External-beam radiation therapy (EBRT) is a treatment where radiation beams come from a source outside the body. Usually, it comes from a machine called a linear accelerator (also called a LINAC).
These beams are carefully pointed exactly at your tumor. For example, if you have cancer in your lung, you will only have radiation aimed at your chest, not your entire body. This is the most common type of radiation therapy that people get to treat cancer.
EBRT includes the following types of treatments, which are all offered at Fred Hutch:
Electron therapy is also called electron beam therapy (EBT). It is most often used to treat tumors on or near the surface of the body, like skin cancers. This is because electrons do not go as deeply into the body as other types of radiation, like X-rays or photons.
Three-dimensional conformal radiation therapy (3D-CRT) allows radiation to be customized to the patient’s body. First, the radiation therapist does a computed tomography (CT) scan of the part of the body being treated. These images are loaded into a special computer and used to create the radiation treatment plan.
The plan is designed to send a beam of radiation that closely matches the size and 3D shape of the tumor.
With IMRT, the radiation beam closely matches the patient’s tumor and can be split into smaller beams of different strengths. This helps the radiation oncology team send a higher dose of radiation to the tumor while sending as little as possible to nearby healthy tissue. IMRT is a type of three-dimensional conformal radiation therapy (3D-CRT), which is a computer-based procedure that creates a 3D image of the tumor
When tumors cannot be removed completely from the pelvis or abdomen because they are attached to organs or nerves, IORT might be used. Also, if there are any cancer cells left over after surgery to remove a tumor, IORT might be used.
To prepare for IORT, a surgeon moves healthy body tissues and organs out of the way before surgery, so the tumor can be exposed to high doses of radiation. Next, a machine called a Mobetron is set up for the patient. It has a special cone that aims the radiation beam at a target, with as little radiation as possible for nearby healthy tissues and organs. Finally, a carefully measured dose of radiation is sent to the tumor. The amount of radiation is a small fraction compared to the total radiation given over a traditional multi-week course of EBRT.
IORT is used to treat:
Neutron therapy is a specialized and very powerful form of external beam radiation therapy (EBRT). It is often used to treat tumors that are difficult to destroy using regular X-ray radiation therapy. Neutron therapy targets cancer cells using neutrons (tiny particles that are smaller than an atom). It puts about 20 to 100 times as much energy into the cancerous tissue as radiation therapy does (like electrons, X-rays or protons).
Proton therapy targets tiny, charged particles called protons at cancer cells. It can send high doses of radiation that are carefully targeted, so as little radiation as possible goes to nearby healthy tissue. Doctors can pinpoint the treatment so most of the radiation goes exactly to the tumor site, no matter whether the tumor is near the surface of the skin or deep inside the body.
Stereotactic body radiation therapy (SBRT) aims many beams of high-dose radiation from different angles at tumors. These tumors can be in areas such as the liver, lungs, adrenal glands and spine. To target the radiation beams exactly, special cushions that fit the shape of your body are used. These help you hold still and are used to position you before each treatment.
Stereotactic radiosurgery sends a high dose of radiation to an exact area from many angles, usually in one treatment session.
Gamma Knife is one type of radiosurgery. It is not an actual knife or scalpel — instead, it uses carefully focused beams of radiation. It is usually used on brain tumors or tumors inside the head. The patient wears a mask during treatment to keep their head still, which allows the radiation to be aimed as precisely as possible.
Total body irradiation (TBI) is radiation therapy given to the whole body to get ready for a blood and marrow transplant (BMT).
During your first appointment, you will meet with your radiation oncologist and other members of your radiation therapy team, such as a registered nurse and advanced practice provider. Your radiation oncologist will go over your health history, do a physical exam and discuss the treatment they recommend for you, including what outcomes to expect and any side effects you might have.
Your next visit is usually for simulation. This is when scans and measurements are taken to help plan your treatments. Depending on the treatment, this may involve taking a computed tomography (CT) scan of the part of your body being treated or creating special cushions to help keep your body in the same position every time you are treated.
Our radiation therapists may draw marks on your skin or place small pinpoint tattoos to help make sure you are lined up exactly the same way every time you are treated. If your head is being treated, your team will create a customized positioning mask to help hold your head in place.
Your radiation oncologist, medical dosimetrists and a medical physicist will work together to plan your treatment, using the measurements and images from your simulation. Their goal is to make the radiation work well on your cancer with the least possible effect on the healthy parts of your body. Special computers with state-of-the-art radiation treatment planning software are often used, and the treatment planning process can take several days.
After your doctor has approved your radiation treatment plan, you may need to return to the radiation oncology department for a verification simulation. This is a final check to make sure your positioning on the treatment machine is correct and check other details of your treatment before you begin.
EBRT is usually given in a series of visits that last 20 to 30 minutes each, five days a week. Treatment usually lasts between one day and eight weeks, depending on your tumor type, location and size. Your doctor will see you for a check-up at least once a week while you are having these treatments, too.
After your treatments are complete, you will visit your radiation oncologist to create an individualized follow-up plan.
When a radioactive substance is put inside your body to treat cancer, it is called internal radiation therapy. Often, the substance is a small implant. It could also be a pill that you take by mouth or a fluid that you get intravenously (by injection in your vein). Here are the different types of internal radiation therapy.
Brachytherapy is a treatment where a small radioactive source — such as a seed, pellet, wire, needle or capsule — is put inside the body. A doctor places the source next to or inside the tumor using a tube-like applicator.
Some patients need a high-dose radiation source that stays in the body for a short time (and then is removed), which happens several times. Others might need a low-dose radiation source that is put in once and left for several weeks, months or forever. Depending on the type of brachytherapy, you may need to have a local anesthesia to numb the area being treated so there is no pain, or a general anesthetic, which means you will be unconscious during the treatment.
When radioactive medicines are taken by mouth or injected into a vein, it is called systemic radiation therapy. These medicines collect where there is cancer and give off radiation that kills cancer cells. One example of systemic radiation therapy is radioactive iodine therapy, which is used to treat thyroid cancer.