Radiation therapy, sometimes called radiotherapy, is usually directed by a radiation oncologist and administered by a radiation physicist, dosimetrist, and radiation technician.

 

Radiation therapymay be administered...

externally, in which case a radiation source will be positioned in a very specific location outside of the body and pointed toward the tumor. The energy from the radiation source is focused on the cancer while attempting to protect normal parts of the body. Since tissue between the external radiation source and a deep tumor could be injured by the radiation, sometimes the radiation intensity or dose will be decreased, by applied from different angles around the body. External radiation therapy may require several visits of a period of time.

 

In internal radiation therapy or brachytherapy, a radioactive source such as a seed, wire, or pellet is surgically implanted in or near the tumor. The radioactivity is relatively powerful near the radiation source, but decreases quickly as the distance around the tumor increases. Internal radiation therapy is often chosen when cancer has invaded important tissue (one that should be spared from surgery, if possible), such as the prostate or breast.

 

Radiation therapy may require a radioactive substance to be infused into the bloodstream, as occurs with systemic radiation. In some cases, the radioactive substance is chosen so that it collects in the cancerous tissue. Systemic radiation therapy is the precursor to one of the newest forms of radiotherapy, radioactive antibodies. In this therapy, a substance that emits electromagnetic energy is chemically linked to an antibody that recognizes a protein only found on the cancer cell. This antibody attaches itself very strongly to the cancer and the radiation is delivered very specifically to the cancer. Other places in the body that do not have the protein of the cancer cell are relatively unaffected by the cancer.