What is External Beam Radiation Therapy?

External beam radiation therapy (EBRT) is a type of cancer treatment that delivers radiation from outside of the body. The goal of EBRT is to destroy cancer cells and shrink tumors, although it may also be used to alleviate symptoms rather than cure cancer.

EBRT can be delivered through several different methods, which may be combined or used alone. The type and length of treatment vary based on the location of your cancer or tumor and its size. Techniques for EBRT include:

  • Conventional external beam radiation therapy, which delivers a single beam of radiation from multiple directions. Conventional EBRT is commonly used to treat brain tumors, particularly when the entire brain needs treatment.
  • Intensity-modulated radiation therapy (IMRT), which uses smaller beams with adjustable intensity levels, so the most intense beams can be directed at the tumor. IMRT is used in several types of cancers, including prostate, gastrointestinal, brain, and lung cancers.
  • Orthovoltage, which uses low energy X-rays that do not penetrate the skin very deeply. Orthovoltage is typically used for skin cancers or other skin conditions.
  • Proton therapy, which uses a particle accelerator to deliver positively charged particles (protons) for cancer treatment. Proton beams can be controlled more precisely than X-rays, so there is less risk of damage to healthy tissue. This makes proton therapy a good option for younger patients, as other types of EBRT pose long-term risks such as growth problems and heart disease.
  • Stereotactic radiosurgery (SRS), which is a non-surgical type of radiation therapy that uses 3-D imaging to directly target tumors and avoid healthy tissue. SRS is often used for small tumors, particularly those in the brain (cranial radiosurgery) and spine (spinal radiosurgery). When performed outside of the brain and spine, it is called stereotactic body radiation therapy (SBRT).

Typically, you will undergo treatment for five days a week over the course of several weeks, and you should be able to go home the same day. Each session can take less than an hour, with most of the time spent determining proper positioning of your body. Actual delivery of the radiation may only take a few minutes, and you will wear a lead shield to protect healthy body tissues while receiving your treatment.

EBRT is painless, but it does come with some side effects, such as fatigue. Over the course of your therapy, your oncologist will monitor your condition and adjust your dosage, number of sessions, and length of treatment based on your body's response to the radiation.