Principles of Pressure Directed Therapy with Y90 Radioembolization in Hepatocellular Carcinoma (HCC)
Updated: Mar 10, 2019
In our first podcast on pressure directed therapy, Dr. Charles Nutting and Dr. Nainesh Parikh discuss some of the first principles of Y90 radioembolization delivery, and the potential advantages of pressure directed devices over end-hole catheters in the treatment of HCC.
The BackTable Brief
Treatment of hepatocellular carcinoma (HCC) with Y90 radioembolization relies on sufficient arterial blood flow to transport glass or resin microspheres to the tumor.
The technical goal of radioembolization is to deliver the full dose of Y90 to the tumor.
High interstitial tumor pressures, non-target embolization, and early stasis may impede infusion, resulting in suboptimal delivery of therapy to the tumor.
Pressure directed therapy intermittently stops arterial flow and drives embolic into the tumor using pressure that builds during infusion, overcoming some of the technical limitations related to the tumor microenvironment.
Pressure directed devices like the Surefire Infusion System (SIS) can provide antireflux protection while improving delivery throughout the tumor, increasing dose delivery to the tumor and decreasing non-target embolization.
Disclaimer: The opinions expressed by the participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.
The Fundamentals of Embolic Delivery to HCC Tumors
[Dr. Nainesh Parikh]
“...any time that we're talking about unresectable liver disease, especially HCC, the theory is that the blood flow distribution for these tumors are predominantly arterial, rather than portal venous. So, in these patients, we think about how to take advantage of that fact, and deliver therapy through the artery.
The way we always explain to patients is you've got three choices: you've got radioactive material that's loaded on small spheres that gets delivered to places with increased blood flow; you've got chemotherapy, that's loaded on small pieces of glass, or spheres as well, that also goes predominantly to where the blood flow takes it; and then you've got just spheres in and of themselves, without anything loaded, that goes to where the blood flow takes it.
And each of those three, while they are all predicated upon the blood flow, they all have different outcomes: so for radioembolization, our goal is simply to deliver the radioactive dose to the tumor. And when we think about delivering radioembolization, or Y90 as sometimes people will call it, standing for Yttrium-90 - what it requires is a mapping angiogram, at least for us, and that's one procedure where you go and literally map out the vasculature to the tumors that you're trying to treat.
The most traditional sense is that, if it's Bilobar Disease - there are two arteries that supply the left lobe of the liver, and the right lobe of the liver, and so what you'll do is just treat the right lobe with a certain treatment, and then you'll let the patient heal; and six weeks later, you'll treat the left lobe. And then that's kind of how the practice started....
...the end point that we're trying to achieve is simply the delivery of the entire calculated dose. I'll just say a note on dose calculation: there [are] various ways to calculate the appropriate radioactive dose for HCC, but for the most part the goal is simply to deliver the entire dose into each of those arteries supplying the lobe of the tumor.”
The Tumor Microenvironment Creates a High Pressure System That Impedes Embolic Delivery
[Dr. Charles Nutting]
“...I think it's important for interventional radiologists to realize that the tumor microenvironment is very complex, and there's the interstitial matrix of the tumor, there are interstitial pressure in the tumor that are probably above systolic pressure. So I think some of these devices can help us deliver therapy deeper into the tumor and probably get homogeneous coverage.
It's not just a ball of cancer cells, there's a lot of complex physiology that's actually going on. So I think anything we can do to take advantage of delivering more product or more therapy in the area of the tumor is potentially helpful.”
Pressure Directed Devices Originated As Antireflux Devices
[Dr. Nainesh Parikh]
“...Charlie and I have been talking about how pressure-directed therapy started, and I think here would be an appropriate nod to the fact that it actually started as an antireflux device, the Surefire system in particular.
There have since been the advent of other catheters that are speaking more toward pressure-directed therapy, but just for that person who might not know the nuanced differences between what we're talking about for all these catheters, Surefire in particular started out as an antireflux device. So, the whole point was to protect against non-target embolization of specifically other organs.
Now what research has found, and I think is promising, is that when you use these antireflux devices, you actually improve perfusion through the tumor, there are perfusional changes that occur when normal systole and diastole are altered by any antireflux device such as the Surefire. Balloon occlusion devices also do the same, or similar thing.”
Pressure Directed Therapy May Overcome Technical Challenges of Embolic Delivery
[Dr. Charles Nutting]
“...we use both Y90 products to treat Hepatocellular Carcinoma, and there is definitely a higher embolic load when we talk about the SIR-Sphere product. So, one of the questions, or one of the concerns that's brought up is: as we're infusing the radioactive microspheres into the tumor distribution, what happens if we hit stasis prior to delivery of the entire dose? And this has been a question in my mind: if we give less than the anticipated dose, is that efficacious?
I think that, now that we have some of these pressure-directed methods to deliver the microspheres, especially with chemoemoblization or radioembolization with a higher embolic load, I feel like we're able to give up to a hundred percent of the dose, whereas previously, we may have been limited by stasis.”
Dr. Charles Nutting is a practicing interventional radiologist with RIA Endovascular in Denver, Colorado.
Dr. Nainesh Parikh is a practicing interventional radiologist with Moffitt Cancer Center in Tampa, Florida.
Cite this podcast:
BackTable, LLC (Producer). (2017, November 5). Ep 16 – Pressure-Directed Therapy in Y90 [Audio podcast]. Retrieved from https://www.backtable.com/podcasts
The Materials available on the BackTable Blog are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients.
The podcast referenced in this article was sponsored by Surefire Medical.