Tumor Treating Fields in Glioblastoma and Beyond: An APP Perspective

Key Takeaways

• Oncology APPs should understand tumor treating fields (TTFields) therapy and its role in glioblastoma and other solid tumors so they can explain treatment options and support informed patient decisions.
• Counseling about device use, daily routines, and treatment breaks can help patients incorporate TTFields into their lives, with greater use associated with better survival in glioblastoma studies.
• Proactive skin care education, early recognition of scalp adverse events, and ongoing communication can help maintain comfort and minimize interruptions in TTFields therapy.

Jennifer N. Serventi, PA-C, a neuro-oncology physician assistant and senior research associate at the Wilmot Cancer Center at the University of Rochester in Rochester, New York, discusses tumor treating fields (TTFields) therapy and practical considerations for oncology advanced practice providers, expanding on her article published in the Journal of the Advanced Practitioner in Oncology (JADPRO) in 2025. 

She explains its antimitotic mechanism, its role in glioblastoma and other solid tumors, and its use alongside other treatments. Serventi emphasizes patient education, integration of device use into daily routines, and proactive management of skin irritation to support sustained use. She encourages APPs to develop expertise in TTFields and recognize how assumptions about treatment burden may influence counseling, helping eligible patients make informed decisions while supporting quality of life.

Transcript

Hi there, I’m Jennifer Serventi. I am a neuro-oncology physician assistant and senior research associate working at the Wilmot Cancer Center at the University of Rochester in Rochester, New York.

Tumor treating fields (TTFields) therapy is an FDA-approved therapy in the treatment of several different solid cancers, glioblastoma (GBM) being the original, and that’s what I specialize in. Tumor treating fields are portable, noninvasive. It’s an antimitotic therapy that really utilizes the physics of electric fields to control tumor growth.

The system consists of 4 pads, each about the size of my hand for a patient with glioblastoma. Each pad is called an array, and the arrays are placed on the scalp, again, in the case of GBM, or on the torso in the case of other indications. And each array has a wire that comes out of it that is then attached to a power source that the patient then carries with them.

The FDA approval for tumor treating fields in glioblastoma was obtained over a decade ago. And it’s been something that’s been utilized in this patient population for quite a long time. But despite being on the market and available and approved for over 10 years, there’s still not been widespread or blanket adoption across institutions and across practices.

And I wanted to take some time to remind people out there that this is a category 1 treatment on the NCCN guidelines for patients with glioblastoma. And then, in addition, with some newer FDA indications in the last couple of years, and hopefully more to come, I thought it was time, again, to bring it to the forefront of minds for providers who take care of glioblastoma, but also to wet the whistle of people who take care of other solid tumors, as there are these newer indications, which we’ll talk a little bit about, and then potentially more to come down the road.

If you’re an oncology APP and you don’t treat GBM, but you treat solid cancer, you’re likely to encounter TTFields at some point because of the current indications that are available using TTFields, as well as others coming in the future. And I, in my practice, like to be prepared for patients to come equipped with questions. And I think more and more with time, our oncology APPs are going to have patients sitting across from them who are asking them about tumor treating fields. And so I think it’s best to be prepared and equipped with those answers, or even offering it, or just offering to discuss it with patients who are appropriate for it before they ask you.

I think the first thing I like to remind myself, and that I actually explain to patients, is that we’ve been using electric field therapy in medicine for decades. There are other devices that utilize electric fields. Pacemakers, microwave ablation devices, those all utilize electric fields. Tumor treating fields take that same technology and alternate the field. It goes back and forth. And the field is tuned to a very specific frequency that’s based on the size of the cell that we’re trying to target. And that can impact a mitotically active cell’s ability to divide and grow.

There are several steps during the mitotic process where tumor treating fields can either pause or stop the cell growth, and that’s specifically during microtubule formation and then at the time of cell cleavage, when the cell is trying to break into 2 daughter cells. And when that pause or that stopping of the mitotic process happens, the cell then recognizes that things are not going according to plan. And then that leads to programmed cell death, or apoptosis.

I think TTFields are different in a few ways. Like radiation, TTFields rely on the laws of physics. But instead of utilizing energy like radiation does, TTFields rely on the laws of force to affect a cancer cell. And of course, with chemotherapy, chemotherapy is utilizing the chemical processes to accomplish its goals.

