Proton Therapy – Minimally Invasive Treatment for Esophageal Cancer

MD Anderson Cancer Center
Date: 06/20/2011


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Lisa Garvin: Welcome to Cancer Newsline, a weekly podcast series from The University of Texas M.D. Anderson Cancer Center. Cancer Newsline helps you stay current with the news on cancer research, diagnoses, treatment, and prevention, providing the latest information on reducing your family's cancer risk. I'm your host, Lisa Garvin. Today, we'll be talking about the proton therapy for esophageal cancer patients. And with us today to talk about that is Dr. Daniel Gomez. He is an assistant professor of radiation oncology at M.D. Anderson's Proton Therapy Center. Welcome, Dr. Gomez.

Dr. Daniel Gomez: Thank you. Thank you for having me.

Lisa Garvin: Let's first talk about esophageal cancer. It's one of the more difficult cancers to treat and has a poor prognosis than some. Correct?

Dr. Daniel Gomez: That's correct. There're about 15 to 20,000 cases of esophagus cancer diagnosed every year in the United States. And it is one of the more--considered to be one of the more aggressive types of cancer. With five-year survival rates with this cancer are usually quoted as 20 percent or lower, not only as an aggressive cancer but it requires aggressive treatment and particularly in the more advanced stages of the disease, the more locally advanced stages, the treatment entails a combination of chemotherapy radiation and surgical therapy. So the patients receive aggressive treatment for disease that is open very deadly.

Lisa Garvin: Let's talk about proton therapy. It's really only been widely available I'd say in the last decade and probably not even that many years. Esophageal cancer is one of the cancers that you do focus on at the Proton Therapy Center. Do you have enough data to know whether proton therapy is working or providing a better solution for esophageal cancer treatment?

Dr. Daniel Gomez: That's a very good question. So yup, you're correct in that proton therapy has become more widely available in the past decade. However, I wouldn't--it's still relatively limited in scope in terms of locations. There's about 5 to 10 centers open currently in the United States with several others plan. But in Texas, this is the only proton therapy center currently open and available. With regards to your question about esophagus cancer and proton therapy, we've been studying proton therapy in this scenario for several years now and the way we started is by studying--doing dose symmetric studies. We'll look at the dose delivered, those critical structures with radiation and using these comparisons in comparing proton therapy with other techniques that are more widely available and present nationally that proton therapy was able to spare normal structures--critical normal structures of the thorax such as the spinal cord, the lungs, and the heart better than other modalities of radiation. We have now begun to treat patients clinically with this technique. And had begun to produce some preliminary data demonstrating that efficacy is analogous to that of other mode--treatment--other radiation treatment modalities about with potentially less side effects related to radiation.

Lisa Garvin: And I think we need to at this point talk about standard radiation treatment versus proton therapy. What is proton therapy exactly?

Dr. Daniel Gomez: So proton therapy is different than other types of radiation in terms of the way that it delivers dose, its dose distribution properties. So the way that other techniques deliver dose--and particularly what we call photon techniques which are the more widely available modalities is that they deliver a lot of those near the surface and that dose falls off as the particle enters in the body. So as a result, you have--or the way that you deliver a conformal dose in these--in patients treated with this technique, as you deliver a lot of different beams and they sort of meet at the center to deliver a very high dose of radiation. The problem with these techniques is that by doing so, you're delivering a lot of low dose in areas that are away from the tumor. Proton therapy is different. Proton therapy delivers very little dose at the surface and very little dose after the region of the tumor that we're treating so that it's able to selectively deliver dose in this target. And we're able to reduce the amount of dose to surrounding tissues and particularly this lower dose radiation, they can also potentially cause side effects.

Lisa Garvin: So it seems like it's ideally suited to esophageal. We never--because it's kind of a tight space you're working in there, a lot of critical structures.

Dr. Daniel Gomez: That's exactly correct. And esophagus cancer proton therapy appears to have a great deal of potential in esophagus cancer for exactly that reason. One is that we're delivering a relatively high dose in this disease in order to effectively attempt to control the disease. And the second is because of the location of the organ, the esophagus is located in a region called the thorax, in the center of the chest where it's surrounded by the spinal cord, heart, and lungs. So as you can guess, if we could effectively be able to deliver a treatment that good spare these surrounding structures while treating the central structure of the esophagus, that would be greatly desired in terms of reducing patient's toxicity and allowing them to tolerate the therapy better.

Lisa Garvin: Now, is proton being used as a frontline or a single line therapy for esophageal at this point or are they coming to you after surgery or chemotherapy?

Dr. Daniel Gomez: So, we typically see patients in esophageal cancer that have more locally advanced disease in our department. Earlier stage esophagus cancer is usually treated without radiation therapy that with surgery or some other less invasive surgical procedure and more locally advanced disease has been showing that proton therapy--or that radiation therapy in combination with chemotherapy and surgery are more effective than those techniques alone. So in that scenario, radiation therapy is an integral component of the treatment approach and those are the patients that we're typically referring for radiation therapy and hence, to proton therapy.

Lisa Garvin: So they're coming to you without any prior treatment?

