Carl Maronich (Host): Welcome to BayCare HealthChat. I'm Carl Maronich, and today I'm joined by Dr. John Greskovich, a radiation oncologist and medical director for BayCare's department of radiation oncology. And today we're going to be talking about proton and photon therapy for the treatment of cancer patients. Dr. Greskovich, welcome to the podcast.

Dr. John F. Greskovich: Thank you, Carl, for having me today for this podcast on proton and photon radiation therapy.

Carl Maronich (Host): Yeah, appreciate you being with us. Doctor, perhaps we could start with having you explain the difference between proton and photon radiation therapy.

Dr. John F. Greskovich: Absolutely. Let's start with a photon. A photon is a type of electromagnetic radiation, and it has a discreet packet of energy. And a few common examples of photons are things such as radio waves, ultraviolet rays, and x-rays. When we're speaking of photon therapy for cancer, it typically means the use of high energy x-rays.

So I believe most people have had an x-ray of their body previously. X-rays for cancer treatment are a little different. They're higher energy x-rays, about a hundred times higher energy than a diagnostic x-ray. But that x-ray has no mass, has no electric charge, but it can carry energy and momentum and it travels through the body. And in cancer therapy, it interacts with those cells.

On the other hand, a proton is a charge particle. It does have mass, and it does have a positive electric charge. Protons are one of the three main subatomic particles that make up an atom. The other two being a neutron and an electron. But since protons are charged, they interact differently with tissue than do photons or x-rays.

Both x-ray therapy and proton therapy can be used to treat cancer. They both work by damaging the DNA of the cancer cell, which leads to cancer cell death. The main difference between the two is how the radiation travels through the body and how precisely it can stop in the body. X-rays, as I mentioned, are rays, they can travel straight through the body, and protons, being particles, actually stop inside the body.

Both of them are carefully aimed at the cancer. They both interact with the DNA causing the DNA damage, and what we call double strand DNA breaks. But x-rays exit the body and protons stop in the body. A proton can also deposit a higher amount of energy at the end of its path.

So, for a proton, once it travels through the body, when it enters the body, it's depositing a lower amount of energy. And when it gets to the end of its path, the last two to four millimeters, it drops a higher density of energy. This area where this peak of energy is deposited is called the “brag peak.” And that really makes a big difference between the two types of treatment.

And therefore, the major difference between x-ray and proton therapy is a proton could be programmed to stop at the cancer cell, drop the high dose, and the brag peak, and expose less of the healthy normal tissue to radiation.

Carl Maronich (Host): So, it's a more targeted ray of energy that goes right to the source of that cancer.

Dr. John F. Greskovich: What I would say is they're both highly targeted. They're both very precise, but the difference is, the proton can drop the energy where you want it, where the x-ray has energy that's deposited other healthy tissues beyond the target. And that's the advantage of proton. It's not that protons cure more cancer and in general, the studies that have been done, you get the same cure rates.

It's that the protons can spare the healthy tissue and therefore cause less acute and late side effects.

Carl Maronich (Host): Ah, I see. So Doctor, what patients are better candidates for proton therapy?

Dr. John F. Greskovich: So there are a number of patients, and patient tumor types that are recommended for proton therapy. In other words, we've done studies that show a benefit to proton therapy. The first one that comes to mind is childhood cancers. Proton therapy is recommended for childhood cancers, including tumors that involve the brain, the spinal cord, the bone, soft tissues, head and neck, since kids have organs which are still developing.

So, as you can imagine, having the proton therapy to be able to stop the dose right at the target and exposing less of the nearby healthy tissues would decrease the risk of late effects. And what are late effects in kids? Well, if certain organs that are developing have too high of a radiation dose, you could get learning disabilities, growth delays, hormonal insufficiency, and later in life you could have a slightly higher risk of second cancers.

Another type of tumor that benefits highly from proton therapy in adult and kids are brain tumors. So treating the brain or other CNS tumors decreases the risk of late effects. And we mentioned some of these, like the hormone insufficiency in kids can also occur in an adult and just likely in adults or kids. You could have problems with vision, memory, or balance if the healthy brain gets too much radiation dose.

