A promising cancer treatment that destroys tumors using sound waves has been approved in the US.
A machine that uses histotripsy, a technique that uses sound waves to break down tumors, has been approved by the U.S. Food and Drug Administration (FDA) for the treatment of liver tumors.
It uses focused sound waves – like an ultrasound machine – to form microbubbles in the tumor.
The forces generated as the bubbles expand and rapidly collapse cause the cancerous mass to fall apart, destroying the tumor cells and leaving behind debris that is eliminated by the immune system.
The treatment’s approval means patients may be able to receive treatment for liver cancer without the side effects of radiation or chemotherapy.
Minneapolis-based HistoSonics, a University of Michigan spinoff company founded in 2009, pioneered the treatment.
HistoSonics can now sell its histotripsy delivery platform, called Edison, to hospitals and physicians for use on patients. It costs $12,500 per procedure.
The procedure is performed under general anesthesia and is performed alongside a live ultrasound of the liver so that the radiologist can locate and destroy the tumor.
A bedside machine with a robotic arm is moved into position over the patient’s abdomen like a traditional ultrasound machine, and a doctor locks it over the target tumor.
The rest of the procedure is fully automated.
Attached to the end of the robot arm is a transducer, a device that converts electrical energy into ultrasound energy.
The machine’s software then calculates how much energy is needed to create a cloud of bubbles powerful enough to kill the tumor, with focused ultrasound waves converging on a focal point in the center.
Once the tumor debris has liquefied, it is naturally absorbed by the body before being eliminated as waste.
The dirt formed becomes scar tissue.
Although it is considered a safe treatment, there is a small risk of nearby blood vessels (or, in the case of liver cancer, bile ducts) being damaged by the heat.
The duration of the procedure depends on the number and size of the tumors, but can take as little as seven minutes.
A human trial is currently underway and previous animal studies have shown promising results.
In the first study, 50 to 75 percent of the liver tumor volume in rats was destroyed by histotripsy, while the rats’ immune systems cleared the rest. In more than 80 percent of the animals, tumors did not return or spread.
A second study showed that the sound waves also break down the ‘coat’ of the cancer cell wall, revealing proteins that the immune system can use to recognize threats.
Killing the outer lining of the cancer cell exposes the tumor’s antigens so the immune system can use them for targeted attacks on other cancer cells to prevent tumors from recurring.
As of 2021, a human trial has been ongoing at the University of Michigan Rogel Cancer Center and other locations, treating patients with both primary liver tumors and liver cancer tumors that have spread beyond the liver.
Zhen Xu, professor of biomedical engineering at the University of Michigan, inventor of the histotripsy approach and co-founder of HistoSonics, said: ‘We want to harness the immunostimulation effects of histotripsy and hopefully combine it with immunotherapy or drug delivery.
‘This will shift histotripsy from a local therapy to a therapy that can treat tumors all over the body and ultimately lead to a cure. As far as cancer treatment goes, that will be the next step, and I’m very excited about the possibilities.”
Despite the new promising treatment, cancer patients should not expect to immediately abandon their chemotherapy and radiation treatments.
The device is only approved for use in liver cancer patients, and its limited availability and high price tag can make it prohibitively expensive for doctors to prescribe to patients.
Although the machine represents a breakthrough in treatment, it may not be suitable for every liver cancer patient. Doctors will assess each case and determine the best course of action.
Liver cancer is the third leading cause of cancer-related deaths in the US. According to the American Cancer Society (ACS), the average five-year survival rate for all stages is 20 percent.
By 2023, more than 40,000 cases of live cancer will be diagnosed, the ACS predicts, and nearly 30,000 people will die.
Drinking alcohol can increase the risk of liver cancer.
Histotripsy could be used in the future to treat kidney and pancreatic tumors, Edison’s makers say.