Liver cancer is the third leading cause of cancer deaths worldwide. In 2020, approximately 830,180 people died of liver cancer worldwide. The American Cancer Society, ACS, estimates that in 2022, about 41,260 new cases of liver cancer will be diagnosed, and about 30,520 people will die of it in the United States of America.
Histotripsy Ultrasound Array Transducer. Credit: University of Michigan
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Over the years, several treatment options for liver cancer have been developed. They may be invasive or non-invasive. Treatment is said to be invasive if it requires cutting the skin or inserting instruments into the body, like in surgery. Other treatment options such as chemotherapy and radiation therapy are non-invasive but come with side effects such as a suppression of the patient’s immune system.
In recent times, using a technique known as histotripsy, a team led by Zhen Xu, a Professor of Biomedical Engineering at the University of Michigan has been able to eradicate liver cancer in rats using sound waves. This technique is not only non-invasive but also supports the immune system instead of suppressing it.
Histotripsy, the future of non-invasive cancer treatment
Histotripsy is a non-invasive technique that involves the use of ultrasound focused against a cancerous tumor. These ultrasound waves are generated by an ultrasound transducer. Hitherto, ultrasound waves have been used for generating images of internal structures, however, it has been discovered that when focused against the tumor, the waves from the ultrasound transducer physically disrupt the cancerous tumors leading to the death of the cancerous cells.
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Histotripsy works by ultrasound cavitation, a technique similar to the method used to non-invasively break down fat cells for weight loss treatments. When the waves are directed to the target cancerous tissue, they cause the production of bubbles within the tissue. The collapse of these bubbles disrupts the architecture of the tissue which results in cell death of the tissue.
Trials and results
To test the efficacy of histotripsy, scientists used about 22 lab rats implanted with liver cancer. Half were left as a control group while the remaining 11 were treated using histotripsy. About 50 to 75 percent of the tumor volume was targeted. In an additional 3 rats, only 25 percent of the tumor volume was targeted thus signifying a partial treatment using histotripsy.
After the treatment, both rat groups were euthanized and dissected to determine the success of the technique. It was discovered that in 80% of the rats completely treated with histotripsy up to 75% of the tumor was destroyed with no sign of metastasis or recurrence even after 3 months of observation. The rats partially treated with histotripsy also showed a good prognosis but those used for control showed dire signs of tumor progression.
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This study demonstrated the potential of histotripsy for successful non-invasive tumor ablation and prevention of local tumor progression and metastasis. Scientists have expressed hope in the application of this technique safely and efficaciously in the clinics and not just the labs.
Conclusion
Chemotherapy, radiotherapy, and surgery are good treatment options for liver cancer however, a common denominator to these options is the risk of side effects that either overwhelm the body as in surgery and radiotherapy, or damage the immune system, as in chemotherapy. However, histotripsy proposes a better solution. It is a technique that when perfected will usher the world into a new age. An age marked with better treatment of liver cancer and probably other forms of cancer.
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References
Worlikar, T., Zhang, M., Ganguly, A., Hall, T. L., Shi, J., Zhao, L., Lee, F. T., Mendiratta-Lala, M., Cho, C. S., & Xu, Z. (2022). Impact of histotripsy on development of intrahepatic metastases in a rodent liver tumor model. Cancers, 14(7), 1612. https://doi.org/10.3390/cancers14071612
Lynch, J. (2022, April 18). Tumors partially destroyed with sound don’t come back: Technique pioneered in rats at the University of Michigan could improve outcomes for cancer and neurological conditions. University of Michigan News. https://news.umich.edu/tumors-partially-destroyed-with-sound-dont-come-back/
