Radiation Therapy

Medically Reviewed By William C. Lloyd III, MD, FACS

What is radiation therapy?

Radiation therapy, or radiotherapy is a treatment for cancer that uses radiation to kill cancer cells and shrink tumors. Cancer occurs when old or damaged cells divide and multiply uncontrollably. Cancer cells rapidly reproduce even when your body signals them to stop. The goal of radiotherapy is to cure cancer, control cancer, or relieve cancer symptoms. Radiation treatment kills your normal cells as well as cancer cells. To minimize radiation treatment side effects, a radiation oncologist uses specialized equipment and techniques to precisely target your tumor and reduce damage to healthy cells.

Radiation therapy is only one method to treat cancer and other conditions. Discuss all cancer-specific treatment options with your doctor to understand which treatments are right for you.

Types of radiation therapy

The types of radiation therapy include:

  • External beam radiation therapy delivers radiation from a machine outside the body to treat many types of cancer. A radiation oncologist or technician directs the radiation beam precisely at the tumor or cancer. Stereotactic radiosurgery (Gamma Knife and CyberKnife) and proton therapy are specialized types of external beam radiation therapy.

  • Internal radiation therapy, or brachytherapy involves placing radioactive material inside a tumor or right next to the tumor or cancer. For example, a radiation oncologist places radioactive seed implants at the prostate gland to treat prostate cancer.

  • Radiopharmaceuticals are radioactive medications. They are given through an IV, in pill form, or are placed in a body cavity. For example, a radiation oncologist uses radioactive iodine to treat thyroid cancer and radioactive antibodies to treat certain cases of non-Hodgkin lymphoma. Radiopharmaceuticals can also treat certain brain tumors and bone pain from bone cancer.

Other procedures that may be performed

Your doctor may recommend one or more procedures in addition to radiation therapy to treat cancer. These include:

  • Immunotherapy boosts or stimulates your body’s immune system to help fight cancer.

  • Chemotherapy treats cancer with medications that slow or stop the growth of cancer cells.

  • Hormone therapy blocks the effects of hormones that stimulate growth of certain cancers.

  • Laser therapy removes tumors and treats cancer symptoms with a laser.

  • Photodynamic therapy combines special light-sensitive drugs with specific wavelengths of light. Your doctor injects the drug into your tumor and exposes it to the light. This produces a reaction that kills cancer cells.

  • Surgery removes cancerous and noncancerous tumors. Your doctor may also use surgery to prevent cancer by removing pre-cancerous tissues.

Why is radiation therapy performed? 

Doctors use radiation therapy most often to treat cancer. Your doctor may recommend radiotherapy to:

  • Destroy a cancerous tumor

  • Lower the risk that cancer will grow again after other treatments such as surgery or chemotherapy

  • Shrink a tumor before surgically removing it

  • Shrink a tumor to ease pain or other cancer symptoms

Your doctor may recommend radiation treatment for:

Doctors sometimes recommend a special type of radiation therapy, called stereotactic radiosurgery (Gamma Knife and CyberKnife). This is used to treat certain noncancerous brain diseases, including epilepsy, arteriovenous malformations, Parkinson’s disease, and trigeminal neuralgia.

Doctors also use radiation therapy to treat hyperthyroidism (overactive thyroid).

Who performs radiation therapy?

A radiation oncologist or an oncologist performs radiation therapy. Radiation oncologists specialize in treating cancer and related diseases with radiation. Oncologists specialize in diagnosing, treating and preventing cancer.

How is radiation therapy performed?

Your radiation therapy will be performed in a hospital radiology department or an outpatient radiology setting. Radiation therapies vary depending on the type, size and location of the cancerous tumor, and other factors.

External beam radiation therapy generally includes a treatment every day for several weeks and involves the following steps:

  1. Your care team will plan your radiation therapy using imaging exams, such as CT or MRI, to pinpoint the tumor and normal tissues around it.

  2. Your care team will create individualized molds or other devices to hold you in exactly the same position for each treatment. This ensures that the radiation beam treats the cancerous tissue and only a small amount of normal tissue around it. The team may also mark your skin to help with exact positioning.

  3. Your care team will determine the exact type and dose of radiation to treat your tumor.

  4. You will dress in a patient gown and may need to remove jewelry, wigs, glasses, or any other item that could interfere with the radiation treatment.

  5. Your care team will position you on a table.

  6. Your team may start an intravenous (IV) line to give you fluids and a mild sedative or other medication. Your team may apply a special head frame and use other procedures to help you hold still for some types of radiation therapy.

  7. Your care team will leave the treatment room, but they will observe you by video. You will be able to talk with them over an intercom.

  8. The radiation therapy machine will deliver a precise amount of radiation. You will not feel anything during this process.

  9. You will likely go home the same day, usually right after your radiation therapy session.

Internal radiation therapy or brachytherapy involves placing a radioactive material directly inside your tumor or right next to your tumor or cancer. For example, a radiation oncologist places radioactive seed implants at the prostate gland to treat prostate cancer. The exact procedure will vary depending on the type and location of your cancer.

