Radioimmunotherapy is mainly used to treat lymphoma and lymphocytic leukemia. It combines a radioactive substance with a monoclonal antibody that's injected (infused) in your body. The monoclonal antibody targets, and sometimes reacts with, proteins on cancer cells called antigens. The radioactive molecule destroys the cells.
Monoclonal antibodies are immune proteins made in the laboratory. Two common monoclonal antibodies used for blood cancer are ibritumomab (Zevalin®) and tositumomab and iodine I 131 tositumomab (Bexxar®).
Radioimmunotherapy has a less toxic effect on normal tissues than chemotherapy does. The treatment doesn't cause hair loss, often doesn't cause nausea and causes only mild degrees of fatigue and lowered blood counts. The recovery period is generally brief.
What to Expect
Your doctor will give you anti-nausea drugs before treatment to ward off nausea and vomiting, which some patients experience. You'll also be given iodide pills before receiving the radioactive iodine-linked antibodies. This prevents your thyroid gland from absorbing the radioactive iodine.
In most cases, patients are treated with Zevalin or Bexxar in an outpatient facility. Each treatment can take several hours to complete over the course of one to three weeks. Before you receive the treating dose of radioimmunotherapy, you'll get preparatory intravenous (IV) infusions of the antibody, first with no radiation attached, then with low-dose radiation. Over the next few days, technicians take scans of your body to identify the sites of cancer cells where the antibodies have attached themselves. On treatment day, you receive the antibodies via infusion, but this time a full dose of the radiation is attached.
Occasionally, patients have a severe allergic reaction to the infusion. Discuss this and other risks with your doctor before treatment. Fever, chills and aches can occur after treatment. Your doctor may give you drugs to reduce these effects.
After treatment, you'll need routine blood work for a few months to ensure you have a full blood count recovery. Most patients have a mild to moderate decrease in blood cell production for a short time. If you had chemotherapy or external radiotherapy before radioimmunotherapy, you may have a greater degree of cytopenia (low blood counts).
Some patients have mild to moderate reactions that tend to be short-lived. These include:
- low blood pressure
- rash or swelling at the injection site
You must take certain precautions to protect the people around you from radiation exposure. Your doctor and nurse will explain the precautions, which aren't restrictive and are easy to understand. Specific instructions depend on whether you're treated with Zevalin or Bexxar.
Radioimmunotherapy works gradually, so it may take several months for cancer cells to die and tumors to shrink. Your doctor monitors the treatment's effects with physical exams and imaging tests such as computed tomography (CT) scans and positron emission tomography (PET) scans. Overall, radioimmunotherapy is usually well tolerated.