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Questions and Answers About Radiation Therapy

What is radiation therapy?

Radiation therapy (also called radiotherapy) is a cancer treatment that uses high doses of radiation to kill cancer cells and stop them from spreading. At low doses, radiation is used as an x-ray to see inside your body and take pictures, such as x-rays of your teeth or broken bones. Radiation used in cancer treatment works in much the same way, except that it is given at higher doses.

How is radiation therapy given?

Radiation therapy can be external beam (when a machine outside your body aims radiation at cancer cells) or internal (when radiation is put inside your body, in or near the cancer cells). Sometimes people get both forms of radiation therapy. To learn more about external beam radiation therapy, see External Beam Radiation Therapy. To learn more about internal radiation therapy, see Internal Beam Radiation Therapy.

Who gets radiation therapy?

Many people with cancer need radiation therapy. In fact, more than half (about 60 percent) of people with cancer get radiation therapy. Sometimes, radiation therapy is the only kind of cancer treatment people need.

What does radiation therapy do to cancer cells?

Given in high doses, radiation kills or slows the growth of cancer cells. Radiation therapy is used to:

  • Treat cancer. Radiation can be used to cure, stop, or slow the growth of cancer.
  • Reduce symptoms. When a cure is not possible, radiation may be used to shrink cancer tumors in order to reduce pressure. Radiation therapy used in this way can treat problems such as pain, or it can prevent problems such as blindness or loss of bowel and bladder control.

How long does radiation therapy take to work?

Radiation therapy does not kill cancer cells right away. It takes days or weeks of treatment before cancer cells start to die. Then, cancer cells keep dying for weeks or months after radiation therapy ends.

What does radiation therapy do to healthy cells?

Radiation not only kills or slows the growth of cancer cells, it can also affect nearby healthy cells. The healthy cells almost always recover after treatment is over. But sometimes people may have side effects that do not get better or are severe. Doctors try to protect healthy cells during treatment by:

  • Using as low a dose of radiation as possible. The radiation dose is balanced between being high enough to kill cancer cells yet low enough to limit damage to healthy cells.
  • Spreading out treatment over time. You may get radiation therapy once a day for several weeks or in smaller doses twice a day. Spreading out the radiation dose allows normal cells to recover while cancer cells die.
  • Aiming radiation at a precise part of your body. New techniques, such as and 3-D conformal radiation therapy, allow your doctor to aim higher doses of radiation at your cancer while reducing the radiation to nearby healthy tissue.
  • Using medicines. Some drugs can help protect certain parts of your body, such as the salivary glands that make saliva (spit).

Does radiation therapy hurt?

No, radiation therapy does not hurt while it is being given. But the side effects that people may get from radiation therapy can cause pain or discomfort. This book has a lot of information about ways that you, your doctor, and your nurse can help manage side effects.

Is radiation therapy used with other types of cancer treatment?

Yes, radiation therapy is often used with other cancer treatments. Here are some examples:

  • Radiation therapy and surgery. Radiation may be given before, during, or after surgery. Doctors may use radiation to shrink the size of the cancer before surgery, or they may use radiation after surgery to kill any cancer cells that remain. Sometimes, radiation therapy is given during surgery so that it goes straight to the cancer without passing through the skin. This is called intraoperative radiation.
  • Radiation therapy and chemotherapy. Radiation may be given before, during, or after chemotherapy. Before or during chemotherapy, radiation therapy can shrink the cancer so that chemotherapy works better. Sometimes, chemotherapy is given to help radiation therapy work better. After chemotherapy, radiation therapy can be used to kill any cancer cells that remain.

Who is on my radiation therapy team?

Many people help with your radiation treatment and care. This group of health care providers is often called the "radiation therapy team." They work together to provide care that is just right for you. Your radiation therapy team can include:

