Conventional radiation therapy delivers beams of high energy x-rays to cancer cells through the skin's surface, into the areas of the body where tumors lie. Though it is an effective treatment for many types of cancer, it only kills cells in the path of the beam, including the healthy ones. Radiation therapy is also time consuming. It is given in divided doses over a period of many weeks-enough to kill cancer cells but allow the normal cells to recover. Most often it requires numerous trips to the treatment center each week, for up to eight weeks. And though it is more localized in its effect than chemotherapy, patients still suffer from a host of side effects.
For certain types of cancers, however, there is a new approach to radiation treatment. Scientists have developed a way to attach radioactive "tags" to specific cancer medications called monoclonal antibodies. Monoclonal antibodies are medications designed to target specific types of cancer cells wherever they are in the body, and stop their growth. In radioimmunotherapy, radiation is added to this targeted therapy. Radioisotopes are attached to the antibodies, and once delivered via injection, they target strictly the cancer cells-sparing the healthy cells. "Radioimmunotherapy gives targeted therapy an added kick... that's how I like to think of it, " says Dr. Leo Gordon of Northwestern University.
Below, Dr. Gordon talks about the special care that people receiving radioimmunotherapy require and the safety measures that should accompany treatment.
In what types of cancer is radioimmunotherapy currently being used?
Right now radioimmunotherapy is primarily being used in the fight against non-Hodgkin's lymphoma. Traditional radiation targets a tumor mass, but it can miss cancerous, single cells that might be floating away from the main tumor. So traditional radiation is very effective in treating a localized tumor, while radioimmunotherapy offers the opportunity to deliver radiation to multiple sites in a targeted fashion.
How do the side effects of radioimmunotherapy compare to traditional chemotherapy?
The major consideration is a lowering of the white blood count and lowering of the platelet count. Traditional chemotherapy certainly does that also, but in an expected timeframe of about a week to two weeks, maybe ten to fourteen days. Regarding radioimmunotherapy, on the other hand, we've found that the maximum drop in the white blood count doesn't occur until four to seven weeks after the treatment. So while the drop in the blood count is about the same as we might expect with chemotherapy, it happens later.
The other side effect that we do see with chemotherapy but we don't see with radioimmunotherapy that is what we call mucositis. Chemotherapy agents have a way of affecting all rapidly-growing tissue, like the tissue in the inside of the mouth or the esophagus. And when these tissues break down, one of our major barriers against infection also breaks down. So we see infections occurring frequently after chemotherapy, because the barrier in the mucus membranes has broken down, at a time when, on top of it, the white blood count is lower.
With radioimmunotherapy the white count can be lower, but we're not seeing such infections very commonly. Still, we need to be aware that the white blood cell count is, in fact, lower.
What precautions must patients take to protect family and coworkers from the radiation in their bodies?
One of the most common questions that we get from patients after this type of therapy is: "Will I glow? Will I be a risk to my family?" Generally, people need to take simple precautions, equal to the universal precautions for traditional radiation therapy. There have been studies that measure radiation exposure of family members and it equals exposure to background radiation. So we think the risk is very small. Especially if the agent has a very short half-life. I think we feel rather comfortable in saying that family members can feel fairly safe after their loved one has been treated.
We do recommend however, that for about five days to a week after treatment that condoms be used for sexual relations. We regard the precautions for radioimmunotherapy equal to simple universal precautions in the disposing of wastes-you can use the toilet to dispose of waste. People receiving treatment should use condoms for sexual relations for about a week after treatment and hand washing after bowel movements or using the bathroom. There are no special agents that are used. Just warm water and soap.
We do know that blood contains very little of the radioactivity, so if a patient were to suffer a cut or have bleeding from somewhere else, we think that there's no real increased risk of radiation exposure to family members from that bleeding episode. We know that saliva and urine have very little radiation; it's been measured very carefully.
This is a new approach to radiation treatment. What does the process entail?
There is a team of physicians, nurses, coordinators, radiopharmacists, radiotechnicians, nuclear medicine physicians and radiation oncologists, who are all involved in the care of the patient who is receiving radioimmunotherapy for lymphoma.
Unlike chemotherapy or radiation, where there's a fairly standard practice and a standard approach to treatment, radioimmunotherapy requires logistical organization and planning. The nuclear medicine department or the radiation oncology department at the hospitals have to set up arrangements with regional nuclear pharmacies for the delivering and handling of these radioisotopes. And there have to be people with experience, with licenses to deliver radioisotopes involved in the care.
So even though the whole treatment takes just two weeks, there is approximately three weeks previous to that of planning.
What role does the nuclear medicine physician play in treatment?
It's important that the nuclear medicine physician or the radiation oncologist be involved early on when a decision is being reached about whether a patient is a candidate or not for radioimmunotherapy because, number one, the nuclear medicine physician is the one who will administer the radioimmunotherapy drug.
Number two, the nuclear medicine physician will interpret the scans that are done in the week between the imaging dose and the treatment dose to determine if it's safe to go ahead. We rely on the interpretation of the nuclear medicine physician to tell us that the distribution of the drug in the body is appropriate and what we expect. So the nuclear medicine physician plays a critical, new role in oncology.
