Research: Tumors destroyed by sound do not come back

Non-invasive sound technology developed at the University of Michigan breaks down liver tumors in rats, kills cancer cells, and stimulates the immune system to prevent them from spreading - a major advance that could lead to improved cancer outcomes in humans.

By destroying only 50% to 75% of the liver tumor volume, the rats' immune systems were able to clear the rest, with no evidence of recurrence or metastasis in more than 80% of the animals. Even if the entire tumor is not eliminated, it is still possible to cause tumor regression and also reduce the risk of future metastases.
The results also showed that the treatment stimulated the rats' immune responses, which likely contributed to the eventual regression of the non-targeted part of the tumor and thus prevented cancer from spreading further.

The treatment, called histotripsy, non-invasively focuses ultrasound waves on the mechanical destruction of target tissue with millimeter precision. This relatively new technique is currently being used to test liver cancer in humans in the United States and Europe.

In many clinical situations, treatment cannot directly target the entire cancerous tumor for reasons that include mass size, location, or stage. To investigate the effects of partially destroying tumors with sound, this latest study focused on only a portion of each mass, leaving behind a viable, intact tumor. It also allowed the team, including researchers from Michigan Medicine and the Ann Arbor VA Hospital, to show the effectiveness of the approach under less-than-optimal conditions.
Histotripsy is a promising option that may overcome the limitations of currently available ablation modalities and provide safe and effective noninvasive liver tumor ablation. The researchers hope that their findings from this study will motivate future preclinical and clinical histotypes toward the ultimate goal of clinical acceptance of histotripsy therapy in liver cancer patients.

Liver cancer is among the top 10 causes of cancer-related deaths worldwide. Even with multiple treatment options, the prognosis remains poor with a five-year survival rate of less than 18%. The high prevalence of tumor recurrence and metastasis after initial treatment highlights the clinical need to improve liver cancer outcomes.
Where typical ultrasound uses sound waves to create images inside the body, engineers at the University of Michigan are pioneering the use of these waves for treatment. Their technique works without the harmful side effects of current approaches, such as radiation and chemotherapy.

Their transducer, designed and manufactured at the University of Michigan, delivers high-amplitude microsecond ultrasound pulses—acoustic cavitation—to target and break up the tumor. Traditional ultrasound machines use a lower amplitude pulse for imaging. Microsecond-long pulses from the transducer create microbubbles in target tissues – bubbles that expand rapidly. These violent but extremely localized mechanical stresses kill cancer cells and break up the structure of the tumor.

Source: https://www.sciencedaily.com/releases/2022/04/220418093955.htm