adverse events attributed to HIFU treatment were noted in this pilot study. In treated areas, hemorrhage as well as coagulative and lytic necrosis were observed microscopically and were more extensive than in untreated tissues. There was a statistically significant difference in the level of serum MCP-1 after HIFU treatment, but no significant changes in any other analytes. No differences in the infiltration of CD3-, CD79a-, or IBA1-positive cells were noted between treated and untreated samples. Overall, findings suggested that HIFU may offer a viable alternative to conventional therapies for feline STS, with pilot results showing effective tumor ablation in cats with STS without significant adverse events. Some preliminary evidence of immunomodulation following treatment was observed, but HIFU as an immunotherapeutic treatment option needs to be further investigated.