Histotripsy

What is histotripsy?

Histotripsy is a new, noninvasive treatment for liver cancer that uses ultrasound technology to destroy tumors. The U.S. Food and Drug Administration (FDA) approved histotripsy for treating liver tumors in October 2023.

During histotripsy, a machine directs high-intensity sound pulses toward one or more tumors. The pulses create a cloud of tiny gas-filled bubbles within the diseased tissue. The bubbles heave and expand in ways that resemble boiling water — except there’s no heat involved. As the cloud moves through the tissue, it breaks down cancer cell walls. It leaves behind harmless liquefied cell debris in its wake.

Medical experts still have a lot to learn about the potential uses of histotripsy. For now, we know that this procedure effectively harnesses sound to break up cancerous masses. It’s also proven to be impressively safe.

What does this procedure treat?

Your healthcare provider may use histotripsy to treat a primary or secondary liver tumor. Primary tumors start in your liver. Secondary liver tumors start in an organ other than your liver, but then spread there.

While the main treatment (and best chance of a cure) for liver cancer is surgery, histotripsy may be an alternative if surgery isn’t an option. Generally speaking, this procedure works best for people with:

• No more than three tumors
• Tumors smaller than 4 centimeters (about 1.5 inches)
• Tumors that aren’t out of reach behind your rib cage, lungs or GI tract (an ultrasound can’t penetrate bone or air)

How should I prepare for histotripsy?

Your healthcare provider will tell you how to prepare for your procedure. For example, you may need to stop eating certain foods or avoid taking certain medications beforehand.

You’ll need someone to drive you home afterward, as you’ll receive general anesthesia that puts you to sleep during histotripsy. Make arrangements with someone you trust.

What happens during this procedure?

A healthcare provider will position you on a table beneath a robotic arm with a transducer device. The transducer directs the sound pulses toward your abdomen. The general steps involved during histotripsy are:

1. You’ll likely get general anesthesia. You’ll be asleep for the procedure. Being asleep keeps you still so the transducer can direct the sound pulses with more precision.
2. Your provider will identify the treatment area. Using an ultrasound (the same type of technology used for treatment), your provider will locate the tumors inside your liver. They’ll show up on a screen.
3. Your provider will deliver the treatment. Your provider will program the machine so the transducer directs the sound pulses toward the targeted area. The pulses create a bubble cloud within the tissue.
4. Your provider will monitor treatment progress. The screen will show the bubble cloud as it moves through the diseased tissue, virtually erasing the cancer cells.

On average, histotripsy takes about an hour. Timing varies depending on the size of the treatment area.

What happens after this procedure?

Most people wake up after histotripsy with little to no pain. You may even feel as if you haven’t had a procedure. Most people go home on the same day as their procedure.

Over the next couple of months, your body will absorb the debris from the destroyed cancer cells. Your lymphatic system will help flush out the material. The liquefied cell debris is perfectly safe. Eventually, healthy liver tissue will replace the debris.

What are the benefits of histotripsy?

Unlike many other types of cancer treatment, histotripsy causes minimal to no side effects. Histotripsy isolates cancer cells for destruction without harming essential structures in your liver, like blood vessels and bile ducts. Several other types of treatments can destroy cancer cells. But they often cause residual damage that leads to unpleasant side effects.

Compared to other cancer treatment types, histotripsy:

• Avoids physical cuts or scars: Unlike traditional cancer surgery, histotripsy doesn’t require incisions.
• Doesn’t cause burns or hair loss: Histotripsy doesn’t cause common radiation side effects, like burns or hair loss at the treatment site.
• Doesn’t trigger widespread symptoms: Histotripsy doesn’t cause common chemotherapy side effects, like fatigue and nausea.
• Retains effectiveness near blood vessels: Unlike thermal ablation (a liver treatment that burns tumors), histotripsy isn’t less effective when a tumor is near a blood vessel.
• Spares antigens: Unlike cancer treatments that use heat and X-rays, histotripsy doesn’t harm antigens. Antigens are proteins that your immune system needs to identify and fight cancer.

Some studies suggest that after histotripsy, your immune system may get better at fighting tumors throughout your body. This includes those not directly targeted by histotripsy. Research is ongoing to learn more about how histotripsy may impact your immune response.

What is the success rate of histotripsy?

Histotripsy has a 95.5% success rate. These results come from the #HOPE4LIVER clinical trials to test its safety and effectiveness. This study tested histotripsy on people in the U.S. and Europe at 14 different locations. The results played an essential role in getting FDA approval for histotripsy.

The long-term follow-up from this trial showed that 9 out of 10 treated tumors remained successfully treated one year after surgery.

What are the risks or complications of this procedure?

With histotripsy, you may experience a reaction related to the anesthesia. Most are minimal and go away within the first 24 hours. Also, it’s possible to have bleeding or infection in the areas where the machine destroys tissue.

Still, one of the biggest benefits of histotripsy is that it’s low risk. Some people experience abdominal pain or fatigue afterward, but side effects are generally minimal and don’t last long. Only 1 out of 100 people has a serious or major complication after this procedure.

What is the recovery time?

It’s a good idea to relax on the day of your procedure. If you’re experiencing pain, your healthcare provider may recommend over-the-counter pain meds.

You may be able to resume your routine as soon as the day after histotripsy. Your provider can advise you on what to expect.

When should I call my healthcare provider?

Contact your provider immediately if you’re experiencing serious side effects of anesthesia, including:

• Severe itching or swelling
• Numbness in your body
• Slurred speech
• Trouble breathing
• Trouble swallowing

What is the difference between lithotripsy and histotripsy?

Lithotripsy and histotripsy are both procedures that use sound waves to destroy diseased tissue. Lithotripsy breaks apart large kidney stones into tiny pieces so you can pass them. Histotripsy obliterates small liver tumors.

Is histotripsy the same as ablation?

Yes and no. Histotripsy is an “ablative” technique. In other words, it removes or destroys liver tumors at the site where a treatment is applied. But when most people talk about ablation relating to liver tumors, they usually mean thermal ablation. This treatment uses heat to burn tumors. Histotripsy destroys the tumor without using heat, X-rays or drugs. Instead, it harnesses the energy that sound waves produce to destroy cancer cells.