Ultrasound mechanically destroys liver cancer tumors

Researchers evaluate tumor recurrence and metastases after using a non-invasive ultrasound treatment, called histotripsy, on liver cancer in rats.

Histotripsy is the first non-ionizing and non-thermal ablation technique that uses ultrasound technology to target and destruct liver cancer tumors and was developed by researchers at The University of Michigan (MI, USA). In this recent paper, the same research group looked at the effect of this method on tumor recurrence and metastases, which is especially important to consider as this remains high with current treatment options.

“Histotripsy is a promising option that can overcome the limitations of currently available ablation modalities and provide safe and effective non-invasive liver tumor ablation,” says Tejaswi Worlikar, the first author of the study, and does so by mechanically destroying the tissue with millimeter precision.

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In clinical applications, it’s often not possible to target the entirety of cancerous tumors due to their size, location, or stage. Because of this, the researchers evaluated the effect of only partially targeting and destroying tumors with their ultrasound technology, leaving behind some of the tumor tissue intact. They found that targeting 50% to 75% of the liver tumor volume was sufficient, as the rats’ immune systems were able to destroy the rest. Additionally, in more than 80% of the rats in the study, there were no signs of tumor recurrence or metastases.

“Our transducer, designed and built at [The University of Michigan], delivers high amplitude microsecond-length ultrasound pulses – acoustic cavitation – to focus on the tumor specifically to break it up,” explains Zhen Xu, who leads the research group. “Traditional ultrasound devices use lower amplitude pulses for imaging,” she adds.

These ultrasound pulses create microbubbles localized in the tumor that rapidly expand and collapse, generating high mechanical stress in the tumor, causing them to break up and destroy the cancer cells.

“We hope that our learnings from this study will motivate future preclinical and clinical histotripsy investigations towards the ultimate goal of clinical adoption of histotripsy treatment for liver cancer patients,” says Worlikar. This relatively new technique is currently in human liver cancer trials.

It seems this non-invasive ultrasound technology is a triple threat as it can break down tumors in rats, kill cancer cells and prevent metastasis – all without the side effects of chemotherapy or radiation therapy.