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 (linac) — to direct radiation to the tumor. The procedure lasts a few minutes, and is typically repeated several times a week over several months.
Types of external beam radiation treatments include:
- Three-dimensional conformal radiation therapy — a technique where the tumor is mapped with imaging equipment and then treated with multiple beams of radiation. Learn more about 3D conformal radiation therapy.
- Intensity-modulated radiation therapy (IMRT) — a 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.
Learn more about IMRT.
How is external beam radiation done?
Before you begin radiation treatment at UPMC CancerCenter, we will take an image of the tumor and determine your course of treatment.
In order to pinpoint the location of your tumor, you will have a simulation (or planning) session, which can take up to an hour.
During simulation, a radiation therapist:
- Creates a thermoplastic or foam mold that supports your head, neck, back, pelvis, and thighs. This mold, sometimes called a cradle, ensures accurate positioning over the course of your radiation treatments.
- Takes images and an x-ray of the tumor while you are lying in the mold.
- Marks the treatment area on your skin, using the x-rays as a guide. These marks serve as a temporary map of the treatment area; after a few treatments, the outline is replaced with tiny tattooed dots.
What can I expect during my radiation therapy session?
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 oncologist will determine your treatment schedule and how often you will need to repeat the treatment process.
What are the benefits and risks of external radiation therapy?
External radiation therapy is an outpatient procedure.
Compared to other, more invasive techniques, external radiation treatment sessions are:
External radiation treatment may require an investment of time — a course can involve daily sessions over several weeks.
Common side effects of external beam radiation therapy include irritation of the treated region and fatigue.
Your oncologist will talk with you about any side effects for your condition and form of treatment.
Who provides this treatment at UPMC CancerCenter?
External beam radiation therapy, including IMRT, is available at many UPMC CancerCenter radiation oncology network locations.