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Washington: The University of Michigan has developed noninvasive sound technology that breaks down liver tumors in rats, kills cancer cells and boosts the immune system to prevent further spread.

According to the researchers, this development could be a breakthrough that could lead to improved cancer outcomes in humans.

By destroying only 50-75% of the liver tumor volume, the rats’ immune system was able to eliminate the rest, with no signs of recurrence or metastasis in more than 80% of the animals.

“Even if we don’t target the entire tumor, we can still regress the tumor and also reduce the risk of future metastasis,” said Zhen Xu, professor of biomedical engineering at UM and corresponding author of the study. on cancer.

The results also showed that the treatment boosted the rats’ immune responses, possibly contributing to the eventual regression of the untargeted part of the tumor and preventing the cancer from spreading.

The treatment, called histotripsy, noninvasively focuses ultrasound waves to mechanically destroy target tissue with millimeter precision. The relatively new technique is currently being used in a human liver cancer trial in the United States and Europe.

In many clinical situations, the entirety of a cancerous tumor cannot be directly targeted in treatments for reasons such as the size, location or stage of the mass. To investigate the effects of partially destroying tumors with sound, this latest study targeted only a portion of each mass, leaving behind a viable intact tumor.

It also allowed the team, including researchers from Michigan Medicine and Ann Arbor VA Hospital, to show the approach’s effectiveness in less than optimal conditions.

“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,” said Tejaswi Worlikar, PhD student in biomedical engineering.

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

Liver cancer ranks among the top 10 causes of cancer-related death worldwide and in the United States. Even with multiple treatment options, the prognosis remains poor with five-year survival rates of less than 18% in the United States. The high prevalence of tumor recurrence and metastasis after initial treatment highlights the clinical need to improve liver cancer outcomes.

Where a typical ultrasound uses sound waves to produce images of the inside of the body, UM engineers have pioneered the use of these waves for treatment. And their technique works without the harmful side effects of current approaches such as radiation therapy and chemotherapy.

“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 said. “Traditional ultrasound devices use lower amplitude pulses for imaging.”

Microsecond-long pulses from the MU transducer generate microbubbles in targeted tissue – bubbles that expand and collapse rapidly. These violent but extremely localized mechanical stresses kill cancer cells and break down the tumor structure.

Since 2001, Xu’s lab at UM has pioneered the use of histotripsy in the fight against cancer, leading to the “#HOPE4LIVER” clinical trial sponsored by HistoSonics, a spin-off company. of the UM. More recently, the group’s research has produced promising results on the histotripsy treatment of brain therapy and immunotherapy.

The study was supported by grants from the National Institutes of Health, Focused Ultrasound Foundation, VA Merit Review, UM’s Forbes Institute for Discovery, and Michigan Medicine-Peking University Health Sciences Center Joint Institute for Translational and Clinical Research.