Expert discusses study of histotripsy in small renal masses

In this interview, Arun Rai, MD, MBA, MSc, discusses the histotripsy procedure using HistoSonics’ Edison System, which was highlighted during a Tech Talk session at the 2024 American Urological Association (AUA) Annual Meeting in San Antonio, Texas. Rai is an assistant professor of urology and the director of surgical innovation at the Smith Institute for Urology at Northwell Health in New Hyde Park, New York.

Arun Rai, MD, MBA, MSc

Could you preview the HistoSonics technology that was exhibited at this year's AUA?

So, I'm not affiliated with HistoSonics; I am an independent investigator. HistoSonics is a histotripsy company. Histotripsy was a technology developed at the University of Michigan, and it uses a non-invasive ultrasound to create micro bubbles within tissue that causes a mechanical effect within a precise targeted area. The Edison system is HistoSonics’ currently marketed device therapeutic arm that is FDA cleared for the destruction of liver tumors and now, with the #HOPE4KIDNEY Trial, being used in the United States to treat small renal masses.

At this year’s AUA, you participated in an Tech Talk on histotripsy. Could you recap this session?

The AUA Tech Talk was to discuss our experience so far with the #HOPE4KIDNEY Trial (NCT05820087). We’ve seen 12-month data coming out of #HOPE4LIVER (NCT04573881) Trial, which is the FDA pivotal trial for histotripsy in liver cancer. Now, in the United States, we are at a total of 7 cases nationwide with this therapy–being done at my institution and in Celebration, Florida with Dr. Michael McDonald–being used to treat kidney cancer. There has obviously been a little bit of a learning curve. The point of my talk was to discuss what we're seeing with early clinical experience in treating patients, some of the common clinical scenarios where this is an applicable technology, some of the caveats, some of the tips and tricks that we're learning as we go through this process, and some of the more interesting future applications of this technology, not only in kidney cancer, but also in other urological organs.

Could you give an overview of the actual procedure?

In general, the patient undergoes imaging of some type, whether that is a CT or MRI, to identify a lesion. For the purpose of the trial, it's a 3 centimeter or less lesion, and it has to be biopsy proven. We also look for its proximity to other organs and structures and whether it will be accessible through a planning tool to visualize whether the treatment arrays and the planned treatment volume can be adequately treated with the technology. Once the patient is deemed as a suitable candidate, during the actual procedure, they're positioned in the most ideal position to enable a beam path to treat the lesion. We go through the calibration process and treatment time, making sure we are marking out the areas of where that lesion is located, and we work with anesthesia to control as much as we can. The we deliver the energy treatment.

What's happening during the procedure is that you're using a GE ultrasound aside from the HistoSonics Edison unit to localize your lesion in multiple dimensions. Once that has been localized, there are some exciting capabilities around imaging fusion with the pre-procedure MRI or CT scan. During the calibration process, you’re ensuring that you're achieving an energy level high enough to generate that bubble cloud that we discussed earlier in the targeted tissue. Obviously, different folks have different tissue densities, and we want to make sure that there's enough of that voltage being applied to generate the bubble cloud that's required to have the desired effect. Once that's been calibrated at multiple points in the lesion, you begin your automated treatment process, and there's an algorithm in the Edison software that determines how to deliver treatment at various points, then the actual treatment is delivered. Then post-procedurally as part of the trial, patients’ first imaging is within 36 hours, and then usually again at 90 days, and so on and so forth at regular intervals.

How do you envision this technology fitting into the current treatment landscape?

There’s potentially a role here for patients with small renal masses that may not want to proceed with a minimally invasive laparoscopic or robotic procedure. But potentially the bigger picture is maybe there's an opportunity down the line to treat large renal masses as HistoSonics technology matures. There may be some other exciting applications in other urologic organs, such as prostate, or even other non-urology fields as well.

I think potentially even treating large kidney stones may be an option. We know that histotripsy could possibly be configured for treating calculi, so it could potentially be a non-invasive option for that as well. Outside of urology, I think the sky's the limit. There may be some opportunities looking at other solid organ malignancies, potentially pancreas, or areas that may have been harder to get to for other reasons, or for patients that may not have been surgical candidates before.

Is there anything else you wanted to add about some of the ongoing research or clinical trials for this technology?

We're excited to see what the outcomes are going to look like. It's pretty early on in the #HOPE4KIDNEY Trial, so we're excited to see not only what our institution is capable of, but what the outcomes are going to look like from other institutions. The group that is contributing these data is going to learn a lot about the technology, and hopefully, it will be helpful in informing other urologic applications and seeing whether there are opportunities for improvement of the technology going forward.