Systemic radiation therapy involves taking a radioactive medication through an injection or in pill form. For example, radioactive iodine treatment for thyroid cancer is a pill or liquid. The exact procedure will vary depending on the type and location of your cancer.

Will I feel pain?

Radiation treatment itself is painless. You may have some discomfort with a specific procedure, such as attaching a special head frame for stereotactic radiosurgery. You will receive pain and sedative medications as needed so you stay comfortable during and after your procedure.

What are the side effects of radiation therapy?

Potential complications and side effects of radiation therapy vary depending on the type and dose of radiation, and the body area needing treatment. Side effects are usually temporary, and some people experience no side effects. 

Talk to your doctor about the possible complications and side effects of your radiation therapy. General risks and potential complications include: 

  • Development of a new cancer (rare)

  • Difficulty swallowing if radiation is near the head or neck

  • Fatigue

  • Hair loss near the treatment site

  • Infertility

  • Joint problems

  • Nausea, vomiting and diarrhea

  • Skin irritation, dryness, itching, peeling or blistering

  • Swelling

Reducing your risk of complications

You can reduce the risk of certain complications by following your treatment plan and: 

  • Avoiding pregnancy as directed by your doctor. Notify your doctor immediately if there is any chance of pregnancy.

  • Following activity, dietary and lifestyle restrictions and recommendations before and after your treatment

  • Notifying your doctor immediately of any concerns

  • Taking your medications exactly as directed

How do I prepare for radiation therapy?

You are an important member of your own healthcare team. The steps you take before your treatment can improve your comfort and outcome.

You can prepare for radiation therapy by:

  • Answering all questions about your medical history, allergies, and medications. This includes prescriptions, over-the-counter drugs, herbal treatments, and vitamins. It is a good idea to carry a current list of your medical conditions, medications, and allergies at all times.

  • Stopping smoking. Smoking compromises blood flow to the tissues, which can worsen the side effects of radiation.

  • Taking or stopping medications exactly as directed

Questions to ask your doctor

Having radiation therapy can be stressful. You may have many questions and concerns. It is common for patients to forget some of their questions during a doctor’s office visit. You may also think of other questions after your appointment. Contact your doctor with concerns and questions before your procedure and between appointments.

It is also a good idea to bring a list of questions to your appointments. Questions can include:

  • Why do I need radiation therapy? Are there any other options for treating my condition?

  • How many treatments will I need?

  • How long will each treatment take? When can I go home?

  • What restrictions will I have? When can I return to work and other activities?

  • What medication plan should I follow before and after my treatment?

  • How will you treat my pain or discomfort such as nausea?

  • What other tests or treatments might I need?

  • When should I follow up with you?

  • How should I contact you? Ask for numbers to call during and after regular hours.

What can I expect after radiation therapy?

Knowing what to expect after radiation therapy can help you get back to your everyday life as soon as possible.

How will I feel after radiation therapy?

People often feel fine right after radiation therapy. Side effects, such as fatigue and skin irritation, may develop after a couple treatments. They are generally mild and temporary. 

Side effects vary depending on the type and dose of radiation therapy, and the body area needing treatment. Some side effects may not occur for six months or more after your radiation therapy. Some people have no side effects from radiation therapy. 

Ask your doctor about the potential side effects of your type of radiation therapy and how you can control or minimize them. Your doctor can recommend medications to help ease some side effects. Call your doctor if you have trouble controlling side effects.

When can I go home?

You will likely go home after your radiation therapy. Some people may need to stay briefly in the hospital or be admitted for further observation and treatments. 

When should I call my doctor?

You should keep your follow-up appointments after radiation therapy. Contact your doctor if you have any concerns between appointments. Call your doctor right away if you have side effects or symptoms that are difficult to control or are getting worse. 

Was this helpful?
  1. Brachytherapy. Radiological Society of North America. http://www.radiologyinfo.org/en/info.cfm?pg=brachy
  2. Gamma Knife. University of California San Francisco Medical Center. http://www.ucsfhealth.org/treatments/gamma_knife/index.htm
  3. Radiation Therapy for Cancer. National Cancer institute. http://www.cancer.gov/cancertopics/factsheet/Therapy/radiation 
  4. Radiation Therapy (Oncology). American College of Radiology. http://www.radiologyinfo.org/en/sitemap/modal-alias.cfm?modal=onco
  5. Radiation Therapy and You: Support for People With Cancer. National Cancer Institute. https://www.cancer.gov/publications/patient-education/radiation-therapy-and-you 
  6. Systemic Radiation Therapy. American Cancer Society. https://www.cancer.org/content/cancer/en/treatment/treatments-and-side-effects/treatment-types/radia...
  7. Radiation Therapy. American Cancer Society. https://www.cancer.org/content/cancer/en/treatment/treatments-and-side-effects/treatment-types/radia...
Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Nov 2
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