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Melanie Cole (Host): Welcome to Emory Healthcare Rounds, I'm Melanie Cole. Today's topic is proton therapy, and my guest is Dr. Bree Eaton. She's a board certified radiation oncologist in the Department of Radiation Oncology at the Winship Cancer Institute of Emory University and Emory University Hospital. Dr. Eaton, tell us a little bit about proton therapy. What is it?

Dr. Bree Eaton, MD (Guest): Well, proton therapy is an advanced form of external beam radiation therapy. It has a unique dose deposition pattern that enables us to treat tumors while sparing radiation exposure to the normal healthy tissue that is nearby.

Melanie: What cancers is it being used for these days?

Dr. Eaton: Like conventional external beam radiation therapy, proton therapy is used for the majority of solid tumors. So it can be used for anywhere from tumors in the brain down to prostate cancer in men, all different ages, and both men and women. It's primarily beneficial for patients who are receiving a curative cancer treatment.

Melanie: So as we're talking about the age of cancer patients, what are some of the advantages of proton therapy for pediatric and adult patients?

Dr. Eaton: Well again, the primary benefit of proton therapy is that it allows us to treat tumors while minimizing radiation dose exposure to normal tissue. And so what this does is it translates into significantly reduced long-term and permanent side effects for the patient. Now in children, they are particularly vulnerable to the side effects of radiation therapy, and so by reducing the radiation that's received to their normal organs that are still growing and developing, you can significantly reduce side effects that have the potential to be very severe and cause long-term problems with quality of life and long-term medical problems.

And for adult patients, it is a similar benefit in that when we're treating a tumor that is next to a sensitive organ such as the heart, or a normal brain, we can reduce side effects for adult patients as well.

Melanie: Tell us a little bit about how the therapy works, and as a result of its dose distribution characteristics, how can you use this as a radiation oncologist to tailor it for each patient?

Dr. Eaton: A proton beam is a completely painless and non-invasive treatment. So in terms of how it works, a patient is typically lying on a table, they may see or hear a machine moving around them, but they can't feel a thing. And we designed high energy proton beams that are unique and customized to each patient based on their tumor, tumor shape, size, position, and relationship to the other patient's normal anatomy. And that proton beam enters the patient, and is specifically targeted to the tumor where it causes damage in the DNA of the tumor cells, which effectively kills the tumor and prevents it from growing further.

Melanie: What specific planning is involved in this type of therapy? People think of radiation, Dr. Eaton, as you get marked, and the surrounding areas are covered, whatever. What specific planning is involved in proton therapy?

Dr. Eaton: Well, in general the process is very similar to photon or x-ray therapy, where just as you mentioned, the patient gets marked. That is a procedure that we call a simulation where some type of imaging is done. It may be a CT scan and/or an MRI that's done in the patient's treatment position. And then after that, there is a lot of work that is done behind the scenes. As a physician, we use the patient's diagnostic imaging such as MRI or PET CT or other CT scans. We are then able to fuse that with the CT scan or MRI that we took in the treatment position at the time of the marking or simulation, and we are able to draw out essentially in three dimension using very high quality imaging the areas that we want to treat with radiation. And we are also able to draw out all of the areas that we want to avoid radiation being received. So all of the normal tissues, the normal organs within the body.

Then we work with a team of dosimetrists who help us design the radiation beam, the proton beam. So the number of beams, the angles that we use, and then we also work with a team of physicists who help us evaluate the plan that we have created and make sure that it is safe and accurate. We do a process of QA for each plan that is patient specific, and we also do beam and equipment QA on a regular basis.

So there are multiple people that are involved, and this is actually a very extensive process that typically occurs over a period of one to two weeks in between when the patient has the markings or the simulation done and when they actually start their treatment.

Melanie: Dr. Eaton, how does proton radiation therapy compare to photon radiation therapy? What have you been seeing are the outcomes for proton therapy?

Dr. Eaton: Well, proton therapy is relatively similar to photon therapy in the way that it works at curing a tumor. So we believe that for the most part they are equally efficacious. There are unique situations where a very high dose of radiation therapy is needed to cure a specific type of tumor, and in that case, protons may be better able to deliver a curative therapy because it's able to be more safely delivered with such high doses. However, for the majority of cases, we believe that it's again equally efficacious. And so the main benefit or the main difference, again, is the sparing of normal tissues and the reduction in side effects.

So what we've seen in the patients that we've treated or that have received proton therapy across the country and even across the world is that we're having, again, similar cure rates as would be expected. So we don't see any detriment to tumor control, and we're seeing better outcomes in terms of long-term quality of life and a reduction in side effects.

Now but the data that we have is specific to different patient populations and tumor types, and so in some areas we have more robust data than we have in others. In an area where I specialize, which is the treatment of pediatric cancers, we have now more growing and growing data to show that we are seeing these expected reductions in side effects for patients.

So for example, one of the more common uses of proton therapy is in a tumor called a pediatric medulloblastoma. We now have really good data that we're able to reduce the amount of long-term hormone problems that these patients have. So they have a significantly lower risk of needing medications for hormone replacement therapy throughout the rest of their life after a proton therapy than they would have if they had had the conventional photon therapy, and that's just one example.

Melanie: As part of an academic medical center, how does Winship's unique position to lead research and clinical trials in proton therapy help as a treatment modality and help other centers around the country?

Dr. Eaton: Well, as Winship being a main tertiary academic center and an institution with access to multiple resources, we now have this tool just as one treatment option that we can offer to our patients along with other advances in surgery and systemic therapy. We can really create the best treatment option for patients out there.

We also have a strong clinical research program and we are hoping and planning to put almost every patient that we see and treat here at the Emory Proton Therapy Center on a clinical trial or a prospective outcomes registry where we will collaborate with other institutions across the country in order to make sure that we are learning as much as we can from the use of proton therapy in patients, and we can push the field forward through discovery with new advances in techniques to even further improve the benefit of proton therapy over other conventional radiation modalities.

Melanie: In summary, Dr. Eaton, please tell other physicians what you'd like them to know about proton therapy available at Winship Cancer Institute, and when you feel it's important for them to refer.

Dr. Eaton: Well, we will be operational here at the Emory Proton Therapy Center in December of 2018, early December, and we are available to see patients for evaluation of proton therapy starting in October. We are excited to work with referring physicians from all across the state, and all across the region and country, to provide the best care and the most options we can for patients. We are looking forward to working with referring providers in a very collaborative manner, and again, we'll have clinical trial opportunities that our patients can participate in. We expect that the most common diagnoses we will treat here are brain tumors, pediatrics, head neck cancer, lung cancer, prostate cancer, and other breast cancers and GI malignancies.

We do have disease site experts that have access to and will be treating with proton therapy, but also are part of the greater Winship disease site expert teams. So when we see a patient in consultation, we will not only consider proton therapy, but if protons is not the best option for them, we certainly are not biased or selective in that manner, and are really just looking for the best thing- the best treatment available for each patient.

Melanie: Thank you, Dr. Eaton, so much for joining us today and sharing your expertise on this exciting form of proton therapy and radiation oncology. You're listening to Emory Healthcare Rounds. For more information on the latest advances in oncology, please visit www.EmoryHealthcare.org/referwinship. That's www.EmoryHealthcare.org/referwinship. This is Melanie Cole, thanks so much for listening.