Another difference, I think, is that tumor treating fields are highly localized. They’re localized just to the head. There are no systemic side effects or toxicity. And because the electric fields only affect cells undergoing mitosis, they can then spare those quiescent cells, spare those normal brain cells from any damage, unlike radiation or chemotherapy that are far less selective.

And then the last big difference, and I talk to my patients about this difference as well, is that tumor treating fields have no known or recognized maximum tolerated dose. In other words, with tumor treating fields, the more the better. The data show that the more time, on average, a patient with a glioblastoma is wearing the device and utilizing the device, the better their survival is likely to be. And we can’t really say that about radiation or chemotherapy, right? I can’t tell a patient, “The more radiation we give you, the better you’re going to do.” There’s clearly a maximum tolerated dose in both of those therapies, both of those modalities.

I think, and again, speaking specifically to GBM, where we’re combining this with radiation that the patient has already had, and then we’re combining this with adjuvant chemotherapy, I think we’re seeing in cancer in general, in oncology in general, that having a multimodality approach where we’re really hitting the cancer from multiple different directions and multiple different mechanisms is really making the most impact and getting the best outcomes for patients.

Worldwide, there have been tens of thousands of patients with glioblastoma treated with TTFields. And there’s really a wide breadth of understanding of both the safety and the efficacy in patients with GBM. The other indications are newer. And we’ve got some time still to gather some more information about the efficacy and safety and postmarketing analyses. And I think we’ll have a better idea 5 or 10 years from now about what kind of impact it’s making in those other solid cancers.

But I think that there are also far more options for patients with the other solid cancers. And I think that’s one of the reasons that TTFields has been so focused in the glioblastoma population, because it’s such an orphan disease. We have such a limited toolbox for it. And that’s really where we’ve seen the big push to use this therapy. But I think the sky’s the limit in terms of what we’re going to find with this therapy.

In the glioblastoma space, it’s FDA approved for both newly diagnosed and recurrent GBM. There is a device that delivers tumor treating fields at a specific frequency that’s different from GBM to both metastatic non-small cell lung cancer, and that’s in combination with immunotherapy or chemotherapy. And then the same device can deliver tumor treating fields to malignant pleural mesothelioma, also in combination with chemotherapy. And then there’s a third device that is used to treat locally advanced pancreatic cancer, also in combination with chemotherapy. As you can see, it’s that package deal that we’re doing in cancer right now, where the intention is to really combine this therapy with other therapies to get the most bang for our buck, so to speak. 

For glioblastoma, I think one of the things to remember about TTFields is that this is the first therapeutic breakthrough in over 20 years. And it’s the only therapeutic breakthrough in the last 20 years. This is a therapy that is really the newest thing that we have for glioblastoma that can prolong survival and do that without adding significant toxicity and without negatively affecting quality of life, which we know is really, really important. And then, as other indications are approved down the road, I think that’s going to help to solidify this technology as a mainstay of treatment for solid cancer tumors.

Tied to the indications that already exist, they’re trying different combinations of different things in those same disease states. There are ongoing studies in glioblastoma, in lung cancer, in lung metastases, and then also in pancreatic cancer. There’s a study that’s looking at using TTFields for glioblastoma, but earlier in the GBM journey. The way the FDA approval is now, and the way that the data show us to do it now, is to start TTFields along with adjuvant temozolomide, after the patient has completed their radiation therapy. And this particular study is looking at adding the TTFields to the radiation as well and then continuing it through.

There’s another study in GBM that’s currently enrolling, and that is looking at TTFields in the same adjuvant setting that we’re using it now, but also adding in pembrolizumab in an effort to see if maybe the TTFields can change the tumor microenvironment in a way that would allow immunotherapy to work in a GBM like we haven’t really seen it work in other cancers to date.

And then there’s a trial looking at non-small cell brain metastases. That’s done enrolling, and they’re just waiting for the data to mature and for the FDA to review that. And then, in our torso cancers, they’re looking at non-small cell lung cancer, but with a different chemotherapy combination than the current FDA approval, and then something similar in pancreatic cancer.

This therapy, like many therapies, requires a good amount of education. And at our particular institution, I’ve become the institutional champion for tumor treating fields. And I’m a big advocate for APPs to find something that they’re really passionate about and become an expert in it. And this is low-hanging fruit for a lot of APPs who treat patients, especially with glioblastoma.