A third area that has been proven that protons are more effective than photons for specific types of head and neck cancers. The head and neck has numerous critical organs, and they seem to be all packed in a small area. So proton therapy for head and neck tumors has been shown to decrease the risk of damaging some of these healthy organs, which can result in problems such as dysphagia, which is swallowing problems. xerostomia or dry mouth and dysgeusia, which is an abnormal taste. And so by having proton therapy, dropping it on the tumor not hitting the swallowing muscles or the salivary glands or the taste organs, etcetera, you can prevent those late effects and have a better quality of life and possibly prevent the need for a feeding tube if you really damage someone's swallowing muscles.

Another area which proton therapy is very useful is spine or spinal cord tumors. The spinal cord obviously transfers the neurons from the brain to the rest of your body, and if you damage the spinal cord, you could have severe problems such as paralysis. So proton therapy is used quite often when there's tumors that are close to the spinal cord or brainstem.

That way we can stop the dose right at the kind of the junction of the tumor and the spinal cord by putting the brag peak at the right location. And that way we're not going to lead to any really severe complications such as paralysis.

Another organ that's very radio sensitive is the heart. So similar to the spinal cord, the heart cannot tolerate very high doses of radiation. So thinking of tumors that occur in the chest, central chest tumors, some lung cancers, esophageal cancers, lymphomas develop in the central chest. Even left sided breast cancers lie over top of the heart. All those cancers can benefit from proton therapy, which would decrease the dose to the heart, and that lowers the risk of heart failure as you age.

And I would say the final group that really has been proven that proton therapy works better than standard photon radiation is patients who have already had a course of radiation. Say you've had a course of radiation to your lung, and three years later you have a new cancer. Not exactly in the same spot of lung, but nearby, and you have to overlap or treat the same area that you treated before. Well, if you have to do a second course of radiation or something that we call reradiation, proton therapy is recommended. And for the same reasons we've listed above, you can prevent overlap of the dose to the previously treated areas.

A higher volume of overlap is seen when you use photon radiation or x-ray therapy versus proton therapy where you can hopefully prevent the overlap or minimize the overlap. And what happens if the healthy tissues of the body get too much radiation? They basically can die. You know, it's called necrosis or death of the tissue.

And that's really because you've overdosed the blood vessels in that area. The blood vessels kind of get scarred down and they get blocked and you have death of part of that organ. So patients who have had previous radiation are great candidates for proton therapy.

Carl Maronich (Host): So Doctor, for some of the reasons that you've mentioned in some of the circumstances it might stand to reason that some patients would be concerned, when prescribed with traditional photon radiation treatment. Talk a little bit about how you speak to patients that may have that concern.

Dr. John F. Greskovich: Well, that's a great question, Carl. I think I would have that same question if I came to see someone who had a new proton machine, high technology, treatment for cancer, but the way we discuss it with patients is we basically say we've already studied proton therapy versus x-ray therapy for decades.

As I mentioned earlier, there's no difference in curing your cancer. So that should be calming to the patient that if we choose x-ray therapy, because we don't think protons are going to make a difference with sparing healthy tissues and the outcome's going to be the same. If your cure rate's the same, that's number one.

That's what we're going for, that's the home run we want. Number two, if you have a little bit more radiation to the normal tissue, but say it's in the liver or in the lung where there's a lot of healthy tissue. That little extra bit of damage to that healthy tissue from x-rays is not going to change your quality of life.

It's not going to put you at any higher risk for long-term effects. So that's what we really have to discuss. People come in for protons and we're going to have a discussion of what other organs are around the target. What is the health of their organs? Say someone has a lung cancer and that's typically treated with x-ray therapy, but they have really poor lung function. We probably could argue that proton therapy would be better because even sparing a little bit more lung function with protons may make their quality of life better. So I think modern x-ray therapy techniques such as intensity modulation therapy where we can kind of paint the radiation into the body around the tumor.

Something called stereotactic body radiation therapy, where we give very high doses of x-ray therapy over one to five days. Those types of treatment have increased our abilities to, number one, cure more cancers. Number two, spare more healthy tissue. So proton therapies is a step above these, but it may not be necessary, and that's kind of the discussion we have with patients.

Carl Maronich (Host): Well, Doctor, is there a pretty good, in a percentage perhaps, what number of cancer patients get one versus the other?

Dr. John F. Greskovich: Well, I think. That's a great question too. There's probably different numbers out there. If I had to estimate, I would say maybe 10 to 15% of cancer patients may be candidates for proton therapy at this point. But as we all know, we're studying proton therapy for all types of cancer, and new studies come out every month, every year.

