Scientists say they partially destroyed liver tumors in mice using sound waves

by Alexandra May Jones

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TORONTO (CTV) — There may be a non-invasive way to destroy cancer cells forever, according to new research involving mice: the power of sound.

Using only targeted sound waves, researchers at the University of Michigan were able to destroy liver tumors by up to 75 percent in mice, prompting the animals’ immune systems to attack the remaining cancerous substance.

A key detail from this new research is that even destroying only a portion of the tumors had a lasting effect. In 80 percent of people, there was no evidence of cancer recurrence afterward.

“Even if we don’t target the entire tumor, we can still cause tumor regression and reduce the risk of metastasis in the future,” said Chen Shu, a professor of biomedical engineering at the University of Michigan and corresponding author of the study. In a press release.

The treatment is called lithotripsy, which uses focused ultrasound to precisely destroy tissue. Created by researchers at the University of Michigan, they believe this relatively new treatment, which is already being tested in a separate human liver cancer trial in the United States and Europe, could revolutionize cancer treatment.

“Tissue lithotripsy is a promising option that can overcome the limitations of currently available resection methods and provide safe and effective non-surgical resection of liver tumor,” Tejaswi Worlikar, a biomedical engineering doctoral student and first author of the study, said in the statement. “We hope that what we have learned from this study will motivate future preclinical and clinical lithotripsy investigations toward the ultimate goal of clinical accreditation of lithotripsy therapy for patients with HCC.”

It’s often not possible to target the entire tumor and remove it with surgery or current treatments due to the location or stage of the disease. Although shredding can treat more tumors since it is a non-invasive treatment, it is possible that it may still not be logistically feasible to target all of the tumor with shredding. So how much tissue must be destroyed for long-term treatment to be successful?

This new study, published at the end of March in the journal Cancers, was the first to focus on whether the partial use of tissue fragmentation would have a lasting effect.

In order to see if the tumor would regress again, the researchers purposely destroyed only 50-75 percent of liver tumors in mice.

Among the 11 treated mice, complete tumor regression was seen in nine, with no local recurrence of target tumor tissue in all 11 rats even after 12 weeks. In comparison, 100 percent of the control group of mice with liver tumors that were not treated in the same time period experienced consistent tumor growth.

The study stated, “The survival outcomes in animals treated with lithotripsy were significantly improved compared to controls.”

Ultrasound is usually used to produce a picture of what is going on in the body, but in tissue fragmentation, these sound waves are designed to make small, controlled incisions within the tissue.

“Our transducer, designed and built at UM, delivers microsecond-long amplitude ultrasonic pulses — an acoustic cavity — to specifically target the tumor to break it up,” Shaw said. “Conventional ultrasound devices use pulses of lower amplitude for imaging.”

These pulses create tiny bubbles inside tumors that expand and collapse, physically destroying the tumor’s structure and killing cancer cells.

Researchers say liver cancer is one of the deadliest cancers worldwide, so finding a treatment that has a high chance of preventing its recurrence is imperative. According to the Canadian Cancer Society (CCS), the incidence and death rates associated with liver cancer mean that in 2021, an estimated 3,300 Canadians had developed liver cancer, and 1,600 people died from it. Liver cancer survival is among the lowest—22 percent of people with liver cancer are expected to exceed the five-year mark, according to CCS data.

Xu’s team has been working on tissue fragmentation for years, and this study is only the latest step forward toward a treatment that becomes a viable option for future patients.

The currently ongoing human trial of tissue fragmentation, called #HOPE4LIVER, is sponsored by HistoSonics, a company set up by the University of Michigan. So far, only a handful of patients have been successfully treated with the trial in the US and Europe in 2021, with the most recent patients receiving lithotripsy in the UK last September. A press release from the NHS stated that it only took six minutes and 58 seconds to destroy the tumor in one patient.

Patients are being monitored to see if the cancer has returned — if the trial follows its original schedule, it will be completed in 2023.

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Sonia Bozic

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