Histotripsy, a novel non-invasive technique that uses high-frequency ultrasound waves to destroy tumors, is currently being explored beyond its initial application in liver tumors. While the technology has shown promising results in liver cancer treatment, medical experts are cautiously optimistic about its potential applications in other solid tumors.
Dr. Shaun P. McKenzie, a surgical oncologist with Texas Oncology, explains that histotripsy's initial focus on liver tumors was strategic rather than limiting. "The reason that we've really started in the liver is because that is where [we have the] most of the experience with what we refer to as ablative therapy," Dr. McKenzie stated. "The liver is a solid organ that tends to push other critical structures away, making it a safe target. Plus, our liver is pretty durable."
Expanding Applications Beyond Liver Cancer
Although histotripsy is currently primarily used for liver tumors, Dr. McKenzie has already treated patients with various cancer types using this technology. "I've treated two patients with breast cancer, I've treated a patient with metastatic pancreatic cancer, but then also bile duct cancer and hepatocellular carcinoma," he noted.
The technology is now being investigated for use in other organs, including kidney, prostate, and pancreas. This expansion reflects growing confidence in histotripsy's mechanism of action and safety profile. However, researchers chose to begin with liver applications due to the established success of other ablative therapies in this organ.
Current Data and Future Research Needs
One significant limitation of histotripsy is the lack of long-term outcome data. While safety data has been published, leading to FDA approval, information on recurrence rates and survival outcomes remains limited.
"What we don't know—and this is always the concern about being on the front edge of some of these new technologies—is there has been no publication that has described recurrence rates over a 2- or a 5-year period," Dr. McKenzie explained. "Does [histotripsy] really help people live longer? And the answer is, we don't know yet."
To address this knowledge gap, a national study is being planned across multiple treatment sites to track patients' recurrences and survival outcomes. This data will be crucial in determining histotripsy's place in standard cancer care protocols.
Patient Selection Criteria
Not all patients with liver tumors are suitable candidates for histotripsy. Dr. McKenzie outlined several important considerations for patient selection:
"We want to see relatively normal liver function," he emphasized. "You don't want to do this to someone who's already approaching liver failure."
Other key factors include:
- Ability to undergo general anesthesia
- Limited or well-controlled disease outside the liver
- Tumor location away from critical structures
- Tumor size under 4 centimeters (optimal range)
"This treatment is best for tumors under 4 centimeters," Dr. McKenzie stated. "You can try overlapping treatment zones for bigger tumors, but the reality is—and all of the ablative treatments we've developed so far have been the same—as you get larger than 3 to 5 centimeters, the likelihood that an ablative treatment is going to be completely effective goes down."
Integration with Existing Treatment Approaches
Dr. McKenzie emphasized that histotripsy is not intended to replace current standard treatments but rather to complement existing approaches. "This is another treatment modality that works in concert with everything else we have so far. This is not something that we've developed in lieu of everything else."
In some cases, histotripsy may even be used to enhance surgical outcomes. "We see opportunities to even use this treatment to help make surgery safer. For example, if I have a patient who has a tumor that on one side is attached or wrapped around a critical blood vessel, could I use histotripsy to treat that edge and then remove the tumor?"
Multidisciplinary Approach Remains Essential
Despite the promise of histotripsy, Dr. McKenzie stressed that cancer treatment still requires a comprehensive, multidisciplinary approach. "A patient with tumors in the liver needs a multidisciplinary team of physicians reviewing their case. It requires a cancer surgeon who has specialty in liver tumors, a medical oncologist who has specialty experience in the tumor that are being treated, whether they started in the liver or they've spread there, and then sometimes it even requires interventional radiologists and radiation oncologists."
As research continues and more data becomes available, histotripsy's role in cancer treatment will likely become clearer. For now, it represents an exciting addition to the oncologist's toolkit, particularly for patients with liver tumors who may benefit from non-invasive treatment options.
