Radiation therapy uses strong X-rays or other beams of energy to kill cancer cells or stop them from growing. There are different types of radiation therapy. External beam radiation therapy is the kind most often used to treat non-Hodgkin lymphoma (NHL). A large machine aims the beams of energy at the cancer without touching your body.

Your doctor may suggest external beam radiation as part of your treatment plan in any of these cases:

• As the main treatment for certain types of NHL that are found early (stage I or II) and have not spread
• As the main treatment if you have a type of NHL that responds well to radiation and is only in a few places that are close to each other
• As part of the treatment for NHL that's growing fast, especially if you have a large or bulky tumor. (You might get chemotherapy along with the radiation.)
• To help ease symptoms, such as pain, since radiation shrinks tumors that are pressing on organs and nerves
• As part of your treatment if you are getting a stem cell transplant (also called bone marrow transplant). In this case, radiation is given to most of your body over a short period of time. This is known as total body irradiation or TBI.
• As the main treatment for some types of lymphoma that involve the skin (T-cell and B-cell lymphomas). A special type of external radiation called electron beam therapy may be used. This type does not go deep beyond the skin surface.

For this treatment, a doctor called a radiation oncologist creates your treatment plan. The plan outlines what kind of radiation you'll get, the dose of radiation, the exact location, and how long the treatment will last. This doctor will talk with you about how you may feel during and after the treatment.

Radiation treatment is most often done as an outpatient in a hospital or a clinic. This means you go in for the treatment each day. You don't need to stay overnight in the hospital.

To get ready for your treatment, you'll have a planning session called a simulation. This is needed to find exactly where on your body the radiation beam needs to be directed and what position you'll need to be in for your radiation treatments. Your healthcare provider will want to make sure that the radiation is focused on the exact same spot each time. This first appointment may take up to 2 hours. Here's what you can expect during simulation:

• Imaging scans, such as MRI or CT scans, might be done. These scans are used to see exactly where the lymphoma is inside your body. They help clearly outline the size and shape of the tumor. Your healthcare provider then knows where to aim the radiation.
• You'll lie still on a narrow table. A radiation therapist will use a machine to define your treatment field. This field is the exact spot on your body where the radiation will be aimed. Sometimes it's called your port. You may have more than one treatment field if you have lymphoma in more than one place.
• You'll get into the best position. A mold or cast may be made to hold you in the exact same position for each treatment and keep you from moving.
• The therapist may mark your skin with tiny dots of semi-permanent ink or tattoos. This is so the radiation will be aimed at the exact same place each time.
• If you're having total body irradiation (TBI), you may have to stand in a special machine. Or you may lie down on your stomach or your back.

Radiation treatment is a lot like getting an X-ray. It doesn't hurt, and you don't see the radiation during the treatment. You stay in the radiation room for about 20 to 30 minutes. Most of this time is used to get you ready and into the right position. The treatment itself will take just a few minutes. You should plan on being there for about an hour total.

You'll lie on a table while the machine is placed over you. The radiation therapist will line up lights on the machine with the marks on your skin. You may have blocks or heavy protective shields put over organs, such as your lungs, heart, and kidneys. This helps to protect them from exposure to the radiation.

The radiation therapist will leave the room to turn on the machine. You'll be able to talk with and hear each other over an intercom. The therapist can see you the whole time. You may hear whirring or clicking noises as the machine moves. This may sound like a vacuum cleaner. The machine won't touch you.

You'll likely need radiation treatment every day for 5 days in a row (Monday through Friday) for several weeks. You will not be radioactive during this time.

Radiation therapy affects normal cells as well as cancer cells. This can lead to side effects. The side effects of radiation depend on the part of your body being treated, the dose of radiation, and other factors. Talk to your doctor about what side effects you can expect. Also talk about what can be done to prevent or ease them and when to call your healthcare team.

Many times, side effects don't start until you're well into or even done with treatment. You may feel better during your radiation treatment if you get plenty of rest and eat well. Almost all side effects get better over time once treatment is over.

Common side effects include:

• Skin in the treatment field becomes dry, irritated, and sensitive. A reddened "sunburn" can develop, which may lead to blistering and peeling.
• Hair loss in the area being treated (This may be permanent. Ask your doctor.)
• Extreme tiredness (fatigue)
• Feeling weak
• Chemotherapy side effects get worse

Radiation to your chest, neck, or mouth area can cause:

• Dry mouth, which can be permanent. (Ask your doctor.)
• Mouth sores that can make it hard for you to eat and drink.
• Pain with swallowing or burning in your throat.

Radiation of your stomach can cause:

• Nausea and vomiting.
• Loose stool or diarrhea.

Total body radiation can cause:

• Low blood cell counts.
• A higher risk for infection, from low white blood cell counts and damaged skin and mucous membranes.

If you have any of these side effects, talk with your doctor about how to deal with them and what to do if they become more serious. Make sure you know how to contact your healthcare team if you have questions or problems. Ask how to reach them on holidays, evenings, and weekends.

Radiation can also sometimes cause damage that may not show up until months or even years after treatment. These depend on the dose of the radiation and the area that's treated. These also depend on how many times you have treatment. Ask your doctor what you may expect.

Long-term side effects can include:

• Lung or heart damage, from radiation to your chest
• Damage to the thyroid gland, from radiation that reaches your neck
• Headaches or memory loss, from radiation to your head
• Fertility and sex-related problems from radiation to your pelvis. Before you start treatment, talk to your healthcare team about the possible impact on your fertility and choices for preserving your fertility.
• An increased risk for another cancer in the treated area many years later