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Radioimmunotherapy for Non-Hodgkin's Lymphoma

Posted Aug 24 2008 1:49pm
ANNOUNCER: It's always exciting when medical research provides new treatment options. Such is the case with radioimmunotherapy for non-Hodgkin's lymphoma. Like traditional radiation therapy, this new technique uses radiation. But with radioimmunotherapy the radiation is not delivered externally through a beam, but in the form of medication containing special antibodies.

Normally, your immune system uses antibodies, which are proteins that circulate through the bloodstream and attack foreign substances. Today, science can artificially produce substances known as monoclonal antibodies, which are designed to target cancer cells. A radiation source is attached to these antibodies, providing an extra punch in destroying these cells.

RUSSELL SCHILDER, MD: Radioimmunotherapy is a more targeted way of delivering the radiation. It is usually bound to an antibody which is specific for the lymphoma and thus quickly distributes the radiation to the areas of interest and thus spares a lot of the normal tissue.

ANNOUNCER: Currently there are two medications, Zevalin and Bexxar, which are approved by the FDA for radioimmunotherapy. Both utilize the power of different radiation particles called isotopes

STEPHEN SCHUSTER, MD: Iodine-131 is the isotope that's used in the Bexxar antibody. Yttrium-90 is isotope that's used in the Zevalin antibody.

ANNOUNCER: The radioactive particles in Zevalin emit beta radiation, which travels over a relatively short distance. The radioactive particles in Bexxar give off beta and gamma radiation. The gamma radiation travels a longer distance.

STEPHANIE GREGORY, MD: Beta radiation has a short path length and doesn't penetrate deeply into tissue and outside of the body. Gamma radiation is not stopped by anything short of lead, so it passes straight through the body out into the external environment and actually hits whatever is in its pathway.

ANNOUNCER: Safety issues for those in close contact with the patient depend on which medication is administered.

RUSSELL SCHILDER, MD: Yttrium-90 source of radiation is a pure beta emitter so there's absolutely no radiation that escapes the body. The only instructions they really have is to wash their hands, clean up any spills of bodily fluids quickly, to not share utensils for three days, to use condoms during sexual relations for the first week, though it's recommended that birth control be used for up to a year. The other, if it's using iodine, as in I131, it is mostly a beta emitter but there's some gamma radiation and there are some slight differences depending on what state you live in as to the regulatory issues.

ANNOUNCER: Side effects for the patients themselves appear to be minimal.

STEPHEN SCHUSTER, MD: There's some lowering in the white count, platelet count. It's, in general, very mild. And rapidly reversible by the eighth week following treatment and has little clinical consequences. But nevertheless, patients need to be monitored carefully.

ANNOUNCER: A benefit from these types of radiation could be a "crossfire effect." Experts believe the radiation can attack not only the cells to which the radioactive antibody is attached, but also destroy adjacent tumor cells as well.

STEPHEN SCHUSTER, MD: The crossfire effect is the same for Bexxar and Zevalin in the sense that radiation is delivered over a distance from where the antibody's localized and will treat adjacent cells. The difference, however, is in the magnitude of the crossfire effect.

The radiation travels 1 to 2 mm in distance with Bexxar, where it travels 5 to 10 mm with Zevalin. So the area of crossfire is greater with Zevalin than with Bexxar.

ANNOUNCER: The results for both of these medications are very promising.

STEPHANIE GREGORY, MD: A complete response with Bexxar is a median duration of three years, and there are patients with complete responses out to eight years with Bexxar. We don't have as long follow-up with Zevalin, but the complete responders are out two years with Zevalin, and they do have complete responders who are out four years at the present time.

ANNOUNCER: Both therapies are delivered through a vein and generally require several visits over a period of time lasting one to two weeks. Balancing the administration of these unique treatments requires a coordinated effort between a team of skilled experts.

STEPHANIE GREGORY, MD: We often say that it's a multi-disciplinary approach between the oncologist, the nuclear medicine physician or the radiation therapist, and certainly a nursing staff.

STEPHEN SCHUSTER, MD: I don't know that there are many more people involved in radioimmunotherapy than in other cancer therapies. It's just that there is new people or different people that are on the scene.

ANNOUNCER: Many feel radioimmunotherapy holds new hope for patients with non-Hodgkin's lymphoma.

STEPHANIE GREGORY, MD: The future of targeted therapy is very bright. We are going to see more and more combinations of targeted therapy.

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