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radiation therapy Alternative Names
radiation treatment
Definition
Radiation can be used to treat many forms of cancer. It is considered a mainstay of cancer treatment. It can be delivered in two ways. One method uses a beam outside the body, and is called external beam radiation. The other method is to implant radioactive material inside the body. This is known as brachytherapy. Radiation affects molecules, proteins, and DNA in cells. The cells become damaged and are then unable to function and divide normally.
Cancer cells are more susceptible to radiation because they can't repair the damage. Some cancers are considered "radiosensitive" and curable with radiation. Other cancers are resistant to radiation.
Who is a candidate for the procedure?
Before its toxicity was well known, radiation was used for many conditions much less serious than cancer. This happened mostly in the early part of the 20th century. Acne, arthritis, and goitre, which is an enlarged thyroid gland, were all treated with radiation. Low-energy radiation is still used for a few non-cancerous conditions. These include psoriasis, a chronic disease that causes thickening of the skin.
Because it works so well, radiation is now used in at least half of all cancer patients. Many cancers are treated only with radiation with an intent to cure. Some of these are lymphomas, Hodgkin's disease, germ cell cancer, and cancers of the cervix, larynx, and prostate.
Other cancers are treated with radiation to improve symptoms, not to cure the person. These include cancers of solid tissues such as the lung, breast, and gastrointestinal tract, and melanoma, which is a skin cancer.
The decision to use radiation therapy, and how to use it, depends on a number of factors. Among them are the tissue type, the location and stage of the cancer, the symptoms, and whether the intent is cure or symptom improvement.
How is the procedure performed?
Implants can be placed anywhere inside the body. Implants may use wires or rods that are placed at the site of the tumour. Implants involve radioactive cesium, radium, 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. These pellets do not hurt and are not generally able to be felt once they are in the body.
Electron beams are low energy. They are often used for skin or other surface problems. High-energy particles can penetrate deeply, and are used for brain or deep solid tumours. 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.
Any form of radiation can be combined with chemotherapy. This combination therapy has more benefits and more side effects. Drugs such as fluorouracil (5-FU), doxorubicin, hydroxyurea, and cisplatin are radio-sensitising chemotherapy drugs. That means they make the targeted cancer tissue more susceptible to radiation.
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. Radioactive iodine has a short half-life, so the radioactivity disappears within a few days.
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 that delivers the radiation is lined up as well. The machine is then activated and delivers the radiation to the desired area. External beam therapy involves cobalt and protons or electrons. It is given over several minutes, usually once a day for several weeks. Penetration of external beam radiation depends on its energy level. The higher the energy, the deeper into the body the radiation can go. Benefits and side effects depend on the total dose, when it is given, the use of chemicals, and other factors.
The dose is measured in centigrey. Doses range from 2,000 to 6,500 centigrey. The energy of the radiation is measured in millions of volts. It can range from 5 to 50 million volts. Less energy is needed for radiation implants. That's because the source of the radiation is placed right at the tumour site.
What happens right after the procedure?
Some medications may be used to relieve acute or late side effects. However, they may not be very effective. Corticosteroids, such as prednisone, can reduce damage to the lungs, brain, and possibly other organs. People can often go home after the procedure if they have no reason to stay in the hospital.
People who receive external beam therapy do not put others at risk. They are not radioactive during or after treatment. Patients who have the implants can emit radiation. Precautions are taken to prevent other people from being exposed.
What happens later at home?
The doctor will give any needed instructions. Radiation therapy can lessen the symptoms of cancer. These include pain, numbness, headaches, and problems with nerves or hormones. Blood vessels, lymph nodes, or skin masses can be repaired or destroyed. Radiation is used to try to cure cancer, as well as to treat symptoms.
Radiation treatment with intent to cure delivers a tolerable dose. People who are cured can live healthy lives with no long-term problems. They can be treated again at the same site if a relapse occurs.
Almost all cancers require watching out for a return of the cancer. Monitoring may last for 2 to 10 years, depending on the type of cancer.
What are the potential complications after the procedure?
Side effects occur because any living tissue is sensitive to radiation. They result when normal cells that are damaged by radiation aimed at cancer cells. Side effects can be acute, mild, and temporary, or they can be more serious and permanent.
Normal cells that are rapidly growing or regenerating are more prone to side effects. Examples are bone marrow, intestines, hair follicles, the lenses of the eyes, kidneys, liver, and lungs. The brain, heart, cartilage, and bone are less sensitive.
Some side effects are acute, but go away on their own. These include hair loss, skin burn, nausea, fatigue, mouth sores, diarrhoea, and drops in blood cell counts.
Other side effects can develop more slowly and are permanent. These include necrosis or death of bone, and pneumonitis, an irritation of the lungs. Later side effects also include fibrosis, loss of skin blood vessels, intestinal damage, and bowel obstruction. Organ failure, such as the loss of kidney or heart function, may also occur. Radiation to the brain can cause delayed mental problems. These may include personality changes, memory loss, and dementia.
Long-term effects may include scarring, loss of organ function, or even secondary cancers. In many cases, the cancer can be cured with no long-term effects.
Combining radiation and chemotherapy can cause more acute and late side effects. Combination therapy is more likely to cause permanent damage to the bone marrow and secondary cancers.
Superficial electron beam radiation is usually free of serious side effects. Implanted radiation tends to cause local reactions. There can be some late complications, such as scarring. Radioactive iodine in the usual doses rarely causes any problems.
Author: Miriam P. Rogers, EdD, RN, AOCN, CNS
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Contributors
Potential conflict of interest information for reviewers available on request |
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