What is External Beam Radiation Therapy?

A planning simulation used by a radiation oncologist.
Left images show larger dose via 3D conformal radiation therapy;
right images show smaller dose with IMRT

External beam radiation therapy uses a high-energy x-ray machine called a linear accelerator to direct radiation to the tumor. The procedure lasts a few minutes at a time, and is typically repeated several times a week over several months. Types of treatment include:

• Three-dimensional conformal radiation therapy - a technique where the tumor is mapped with imaging equipment and then treated with multiple beams of radiation. More information is available on our conformal therapy page.
• Proton beam radiation therapy - a treatment similar to 3D conformal radiation therapy. However, instead of x-rays, this technique uses protons to kill the tumor. Protons are parts of atoms that can pass through healthy tissues with little damage, and destroy tumor cells at the end of their path. As a result, proton beam therapy may be able to deliver more radiation to the tumor while not affecting healthy tissue near the cancer.
• Intensity-modulated radiation therapy (IMRT) - a new treatment method in which the intensity of the radiation can be changed during treatment. In conventional therapy, intensity is set for the entire treatment session. More information is available on our IMRT page.

How is this procedure done?

Before radiation treatment begins, the tumor is imaged and your treatment course is determined. In order to pinpoint the location of your tumor, a planning session or simulation is required to pinpoint your tumor, which can take up to an hour. During simulation, a radiation therapist creates a thermoplastic or Styrofoam mold that supports your back, pelvis and thighs. This mold, sometimes called a cradle, ensures accurate positioning over the course of your radiation treatments. Images of the tumor and a x-ray is taken while you are lying in the mold. Using the x-rays as a guide, the radiation therapist then marks the treatment area on your skin. These marks serve as a temporary map of the treatment area; after a few treatments, the outline is replaced with tiny tattooed dots.

A radiation therapy session typically takes about 15 minutes. The therapist sets up the treatment according to the map on your skin and the information obtained from the simulation. You lie in the mold on the x-ray table. The linear accelerator moves in a circular fashion around the tumor area. The actual treatment lasts only a few minutes. Your treatment schedule will be determined by your oncologist, and the treatment process is repeated as needed.

What can I expect from this procedure?

External radiation therapy is an outpatient procedure; treatment sessions are short, there are none of the standard risks of surgery, and treatment is painless. Treatment sessions can be daily and last for months, and as such requires an investment of time. Common side effects of external beam radiation therapy include irritation of the treated region, and fatigue. Your oncologist will be able to tell you about any side effects for your particular condition and form of treatment.

Who provides this treatment at UPMC Cancer Centers?

External Beam Radiation Therapy, including IMRT, is available at most UPMC Cancer Centers network locations.