  • Radiation oncologist. This is a doctor who specializes in using radiation therapy to treat cancer. He or she prescribes how much radiation you will receive, plans how your treatment will be given, closely follows you during your course of treatment, and prescribes care you may need to help with side effects. He or she works closely with the other doctors, nurses, and health care providers on your team. After you are finished with radiation therapy, your radiation oncologist will see you for follow-up visits. During these visits, this doctor will check for late side effects and assess how well the radiation has worked.
  • Nurse practitioner. This is a nurse with advanced training. He or she can take your medical history, do physical exams, order tests, manage side effects, and closely watch your response to treatment. After you are finished with radiation therapy, your nurse practitioner may see you for follow-up visits to check for late side effects and assess how well the radiation has worked.
  • Radiation nurse. This person provides nursing care during radiation therapy, working with all the members of your radiation therapy team. He or she will talk with you about your radiation treatment and help you manage side effects.
  • Radiation therapist. This person works with you during each radiation therapy session. He or she positions you for treatment and runs the machines to make sure you get the dose of radiation prescribed by your radiation oncologist.
  • Other health care providers. Your team may also include a dietitian, physical therapist, social worker, and others.
  • You. You are also part of the radiation therapy team. Your role is to:
    • Arrive on time for all radiation therapy sessions
    • Ask questions and talk about your concerns
    • Let someone on your radiation therapy team know when you have side effects
    • Tell your doctor or nurse if you are in pain
    • Follow the advice of your doctors and nurses about how to care for yourself at home, such as:
      • Taking care of your skin
      • Drinking liquids
      • Eating foods that they suggest
      • Keeping your weight the same
You are the most important part of the radiation therapy team.
Be sure to arrive on time for ALL radiation therapy sessions.

Is radiation therapy expensive?

Yes, radiation therapy costs a lot of money. It uses complex machines and involves the services of many health care providers. The exact cost of your radiation therapy depends on the cost of health care where you live, what kind of radiation therapy you get, and how many treatments you need.Talk with your health insurance company about what services it will pay for. Most insurance plans pay for radiation therapy for their members. To learn more, talk with the business office where you get treatment. You can also contact the National Cancer Institute's Cancer Information Service and ask for the Financial Assistance for Cancer Care fact sheet. See Resources for Learning More for ways to contact the National Cancer Institute.

Should I follow a special diet while I am getting radiation therapy?

Your body uses a lot of energy to heal during radiation therapy. It is important that you eat enough calories and protein to keep your weight the same during this time. Ask your doctor or nurse if you need a special diet while you are getting radiation therapy. You might also find it helpful to speak with a dietitian.To learn more about foods and drinks that are high in calories or protein, see Foods and Drinks That Are High in Calories or Protein. You may also want to read Eating Hints, a book from the National Cancer Institute. You can order a free copy online at or 1-800-4-CANCER.

Ask your doctor, nurse, or dietitian if you need a special diet while you are getting radiation therapy.

Can I go to work during radiation therapy?

Some people are able to work full-time during radiation therapy. Others can only work part-time or not at all. How much you are able to work depends on how you feel. Ask your doctor or nurse what you may expect based on the treatment you are getting.You are likely to feel well enough to work when you start radiation therapy. As time goes on, do not be surprised if you are more tired, have less energy, or feel weak. Once you have finished your treatment, it may take a few weeks or many months for you to feel better.You may get to a point during your radiation therapy when you feel too sick to work. Talk with your employer to find out if you can go on medical leave. Make sure that your health insurance will pay for treatment when you are on medical leave.

What happens when radiation therapy is over?

Once you have finished radiation therapy, you will need follow-up care for the rest of your life. Follow-up care refers to checkups with your radiation oncologist or nurse practitioner after your course of radiation therapy is over. During these checkups, your doctor or nurse will see how well the radiation therapy worked, check for other signs of cancer, look for late side effects, and talk with you about your treatment and care. Your doctor or nurse will:

  • Examine you and review how you have been feeling. Your doctor or nurse practitioner can prescribe medicine or suggest other ways to treat any side effects you may have.
  • Order lab and imaging tests. These may include blood tests, x-rays, or CT, MRI, or PET scans.
  • Discuss treatment. Your doctor or nurse practitioner may suggest that you have more treatment, such as extra radiation treatments, chemotherapy, or both.
  • Answer your questions and respond to your concerns. It may be helpful to write down your questions ahead of time and bring them with you. You can find sample questions in Questions To Ask Your Doctor or Nurse.

After radiation therapy is over what symptoms should I look for?

You have gone through a lot with cancer and radiation therapy. Now you may be even more aware of your body and how you feel each day. Pay attention to changes in your body and let your doctor or nurse know if you have:

  • A pain that does not go away
  • New lumps, bumps, swellings, rashes, bruises, or bleeding
  • Appetite changes, nausea, vomiting, diarrhea, or constipation
  • Weight loss that you cannot explain
  • A fever, cough, or hoarseness that does not go away
  • Any other symptoms that worry you
Make a list of questions and problems you want to discuss with your doctor or nurse. Be sure to bring this list to your follow-up visits. See "Questions To Ask Your Doctor or Nurse" for sample questions.
This information is not intended to replace the advice of a doctor. Navigating Care disclaims any liability for the decisions you make based on this information. This information was sourced and adapted from the National Cancer Institute's web site,

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