Histotripsy – using ultrasound to destroy liver tumors

Histotripsy – using ultrasound to destroy liver tumors

A non-invasive sound technology that breaks down liver tumors in rats, kills cancer cells and stimulates the immune system to prevent their spread (metastasis), has been developed by biomedical engineers at the University of Michigan (UM) in the States -United.

The treatment, called histotripsy, focuses ultrasound waves to mechanically destroy target tissue with millimeter precision.

In a new study, the team showed that by destroying only 50% to 75% of the liver tumor volume with bran, the rats’ immune system was able to eliminate the rest, and there was no evidence of recurrence or metastasis in 81% of animals after 12 weeks.

“Even if we don’t target the entire tumor, we can still regress the tumor and also reduce the risk of future metastasis,” says Zhen Xu, professor of biomedical engineering at UM and lead author of the new research. published in Cancers.

Liver cancer is one of the top 10 causes of cancer-related death worldwide, and although there are several treatment options available, the prognosis remains grim. Five-year survival rates are less than 18% in the United States.

Due to the high incidence of tumor recurrence and metastasis after initial therapy, there is a strong clinical need to improve these outcomes. Histotripsy, a relatively new technique developed by UM engineers, is currently being tested in human liver cancer in the United States and Europe.

It relies on a process known as acoustic cavitation, where high-energy ultrasound pulses lasting one microsecond generate microbubbles in targeted tissues that rapidly expand and collapse.

These violent but extremely localized mechanical stresses kill the cancerous cells and break down the structure of the tumor so that it can be eliminated by the organism, without the harmful side effects associated with the other currently available treatments (chemotherapy, radiotherapy, ablation).

“Our transducer, designed and built at UM, delivers high-amplitude, one-microsecond ultrasound pulses — acoustic cavitation — to focus on the tumor specifically to break it up,” Xu explains. “Traditional ultrasound devices use lower amplitude pulses for imaging.”

Zhen Xu, professor of biomedical engineering at the University of Michigan (left), and Tejaswi Worlikar, doctoral student in biomedical engineering, discuss the 700 kHz, 260-element histotripsy ultrasound transducer they use in the professor’s lab Xu.

Engineers wanted to study the effect of partial tumor destruction by histotripsy because in many clinical situations the entirety of a cancerous tumor cannot be directly targeted due to size, location or stage. mass progression.

In rats, they only targeted a portion of each mass and left a viable intact tumor to show the effectiveness of the approach under less than optimal conditions.

The treatment boosted the rats’ immune responses, indicated by increased immune cell infiltration into the tumor tissue, which may have contributed to the eventual regression of the untargeted part of the tumor and prevented the cancer from spreading.

“Histotripsy is a promising option that can overcome the limitations of currently available ablation modalities and provide safe and effective non-invasive ablation of liver tumors,” says Tejaswi Worlikar, PhD student in biomedical engineering at UM.

“We hope that the insights gained from this study will motivate future preclinical and clinical investigations of histotripsy toward the ultimate goal of clinical adoption of histotripsy treatment for patients with liver cancer.”

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