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Targeting Tumors -- In-Depth Doctor's Interview

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Reported March 23, 2005

Targeting Tumors -- In-Depth Doctor's Interview

Alan Forbes, M.D., explains a new technology that allows for more effective radiation treatment of lung cancer and without as many side effects as traditional radiation treatment.

Ivanhoe Broadcast News Transcript with

Alan Forbes, M.D., Ph.D., Radiation Oncologist

M. D. Anderson Cancer Center, Orlando, Florida

TOPIC: Targeting Tumors

What is the new technology?

Dr. Forbes: It’s a new technology that’s developed so you can target the cancer in the lung even when it’s moving. It’s the ability to precisely target just the cancer in the small area surrounding lung tissue, and not have to treat a wide area.

How are you able to accomplish that?

Dr. Forbes: The first thing we do is to put a marker coil into the lung tumor that we can then image as the patient is being treated. You can see a bright gold coil showing up very clearly on the X-ray equipment. Then as the person breathes in and out, you can see when the tumor is exactly in the crosshairs. When we’ve done that, then the equipment identifies how the person is breathing in and out and automatically turns the beam on and off at the right point during the person’s breathing.

So, you basically are using an X-ray at the same time as the radiation?

Dr. Forbes: In fact it’s a whole lot of things. We have the stereoscopic X-ray paired to identify where the tumor is from the marker coil. We have an infrared camera to identify the person’s breathing and out and then a computer system that puts that all together and carefully turns the beam on and off as the person breathes.

What are the limits with traditional radiation?

Dr. Forbes: Traditionally, you would choose a beam size that was large enough to make sure that no matter how the person was breathing the tumor was within your target beam. So you had to treat a large area, sort of a scattergun beam, in order to make sure you hit the tumor. And that caused, of course, a lot more lung irritation, lung damage.

What does the large amount of radiation do to a patient?

Dr. Forbes: The larger treated area leaves more scarring, more difficulty with breathing. It’s hard on the quality of life. Then you’re limited in the radiation dose that you can give, which starts to compromise the cure rate. So, treating a large area will create a higher complication rate.

What does this new technology mean for patients?

Dr. Forbes: Less side effects, less fatigue during treatment, less scarring afterward of the lung, less likelihood of shortness of breath due to the treatment, and higher cure rate.

Are there any risks with this new treatment?

Dr. Forbes: It’s really an extension of what has been done in the past, and now we’re just able to do it much more precisely. This has really been the goal of lung cancer treatment with radiation over the past 20 years, which is to get to the point where you’re just treating the tumor, even though the lung is moving.

Who would be a candidate for this?

Dr. Forbes: At this point, we see patients who are very early in their cancer, stage 1 and stage 2. It is, for example, a small golf-ball-sized cancer in the periphery of the lung that was picked up on an X-ray, and the surgeon says he can’t operate because of the patient's medical problems.

How new is this procedure?

Dr. Forbes: It’s very new . There are some other approaches that have been developed but they just don’t have the same ability to target. They generally are predictors, so they predict how the person is going to breath and where the tumor is going to be when you turn the beam on. Of course if someone takes a deep breath, then that disrupts everything. Let's say you have a patient with sleep apnea, so his breathing is very irregular, we just couldn’t use it for him. To be treating exactly where the tumor is, not where we think it is, this is the first-available mechanism for doing that.

How many centers have this technology around the country?

Dr. Forbes: We are the only center in the United States and I believe worldwide. There was one patient treated in Belgium prior to the FDA approval, and the equipment was so good that the FDA gave very rapid approval. A company called Raynet Technologies produced it, and they asked us to be the first site to use it. I believe they’re going to give it to one other site. Then after they feel comfortable with the preliminary results, they’ll allow general usage of it.

How exciting is that for you?

Dr. Forbes: It’s fantastic. It’s at the point now where someone comes in with a stage 1 lung cancer, and it’s the only option because the dose is so much less to the surrounding tissue.

Have there been studies of this? Is it more successful than standard radiation?

Dr. Forbes: Obviously, we’re just a month into utilizing this technique. But the data are very clear that the higher the dosage you use, the better the results. The dose that I will be able to go to will increase the response rate from 60 percent to 85 percent. We know from the basic biology that the complication rate will be less because you treat less tissue, you get less side effects.

Does the device have to be programmed for each patient? Does it compensate for the fact that everyone takes different breaths?

