External beam radiation therapy (EBRT) is a standard cancer treatment and the most common form of radiation therapy. It uses a machine to send energy beams that destroy tumors. The machine never touches your body. EBRT relies on advanced technology that designs radiation treatments to destroy cancer cells while minimizing damage to surrounding healthy tissue.
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.
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.
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:
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.
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.
EBRT kills cancer cells and shrinks tumors. It may be used to:
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:
EBRT requires a team-based approach. Your radiation oncology team includes:
The planning phase of your treatment, called simulation, is essential to EBRT. Simulation ensures that everything is ready for your first treatment session. It also provides a preview of what to expect during treatment.
Over the next few days or weeks, your radiation oncology team will use the information from simulation to design your treatment.
Simulation sessions usually take longer than treatment sessions. Collecting the details in the beginning is essential to designing an effective EBRT. Simulation may be as brief as 30 minutes or as long as two hours.
You’ll receive treatment in a hospital or treatment center and leave that same day. During treatment:
The machine won’t send constant radiation during your session. Instead, it’ll send radiation up to a few minutes each time its position changes.
EBRT is painless. You won’t feel the radiation at all.
Still, you may notice things in your environment that seem stressful. For example, the machine will make clicking and whirring sounds as it moves. You may see flashes of light, especially if you’re receiving radiation therapy directed at your head. You may notice odd smells from the machine, too.
These experiences are normal.
Treatment time usually lasts between 15 and 30 minutes, with most time spent positioning you correctly. The therapist will tell you when the radiation starts.
Most cancer treatments involving EBRT take place daily, from Monday to Friday. Treatment may last anywhere from two to eight weeks. Spreading out your treatment allows healthy cells recovery time, lessening side effects.
There are some exceptions. For example, stereotactic radiosurgery often involves receiving a single strong dose in one treatment session.
You’ll be able to leave the hospital or treatment facility after treatment. Depending on how you’re feeling, you may be able to return to your routine immediately.
Radiation therapy has been around in various forms for over a century. Its uses include killing cancer cells, slowing tumor growth, preventing cancer from returning and easing symptoms. Advances in radiation therapy that allow energy beams to attack a tumor from multiple angles have made it a safer, more precise and more effective treatment.
Although your care team will work to minimize harm to healthy cells, it’s nearly impossible to prevent all damage. When healthy cells are damaged, you experience side effects. The most common side effect of radiation treatment is fatigue, or feeling tired. Other side effects depend on the damaged cells’ location and may include:
Still, your experience will be unique. Two people with the same type of cancer receiving EBRT may experience different side effects.
Everyone’s experience is different. Some people leave radiation therapy treatments and resume their routine. Others experience fatigue so severe that they must take time off from work to rest.
Often, people experience more side effects as treatment progresses. Radiation therapy doesn’t kill cancer cells immediately. It takes days or weeks of treatment before cancer cells are damaged enough to die. It’s possible that while you may feel OK in the beginning, you may have to allow more recovery time once cells begin dying.
Similarly, side effects vary after treatment ends. You may take a few weeks to feel back to your old self, or it may take several months before you can resume normal activities.
Before starting treatment, ask your radiation oncologist what side effects you should expect, including which ones are severe enough for an office visit or even a visit to the ER. Your healthcare provider is your best resource for understanding likely side effects or complications.
A note from Cleveland Clinic
When people refer to radiation for cancer treatment, they usually mean external beam radiation therapy (EBRT). EBRT is a standard cancer treatment that’s much more sophisticated than early forms of radiation treatment that were around a hundred years ago. EBRT relies on precise technologies that can target tumors while shielding healthy tissue from harmful radiation exposure. Ask your provider what to expect during treatment and recovery. Discuss potential side effects and treatment outcomes that you should expect with EBRT.
Last reviewed by a Cleveland Clinic medical professional on 08/08/2022.
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