External Beam Radiation Therapy

The goal of radiation therapy is to get a high enough dose of radiation into the body to kill the cancer cells while sparing the surrounding healthy tissue from damage.

Depending on the location, size, and type of tumor, you may receive one or a combination of radiation therapy techniques. One of the most effective and least invasive of these techniques is external beam radiation therapy.

During external beam radiation therapy, a beam of radiation is directed through the skin to a tumor and the immediate surrounding area. This beam delivers high-energy rays directed at the tumor in order to destroy it and any nearby cancer cells.

Because it is a highly precise, local treatment—meaning it only treats one specific area of your body—the side effects of external beam radiation are minimal. To minimize side effects, cancer treatments are typically given every weekday for a number of weeks.

Today, external beam radiation is the most popular form of radiation. If your Charlotte cancer treatment team has prescribed external beam radiation therapy as part of your treatment plan, it can be helpful to understand EBRT and know what to expect from your treatments.

What is External Beam Radiation Therapy?

Receiving external beam radiation is similar to having an X-ray taken. It is a painless, bloodless procedure.

During external beam radiation therapy, a machine located outside of your body aims a radiation beam at your tumor. The machine does not touch you and delivers the radiation beam through your skin.

EBRT is a “local” treatment, which means it treats only a specific area of your body, not your whole body. For example, if you have prostate cancer, it will only treat your prostate. This alleviates some of the side effects of other whole-body treatments. For a complete guide on Prostate Cancer, download our eBook.

Using sophisticated treatment planning software, your radiation oncology treatment team plans the size and shape of the beam, as well as how it is directed at your body. This effectively treats your tumor while sparing the normal tissue surrounding the cancer cells.

The most common type of machine used to deliver external beam radiation therapy is called a linear accelerator, sometimes called a “linac.” It produces a beam of high-energy X-rays or electrons.

Several special types of external beam therapy are discussed below. These are used for particular types of cancer. Your radiation oncologist will recommend one of these treatments if he or she believes it will help you.

Cancers Treated with External Beam Radiation Therapy

The Science Behind External Beam Radiation Therapy

During external beam therapy, the machine may use one of three different types of molecules: photons, protons, or electrons.


Most radiation machines use photons. X-ray machines also use photons but in lower doses. Photon beams can travel through the body to reach tumors. Along the way, the beam deposits radiation particles. Photon radiation can also travel through the tumor to affect the tissues behind it.


Some radiation therapies use protons instead of photons. This may be preferable because, unlike photons, protons do not deposit radiation particles en route to the tumor, nor do they continue to travel beyond the tumor. Because of this, they may affect fewer tissues than photon therapies.


Electrons are not able to travel deep into the body to reach tumors. Therefore they are not often used in radiation therapy.

Types of External Beam Radiation Therapies

There are many types of external beam radiation therapies available today. Based on the type and size of your tumor, your radiation oncologist will decide which EBRT treatment will be best for you.

Your doctor may refer to these by the machine’s name, rather than the treatment name. If you ever have questions about the treatment you are receiving, please ask someone on your SERO cancer care team to explain.


Three-Dimensional Conformal Radiation Therapy (3D-CRT)

Tumors usually have an irregular shape. Three-dimensional conformal radiation therapy (3D-CRT) uses sophisticated computers and computer-assisted tomography scans (CT or CAT scans) and/or magnetic resonance imaging scans (MR or MRI scans) to map the shape of your tumor.

These scans create detailed, three-dimensional representations of the tumor and surrounding organs. Your radiation oncologist can then shape the radiation beams exactly to the size and shape of your tumor. These beams are delivered from several different directions.

Because the radiation beams are very precisely directed, nearby normal tissues receive minimal radiation exposure.


Intensity Modulated Radiation Therapy (IMRT)

Intensity modulated radiation therapy (IMRT) is a type of 3D-CRT. In addition to changing the direction of the beams, IMRT can also change the strength of each beam.

This allows the treatment to direct higher doses of radiation at certain areas of the tumor. It also reduces the impact of the therapy on surrounding tissues.