Dr. Forbes: Yes. There’s a whole program that the patient goes through of training their breathing so that they’re able to take relaxed, steady breathes. We don’t exactly need that but it’s nice to have a nice uniform breathing in and out. Once that’s done, then you proceed with the treatment. We do initial tests, run to get the person comfortable to the equipment, and then proceed with the treatment. Once you start, it does not take any longer than the regular treatments.

Which is about how long?

Dr. Forbes: Bringing this on, about 30 seconds. Once the patient is in the treatment room, it takes about 10 minutes.

Are there any immediate side effects to the treatment?

Dr. Forbes: I expect that for most of his treatment, he’ll probably have no side effects. Then towards the end he’ll start having some fatigue, and that probably will be it. This way we’re avoiding critical structures like the esophagus that could give him a sore throat.

Why is this a medical breakthrough in your opinion?

Dr. Forbes: It’s the first technique that allows us to precisely target the tumor where it is at any one point in time. Right now it’s for stage 1 and 2. It’s applicable to a lot more things than just early stage cancer, and they expect us to be using this in the future on locally advanced lung cancer. We’ve also treated one patient with liver metastasis where he was otherwise doing very well, and this was the only site of disease. We have had several protocols, we’re using one now, and one is in the works for looking at high-fractionated radiation. We deliver the dose in much shorter time, so patients won’t have to be under treatment for six or seven weeks.

Are there any other organs that are affected by the movements of the lungs when breathing?

Dr. Forbes: The pancreas, but we’re not there yet for using it for this. But maybe one day.

Does insurance cover this?

Dr. Forbes: Yes. It doesn’t add any extra cost to the procedure.

When you say you hope that one day you’re going to be able to use it for more advanced cancer, what are the certain obstacles you are going to have to overcome before you can get there?

Dr. Forbes: There’s a size limitation to the beam at this time. That is we use the adaptive gating with equipment that allows a larger beam, for example, and we’ll be able to go to larger chambers.

It is promising to be hearing about advances in lung cancer because in the past there have not been many.

Dr. Forbes: Lung cancer research is now the national hot area to be in. There are so many things happening, not only the new chemotherapies like Gemzar, but also the biologics like going after particular enzymatic processes including growth factor stimulation. There are also improvements in radiation therapy, where the radiation sensitizes and the radiation protectors like Amifostine selectively protect the lung tissue but not the tumor. A lot of things are going on. It’s as fast as we can go because it’s very much an integrated process. For someone with stage 2, they may actually start to add in chemotherapy and enhance the cure rate by another 15 percent.

Potentially any patient coming in for radiation therapy in stage 1 could have this treatment as a substitute for standard radiation therapy?

Dr. Forbes: It’d be applicable to any patient. If someone has stage 1 and he is medically operable, standard of care is surgery. It's hard when we compare it to surgery. Some of the reports out there are very favorable for radiation therapy, but it's too early to really quote. Standard of care at this point is surgery for medically operable and then radiation therapy for medically inoperable with chemotherapy added in as the stage of the disease becomes more.

Since you are targeting a smaller area, you’re increasing the dosage. Does that create any problems in the cells?

Dr. Forbes: Well, it could. So you need to go by the literature that avoids that. The literature shows that I can go to a dose of 70 gray without increasing the complication rate. I’m still staying within the normal bounds, even though I am using this new technique that narrows the field further. The next step is to say well, now we’ve done that. Let’s start to increase the dose, which you couldn’t do in the national trials because they didn’t have the equipment to limit the lung fibrosis.

You're not doing that yet though?

Dr. Forbes: We’re not doing that yet. This is not a research protocol, its clinical treatment.

This article was reported by Ivanhoe.com, who offers Medical Alerts by e-mail every day of the week. To subscribe, go to: http://www.ivanhoe.com/newsalert/.


This information is intended for additional research purposes only. It is not to be used as a prescription or advice from Ivanhoe Broadcast News, Inc., or any medical professional interviewed. Ivanhoe Broadcast News, Inc., assumes no responsibility for the depth or accuracy of physician statements. Procedures or medicines apply to different people and medical factors in different ways; always consult your physician on medical matters.

If you would like more information, please contact:

Alan Forbes, M.D., Ph.D.

M. D. Anderson Cancer Center Orlando

Department of Radiation Oncology

1400 S. Orange Ave. MP 760

Orlando, FL 32806

(407) 841-5183

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