External Beam Radiation Therapy (EBRT)

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External Beam Radiation Therapy (EBRT) is the most commonly used form of radiation therapy. This type of therapy uses a machine similar to an X-ray machine to deliver radiation to a tumor site from outside your body.

EBRT is used in the treatment of a variety of cancers:

  • Prostate
  • Breast
  • Lung
  • Skin
  • Head and neck
  • Brain and spinal cord
  • Stomach
  • Pancreas
  • Rectum
  • Bladder
  • Cervix
  • Endometrium
  • Anal canal
  • Lymphoma

Types of External Beam Radiation Therapy

There are many types of radiation therapy that use complex names and acronyms. Some forms of radiation therapy are unique and some combine multiple elements together. 

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

Tumors are not regular — they come in different shapes and sizes. Three-dimensional conformal radiation therapy, or 3D-CRT, uses computers and special imaging techniques to show the size, shape and location of the tumor.

Computer assisted tomography (CT or CAT scans), magnetic resonance imaging (MR or MRI scans) and/or positron emission tomography (PET scans) are used to create detailed, three-dimensional representations of the tumor and surrounding organs. Your radiation oncologist can then precisely tailor the radiation beams to the size and shape of your tumor.

Because the radiation beams are very precisely directed, nearby normal tissue receives less radiation decreasing the chances for side effects.

Image-Guided Radiation Therapy (IGRT)

Radiation oncologists use Image-Guided Radiation Therapy (IGRT) to help better deliver the radiation to the cancer since tumors can move between treatments due to differences in organ filling or movements while breathing.

IGRT involves radiation delivery guided by imaging, such as CT, ultrasound or X-rays, taken in the treatment room by the Linear Accelerator just before the patient is given their treatment. The imaging information from the original planning CT scan is availble in thet reatment room to allow doctors to compare the earlier image with the images taken just before treatment.

During IGRT, doctors compare these images to see if the treatment needs to be adjusted. This allows doctors to better target the cancer while avoiding nearby healthy tissue. In some cases, doctors will implant a tiny marker in or near the tumor to pinpoint it for IGRT. IGRT is often used in conjunction with other forms of radiation therapy and is always incorporated into IMRT, VMAT, SBRT, and SAR treatments.

Intensity-Modulated Radiation Therapy (IMRT)

Intensity Modulated Radiation Therapy (IMRT) is a specialized form of Three-Dimensional Conformal Radiation Therapy (3D-CRT) that allows radiation to be more exactly shaped to fit the tumor. 

With IMRT, the radiation beam can be broken up into many “beamlets,” and the intensity of each beamlet can be adjusted individually. Using IMRT, it may be possible to further limit the amount of radiation that is received by healthy tissue near the tumor. In some situations, this may also allow a higher dose of radiation to be delivered to the tumor, potentially increasing the chance of a cure.

Volumetric Modulated Arc Therapy (VMAT)

Volumetric Modulated Arc Therapy (VMAT) is the most advanced way to deliver IMRT treatments currently available, With VMAT, your radiation oncologist along with a medical physicist can create a radiation plan that is delivered continuously as the gantry of the Linear Accelerator rotates around the patient in a 360-degree arc.

The speed of the gantry rotation, the shape of the radiation, and the intensity of the radiation can be modulated over each degree of rotation allowing the creation of very complex plans that maximize the sparing of normal tissue. 

These plans are also delivered quicker than other methods with a typical "beam on" time of only 2-3 minutes. Each patient benefits from increased comfort as well as the speed, efficiency and precision of this powerful treatment tool.

NHRMC’s Radiation Oncologists use Rapid Arc technology to deliver varying types of radiation therapy. The Rapid Arc machine distributes each dose of radiation in one continuous arc around the patient in a matter of just a few minutes. Each patient benefits from increased comfort as well as the speed, efficiency and precision of this powerful treatment tool.

Stereotactic Body Radiation Therapy (SBRT)

Stereotactic Body Radiation Therapy (SBRT) combines the planing and delivery efficiency of VMAT and the imaging advances of IGRT to allow the safe delivery of extremely high doses of radiation to small, well defined targets in the body and the brain.

SBRT schedules ar eoften anywhere from one to five sessions total. SBRT is most commonly used to treat newly diagnosed cancer in the prostate, lung and pancrease. It has also been shown to be very effective at treating more advance dcancers that have spread to the lung, bone, brain, spine and adrenal gland. SBRT use has increased dramatically because of its effectiveness and convenience for patients as it requires fewer treatment visits than other forms of radiation therapy.

Stereotactic Radiosurgery (SRS)

Stereotactic Radiosurgery (SRS) is not really "surgery" at all, but rather precisely focused, high-dose radiation therapy delivered to small, localized areas within the brain. SRS is very different than open surgery; it is non-invasive and relatively painless. SRS uses a much higher dose of radiation therapy than traditional Radiation Therapy.

SRS is used in the treatment of some primary brain tumors, meningiomas, and brain metastases, as well as benign conditions like blood vessel malformations and neurologic problems such as movement disorders.

Standard Fractionation, Hypofractionation, Extreme Hypofractionation (SBRT, SABR, SRS)

Fractionation is the process of breaking up a total radiation dose into smaller doses that can be delivered over time. Historically, relatively low doses were given each day for many weeks depending on the type of cancer and the part of the body being treated. As treatment delivery techniques and "on-board imaging" have improved, we are now able to safely give higher doses each day and shorten the overall number of treatment days required.

The following is a sample table describing the various fractionation definitions. In general, the larger the area of the body receiving radiation therapy, the more likely it is to need standard fractionation to be able to deliver the total dose needed and keep normal tissues safe. The decision on total dose and fractionation is made by the radiation oncologist after xynthesizing all the diagnostic and imaging information and discussing goals of care with you.

Fractionation Type Typical Daily Dose (cGy) Type of RT Types of Cancers
Standard 180 - 200 3D-CRT VMAT Brain, Head and Neck, Lung, Gastrointestinal, Breast, Gynecologic, Prostate
Moderate   250 - 400 3D-CRT VMAT Brain, Breast, Prostate, Bone
High  500 - 2,400 VMAT SRS Brain. Lung, Prostate, Liver, Pancreas