Again, we spend a lot of our time educating patients about their therapeutic options. This is no different than the education that we need to provide them about chemotherapy, about radiation. And we really need to be as familiar with this option as we are with the others so that we can make sure that we are there to give our recommendations to patients in a way that they can absorb it, and so that they can have all the information that they need to make an informed decision about their treatment and to really be confident in their choice. And that’s really where I see the role of the APP in this.

I talk a lot about usage. And I arm them with that data that the more is better and that the more a patient is exposing their cancer cells to the tumor treating fields, the better their survival may be, at least statistically in the studies. We talk a lot about finding time to take breaks from the therapy, to have a date night or to take a swim. And we talk really proactively with patients who are still working on how they can incorporate this into their daily life.

I do a lot of counseling about skin care. I remind patients and care partners that open communication about their skin and notifying me at the first sign of a problem is really paramount so we can make sure that their skin stays happy. We want their skin to stay happy, not just for their quality of life—it’d be really uncomfortable to have skin irritation or other skin issues—but also, in order to get that fantastic usage that I want them to get, they need to have their skin doing well so that we don’t have to take prolonged breaks from the therapy.

I also spend some time reminding patients that the point of this therapy is not to tie them down, but to really offer them a way to manage their cancer on a daily basis while still doing the things that they want to do. And that’s why this is portable, this is noninvasive. We want them riding their bike. We want them going on family vacations. We want them doing all the things that they want to do while still treating their cancer.

We talk a lot about the published expectation that we’ve seen in a lot of the literature, especially the patient-facing literature, that says that they need to wear this device for at least 18 hours a day on average. But again, I talk to my patients about that lack of maximum tolerated dose. I explain to them that if we’re going to do this, if they’re going to go through the education process, which is a little bit in the office with me, and then somebody actually comes to their home from the manufacturer to teach them exactly how to apply the device, how to manage the device, they do have to have a shaved head.

If we’re going to go through all of that, I don’t want them to do 18 hours a day and then have them take it off and say, “OK, I’m done for the next 6 hours.” If we’re going to do this, I really want them to get the most out of it. And I want them wearing it as much as possible and as close to 24/7 as possible, obviously with some built-in times for those breaks like I talked about. And helping them realize that they have control over this, that they have control over how much they wear it or how much they don’t wear it, can actually be really empowering for patients. And that’s something that I like to encourage in them.

When we’re having our first conversations, I ask them to commit to wearing this for a month. If they make it that far, and most people do, then most people are willing to continue it. One of the biggest questions that I get is, “How long do they have to wear it in total?” And the common question is, “Do I have to wear this for the rest of my life?” And I think that that’s really hard to swallow. Asking anybody to do anything for the rest of their life, that’s a lot. I try to pare it down a little bit for them.

And I explain that it’s an ongoing conversation, that it’s something that we’ll readdress with each of their visits. But most patients, if things are going well and if their cancer is stable, once they jump on that train, they’re not really willing to get off.

Again, this is a localized therapy. Patients are not going to see any sort of systemic side effects. And they’re not going to see issues with blood counts, GI disturbance, fatigue, those kinds of things. We can see a little bit of headache. I’ve never worn the device. And I can’t say this firsthand, but when I ask patients about it, what I hear is it’s almost like a ponytail headache that those of us with long locks understand. You just get that ache in your scalp after it’s having some tension on it for a few hours.

Outside of that, we see some skin irritation. Those are really the only side effects. And the skin irritation, as you can imagine, is caused by the shaving of the skin. There can be some trauma to the skin from the shaving and then from the arrays themselves, just because they’ve got an adhesive on them. You’re taking them off every few days. You’re reshaving the scalp. There can be some drying of the skin. And all of that can lead to some discomfort in some patients.

The most common thing I see is just a common dermatitis. Patients will get some patchy, red, itchy, sometimes burning skin. Upon occasion, we’ll see some erosions on the skin. That’s just the removal of the very top layer of the epidermis. And that’s often from mechanical trauma to the skin, again, taking those arrays off. I see a little bit of folliculitis at times, and then some patients get pruritus from it.

I am a true believer that, and I say this to patients all the time, an ounce of prevention is worth a pound of cure. Once a patient has decided to do this therapy, as we’re getting near to their start date, I do a little bit of education on how to keep their skin happy. For providers who aren’t familiar or providers who don’t do a lot of this but have a patient once or twice a year, there are published guidelines to help assist in this.

