# Study of Biological Effects Induced in Solid Tumors by Shortened-Duration Thermal Ablation Using High-Intensity Focused Ultrasound

## TL;DR

This study explores a new, shorter HIFU ablation method for breast cancer in rats, showing effective tumor destruction with minimal damage to healthy tissue.

## Contribution

A low-cost HIFU system and shortened ablation protocol were developed and validated in a rat breast cancer model.

## Key findings

- Shortened HIFU ablation caused massive tumor cell death and immune response without harming healthy tissue.
- The new ablation plan significantly reduced procedure duration while maintaining efficacy in tumor treatment.
- No damage was observed in healthy tissues beyond the safety margin after HIFU treatment.

## Abstract

Breast cancer is one of the most dangerous cancers affecting women, so animal models of breast cancer have been created, new drugs are constantly being sought, and new procedures are being developed to destroy tumor cells. As to this last aspect, the use of high-intensity focused ultrasound is promising. It is a non-invasive technique, but its availability is significantly limited due to such devices’ costliness and lack of versatility. Therefore, this project aimed to construct a low-cost, compact HIFU for precise destruction of cancer cells in the region of interest and to test the efficacy of the shortened-duration ablation procedure in a rat model of implantable breast cancer. Our research is preclinical and may also be applicable in veterinary medicine.

The HIFU ablation technique is limited by the long duration of the procedure, which results from the large difference between the size of the HIFU beam’s focus and the tumor size. Ablation of large tumors requires treating them with a sequence of single HIFU beams, with a specific time interval in-between. The aim of this study was to evaluate the biological effects induced in a malignant solid tumor of the rat mammary gland, implanted in adult Wistar rats, during HIFU treatment according to a new ablation plan which allowed researchers to significantly shorten the duration of the procedure. We used a custom, automated, ultrasound imaging-guided HIFU ablation device. Tumors with a 1 mm thickness margin of healthy tissue were subjected to HIFU. Three days later, the animals were sacrificed, and the HIFU-treated tissues were harvested. The biological effects were studied, employing morphological, histological, immunohistochemical, and ultrastructural techniques. Massive cell death, hemorrhages, tissue loss, influx of immune cells, and induction of pro-inflammatory cytokines were observed in the HIFU-treated tumors. No damage to healthy tissues was observed in the area surrounding the safety margin. These results confirmed the efficacy of the proposed shortened duration of the HIFU ablation procedure and its potential for the treatment of solid tumors.