What is external beam radiation therapy (EBRT)?
External Beam Radiation Therapy (EBRT) uses a machine called a linear accelerator or Linac to deliver high-energy treatment beams or electrons from outside of the body into the tumor. Your cancer treatment team, the doctor, physicist and dosimetrist, will design a specific treatment plan for you. The treatment plan will maximize the radiation delivered to the tumor while minimizing the radiation to healthy tissue. The doctor will determine how much radiation is needed, and how many treatments are needed. Commonly, treatments will be delivered over the course of several weeks through outpatient visits to a hospital or cancer treatment center.
How does your doctor plan treatment?
After a physical examination, a thorough review of your medical history and test results, the doctor will pinpoint the area(s) to be treated. This process is called simulation, and is done before the actual radiation therapy treatments start. During simulation, the radiation therapist takes x-ray or CT images of the affected area of your body. These images will be used to develop your treatment plan, to determine which beams will be aimed at the tumor.
Radiation beams are aimed very precisely. A special immobilization device may be used to help keep you still during your treatment and ensure that you are in the same position for each of your treatments. The radiation therapist may mark the treatment field with small dots using a tattoo or marker, to help ensure the precise beam placement.
How long do treatments take?
The total radiation therapy treatment is divided into smaller doses called fractions. The most common way to deliver this, is 5 days a week, Monday through Friday for 5-8 weeks. The total dose of radiation and the number of treatments is based on several factors and is different for each patient.
Other treatment schedules may be used, on a case by case basis. Using newer technologies the total treatment may be given in fewer fractions (hyperfractionated radiation).
What happens during each treatment?
During treatment, you’ll be asked to lie on a treatment table under the radiation machine (accelerator or linac). The machine has a wide arm that extends over the table. The radiation comes out of this arm. Once you’re in the correct position, the radiation therapist will go into a nearby room to operate the machine, and watch you on a television monitor. The therapist cannot stay in the room with you due to the radiation.
The linear accelerator will make clicking or whirling noises as it moves to aim the radiation beam from different angles. The radiation therapist is controlling the movement of the machine, ensuring its working properly.
You cannot feel or sense radiation; radiation is similar to having an x-ray taken. An entire session can last from 15 minutes to 30 minutes because of the time it takes to setup the equipment and put you into the correct position. The actual delivery of radiation is painless and takes only a few minutes.
Will I be radioactive during or after external beam radiation?
No! External Beam Radiation therapy affects only the cells in your body during the course of treatment. Since there is no radiation source inside your body, you are not radioactive at any point during or after your treatment.
What are the different forms of External Beam Radiation Therapy?
Image Guided Radiation Therapy (IGRT):
This is a type of conformal treatment that shapes the beams around the tumor. IGRT uses x-rays and CT scans before and during treatment to improve the precision and accuracy of the delivery of the radiation treatment.
Three-Dimensional Conformal Radiation Therapy (3D-CRT):
This type of radiation therapy uses computers and special imaging techniques (like CT, MR or PET scans) to show the size, shape and the location of the tumor as well as the surrounding organs. Your Radiation Oncologist will tailor the radiation beams to the size and shape of your tumor with special shielding. Since the beams are so precisely targeted, surrounding tissue will receive less radiation.
Intensity Modulated Radiation Therapy (IMRT):
IMRT is a specialized form of 3D-CRT which uses an advanced software to plan a precise dose of radiation, based on the tumor size, shape and location. The linear accelerator, or Linac delivers radiation in sculpted doses that match the exact 3D shape of the tumor. With IMRT, higher doses of radiation are delivered than traditional radiation therapy methods, while sparing healthy tissue.
Stereotactic Radiosurgery (SRS) & Stereotactic Body Radiation Therapy (SBRT):
Radiosurgery is NOT a surgical procedure. This type of treatment is used to treat small abnormalities, and small tumors of the brain. SRS delivers precisely, and targets radiation in fewer treatments than traditional radiation therapy. When SRS is used to treat body tumors, it’s called Stereotactic Body Radiation Therapy (SBRT). With SBRT, treatments are shorter and can range from 1-5 treatments. SBRT involves the delivery of a single high dose radiation treatment or a few fractionated radiation treatments.
Intraoperative Radiation Therapy (IORT):
This is an intensive radiation therapy treatment administered during surgery. This treatment type allows for direct radiation to the target area while sparing healthy tissue. IORT is used to treat cancers that are difficult to remove during surgery with concerns that microscopic amounts of cancer remain. IORT can be combined with conventional radiation therapy, which is typically administered before surgery.