In our practice, we’ve created our own smart phrase for patient summaries that really just reminds them of some of the best tips and tricks about things like how to carefully remove their arrays from their scalp so as to create the least impact on their scalp. What are the first steps they should take if they notice any irritation? And then, again, just being really communicative with our team, sending us pictures through their patient portal or reaching out to us if they’re having any problems.

Clinically, the skin adverse event management is really paramount. Again, we don’t want them to be uncomfortable because, if they’re uncomfortable, not only is their quality of life going to be worse, but they may stop therapy simply because they’re uncomfortable. And we really want to be proactive in that.

I also think, again, just to mention for a second time, that empowerment that patients can get by doing a therapy like this, somehow it’s just different than showing up to radiation or popping a chemotherapy pill each day. It just feels different to them. They really feel like this is in their hands to control. And I do like to introduce them to other patients who are using the device or encourage them to join Facebook groups or open houses that are available so that they can network and share tips and tricks with others. And then I also remind them when they’re getting good news, when they’re getting an MRI scan that looks great, that it’s really the combination of all of the things that we’re doing together that’s working to control their cancer.

Well, I feel like I waited about a decade from the FDA approval to the time we’re here and now, where we’re seeing those additional indications. And I was always saying, “Once we can show that it works in other cancers, I’m hoping that some of the naysayers in the glioblastoma community would say, ‘Well, I’m going to swallow my words. It works at other things, so it must be working in glioblastoma.’” I’m hopeful that we will continue to identify additional indications and combinations that can really help to improve on the building blocks that we’ve already established.

In addition, there have already been improvements in the device itself from the time of its inception. The device that was used during the studies that led to its FDA approval was twice as heavy as the device that’s used now. Similar to the cell phone, when the cell phone first came out, you needed 2 hands to hold it. And now we slide one in the little pocket of our jeans. I’m expecting to see improvements on the technology itself as we go into the next decade or so.

One of the things I think a lot about when I think about tumor treating fields is just the targeted nature of it. Targeted therapy is such a buzzword in oncology these days. And patients are looking for therapies that are going to go at their particular cancer, with good reason. And just having the knowledge and the understanding that this is a targeted therapy, but the target is just mitosis. And if there are cells that are mitotically active and the tumor treating fields can reach those cells, can get through the tissue, then a new indication might be right around the corner. So we’ve got to be aware of that.

And then just having an open-mindedness. This is a little bit out of left field for patients. When they come into our cancer center and they sit down in our office, they are with a new diagnosis of glioblastoma or some other solid cancer. They’re expecting to hear the buzzwords radiation and chemotherapy. Those are household words. But they’re really not expecting us to talk about a device. And similarly, as clinicians, I think we need just to be open-minded about being willing to accept that a nontraditional therapy utilizing a different aspect of science and physics could actually help, and breaking through some of those norms and just being open-minded to this.

I really encourage providers to consider all possible treatment options for patients with cancer, especially patients with refractory cancer or patients with very, very rare cancers that, again, don’t have a ton of tools in their toolbox. For those in the neuro-oncology space, I think the biggest takeaway is that you can be the champion of this. You can become the expert in this therapy. And in that role, you can ensure that every patient with an appropriate diagnosis who walks through your door is being given the opportunity to make a decision for themselves as to whether or not each therapy that’s available to them is the right one for them.

I think for APPs who are very unfamiliar with this technology, I think the most important takeaway is just to realize that this is not voodoo or Star Trek. This is not experimental. This is just science at its best. And again, we’ve been using electric fields in medicine for decades, and this is just simply a newer application.

I think one misconception that we have about tumor treating fields when we outsiders are looking in at it, we’re talking about shaving our heads and we’re talking about carrying this device around. I think we often, as a medical community, have a bias that this would be a real challenge or this would be something that really negatively affects a patient’s quality of life. And I just want to be sure that both clinicians and patients know that the data did not bear that out. In the studies that led to the FDA approval for this device in glioblastoma, the investigators looked at quality of life, and patients who were using the Optune did not report that their quality of life was any worse than the patients who weren’t using the Optune.

Now, of course, that’s not to say that for an individual patient that this might be a real challenge. But I think it’s just important to remove our biases: just because we don’t think that we would want to do it or we would want to use a therapy where we are right now doesn’t mean that our patient doesn’t want to use it. And again, we’ve got to make sure that we’re offering all possible treatment options to every patient who walks in the door.