Recent research has focused on the use of radioactive monoclonal antibodies, also called radiolabeled antibodies, to deliver doses of radiation directly to a tumor. This process is known as radioimmunotherapy. Antibodies are made by the body in response to the presence of antigens (substances recognized as foreign by the immune system). Large quantities of particular types of antibodies, called monoclonal antibodies, can be made in the laboratory. These monoclonal antibodies can be attached to radioactive isotopes in a process called radiolabeling. When injected into the body, the radiolabeled antibodies circulate in the bloodstream until they locate and bind to the surface of cancer cells. The cancer cells are then destroyed by the radiation carried in the antibody.
Zevalin™ is the first FDA-approved therapy in a new class of cancer treatments called radioimmunotherapies. For patients with non-Hodgkin’s lymphoma (NHL), a cancer of the white blood cells, Zevalin provides a new option to traditional chemotherapy and radiation.
An estimated 300,000 Americans currently suffer from non-Hodgkin’s lymphoma (NHL), a type of cancer that starts with tumors in the lymphatic system but can spread to the entire body. It is the fifth most common cancer in the United States.
For patients with certain types of NHL, there is no known cure. External radiation, chemotherapy and the drug Rituxan can be effective treatments, but many patients eventually stop responding adequately to these standard therapies and need new options. Zevalin, in fact, was approved for use only in patients who have failed to respond to Rituxan and other treatments.
When Zevalin is injected into a NHL patient, it circulates in the body until it locates and binds with a protein found on the surface of the cancerous cells. It then delivers toxic radiation to those cells, and nothing else. The patient’s body develops new, cancer-free white blood cells from its bone marrow, and the isotopes decay into nonradioactive forms over the space of several days or weeks.
Patients take just one dose of Zevalin, which travels in their bloodstreams for about a day before binding completely to cancerous cells. It delivers its course of radiation for several weeks without repeated treatments.
More studies are needed to see if Zevalin keeps its patients cancer-free for long periods of time. But its early success is evidence that radioimmunotherapy can be an alternative to traditional treatments.