Image Guided Radiation Therapy (IGRT)

Image guided radiation therapy (IGRT) is another form of 3D-CRT. In this case, imaging scans are taken before every treatment. Using these updated scans, a computer can measure any changes in the tumor. The radiation oncologist can then adapt the radiation beams based on the exact size and position of the tumor that day.

IGRT’s adaptive approach allows for highly precise and accurate treatment. It also helps prevent any effects of the treatment on surrounding tissues.


Stereotactic Radiosurgery

Despite its name, stereotactic radiosurgery (SRS) is not surgery at all. Instead, the name refers to the surgical precision with which the treatment is delivered.

Stereotactic radiosurgery is used to treat small, well-defined tumors in the central nervous system and brain. When surgery is not an option, your cancer care team may choose stereotactic radiosurgery instead.

During this treatment, many small, very precise, high-energy beams are aimed at the tumor from multiple directions. In order to keep you very still and allow for accurate delivery, your head will be placed in a frame to hold it in place.

Alone, each individual beam has little effect, sparing the surrounding tissue through which it passes. When combined, however, the beams are highly effective in treating the tumor.

Sometimes this treatment is used outside the brain or nervous system. If so, it is called stereotactic body radiation therapy (SBRT). SBRT may be used on cancers in the lung, spine, or liver.



CyberKnife is a machine that delivers stereotactic radiosurgery. The CyberKnife can move around during treatment in order to deliver beams from multiple angles. This allows for maximum effectiveness of treatment.

Planning Your External Beam Radiation Therapy Treatment

A team of experienced medical professionals will work with you to devise the best possible plan for your external beam radiation therapy treatments. This team includes:

  • A radiation oncologist, who will decide if external beam radiation therapy is the best treatment for you. If so, your radiation oncologist will decide which EBRT treatment you will receive and will oversee its application.
  • A radiation therapist, who will actually deliver your daily treatments. The radiation therapist works closely with the radiation oncologist to ensure the accuracy and effectiveness of every treatment.
  • Physicists and dosimetrists, who oversee the exact dosage of each radiation treatment. These professionals ensure you receive the most radiation with the fewest side effects possible.

Together, these members of your cancer care team will plan your EBRT treatments. Before these treatments begin, you’ll have an appointment in which your treatment is planned. Next, you will have what is called “simulation.”


During a simulation, or sim, your radiation oncologist will gather as much information as possible to ensure the effectiveness of your treatment. He or she will provide a full examination and review your history and diagnosis. Most importantly, your radiation oncologist will determine the exact location where your radiation should be delivered.

This precise location where you’ll receive treatment is called the treatment field or treatment part. To identify the treatment field, your radiation therapist will direct imaging scans of the area where your tumor is. Using these scans, he or she will determine the exact treatment part.

Once they identify the treatment field, your radiation therapist will mark it with semi-permanent ink. The marks will only be about the size of a freckle. It is very important that you receive treatment in the exact same area every time, so do not try to scrub away any markings left by your cancer care team. If the markings begin to fade, let your radiation therapist know.

In addition to these markings, you may require additional tools to stay in place. Depending on the location of your tumor, your team may use a specially made mold or mask to hold your body part in place.

All of these strategies are intended to precisely deliver your dose of radiation to the exact same spot during every treatment. Doing so not only guarantees the accuracy of your treatment, it also protects surrounding tissues from being unnecessarily affected by your radiation.

How Much Radiation Will I Receive During External Beam Radiation Therapy?

Many patients are curious how much radiation they will receive during treatment. There is no standard serving of radiation. Every dose of radiation is determined based on the type and size of your cancer as well as other variables.

Your radiation oncologist will work with other members of the cancer care team, including dosimetrists and medical physicists, to decide how much radiation you should receive. They will use information from your simulation and additional tests to determine the amount of your dose, how many treatments you should receive, and the frequency of those treatments.

In addition to information about your case, your cancer care team will rely on other studies and data to determine which amount of radiation is right for you.

How Long Will My External Beam Radiation Therapy Take?

When asking how long your EBRT will take, there are two questions to consider:

  • The length of each treatment and
  • The duration of your treatment cycle

Your medical team will first identify the total dose of radiation you should receive. Because you cannot receive this entire dose at once, this will then be divided into smaller, daily doses, or “fractions.”

