Systemic radiation therapy
A patient ingests or takes an injection of a radioactive substance such as radioactive iodine or radioactive substance attached to a monoclonal antibody, in systemic radiation therapy.
Radioactive iodine (131I) is a kind of systemic radiation therapy generally used in the treatment of thyroid cancer. Thyroid cells naturally take up radioactive iodine. The monoclonal antibody helps targeting the radioactive substance to the correct place. The antibody attached to the radioactive substance moves through the blood and finds and kills tumor cells. For example:
- The drug ibritumomab tiuxetan(Zevalin) has been approved by the Food and Drug Administration (FDA) for the treatment of certain kinds of B-cell non-Hodgkin lymphoma (NHL). The antibody part of this drug identifies and adheres to a protein found on the surface of B lymphocytes.
- The combination drug regimen of tositumomab and iodine I 131 tositumomab(Bexxar) has been approved for the treatment of certain types of NHL. In this regimen, nonradioactive tositumomab antibodies are given to patients first, followed by treatment with tositumomab antibodies that have 131I attached. Tositumomab recognizes and binds to the same protein on B lymphocytes as ibritumomab. The nonradioactive form of the antibody helps protect normal B lymphocytes from being damaged by radiation from 131.
Various other systemic radiation therapy drugs are used in clinical trials for different cancer types.
Some systemic radiation therapy drugs provide relief from pain in cancer that has spread to the bone (bone metastases). This is a type of palliative radiation therapy. The radioactive drugssamarium-153-lexidronam (Quadramet) and strontium-89 chloride (Metastron) are examples of radiopharmaceuticals used to treat pain from bone metastases.