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Understanding Types of Radiation Therapy

Posted Aug 24 2008 1:49pm
ANNOUNCER: Over the years, cancer treatments have tried to get "smarter" by attempting to more precisely target cancer cells. Radiation therapy using an external beam is one answer.

LEO GORDON, MD: The beam is aimed at a certain area of the body. Because the body can only tolerate so much radiation, that beam has to be fairly toned down, fairly direct. So if you have a large tumor in the lung, for example, or under the arm, or in the breast, that radiation can be very effective. It can make the tumor shrink down very well.

ANNOUNCER: However there are some cancers that are hard to fight with this type of therapy, like non-Hodgkins lymphoma, or NHL.

LEO GORDON, MD: It's in multiple locations. So because you can't target external beam radiation to multiple locations, you wouldn't know when to stop and you would wind up with total body radiation, external beam radiation has limited utility, I think, in non-Hodgkin's lymphoma.

ANNOUNCER: But now science has developed an even more targeted form of radiation through a treatment called radioimmunotherapy. NHL is the first type of cancer to be treated with this therapy, using a medicine called Zevalin. In radioimmunotherapy, radiation is linked to antibodies. Typically your immune system uses antibodies to circulate through the bloodstream and attack foreign substances. Like a medical missile, these radioactive antibodies head through the bloodstream to the tumor areas where they attach to cancer cells and destroy them.

LEO GORDON, MD: Radioimmunotherapy takes advantage of the fact that we already have antibodies, which we can target to malignant cells. Radioimmunotherapy adds to that by attaching radioactive particles or radioactive substances to that antibody.

ANNOUNCER: While both external beam therapy and radioimmunotherapy treatments are powerful tools, the nature of the illness will dictate which is the best weapon.

LEO GORDON, MD: If you've got a single large mass that's causing obstruction or symptoms, I think that's a nice role for external beam radiation. If you have multiple masses, multiple tumors, you can't treat them all with external beam radiation. That would be a circumstance where I think radioimmunotherapy would be most effective.

ANNOUNCER: These two therapies differ in the kinds of radiation they use.

ELI GLADSTEIN, MD: External beam therapy refers to a machine that produces radiation. It produces x-rays of very high energy such that they can penetrate tissue.

LEO GORDON, MD: Radioimmunotherapy, the radionuclide has sort of built-in properties where they're either what we call, gamma radiation, such as radioactive iodine, or beta radiation, such as yttrium-90.

ANNOUNCER: Conventional radiation therapy is delivered with an external beam over an extended time, while the radiation in radioimmunotherapy is delivered through the vein over a much shorter time.

LEO GORDON, MD: With radioimmunotherapy, they come once for the tracer and one week later for the treatment dose.

ELI GLADSTEIN, MD: Typically, external beam therapy means that the patient will lie under the machine on a daily basis for 10, 15, 20, sometimes as many as 35 to 40 treatments, days. And each of those treatments may be a couple minutes. With the radiation, external beam radiation, the patient will be irradiated and then have essentially a day to recuperate, and then you repeat the process.

ANNOUNCER: Conventional radiation can be effective, but sometimes there are side effects.

ELI GLADSTEIN, MD: It depends where you're aiming the beam. If you're aiming at the upper abdomen, you might get nausea and vomiting. If you're aiming at the head and neck region, you might wind up with a very painful sore throat.

ROBERT DILLMAN, MD: This is not an issue with the radioimmunotherapy because you're delivering radiation over a very small distance, just a few millimeters in cells all over the body so that you don't concentrate enough of the radiation in any one place to get those types of effects.

ANNOUNCER: The most significant side effects associated with radioimmunotherapy may be a temporary drop in the white blood cell or platelet count.

LEO GORDON, MD: On average I think the data would show that the counts are low for a period of two, maybe even three weeks, and then they return to normal. What we've also observed is that we don't see much in the way of infection, or bleeding. So even though the counts are low, we don't see many infections

ANNOUNCER: One of the benefits of conventional beam therapy is that the radiation is not retained in the patient's body after treatment. Following radioimmunotherapy, some radiation remains in the patient's body for a short time afterwards.

ELI GLADSTEIN, MD: For a few days you will be urinating radioactive urine. But it's not a real health threat unless someone has had an excessive dose or is urinating remarkable amounts of fluid.

ANNOUNCER: However at present, there are no long-term safety concerns with radioimmunotherapy.

ROBERT DILLMAN, MD: The exposure to the patient and the people around them is much, much less than what is considered to be a safe level for even hospital personnel who are allowed to have a higher dose exposure than the normal public is.

ANNOUNCER: While radioimmunotherapy is relatively new, it's already bringing promise to people with non-Hodgkin's lymphoma.

ELI GLADSTEIN, MD: In the future, radioimmunotherapy, I think, will supplant external beam to a large degree, because I think it will be better tolerated. They don't have to deal with toxic chemotherapy or toxic radiation. And that's a huge advantage for these folks.

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