For Thyroid Nodules, New Non-Surgical Techniques in Thermal Ablation Are Taking Center Stage

Thyroid nodules are so common that 65 percent of people will have one in their lifetime.

Four years ago, thyroid surgeon, Jennifer Kuo, MD, started the Interventional Endocrinology Program at the Columbia Thyroid Center, one of the first of its kind in the United States, with the sole purpose of using non-surgical ablative techniques to destroy thyroid nodules.

Most nodules are benign, and not everyone needs interventional treatment, but five percent of that 65 percent are cancerous. That’s a big number.

Radiofrequency ablation (RFA) is a relatively new non-invasive technique that uses ultrasound and electrodes to pulse radiofrequency waves into a targeted nodule, conducting a controlled burn from the inside out. The technique has grown widely in popularity and there have been even more developments in its wake, like the use of microwaves.

We sat down with Dr. Kuo, an international leader in thermal ablation, to get an update on the latest techniques and treatments.

It’s been a few years since you started the program for radiofrequency ablation (RFA) at Columbia. Can you give us an overview of the latest in RFA treatment for thyroid nodules?

We got started in late 2019 and then the pandemic hit. That really stalled a lot of things in the United States in general, and particularly RFA because social distancing and travel restrictions impeded people from getting trained to do it. So, the early adopters of the program really got a head start. And those programs are thriving. Now, there's been a huge interest and enthusiasm for a variety of different people to get trained. And that's where a lot of our focus has been, in training.

Almost every thyroid-related conference or society has offered training programs, and we have been key players in those. Since Columbia is now a known name in this space, we’ve also been a place for a lot of international folks to come and get trained.

The US is doing pretty well in terms of getting people trained through these courses, but the rest of the Americas, so to speak, are a little behind. Canada just got the equivalent of FDA approval in their health system.

How has the adoption of RFA unfolded in Canada?

Canadians have had an interest in coming to get trained, and specifically to see the operational flow. And then I've actually gone to different hospitals in Canada, both in Montreal and Toronto largely to help them get started with their first few cases.

How the two parts of Canada have decided to approach this is very different. In the eastern side, in Ontario, they are doing it largely in the private sector, and that's the group of physicians that I've been training. I've had some role in the training of 10 different surgeons. And it is multidisciplinary, so not just endocrine surgery. It's been a mix of endocrine surgery, general surgery, as well as head and neck surgeons. On the British Columbia side, they're doing it through inpatient hospitals, through the public healthcare system.

Since you were trained in South Korea, has RFA been adopted in other parts of the world too?

Yes, definitely. There’s been a huge uptick in awareness and interest. The approval process varies globally, with initial adoption in Asia, followed by Europe and the U.S. Brazil has also emerged as a hotspot. In the Americas, Canada is gaining approval as I mentioned, and Mexico is expected to follow soon. The slow approval process in some regions contributes to challenges, but we’re dealing with that here too as we wait on our CPT [Current Procedural Terminology] code application.

The CPT code is an approval process that basically clears a procedure to get covered by insurance, is that right?

Yes, it should really facilitate it. We started a new professional society that's dedicated just to interventional thyroidology—the North American Society for Interventional Thyroidology (NASIT). And it's multidisciplinary, so it's surgeons, medical endocrinologists, radiologists, and even pathologists doing RFA procedures. They’re often the only ones in their rural areas willing to learn and offer this to patients.

Through that collaborative effort and support from the dominant associated professional societies, we got together and submitted the application to the American Medical Association (AMA) for the new CPT code to cover these procedures. It's probably going to be another couple of years before it gets approved, realistically 2025. But once we get a dedicated CPT code, that will increase access and affordability.

Let’s get into the world of thermal ablation a bit. What are the new techniques on the horizon, following RFA?

There are actually a lot of other thermal ablative techniques, but microwave just got approval through the FDA. Again, we’re actually one of the first institutions in the US to offer microwave. Now we have the whole gamut. We do ethanol, RFA, and microwave. Whatever is the better treatment for patients, that's what we do.

Will you give us an overview of the differences between ethanol, RFA, and microwave ablation?

Ethanol ablation is a chemical ablative procedure. Essentially, you use 100 percent alcohol to cause inflammation and scarring. And that works really, really well for thyroid nodules that are one big sack of fluid or otherwise a simple thyroid cyst. A very small portion of thyroid nodules are actually true simple cysts, so there are not as many cases that would be good candidates for it, but it does get reimbursed by insurance. 100 percent alcohol is actually very difficult to obtain these days, so we have special arrangements with some of our ancillary services to be able to get it.

RFA and microwave are thermal ablative techniques, both using certain types of energy to create heat that then destroys the cells inside the nodules. RFA uses radiofrequency waves, microwave uses microwaves. Microwave tends to be a much more powerful and efficient energy over RF.

We are going to have to prove this with data, and we're going to do some clinical trials comparing the two that we’re trying to get through the IRB [Institutional Review Board]. But I think microwave is probably going to be more effective for some of the larger nodules we see and nodules that tend to have higher fluid content and vascularity.

Why are microwaves so much more efficient?

