What Is a Radiation Therapist?

These specialists treat cancer by administering radiation treatments

Radiation therapists specialize in administering high doses of radiation to treat cancerous growths in patients. The radiation, which is delivered via various methods and in various forms, helps to damage or destroy cancer cells and shrink tumors.

Young female nurse reading medical records.
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Radiation therapists work in hospitals, physicians' offices, and cancer treatment centers. Radiation therapists work as part of the cancer treatment team, which also includes an oncologist (a physician specializing in the treatment of cancer), nurses, medical imaging professionals, and more.

Radiation therapists are what's known as "allied medical professionals." This designation usually includes any medical professionals—other than medical doctors or nurses—who have direct contact with patients in a clinical setting. Most allied medical professionals are technicians or technologists of some sort.


Radiation therapy (radiotherapy) is one of the most common treatments for cancer. According to the Amerian Cancer Society, more than half of people with cancer get radiation therapy. Sometimes, radiation therapy is the only cancer treatment needed.

Unlike chemotherapy, which often exposes the whole body to cancer-fighting drugs, radiation therapy is usually a local treatment. In most cases, it’s aimed at and affects only the part of the body being treated. Radiation treatment is planned to damage cancer cells, with as little harm as possible to nearby healthy cells.

Radiation therapists will administer radiation therapy for the following purposes:

To cure or shrink early-stage cancer

Some cancers are very sensitive to radiation. In these cases, radiation may be used by itself to shrink the cancer or make it go away completely. Sometimes, a few cycles of chemotherapy may be given first; other times, radiation may be used before surgery to shrink the tumor, or after surgery to help keep the cancer from returning.

To stop cancer from coming back somewhere else

Cancer can spread (aka metastasize) from where it started to other body parts. Doctors often assume that a few cancer cells might already have spread even when they can’t be seen on imaging scans like CT scans or MRIs. In some cases, the area to which the cancer most often spreads may be treated with radiation to kill any cancer cells before they grow into tumors.

To treat symptoms caused by advanced cancer

Sometimes cancer has spread too much to be cured. But some of these tumors can still be treated to make them smaller to improve a patient's quality of life. Radiation might help relieve symptoms like pain, trouble swallowing or breathing, or bowel blockages that can be caused by advanced cancer. This is often called palliative radiation.

To treat cancer that's returned

If a person's cancer has returned (recurred), radiation might be used to treat the cancer or to treat symptoms caused by advanced cancer. Whether radiation will be used after recurrence depends on many factors. For instance, if the cancer has come back in a part of the body that's already been treated with radiation, it might not be possible to give more radiation in the same place.

Procedural Expertise

There are two main types of radiation therapy that radiation therapists perform—external beam and internal.

External Beam Radiation Therapy

This type of radiation therapy comes from a machine, called a linear accelerator, that aims high-energy X-rays directly at specific cancer cells in a patient's body to shrink or remove them. The machine is large and noisy. It doesn't touch you, but can move around you, sending radiation to a part of your body from many directions.

The most common type of radiation therapy, external beam radiation therapy is a local treatment, which means it treats a specific part of your body. For example, if you have cancer in your lung, you will have radiation only to your chest, not to your whole body.

Internal Radiation Therapy

This is a treatment in which a source of radiation is put inside your body. The radiation source can be solid or liquid.

Internal radiation therapy with a solid source is called brachytherapy. In this type of treatment, pellets, seeds, ribbons, wires, needles, capsules, balloons, or tubes that contain a radiation source are placed in your body, in or near the tumor. Like external beam radiation therapy, brachytherapy is a local treatment and treats only a specific part of your body.

Internal radiation therapy with a liquid source is called systemic therapy. Systemic means that the treatment travels in the blood to tissues throughout your body, seeking out and killing cancer cells. Systemic radiation therapy is delivered by mouth, through a vein via an IV line, or by injection.

Training and Certification

Most radiation therapists complete programs that lead to an associate’s degree or a bachelor’s degree in radiation therapy or radiologic technology. However, sometimes a 12-month certificate program suffices. Radiation therapists must be licensed or certified in most states. Requirements vary by state but often include passing a national certification exam. The most widely recognized certifying body is the American Registry of Radiologic Technologists (ARRT). Certified radiation therapists must meet education and clinical competency standards set by the ARRT. Certification must be renewed annually.

Appointment Tips

Before you begin your radiation treatment, you'll meet with your treatment team, including a radiation therapist, to have a treatment planning procedure called a simulation (SIM). You won't receive any treatment during this planning session. According to Memorial Sloan Kettering Cancer Center, a simulation is done to:

  • Map your treatment site
  • Determine the right dose of radiation
  • Minimize the amount of radiation that gets to your nearby tissues

Because it's so important to position the angles and shapes of your radiation beams accurately, this planning session can sometimes last up to an hour. The extra time and care during this session will make future appointments run more smoothly and help you get the most from your radiation therapy.

During your simulation, you'll have X-rays or a CT scan to verify the anatomy that will be treated. If needed, immobilization devices, such as headrests, molds, or plaster casts, will be made and/or used to help you remain still during treatment. Your skin will be marked with tiny permanent dots (called tattoos) that are used as a guide to help the radiation therapist line up the treatment field (the area that will get irradiated) the same way each time you receive treatment. Photographs may also be taken to be sure you're positioned correctly on the treatment table during radiation therapy.

At the end of your simulation, you'll receive an appointment for your set-up procedure. This is the final appointment before your treatment begins.
During the time between your simulation and start of treatment, your radiation oncologist will work with a team to plan your treatment. The details are carefully planned and checked. This takes between one to two weeks.

The set-up procedure, which generally takes about an hour, is like a dry run that's done to verify the whole plan set-up in the treatment room. Special X-rays called beam films are taken of each treatment field to make sure they're set up correctly, and additional markings may be made to better define the confirmed treatment fields. Depending on your treatment plan, you may start treatment on the same day as your set-up procedure or a day or two later.

There are many different radiation therapy options. The number of treatments prescribed will vary depending on your specific cancer type and its location and the purpose of the treatment—for instance, if radiation is being used to relieve symptoms, the treatment may be shorter because the overall dose of radiation will be lower. A full course of therapy may take several weeks, while other treatments may be one day or just a few days. Typically, people have treatment sessions five times a week, Monday through Friday, at the same time each day. Each session is quick and painless, lasting about 15 minutes. This schedule usually continues for five to eight weeks. Weekend rest breaks allow time for normal cells to recover. 

During the course of treatment, radiation therapists will protect patients (and themselves) from improper exposure to radiation, monitor the health of the patient, and adjust for any serious side effects. They also keep detailed records of treatment.

It's very important not to miss or delay treatments because that can lessen how well the radiation kills tumor cells. If you can’t come in for treatment for some reason, you must call your radiation oncologist’s office to let your team know. If you need to change your schedule for any reason, speak with your radiation therapist.

Patients understandably want to know if they'll be radioactive during or after radiation treatment. It depends on the type of treatment. External radiation therapy affects cells in your body only for a moment; because there’s no radiation source in your body, you're not radioactive at any time during or after treatment. Internal radiation therapy is different. With brachytherapy, the radiation source in your body will give off radiation for a short time, depending on the type of implant. With systemic radiation, your body fluids—your urine, sweat, and saliva—will emit radiation for a few days. These treatments require safety measures to protect others from radiation exposure.

12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  12. American Society of Clinical Oncology. What is Radiation Therapy?

By Andrea Clement Santiago
Andrea Clement Santiago is a medical staffing expert and communications executive. She's a writer with a background in healthcare recruiting.