Radioimmunotherapy: Safety Measures During Therapy
Posted Aug 24 2008 1:49pm
ANNOUNCER: One of the newest developments in the treatment of non-Hodgkin's lymphoma, or NHL, is radioimmunotherapy. At a Gilda's Club gathering in Chicago, this treatment was the main topic of discussion.
JOE BASHAW: In 1995 my wife was diagnosed with non-Hodgkin's low grade lymphoma. I was also diagnosed with the same thing. Any time there's any opportunity to go anywhere to get information about the disease, treatments or what's on the horizon, we always try to go.
ANNOUNCER: Radioimmunotherapy uses drugs called monoclonal antibodies, which are similar to antibodies the immune system makes to fight infection. These antibodies have a radioactive component attached to them, which attacks a protein on the surface of a cancer cell and destroys the cell. Currently, radioimmunotherapy is primarily being used in the fight against NHL.
RUSSEL SCHILDER, MD: The reason radioimmunotherapy has been targeted right now for lymphoma is we have the right target, the CD20 antigen. It's limited to B-cells; lymphocytes and lymphoma cells are very sensitive to radiation therapy. So we've always wondered 'Gee it would be great if we could just radiate a lot of these different sites' but with so many normal tissue structures, if you radiate too much of the body, the toxicity becomes excessive. So this is a way, in fact of radiating the whole body without having to expose the same amount of normal tissue.
ANNOUNCER: Radioimmunotherapy differs from traditional radiation therapy in several ways.
LEO GORDON, MD: Traditional radiation targets a tumor mass, but it leaves totally untreated single cells that might be floating in other areas. And so traditional radiation is a very effect way of treating a localized tumor. But radioimmunotherapy offers an opportunity to deliver radiation to multiple sites in a targeted fashion at we hope, safe doses.
RUSSEL SCHILDER, MD: Most radiotherapy in a traditional way is external beam. You get in front of the linear accelerator and obviously the first thing that has to happen is the radiation has to go through skin and other normal tissues before it hits the target of interest. By getting radioimmunotherapy, the radiation is brought right to the tissue of interest by the antibody that the radioactivity is linked to. The other difference between them is external beam often is Monday through Friday for many weeks. Radioimmunotherapy is one treatment one week, one treatment the next week and with just some images obtained to make sure that the radioactivity is distributing itself properly and then the treatment's over.
ANNOUNCER: The current treatment regimen uses a drug called Zevalin. Zevalin has two components: a monoclonal antibody with radioactive yttrium attached to it. But before a patient is given Zevalin, they first receive its non-radioactive counterpart Rituxan.
LEO GORDON, MD: On the first day, a dose of plain Rituxan, cold Rituxan is given first then immediately afterwards, a dose of radioactive antibody is given. We do body scans and look to see where the radioactivity is going. One week later, patients come back, all are outpatient, and they get another dose of cold Rituxan. And then immediately afterwards, they get a dose of yttrium. It's like an IV injection. Then they go home. And then what we have asked people to do is come back and do blood counts once a week. and our experience has been that within about four to six weeks the white blood count drops and the platelet count drops. And those levels that they drop to are potentially serious in that they can result in infections but fortunately what we've seen so far is that there are very few infections that occur following treatment with Zevalin, even though the white blood count is low.
ANNOUNCER: A common question that arises about this treatment: who are the best candidates?
RUSSEL SCHILDER, MD: The patients who are candidates for Zevalin therapy are patients who have recurrent or relapsed refractory low grade or transformed B-cell non-Hodgkin's lymphoma who have not had a lot of prior external beam radiation; who have not had prior transplants, who do not have more than 25 percent bone marrow involvement and have otherwise good organ function.
The side effects other than the radiation side effects, are mostly related to the same cold antibody that we use in rituximab therapy. They're related to fever, chills, a little fatigue, headaches, they're very non-specific very well managed and not very serious.
LEO GORDON, MD: One of the most common questions that we get from patients after this type of therapy is 'Will I glow?' I mean will I be a risk to family members? And we think the answer is the risk is very small. Family members can be fairly, feel fairly safe after exposure to their loved ones, after they've been treated with Zevalin.
We regard the precautions for Zevalin to equal simple universal precautions-- basically disposing of wastes. You can use the toilet to dispose of waste. Condoms for sexual relations for about a week after treatment, a hand-washing after bowel movements or using the bathroom.
ANNOUNCER: Radioimmunotherapy is proving to be a promising new area of treatment for non- Hodgkin's lymphoma patients, that possibly could be used to fight other forms of cancer in the future.
RUSSEL SCHILDER, MD: I think the next step is in how to combine it with other therapies, whether it's chemotherapy like CHOP or other antibodies that are under development. Right now, most of the data with drugs like Zevalin have been in follicular and low grades, but there are a lot of patients who have more aggressive lymphomas or mantle-cell lymphoma and want to know, 'Hey how does this stuff work for me?' And I think that's the questions that are now going to be addressed.