Types of Radiation Therapy

Paul Tamas

Our doctors deliver radiation therapy in a variety of forms depending on the type of cancer, the location of the tumor, and whether it has spread.

External-beam radiation therapy is the most common form of the treatment. It is applied to the body by a machine, most often in the form of x-rays but sometimes as charged particles called protons or other types of energy.

Types of external-beam radiation therapy include image-guided radiation therapy, intensity-modulated radiation therapy, stereotactic body radiation therapy, and proton therapy.

Image-Guided Radiation Therapy


Image-guided radiation therapy (IGRT) uses sophisticated imaging tests to verify the position of the patient and the location of the tumor prior to and during the delivery of the treatment. IGRT requires no anesthesia and side effects are less likely than with traditional methods. IGRT can be used to treat many types of cancer, including those that develop in the spine, lung, prostate, brain, bladder, esophagus, liver, and bone.

Our radiation oncologists use PET simulator technology to more precisely and safely target the tissue that contains cancer cells and avoid harming healthy tissue. We also have a dedicated MRI simulator that allows us to map out the treatment area in order to deliver a higher dose of treatment to a more precise location in the body.

Intensity-Modulated Radiation Therapy

Our radiation oncologists, in close collaboration with medical physics team, played a leading role in developing this type of radiation therapy, sometimes referred to as IMRT. It allows higher, more effective doses of radiation to be delivered to tumors while minimizing exposure to surrounding healthy tissues and organs, increasing your chance for a cure and lessening side effects.

After you have a CT scan that maps your tumor in 3-D, IMRT uses sophisticated computer programs to calculate and deliver varying doses of radiation directly to the tumor from different angles. IMRT is used at MSK to treat cancers of the prostate, head and neck, lung, brain, liver, and breast, as well as lymphoma, sarcoma, and some pediatric cancers.

 Alice Ho

Stereotactic Body Radiation Therapy

Stereotactic body radiation therapy (SBRT) combines image-guided radiation therapy with even more advanced techniques to deliver extremely high doses of radiation to the tumor while minimizing the dose to normal structures nearby. This approach is sometimes used to treat small, early-stage lung and pancreatic cancer, or isolated cancers that have spread to the lung, liver, adrenal gland, or spine.

SBRT usually requires fewer treatments than other forms of radiation therapy and leads to better outcomes and fewer side effects than conventional radiation therapy. This procedure also requires no anesthesia and usually has fewer side effects than traditional radiation approaches.

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Proton Therapy

For some cancer cases, our radiation oncologists can use proton therapy, an advanced form of the treatment, to deliver high doses of radiation to tumors that may be resistant to conventional forms while minimizing exposure to the surrounding healthy tissues. While traditional radiation uses x-rays, proton therapy targets a tumor with charged particles called protons.

With proton therapy, all the energy has been released by the time it reaches the tumor, so there is no dose beyond that point. This lowers the impact to normal tissues surrounding the tumor and reduces the risk of treatment-related side effects. Currently, this cutting-edge technology is available at only 14 locations in the United States.

Learn more about our proton therapy services.

Internal Radiation Therapy (Brachytherapy)

Brachytherapy, a form of internal radiation therapy, involves placing radioactive material into the cancer itself or into the tissue surrounding it. The implants are usually tiny steel capsules (“seeds”) about the size of a grain of rice that contain radioactive material. The seeds deliver most of the radiation to the area around the implant. Some radiation may leave the body, however, so you need to take steps to protect others from radiation exposure while the seeds are still active.

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These radioactive implants may be permanent or temporary and may require a hospital stay. Most temporary implant procedures deliver radiation for just a few minutes. If temporary implants are used for more time, you’ll stay in a private room while the implants are in place to limit others’ exposure to the radiation.

We use advanced imaging techniques to make sure the seeds are placed in the precise spot needed to treat the cancer. In some cases, such as when treating prostate cancer, we use a portable CT unit during the procedure. This allows our physicians to confirm the accuracy of the seed placement. MSK is one of only a few centers in the world routinely using this system during brachytherapy.

Intraoperative Radiation Therapy

Intraoperative radiation therapy (IORT) takes place during surgery to deliver radiation directly to a tumor, either as external-beam radiation therapy or as internal radiation therapy. It is currently used at MSK to treat breast cancer and colorectal cancer. This approach allows our surgeons to move healthy tissue out of the way before radiation therapy occurs; it may be helpful when important organs are located very close to the tumor.

Because this treatment is conducted during the surgical procedure and can be delivered to a precisely defined area, it is possible to use a higher-than-usual — and therefore more effective — dose of radiation and to spare nearby healthy tissues. (If you receive IORT, you usually also receive external-beam radiation therapy prior to the operation.)

Learn more about IORT.

Palliative Radiation Therapy

Many patients receive radiation to treat symptoms that are caused by metastases. For example, symptoms such as headache and weakness caused by metastases in the brain or pain caused by metastases to the bone can be treated with radiation therapy. The goal of these treatments is to improve quality of life for patients.

Learn more about palliative radiation therapy.