Researchers Use Sound To Treat Tumors

Researchers have used a technology that utilizes sound to treat tumors. Apart from breaking down tumors, it also helps prevent the recurrence and further spread of cancer.

The new technique is called histotripsy, and it essentially disrupts tumors using "precisely controlled acoustic cavitation," the researchers noted in their paper, published in Cancers.

"Our transducer, designed and built at U-M, delivers high amplitude microsecond-length ultrasound pulses—acoustic cavitation—to focus on the tumor specifically to break it up," Zhen Xu of the University of Michigan (U-M), the study's corresponding author, explained in the university news release. "Traditional ultrasound devices use lower amplitude pulses for imaging."

The researchers explained that though histotripsy has been used to disrupt tumors, there has been "insufficient evidence" regarding its effects on recurrence and metastases or the spread of cancer to a body part that's different from where it started.

For their work, the researchers looked at the effect of partially destroying tumors using histotripsy. As the university noted, the entire cancerous tumor cannot be targeted in many situations, so the researchers targeted only a part of the mass (50-75%) and left part of the tumor intact to see the treatment's effectiveness.

Interestingly, even if they left a part of the mass still intact in the rats they tested, the animals' immune systems were able to take care of the rest of the tumor.

"Even with partial ablation, complete local tumor regression was observed in 81% of treatment rats, with no recurrence or metastasis," the researchers wrote. "In contrast, 100% of the untreated control animals showed local tumor progression and intrahepatic metastases."

The animals treated with histotripsy also had improved survival outcomes and "increased immune infiltration." According to the researchers, the treatment's stimulation of the rats' immune response may have contributed to the eventual regression of the tumor that was left behind.

The treatment shows promise in improving cancer in humans. So far, histotripsy is being used in the U.S. and Europe for human liver cancer trials. As U-M noted, liver cancer has a high prevalence of tumor recurrence and metastasis after initial treatment.

"Histotripsy is a promising option that can overcome the limitations of currently available ablation modalities and provide safe and effective noninvasive liver tumor ablation," Tejaswi Worlikar, one of the study authors, said in the U-M news release. "We hope that our learnings from this study will motivate future preclinical and clinical histotripsy investigations toward the ultimate goal of clinical adoption of histotripsy treatment for liver cancer patients."