Dr. Daniel Gomez: Typically, the standard approach for this treatment is surgery--or is radiation therapy and chemotherapy followed by surgery and patients with locally advanced esophagus cancer. And by locally advanced, I simply mean that the esophagus can't to that tumor has invaded into the wall of the esophagus rather than being very superficial on the surface of the esophagus.

Lisa Garvin: So typically, patients are coming to you for proton and then they're getting surgery afterwards, is that correct?

Dr. Daniel Gomez: Correct. And when patients are referred to us for potential proton therapy, we really do evaluate on an individual basis. Some patients have tumor that are very amenable to proton therapy where would see distinct advantages with this technique. Other patients we see and we--our assessment is that the photon or proton therapy would be appropriate in terms of controlling their disease and reducing toxicity.

Lisa Garvin: So what is the goal then? Are you trying to shrink the tumor before surgery? Is that the primary goal of proton?

Dr. Daniel Gomez: You could look at it in that sense and some patients were actually able to completely control the tumor eradicate the tumor with proton therapy or radiation therapy before surgery act as dose. However, we found that the percentage of patients that are--in which we're able to control the tumor is significantly increased if we add surgery to the treatment approach which is there have been multiple randomized study showing this which is why the standard approach and recommended approach in patients that can tolerate the treatment is for all 3 modalities to be used, surgery--or radiation therapy, chemotherapy, and surgery.

Lisa Garvin: Now, as far as making it dent in survivorship and prognosis, you really don't have a critical mass of patients to really bump those numbers yet, do you?

Dr. Daniel Gomez: Do you mean in terms of proton therapy?

Lisa Garvin: Yes.

Dr. Daniel Gomez: So no, we're in our initial stages of collecting patient data for--in terms of survival and toxicity outcomes. Buy what we do know is that we've shown that proton therapy can potentially reduce the dose to critical structures while delivering the same dose to the tumor. So using the first principles of radiation therapy, if we're able to effectively deliver less dose to critical structures while delivering the same dose to the tumor--to the tumor have follows that we should be able to obtain analogous control and reduce the morbidity of patients going through this treatment. But you're absolutely correct in that clinical trials are needed and are currently being designed and we're currently treating patients in this regard in order to effectively address these questions.

Lisa Garvin: What sort of research are you doing? I mean where are you going with the treatment of esophageal patients into the future?

Dr. Daniel Gomez: So currently, the--myself and the people in our group are designing a trial where we compare proton therapy to photon therapy in esophagus cancer. Patients are randomized to either photon or proton therapy and we look at patient outcome to determine if there's a true benefit. We have a similar trial that we're doing in lung cancer and we're sort of carrying the same principles over to esophagus cancer because that's really what's going to be needed to answer this question is clinical data, collective in a prospective fashion.

Lisa Garvin: What are--what is the typical esophageal patient that you treat at the Proton Therapy Center?

Dr. Daniel Gomez: So we've seen a shift in esophagus cancer over the past several decades, 20, 30 years ago. There was--many of the patients who developed esophagus had a high prevalence of smoking and drink--with an alcohol use. However, that incidence has somewhat shifted in terms of the type of esophagus cancer patients are getting and instead what we're seeing is a lot of patients that have a history of what we called Barrett's esophagitis or reflux disease that overtime changes the mucosa of the esophagus and predisposes the patient to neoplastic malignant transformation. So typically, the average patient we see would be in their 50's or 60's with a history of reflux disease and that has ultimately transformed into this malignant form, and that then has developed into cancer.

Lisa Garvin: Now, for the person who has been newly diagnosed with esophageal cancer, what question should they ask of their doctor about proton therapy?

Dr. Daniel Gomez: So I think a good basic question would be, do you think I'm a good candidate based on location and size of my tumor? I think that's the first question that needs to be answered and I think the treating radiation oncologist should be able to make a very good assessment by looking at their images, discussing with the patient the potential differences in their particular case. And that's very important in their individualized scenario as to what potential advantages may be of proton therapy over other techniques. And during this discussion, the various potential side effects of radiation therapy and the chances of a benefit will be discussed in depth with the patient to give them a good idea what them--what they in particular on an individual basis are expected to experience during this process.

Lisa Garvin: And in closing, when do you foresee proton therapy being a standardized treatment for esophageal cancer?

Dr. Daniel Gomez: Well, I think that really depends on the rapidity to which clinical trials--the clinical trials are performed and completed and the results of these clinical trials. I think we'll know in the next couple of years, 2 to 5 years. We'll get--start to get a sense of whether the dose symmetric data, the data that I was discussing regarding the radiation dose to the structures translates into a clinical data that we're seeing when we actually treat patients and follow them for toxicity and survival. And I think that's really going to be the primary endpoint and the measure to which we are able to recommend patients to this technique in the--for this technique in the future. So I think that's the real crocks of the issue on what we're currently addressing right now in our department.

Lisa Garvin: Great, thank you very much. If you have questions about anything you've heard today on Cancer Newsline, contact askMDAnderson at 1-877-MDA-6789 or online at [background music] Thank you for listening to this episode of Cancer Newsline. Tune in next week for the next podcast in our series.

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