Partially Destroying Tumors With Sound Allows the Immune System to Finish the Job

Researchers from the University of Michigan have developed a form of noninvasive sound technology that destroys a significant part of cancerous mass and keeps the destroyed portion of the tumor from coming back. The treatment, called histotripsy, uses a transducer to deliver microsecond-long ultrasound pulses to cancerous tissues. The pulses generate tiny bubbles that quickly expand and collapse, destroying cancer cells around them. It’s the first treatment of its kind, having paved the way to treat cancer without heat or ionizing radiation.

“It works by mechanically liquefying the target cancer tissue and demonstrates the potential to increase accuracy and reduce off-target damage for cancer treatment when compared to radiation or thermal-based approaches,” said lead researcher Dr. Zhen Xu, associate professor in the Department of Biomedical Engineering, as she accepted an award on behalf of her team. While the technology was developed to treat liver cancer, Dr. Xu mentioned she hopes it will someday expand to treat tumor metastases, or cancer that has spread to a secondary location in the body.

Dr. Xu’s team first tested histotripsy with rats. According to the study, which was published last week in the oncology journal Cancers, the researchers began by using histotripsy to destroy 50 to 75 percent of each rat’s liver tumor volume, then periodically checked the tumors using MRI. They found that the rats’ immune systems were then able to clear away the rest of the tumors, with no evidence of recurrence or metastases in 81 percent of those treated. All treated rats enjoyed longer lifespans than a control group left untreated.

Since then, histotripsy has been tested with a small group of humans. While information on that experimental treatment is limited, Dr. Xu’s team points out that all eight treated patients experienced complete tumor regression with no adverse side effects. Two of the eight also experienced the stabilization of non-targeted tumors elsewhere in the body. Clinical trials with human patients are expected to continue while Dr. Xu and her colleagues explore the combination of their technology with brain therapy and immunotherapy.