Seeds Fight Brain Tumor -- In Depth Doctor's Interview
Theodore H. Schwartz, MD, a neurosurgeon at NewYork-Presbyterian Hospital, talks about a new treatment for patients with cancer that has spread to their brains.
Radiation seeds for the brain are relativity new, correct?
Dr. Theodore Schwartz: Yes. What we're doing is implanting brachytherapy, which are radiation seeds that go into the brain which prevents brain tumors. What's new about them is the specific type of seeds that were using which are cesium-131. A very specific half life that lend themselves to brachytherapy in the brain. We actually permanently implant these seeds into the cavity after we resect a living brain tumor to prevent a local reoccurrence, which we know after you resect a primary brain tumor rather than a metastatic one; there is a risk of local reoccurrence as high as forty percent. So often we treat these patients with radiation therapy. We give them radiation to the whole brain; it's not very good for the whole brain. It's better to give focal radiation to just half the brain. We do that with a separate procedure, where we put them in a big machine called a gamma knife, but it's more efficient to do it all at once. So right when you take out the tumor, we implant brachytherapy right into the brain where the tumor is to keep it from reoccurring.
How many seeds are implanted?
Dr. Theodore Schwartz: It depends on the size of the cavity. If we take out a very big brain tumor, we put in a lot of seeds. If we take out a small brain tumor, we put in a few seeds. So we put in anywhere from 5 seeds to 35 seeds depending on the size.
How much radiation is emitted from these?
Dr. Theodore Schwartz: It's a very small dose of radiation outside the head. The dose you get right in the cavity is actually fairly high. But if you measure the dose outside the head it's very small, because if falls off very, very rapidly. By delivering the seeds right into the cavity you get a very high dose of radiation focally to the bed of the tumor and prevent radiation from spreading to the rest of the brain.
Compared to the Gamma Knife what is the difference in the radiation amount?
Dr. Theodore Schwartz: With the issue of the gamma knife, is that to get radiation to the brain using that device, the radiation has to pass through the skull. It passes through the brain so you get multiple beams of radiation that are going through the brain to focus on this one area. This technique avoids that so there's much less scatter to the surrounding brain, radiation is only delivered right to the cavity where we take the tumor out, it's much more focal way of delivering radiation to prevent tumor reoccurrence.
What are the differences in side effects between the gamma and the radiation seeds?
Dr. Theodore Schwartz: The side effects are similar in that if you deliver too much radiation to the brain in general you could have what's called radiation perosus. But we deliver in a much more focal area. So for an example the gamma knife would deliver radiation to the entire brain, although higher in one area that low dose of radiation that goes to the whole brain could actually induce another cancer in the brain. Where the risk of that happening in brachytherapy is extremely low, near zero.
Are there any patients you would not implant the seeds in and use the gamma knife instead?
Dr. Theodore Schwartz: No. Patients that we worry about are patients that have already had radiation therapy, that have a tumor that reoccur's. Because if we give more radiation therapy, the accumulative dose can be very high. They might not be as good a candidate for it. But we can also tailor the amount of seeds we put in; we can tailor the amount of radiation in each particular seed. The real advantage is that is saves patients from a second procedure where they have to go and get another radiation effect weeks later. Waiting those weeks later the tumor has already grown. We take the tumor out. If there were cells left behind that we microscopically just can't see, we can treat them right away. Put the radiation right in there; prevent them from growing, before they really start growing. Do additional radiation therapy afterwards, we wait several weeks the tumor is already growing back, you have to give more radiation and it's less effective.
How long do these seeds last in the brain?
Dr. Theodore Schwartz: The seeds will stay in the brain forever. Most of the dose is delivered within two weeks and just fades away.
Are you and staff in danger with the radiation?
Dr. Theodore Schwartz: You do admit a dose of radiation, but it's a fairly low dose. In the old days when they used to do brachytherapy with catheters and very big doses, patients had to be in an isolation room and you had to wear a lead cap. But now, technology is advanced. Patients can be in a room with another patient. Really, you just can't put your head on a lap of pregnant women. That would probably be too much radiation. If your three feet away, it's really not a problem.
Does this give brain cancer patients a new hope?
Dr. Theodore Schwartz: Absolutely. Our goal with brain cancer is to clean the brain of disease, and often we can't do it in surgery alone. We can't sterilize the brain and get it all disease out. So this is a way that after the surgery if there are little microscopic seeds of tumor left behind we clean it up with radiation therapy. It does not require a second surgery. It takes about fifteen minutes, we do it at the time of surgery, just lay the seeds right in there. We use certain techniques to make sure they are separated by a specific distance. It's a huge hope for patients who have brain tumors.
Have the radiation seeds been used for other cancers?
Dr. Theodore Schwartz: Radiation seeds can be used in the body for lung cancer, liver cancer, for cancer in other places. It's used less frequently in the brain, particularly these isotopes cesium-131. This particular isotope has never been used in the brain before. That's what initiative is and new, no one has put cesium-131 seeds in the brain before to treat malignant brain tumors.
Why has no one put cesium-131 in the brain before?
Dr. Theodore Schwartz: Because it's a new device. It's a new isotope that's now in seed form. For many reasons it's much more advantages for the seeds we used to use than other types of radiotherapy.
So is the gamma knife out of business now?
Dr. Theodore Schwartz: No. The gamma knife will never be out of business; it's a great device and has a lot of great uses. Were hoping that for particularly malignant brain tumors that spread from somewhere else in the body, this will be the new standard of care.
Could you explain your patient Beth, what exactly you seen in her brain?
Dr. Theodore Schwartz: Beth had a malignant brain tumor that spread from her body, we took it out. She was a wonderful patient, she was very appreciative, and she did extremely well. We were able to align the cavity with seeds. She's had no reoccurrence of the disease. She hasn't had any disease anywhere else. She doesn't need any further radiation therapy for now. Her brain is clean for now.
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