External Beam Radiation Therapy (EBRT)

What is external beam radiation therapy (EBRT)?

External beam radiation therapy (EBRT) is the main form of radiation treatment used to fight cancer. During EBRT, you lie on a table while a machine sends precisely controlled radiation beams to the tumor. The machine doesn’t touch you. It’s programmed to destroy cancer cells from a distance, while minimizing damage to healthy tissue.

How EBRT works

EBRT uses high-energy beams that can create highly charged particles strong enough to kill cancer cells. Some types can reach deep into your body, affecting both cancerous and healthy cells. The goal is to target tumors while sparing surrounding tissue.

Types of particles used include:

• Photons (X-rays, gamma rays): These are the most common. Penetrate deeply to destroy cancer cells.
• Protons: These are used in proton therapy. These stop at the tumor, better protecting nearby healthy tissue. However, access remains limited, and researchers are still studying how it works biologically.
• Electrons: These don’t penetrate as deeply, so they’re mainly used for skin or surface-level cancers.

Most EBRT treatments use a linear accelerator (LINAC). Proton therapy uses a particle accelerator.

What EBRT treats

Providers use this treatment to:

• Destroy cancer cells or stop them from spreading
• Support other treatments, like shrinking tumors before surgery or eliminating leftover cancer cells after surgery or chemotherapy
• Relieve symptoms by shrinking tumors that cause pain or discomfort as part of palliative care

It’s commonly used to treat cancers that are localized (could be in multiple isolated locations), including:

• Breast, colon, lung, prostate, uterine and head and neck cancers
• Leukemia and non-Hodgkin lymphoma

Types of external beam radiation therapy

EBRT techniques differ based on how beams are shaped, delivered and guided:

• 3D conformal radiation therapy: This procedure uses CT and other imaging to create a 3D model of your tumor. Multiple radiation beams (typically two to four beams) are shaped to match the tumor’s size from these beam directions.
• IMRT (intensity-modulated radiation therapy): This is advanced therapy that uses computer-optimized beams of varying intensity to deliver higher radiation doses to tumors while protecting healthy tissue.
• IGRT (image-guided radiation therapy): This uses imaging during treatment to pinpoint the tumor and track changes, adjusting beams as needed.
• Tomotherapy: This technique delivers radiation in a spiral pattern as you move through a donut-shaped machine. The machine targets your tumor with beams of varying intensity.
• Stereotactic radiosurgery: This procedure delivers high-dose radiation to small brain tumors without surgery, despite its name.
• SBRT (stereotactic body radiation therapy): Similar to radiosurgery, but this is used for tumors outside of your brain, like in your lungs, liver or spine, often when surgery isn’t possible.
• IORT (intraoperative radiation): This is administered during surgery to treat areas where tumors couldn’t be completely removed. Healthy tissue is shielded while you’re under anesthesia.

What happens before external beam radiation therapy?

Your treatment starts with a planning session called simulation. This step ensures everything is ready for your first session and helps you know what to expect.

During simulation:

• You’ll lie in the same position used during treatment.
• You’ll have a CT, MRI or PET scan so your care team can locate the tumor and design the radiation beam directions accordingly.
• You’ll get tiny, freckle-sized skin markings that guide the initial radiation placement. These markings stay on throughout treatment.
• You may be fitted with positioning aids like a mask or cast to help you stay still.

Simulation takes longer than a typical treatment session — about 30 minutes to two hours. In the days or weeks that follow, your care team uses this information to build your personalized treatment plan.

Over the next few days or weeks, your radiation oncology team will use the information from simulation to design your treatment.

What happens during external beam radiation therapy?

EBRT is an outpatient procedure, meaning you’ll go home the same day.

Here’s what to expect at each session:

1. You’ll lie in the same position as during your simulation. Your therapist will use any supports or accessories needed to keep you comfortable and still.
2. Once you’re set, your therapist will step out to operate the machine. They’ll watch you on a monitor and can talk with you through an intercom.
3. The machine moves quietly around you, precisely aiming radiation beams at the tumor.
4. You’ll need to stay still, but you can breathe normally.
5. Radiation is delivered in short bursts, not continuously.

If you have questions or concerns about your sessions, your care team is always available to support you.

Does EBRT hurt?

No, you won’t feel the radiation. But you might hear clicking or whirring, see flashes of light (especially during brain treatments) or notice unusual smells. These are normal and not harmful.

How long will I need this treatment?

Your schedule depends on the cancer type, size and location. You’ll typically receive treatments daily over several weeks. Your radiation oncologist will explain your treatment plan and timeline.

What are the potential benefits and risks of this treatment?

Radiation therapy has been used for more than 100 years — and it’s only gotten safer and more precise. EBRT can:

• Destroy cancer cells.
• Slow or stop tumor growth.
• Prevent cancer from returning.
• Ease symptoms and improve quality of life.

Advanced technology lets radiation beams target tumors from multiple angles, protecting healthy tissue as much as possible.

What are the side effects of external beam radiation therapy?

Radiation can affect healthy cells near the treatment area, which can cause side effects. The most common is fatigue. Others depend on where you’re treated and may include:

• Nausea or vomiting
• Loss of appetite
• Headaches
• Hair loss
• Trouble swallowing
• Shortness of breath
• Skin irritation
• Inflammation or tenderness at the treatment site

Everyone responds differently. Even people with the same cancer may have different side effects. Your care team will help you manage them.

How long will it take for me to feel better?

Recovery varies from person to person. Some people feel well enough to go about their usual activities during treatment. Others may need time off to rest, especially if fatigue becomes overwhelming.

Side effects often build up over time. That’s because radiation doesn’t kill cancer cells right away. It can take days or weeks of treatment before they start to die. You might feel fine at first, then more tired or unwell as treatment continues.

After treatment ends, recovery can also vary. Some people bounce back in a few weeks, while others may need several months to fully return to their routine.

How can I make treatment easier?

Ask your care team for personalized tips based on your treatment plan. In general:

• Get plenty of rest.
• Eat a balanced diet to support healing.
• Stay hydrated.
• Be kind to your body, and scale back activities if needed.

Tell your team about any symptoms you’re experiencing. They can help manage side effects so you feel as comfortable as possible.

When should I call my healthcare provider?

Before starting treatment, talk with your radiation oncologist about which side effects are expected and which might signal a problem. In general, call your provider if you experience:

• Severe or unexpected symptoms
• Side effects that worsen suddenly
• Signs of infection (fever, chills)
• Trouble breathing or chest pain

Your care team is your best source of support. Don’t hesitate to reach out with concerns during or after treatment.