Recently, researchers at the University of Michigan (UM) developed a non-invasive sound technology that “breaks down liver tumors in rats, kills cancer cells and spurs the immune system to prevent further spread.” They were able to reduce liver tumors in rats by 75%, up from 50%, allowing the rats’ immune systems to clear the remaining cancerous cells, “with no evidence of recurrence or metastases in more than 80% [of] animals;” that is, in 80% of the cases, there was no sign of cancer recurring later.
According to IFLScience, the researchers started by injecting 22 rats with liver cancer cells, and they then let the tumors grow for up to nine days, reaching a size of 5–10 millimeters (0.2–0.4 inches). Next, half of the rats were treated with histotripsy, “which involves blasting the tumors with millisecond-long pulses of high-amplitude ultrasound waves.”
Histotripsy is a therapy developed by researchers at UM that employs focused ultrasound waves “to mechanically destroy target tissue with millimeter precision.” This relatively new technique, which is already being tested for human liver cancer in the United States and Europe, is believed by the researchers to have the potential to transform cancer treatment, “[overcoming] the limitations of currently available ablation modalities and [providing] safe and effective noninvasive liver tumor ablation.”
Zhen Xu, a UM professor of Biomedical Engineering and corresponding author of the paper in Cancers, stated in a press release by UM, “Even if we don’t target the entire tumor, we can still cause the tumor to regress and also reduce the risk of future metastasis.”
Due to the mass size, location, or stage of the cancerous tumors, “the entirety of a cancerous tumor cannot be targeted directly in treatments” in many clinical settings. “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,” the press release wrote. “It also allowed the team, including researchers at Michigan Medicine and the Ann Arbor VA Hospital, to show the approach’s effectiveness under less than optimal conditions.”
Full tumor regression was noted in 9 of the 11 rats treated, “with no signs of recurrence of metastasis” after 12 weeks. In comparison, all of the untreated 11 rats in the control group with liver tumors saw continuous tumor development throughout the same time period and “had to be euthanized within three weeks of initiating the study.”
“We hope that our learnings from this study will motivate future pre-clinical and clinical histotripsy investigations towards the ultimate goal of clinical adoption of histotripsy treatment for liver cancer patients,” Tejaswi Worlikar, a doctoral Biomedical Engineering student at UM and first author of the study, stated in the release.
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