A revolutionary way to treat cancer could be on the horizon — and it’s through noninvasive sound. It’scalled histotripsy — and it is “a novel technique that mechanically disrupts tumors, through precisely controlled acoustic cavitation,” according to a new study. In simpler terms, sound waves can be harnessed to destroy cancerous tumors.
Published in Cancers, the new study proposed histotripsy as a way to treat malignant liver tumors that don’t come back — and in a way that is noninvasive. The study conducted the experiment on mice with liver tumors — a form of cancer that has a poor prognosis. The research sought to examine the effects of partially targeting tumors — given how, in many instances, the entire tumor is difficult to treat directly depending on factors like size, location, and stage of the cancer.
And so when scientists targeted tumors in mice, they only destroyed them partially — the mice’s immune systems kicked in to clear away the rest. The icing on the cake, moreover, is that once the cancerous bits were destroyed, the treatment reduced the risk of future metastases. This is just by sound waves targeting 50-70% of the tumor volume — and the treatment was successful in 80% of the animals.
The study focused on liver tumors in particular, but it could have far-reaching implications. The technique uses ultrasound; with human clinical trials are currently underway in the United States and Europe, Science Daily reported. “Our transducer… delivers high amplitude microsecond-length ultrasound pulses — acoustic cavitation — to focus on the tumor specifically to break it up,” Xu said. “Traditional ultrasound devices use lower amplitude pulses for imaging,” said Tejaswi Worlikar, a doctoral student at the University of Michigan, Ann Arbor, told Science Daily.
The use of sound in treating cancer, incidentally, is not brand new; but a growing body of research is aimed toward focusing treatment on tumors without harming normal cells. Previous research explored the use of low-intensity pulsed ultrasound (LIPUS) to avoid the pitfalls of destroying healthy tissue and cells — but this technique hadn’t been tested in humans or animals at the time.
This particular study shows that partial destruction can trigger the immune system to clear away the rest — a novel finding that could minimize the side effects of traditional cancer treatments.
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The researchers found how sound wave bombardment could trigger vibrations that lead to cancer cell death. The key is to engineer sound waves such that they would target and destroy only cancer cells. Understanding the frequencies of sound and their relationship with cell characteristics is, thus, crucial.
“Cancer cells are quite heterogeneous, even within a single tumor, so it would be almost impossible to find a range of settings for the ultrasound that could kill every single cancer cell. This would leave surviving cells that could cause a tumor to regrow,” Peter P. Lee, chair of the Department of Immuno-Oncology at City of Hope, told Caltech.
Moreover, engaging the immune system after the treatment is the important part — which the present research succeeds in doing.
With the study limited to mice, there is still much work ahead before it could potentially be used as a viable treatment intervention. But the technology itself provides hope.
“Histotripsy is a promising option that can overcome the limitations of currently available ablation modalities and provide safe and effective noninvasive liver tumor ablation,” Worlikar added.