One of the reasons why it's much more efficient is it's less subject to the heat sink effect, which can sometimes mitigate your ablation with RF. For those more vascular complex nodules, microwaves may be able to just get through them much more efficiently. So far in our preliminary experiences, we see that we're cutting times for the larger nodules down significantly. It’s the same efficacy when done correctly.

But my personal bias is that because it's so powerful, because it's so efficient, it's actually harder to learn. In the initial data coming out, there were higher complication rates. Any sort of deficiency that you have in your technique is going to be augmented with microwave. So it’s probably not the best energy to establish your learning curve on, but those that do well with it have started with RFA, got the expertise in RFA, and then transitioned over to microwave.

Would you say RFA is the gateway to microwave ablation in general?

We've been using both here in the US for a very long time, for other tumors. RF was the first one explored in the ablation space. Microwave came into vogue later because we were bleeding very large tumors in the liver, and the liver is quite vascular. With RF it takes a long time to ablate certain size tumors. And sure enough, microwave is now the leading or the preferred ablation approach for liver tumors.

So, to answer your question, yes, RF is sort of a gateway. Although historically, I would say laser probably came in sooner than RF, at least in the thyroid space. But it’s a lot less energy than RF or microwave, so it takes a lot of time and it’s fixed.

RFA and microwave are moving techniques? Is the process of ablation different between them too?

Well, this is part of the reason we need a new CPT code and why there’s such a learning curve. When we ablate the liver, when we ablate bone, and even when we're using laser, you want to place the electrode with the applicator in the center of the tumor. Then you leave it there and program how much power you want to give and it stays there until it's done.

With RF and microwave in thyroid nodules, you don't do that. You're constantly moving all the time. It’s called the moving shot technique. That's how you control how much energy you're delivering to any particular spot within the nodule. It's very dynamic. You're keeping track of the electrode tip at all times while the patient is swallowing or speaking. It's very different conceptually than what we're used to with other types of ablation.

If you look at the data for laser, it's safe, but it hasn't been as effective as RF. So RFA was sort of the gateway to the moving shot technique in thermal ablation of thyroid nodules and then microwave came in.

Is the combination of microwave power and the moving shot technique what makes it so much more difficult to learn in the thyroid?

In the liver, liver tumors are surrounded by more liver, right? Generally, other than some vessels, they’re not close to anything else. In the neck there are lots of critical structures, not very much in between. There’s potential for thermal spread when you're heating tissue.

With RFA, we’re changing the temperature of tissue from 36 degrees Celsius to over a hundred degrees Celsius in a matter of seconds. If you're using microwave, that happens in a matter of milliseconds. It doesn't take much time or much energy for you to go beyond what your target might be. If you leave the tip, whether it's electrode or antenna, in place for too long, that energy spreads very quickly and soon it's going to spread out to the trachea, the esophagus. If you're given milliseconds to be able to find yourself, move, and titrate your energy all at once, and you're trying to learn how to do that with microwave, the chances for things to go wrong are much higher.

Will you briefly explain the mechanism of the moving shock technique?

Moving shot technique is really where we are no longer working in a 2D plane. Our working screen is still 2D, but mentally, we're now thinking about the nodule in 3D, and conceptually we are breaking down that nodule into smaller subunits.

The idea behind the moving shot technique is that you're going to work from subunit to subunit to subunit and deliver just enough energy to each subunit to cause the tissue destruction locally, but not enough to have that thermal spread.

As the inaugural president of the North American Society for Interventional Thyroidology (NASIT), what are the society’s aims looking forward?

An organization like this allows those of us who have a really strong interest in interventional techniques to come together, talk, share techniques, and share research. It's necessary because it is so multidisciplinary and there's no other forum where we can focus on interventional thyroid for a day. I was the inaugural president when we had the first meeting last March in New Orleans, and I'm now past president. Our second one is coming up in February in Florida.

Are there any other potential applications of RFA or other interventional techniques that you’re working on?

Yes. When RFA started, it was all for benign disease. We’re one of several institutions that have offered clinical trials for using RFA in small, differentiated cancers. We are gearing up to present and publish our preliminary experience. We've done about 21 of these now and have gotten really good results.

We're also exploring what role these interventional techniques have in the indeterminate nodules. Those are nodules that have some risk of cancer, but we don't necessarily know for sure. And we're able to do that through much greater usage of molecular testing and looking at the genetic signatures of these nodules before we do anything to them.

The third trial we’re doing looks at quality of life, and we now have enough data to start publishing our preliminary experience. A lot of the trials we started back in 2020 are now coming to a preliminary conclusion. So, hopefully a lot more data will be coming out about other different indications where these treatments would be helpful.

Looking ahead, what do you expect the field of interventional endocrinology to look like in 5 years?

Well, right now the current focus is on microwave ablation. It’s the latest development in thermal ablative techniques. I don’t think it’s going to disrupt the field to any large extent, but five years from now there will be a lot of other stuff coming down the pipeline that potentially will disrupt the space a bit.

I, for one, am excited to see the developments coming down the road. I'm helping to consult on some of it. You know, as a potential provider, determining how it would be applied to our patients and stuff like that. It’s exciting.