And we've increased the indications for proton therapy. The newest one really was a head and neck study that came out last year [2025] that really showed a large benefit for patients with respect to keeping their functions, less swallowing problems, less feeding tubes, better salivary gland function, etcetera.

And, I think there's numerous studies ongoing that possibly could make it a larger number than 10 to 15% in the future.

Carl Maronich (Host): Wow. So obviously you and your colleagues at BayCare do a lot of research and are studying the latest protocols and all the technology and to that point, Doctor, maybe you could speak a little bit to what differentiates BayCare's proton program from others.

Dr. John F. Greskovich: Sure. So BayCare did a very good thing in my mind. They looked at what is the value of a new technology and value obviously considers different things. It's not just the technology and what it can do, it's also the cost.

We went with a brand new type of proton therapy machine, which is basically taking the same exact intensity modulated proton therapy technology, putting it in a smaller footprint, and there's some really interesting physics behind that, but it's the same philosophy. You're accelerating protons in a synchrocyclotron, and it's getting up to a very high energy. And then you have a, what we call a fixed beam. So the protons come out of a fixed beam and the patient receives treatment through this fixed beam.

Now, other proton machines that might cost three or four times as much money because the technology requires the proton beam to be rotated or moved, the patient lies down and the machine actually moves, and it's very expensive to build that type of proton machine because of the weight of the gantry, the size of the room and the number of other factors.

With our proton machine the patient actually is not laying down. He's actually, he or she is actually in a seated position. And then we rotate the patient in the seat to create either the different beam angles or what we call proton arc therapy. So it really simplified the solution on how to do the same type of proton therapy.

And I think it might've improved it because a lot of patients I know have difficulty lying down for radiation therapy. It could be that they have bad lungs and they don't breathe very well laying down. It could be that they have a lot of pain in their back and they just don't like laying on their back very much, or it's kind of scary, you know, you're laying down and you're looking up at the ceiling. When you're in a seated position, you can see what's going on and you can be eye to eye with the people that are treating you. So I think, there's a lot of value to have a less expensive machine that can do the same type of treatment.

And it makes it more patient friendly. And so that's why I thought it was a great idea what BayCare did to invest in this machine.

Carl Maronich (Host): Yeah, I mean when it comes down to patient experience and outcomes and, if those are both in the positive category, then that definitely sounds like a great move. Doctor, for someone who is going on a cancer journey, at what point might they want to talk to their oncologist about the type of therapy and proton versus photon therapy?

Dr. John F. Greskovich: I think more and more people are researching cancer therapy. You know, you have a diagnosis, people go online, start looking for information, hopefully going to the National Cancer Institute and some really high quality sites, major cancer centers out there that have information on cancer treatment.

And they see things that come up like radiation therapy as one of the options for their cancer. And then the more they look, there's a lot more coming out with proton therapy now. So I think at any time during your journey, it's a good time to reach out and talk to your oncologist, even your primary care doctor.

They'll have some good information for you. Physicians that you trust, caregivers in your family that you trust, they're all good information sources and hopefully, you'll get a chance to meet with one of our BayCare doctors and discuss this type of treatment.

Carl Maronich (Host): Yeah. Well, Doctor, before I let you go, is there anything, any last message you want to make sure that people connect with when we're talking about this photon and proton therapy?

Dr. John F. Greskovich: Sure Carl. I think just to kind of summarize, for me, the take-home points are proton therapy typically does not improve the cure rate of the cancer and its main advantage is reducing the side effects and especially, the long-term risk that can occur when cancer is close to vital organs. It's very valuable to get an opinion, I think, for proton therapy if you have one of those listed cancer types that I mentioned such as childhood cancers, brain tumors, spine tumors, head and neck cancers, cancers near critical organs like the heart, or if radiation's going to be used a second time.

I really appreciate this opportunity to speak with you, Carl. It's been my pleasure to have this discussion.

Carl Maronich (Host): Dr. John Greskovich, thanks so much for being with us and sharing so much great information.

Dr. John F. Greskovich: Thank you again.

Carl Maronich (Host): For more information, go to BayCare.org. If you enjoyed this podcast, please share it on your social channels and check out the entire podcast library of topics of interest to you. I'm Carl Maronich, and this is BayCare HealthChat. Thanks for listening.