Ultrasound has been around in medicine for a long time. Most people think of it as the quiet, safe way doctors look inside the body without having to do surgery. But now those same sound waves are being used for something much bigger. Scientists have figured out how to use ultrasound not just to look at things, but to actually treat them. It has opened up a new direction for cancer care, one that could help patients avoid long recoveries and some of the pain that comes with traditional surgery.
This whole story started more than twenty years ago with Zhen Xu, who was a PhD student in biomedical engineering at the University of Michigan at the time. She was trying to find a way to remove damaged tissue without cutting into the body. Her plan was to use very focused sound waves to break the tissue apart. During one of her experiments on pig hearts, she made a small adjustment to her ultrasound machine so it would be quieter for her coworkers. What she did not expect was that this simple change would completely change her results.
By increasing the number of sound pulses and shortening each pulse to a tiny fraction of a second, she suddenly found that the ultrasound became far stronger. Within a minute, it had punched a hole straight through the tissue. That accident turned into what we now call histotripsy, which is a new type of ultrasound treatment that destroys tumors without heat or cutting.
In 2023, the United States Food and Drug Administration approved histotripsy for treating liver tumors. A year later, early trials showed that it successfully targeted about 95 percent of liver tumors in the study, with only minor side effects like short lived pain or small amounts of bleeding. The United Kingdom approved it next for certain patients under the National Health Service.
To imagine how this treatment works, picture a normal ultrasound scan. Sound waves go into the body and then bounce back to create an image. Histotripsy uses the same waves, but instead of making a picture, it focuses them on a very small point about the size of a pen tip. A robotic arm guides the device over the tumor in very precise movements.
When the sound waves reach the tumor, they create tiny bubbles inside the tissue. These bubbles appear and collapse extremely quickly, and that motion is strong enough to tear cancer cells apart. After the procedure, the body clears out the destroyed cells on its own. The treatment does not involve cutting, it does not involve heat, and most patients can go home the same day. Usually only one session is needed, although bigger tumors might require more.
Even though histotripsy looks very promising, researchers are still watching carefully to understand long term results. They want to know whether the treatment might accidentally push bits of tumor elsewhere, although animal studies so far have not shown this happening. Another limitation is that sound waves do not travel well through bone or air. Because of this, cancers in the lungs or some other areas cannot be treated with histotripsy yet. Trials are now looking into whether it could work for kidney and pancreatic cancers.
Histotripsy is part of a bigger trend where doctors are finding new uses for ultrasound. Another treatment, called High Intensity Focused Ultrasound, or HIFU, has already been used for several years. HIFU destroys tumors with heat created by strong sound waves. It is used for prostate cancer and can be as effective as surgery but with a faster recovery. Some people feel sore or have temporary urinary issues afterward, but these usually go away in a few days.
Both HIFU and histotripsy are done under general anesthesia so the patient does not move during the procedure. The biggest difference is that histotripsy does not use heat, which means the healthy tissue around the tumor is less likely to get damaged.
Scientists are also testing ways to combine ultrasound with other cancer treatments. One idea involves tiny bubbles that travel through the bloodstream. When ultrasound hits them, they can briefly open the blood brain barrier, which usually blocks things from entering the brain. If doctors can open it safely for just a short time, cancer drugs might be able to reach tumors that were impossible to treat before.
There is also interest in using ultrasound to make chemotherapy or radiation work better. The vibration from sound waves can weaken a tumor’s blood vessels, which allows smaller doses of medicine to have the same effect with fewer side effects. This could make treatment easier for patients over the long term.
Another promising idea is using ultrasound together with immunotherapy, which helps the immune system fight cancer. When ultrasound breaks apart or heats a tumor, it seems to make the cancer cells easier for the immune system to recognise. In theory, treating one tumor could help the immune system start spotting others in the body. It is still early research, but it has caught a lot of attention.
Of course, ultrasound treatments are not perfect. Scientists still need to figure out which cancers respond best and how to make this technology accessible to more people. Still, the progress so far makes the future look hopeful. Focused sound waves might one day replace or improve some of the harsher cancer treatments we rely on now, which is something many patients have been waiting for.