External Beam Radiation Therapy (EBRT)

Overview

What is external beam radiation therapy (EBRT)?

External beam radiation therapy (EBRT) is the most common form of radiation therapy used to treat cancer. With EBRT, you lie on a table while a machine directs radiation beams that are carefully designed for your tumor location toward you. The machine never touches you. Instead, your care team (or radiation oncology team) programs the machine to deliver radiation directly to cancer cells from a distance, destroying them.

EBRT aims to kill cancer cells and shrink tumors while preventing damage to surrounding healthy tissue as much as possible.

What is the difference between external beam radiation therapy and internal radiation therapy?

There are two main types of radiation therapy: external beam radiation therapy and internal radiation therapy. Both types use radiation to kill cancer cells.

What’s different is how they’re delivered. EBRT uses a machine that never touches your body to send radiation to a tumor. With internal radiation therapy, a provider places a radioactive device inside or near a tumor.

What types of energy are used in external beam radiation therapy?

Radiation consists of energy beams that contain supercharged particles. These particles are strong enough to destroy cancer cells. Depending on the type of radiation treatment you receive, the particles are powerful enough to penetrate deep into tissue, damaging cancer cells and healthy cells, too.

A key goal of EBRT is to kill cancer cells without damaging healthy cells.

These supercharged particles include:

• Photons (X-rays and gamma rays): Photons are the basic building blocks of energy. Photons can penetrate deep into your tissue, killing cancer cells. Most types of EBRT use photons.
• Protons: Protons are particles with a positive charge. They’re used in a newer form of EBRT called proton therapy. Protons deliver a burst of radiation that penetrates tumor cells but stops short of passing through healthy cells. This type of treatment can potentially provide better protection to healthy tissue. Still, proton therapy isn’t widely available. Scientists are still studying the biological effects of how protons interact with cells and the benefits of EBRT using protons compared to EBRT using photons.
• Electrons: Electrons are particles with a negative charge. They can’t travel as deeply into tissue as photons or protons, so electron beams are mainly used for skin cancer or tumors located superficially.

Most types of external beam radiation therapy use a linear accelerator (LINAC) machine to speed up the particles and send them to cancer cells. Proton therapy uses a machine called a particle accelerator.

What are the types of external beam radiation therapy?

EBRT uses sophisticated technology to send energy beams to your tumor. Treatments are usually spread out over several days to allow time for your body to heal between sessions.

• 3D conformal radiation therapy directs multiple energy beams toward your tumor that “conform” or fit your tumor’s exact size and shape. First, assisted with computer software, your care team analyzes images of your body (most commonly from a CT scan). Other imaging such as PET or MRI scans acquired during your diagnoses may be used to locate your tumor. The images show your tumor’s size, shape and location. The computer uses this information to create a 3D model of your tumor in relation to your other healthy tissue. Your radiation oncology team uses this model to design the energy beams that target cancer cells.
• Intensity-modulated radiation therapy (IMRT) is an advanced form of 3D conformal radiation therapy. The energy beams not only fit to the shape of your tumor, but each beam also contains several small beams with variable intensities, or strength. IMRT can send higher doses of radiation to concentrated areas of cancer cells while sparing healthy tissue.
• Image-guided radiation therapy (IGRT) uses imaging to ensure radiation beams are delivered precisely during each treatment session. Both 3D conformal radiation therapy and IMRT use imaging and computer software before your first treatment to ensure customized energy beams are directed at the tumor. IGRT repeats the imaging and analysis during every treatment session. The most common imaging used during treatment is on-board CT scans (a simplified CT scanner in the treatment machines). The energy beams can be repositioned based on changes to your tumor during treatment. If your tumor changes substantially during treatment, your radiation oncologist may decide to adjust the dose or redesign the energy beams (called adaptive radiation therapy).
• Tomotherapy/helical tomotherapy delivers radiation in a spiral-like pattern while you’re lying on a table. During treatment, you’ll move through a donut-shaped machine while the radiation encircles you. The machine directs energy beams of varying intensity toward your tumor.
• Stereotactic radiosurgery/GammaKnife radiosurgery directs high radiation doses toward small brain tumors. This treatment is the standard for brain tumors that can’t be safely removed through surgery. Despite the name, this procedure doesn’t involve cutting out a tumor. It’s called “surgery” because it delivers precise results, similar to actual surgery.
• Stereotactic body radiation therapy (SBRT) is similar to stereotactic radiosurgery, but it’s used to treat tumors outside of your brain, especially tumors in your liver, lung or spine. SBRT is also used when surgery is too high-risk because of a tumor’s location or your health.
• Intraoperative radiation (IORT) happens alongside surgery if parts of a tumor can’t be safely removed. Your surgeon will protect healthy tissue with shields while a machine delivers radiation to the cancer site. You’ll be asleep for this type of radiation therapy.

What is external beam radiation therapy used for?

EBRT kills cancer cells and shrinks tumors. It may be used to:

• Destroy cancer cells or prevent their spread. EBRT is the primary treatment for many cancers.
• Complement other cancer treatments. You may receive EBRT alongside other treatments, like surgery, chemotherapy or immunotherapy. EBRT is often used to shrink tumors before surgery (neo-adjuvant therapy). It’s also used to destroy any remaining cancer cells after surgery to prevent cancer from returning (adjuvant therapy).
• Relieve symptoms. EBRT is often part of palliative care for cancer. Palliative care helps people with chronic, or long-term, conditions manage pain and other symptoms. Radiation destroys tumors that may be causing symptoms that interfere with your quality of life.

What cancer does external beam radiotherapy treat?

External beam radiotherapy is the go-to form of radiation treatment for most types of localized cancer. “Local” means that cancer cells are isolated within a specific body part. EBRT treats many of the most common types of cancer, including:

• Breast cancer.
• Colon cancer.
• Leukemia.
• Lung cancer.
• Non-Hodgkin lymphoma.
• Prostate cancer.
• Uterine cancer.
• Head and neck cancer.
• Others.