Radiation Therapy

Alternate Names
radiation treatment



Definition of Radiation Therapy

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. Radiation causes ionization or chemical breaks in molecules, proteins, and DNA in cells. The cells become damaged and are unable to function and divide normally. Cancer cells are more susceptible to radiation because they cannot 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?

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 cervix
• cancer of the larynx
• Hodgkin's lymphoma
• prostate cancer

Radiation therapy is also used to treat tumors that cannot be surgically removed. These include:

• some brain tumors
• some other tumors in advanced stages

Radiation therapy is also used to decrease the risk of recurrence of certain tumors after surgery. These include:

• breast cancer
• head and neck cancer
• rectal cancer
• testicular cancer
• soft 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.

How is the procedure performed?

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.

What happens right after the procedure?

Some medicines 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 healthy organs. People usually return home after each daily treatment procedure if they have no other 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 implants, on the other hand, can emit radiation. Precautions are taken to prevent other people from being exposed. They may stay in the hospital or may go home, depending on the type of implant.

What happens later at home?

Radiation therapy can reduce the symptoms of cancer. Radiation treatment with intent to cure delivers a tolerable dose. People who are cured can live healthy lives. However, they can rarely be treated again at the same site if a relapse occurs, because another course of radiation would exceed the maximum total dose that the surrounding tissue can tolerate. Almost all cancers treated with radiation require monitoring 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 may be acute, mild, and temporary. Other times, 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, kidneys, liver, and lungs. The brain, heart, and bone are less sensitive.

Some side effects are acute but go away on their own. These include:

• diarrhea
• fatigue
• hair loss (may be temporary or permanent)
• mouth sores
• nausea
• skin burn

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 may also include:

• bowel obstruction
• heart disease
• intestinal damage
• kidney failure
• loss of blood vessels that supply the skin
• secondary cancers

Radiation to the brain can cause delayed cognitive impairments. These may include personality changes, memory loss, and dementia. Combining radiation and chemotherapy can cause more acute and late side effects. Combination therapy is more likely to cause secondary cancers and permanent damage to the bone marrow.

Superficial electron-beam radiation is usually free of serious side effects to deeper tissues. 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.