Radiation is usually delivered once daily, Monday through Friday. The weekends away allow cells to recover and the body to rest. These treatments usually last five to eight weeks. However, depending on your cancer, you may receive two treatments a day, or your treatment schedule may last longer.

Each daily treatment will only take a few minutes. Including time to position your body and the EBRT machine, each appointment will take 15 to 30 minutes.

What Will Happen During My External Beam Radiation Therapy Appointments?

External beam radiation therapy is quick and painless, and the appointments are predictable. Here’s what you can expect from each treatment session:

  1. You will likely be asked to change into a hospital gown or robe. Be prepared to change by wearing clothes that are easy to get on and off.
  2. Your radiation therapist will take you into the treatment room, which will be cool. There, you’ll sit in a chair or lie down on a table, depending on the location of your cancer.
  3. Using the colored dots on your skin, your radiation therapist will make sure your treatment part is exactly aligned with the machine delivering your radiation. If you have a mold or mask, they will secure this to ensure alignment. He or she may also put a shield between the machine and your other body parts. This protects those body parts from harmful radiation.
  4. The radiation therapist will go into another nearby room to administer your treatment. They will be able to see you through a tv screen and talk to you through a microphone throughout treatment, so they can quickly respond to you if needed.
  5. You will be asked to hold very still during treatment, which should last one to five minutes.
  6. As the machine begins, you may see colored lights that align with the semi-permanent dots on your skin. These are not painful, they simply mark and align the treatment part. During treatment, the machine will make noises and its arm may move around you, but it will not touch you. You will not feel anything during treatment.

How to Relax Before or During Your External Beam Radiation Therapy

Although EBRT treatments are quick and painless, receiving radiation may be a source of stress for you. It is important for you to remain relaxed throughout your appointment so that you can hold very still during treatment. This ensures that treatment is delivered precisely.

If you are concerned about your upcoming therapy, try these strategies to relax:

  • Bring something for the waiting room. Perhaps you could read a book or magazine or work on a word search or crossword puzzle. Some patients even sketch or knit while in the waiting room.
  • Bring headphones. As you wait for your appointment, it may be helpful to listen to soothing music, a podcast, or a book on tape.
  • Calm your mind. It’s particularly important for you to relax during your treatment. Some patients practice meditation or mindfulness, prayer, or other mental stimuli to relax during treatment.
  • Take deep breaths. Taking deep breaths can signal to your body that everything is ok. Therefore, deep breaths can serve as a natural stress reliever.

Side Effects of External Beam Radiation Therapy

While the precision of external beam radiation therapy leads to fewer side effects, there are still some symptoms you may expect during and after treatment. These may include:

  • Fatigue
  • Skin problems
  • Hair loss
  • Low blood counts
  • Other symptoms depending on the location

Choosing SERO for Your External Beam Radiation Therapy in Charlotte

When planning your external beam radiation therapy, it’s important to have an experienced, dedicated cancer care team on your side. That’s exactly what you’ll receive at SERO.

With more than 30 board-certified radiation oncologists at 20 hospitals and cancer treatment centers around the Charlotte Metro area, it’s easy to access first-class care. Our radiation oncologists, radiation therapists, and other members of our team have more combined experience in delivering external beam radiation therapy than any other cancer center in the region.

As you navigate the tough decisions around your cancer care, including EBRT, we’re here to help.

External Beam Radiation Therapy FAQs

Will external beam radiation therapy make me radioactive?

No, external beam radiation therapy will not make you radioactive. The radiation only affects your cells for a moment.

How effective is external beam radiation therapy?

While effectiveness varies from patient to patient, most studies show success rates of over 90%.

Is external beam radiotherapy dangerous?

No, external beam radiotherapy is not dangerous. It addresses a very specific area where your cancer is located and has little effect on surrounding cells. It is safe to be around other people when you’re receiving treatment, including pregnant women, children, and the elderly.

What are the most common side effects of external beam radiation therapy?

The most common side effects of external beam radiation therapy are fatigue, skin problems, hair loss, and low blood counts.

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