Radiation therapy or radiation oncology involves the use of high-energy x-rays, gamma rays, electrons or atomic particles to treat certain types of cancer. The therapy is most often given with external beams of radiation, in which x-rays or atomic particles are directed to targeted portions of the body. An alternative approach is called brachytherapy, which involves an implant of radioactive material inside the body.
Because it works so well, radiation is now used in at least half of all individuals with cancer. Many cancers can be cured solely with radiation therapy. These include: cancer of the cervixcancer of the larynxHodgkin's lymphomaprostate cancer
Radiation therapy is also used to treat tumors that cannot be surgically removed. These include: some brain tumorssome other tumors in advanced stages
Radiation therapy is also used to decrease the risk of recurrence of certain tumors after surgery. These include: breast cancerhead and neck cancerrectal cancertesticular cancersoft tissue tumors
Other cancers are treated with radiation to improve symptoms, not to cure the person. This is usually when tumor has spread to bones or to the brain
The decision to use radiation therapy, and how to use it, depends on a number of factors. Among them are the tissue type and the location and stage of the cancer. The radiation oncologist will also consider the person's overall state of health. Total body radiation at low doses is used before bone marrow transplants. It destroys the existing bone marrow and suppresses the immune system.
The procedure to deliver external-beam radiation is somewhat similar to giving an X-ray. The person is put into position, and the machine delivers the radiation to the desired area. External-beam therapy involves high-energy X-rays and protons or electrons. It is given over several minutes, usually once a day for several weeks.
The higher the energy, the deeper into the body the radiation can go. This approach is used for deep solid tumors. Higher doses of radiation are used for radiation-resistant cancers and when there is an intent to cure. Lower doses are used for radiosensitive cancers and to relieve symptoms.
Electron beams are low energy, and are used for treating skin cancers and other superficial cancers.
Radioactive implants can be placed anywhere inside the body. Implants may use capsules, wires or seeds that are placed at the site of the tumor. They may contain radioactive cesium, iodine, palladium or iridium. The implants can remain in place for several hours to several days. They are removed after the dose of radiation has been delivered. They do not hurt and are not generally noticeable once they are in the body.
Any form of radiation can be combined with chemotherapy. This combination therapy has more benefits and more side effects. Fluorouracil (5-FU), doxorubicin, hydroxyurea, and cisplatin are examples of "radiosensitizing" chemotherapy medicines, that is, they make the targeted tissue more susceptible to radiation therapy.
Another form of radiation therapy is radioactive iodine. It is swallowed as a liquid and circulates through the body. It is used to treat thyroid cancer. The radioactivity disappears within a few weeks.