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How radiation therapy works

Radiation is a form of energy. Radiation therapy uses this energy to stop cancer cells from growing and multiplying. Radiation therapy is usually given to the patient by a machine that focuses a radiation beam on the body parts being treated. The most common machine used is called a linear accelerator.

Radiation also affects your body's healthy cells that are growing. After radiation is stopped, healthy cells will repair the damage from the radiation and grow normally again.

Uses of radiation therapy

Radiation therapy may be used to treat some leukemias and lymphomas. If your doctor recommends radiation therapy, you should ask about the goals of this treatment for your disease. For some diseases such as lymphoma, radiation therapy may be given to specific areas of the body such as the chest or brain. This is given to help treat the disease and prevent relapse (a return of the disease after a remission). As part of a transplant, radiation therapy may be given to the whole body; this is called total body irradiation (TBI).

Total body irradiation (TBI) before bone marrow or cord blood transplant

Radiation therapy given to the whole body, or TBI, is often part of the transplant preparative or conditioning regimen (treatment used to prepare a patient for a bone marrow or cord blood transplant). TBI involves doses of radiation to the whole body and can destroy cancer cells throughout the body.

TBI can reach cancer cells in scar tissue, the brain and spine where chemotherapy may not reach as well. However, the dose of radiation must be low enough so the body's healthy cells can recover. For this reason, TBI alone cannot be used to destroy large numbers of cancer cells. Instead, preparative regimens may use TBI along with chemotherapy. (Some preparative regimens use only chemotherapy and do not include TBI.)

If you get TBI to help prepare for a transplant, the treatment planning will include body measurements. These measurements are used to give the radiation evenly across your body. Sometimes shields are used to help prevent lung damage.

You will receive treatments over 2 to 4 days immediately before transplant. The schedule will be based on your transplant center's treatment plan, your diagnosis and other factors. During treatment you may be sitting or lying down. You will get treatment to one side of your body and then to the other. Each treatment session may take 30 to 60 minutes. Sometimes patients listen to music with headphones and a portable music player to help pass the time.

What to expect during radiation therapy

If you receive radiation therapy, your doctor will plan the radiation dose, schedule and body areas to be treated. This planning session is called a "simulation." Radiation staff will position you so they can aim the right dose of radiation at the right place on your body. If the radiation is being given to specific areas of the body, you may get small marks or tattoos on your skin to help the radiotherapist aim the radiation dose precisely. The radiation treatment does not hurt. You will not feel it at the time, although you may have side effects.

Local radiation therapy 

When you get radiation therapy to treat a certain body part, you will probably be treated over several weeks. Each session may last 20 minutes or less. During the treatment, you will remain still while a large machine, typically a linear accelerator, gives the radiation to your body. Shields may be used to protect parts of your body that do not need treatment.

Side effects

Radiation therapy damages healthy cells along with the cancer cells, and this damage can cause side effects. Most of the body's healthy cells recover after the therapy is stopped. The side effects you may get depend on your radiation dose and what body parts are treated. Ask your doctor about what side effects you might experience.

This is a basic overview of radiation therapy as a treatment. If you are offered radiation therapy, talk about the treatment with your doctor. Ask your doctor about the goals of treatment, its chances of success and the side effects you might face.