Radiation oncology

Seattle Cancer Care Alliance (SCCA) patients receive radiation therapy from leading radiation oncologists who specialize in particular cancers and are experts in their field.

Our physicians design individualized treatment plans to target your tumor and minimize the effects on healthy tissue. We will work closely with you to manage any side effects and help you take the best possible care of yourself during treatment. Our facilities feature state-of-the-art equipment so your health care team can plan and deliver effective treatment for you. We offer several types of radiation therapy, including access to the latest and most innovative options through clinical studies.

Diseases treated

People with many kinds of cancer receive radiation therapy to cure, stop, or slow their disease; to reduce the risk that it will come back; or to relieve symptoms caused by tumors. Radiation therapy is used to treat the primary site of some kinds of cancer, such as breast, colon, lung, and prostate cancers. It’s also used to treat metastases — areas where cancer has spread — including to the bones, brain, and other organs.

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Types of radiation therapy

There are two main types of radiation therapy: external-beam radiation therapy and internal radiation therapy. Your radiation oncologist will talk with you about the type that is best for your situation and the reasons why.

External-beam radiation therapy

External-beam radiation therapy refers to treatments in which the radiation is generated from a source outside your body, and the beams are then pointed precisely at your tumor. This is the most common type of radiation therapy for cancer.


Internal radiation therapy

Internal radiation therapy refers to treatments in which a radioactive substance is placed inside your body so it can release radiation from within. 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.

Internal radiation therapy includes:

  • Brachytherapy
    • Brachytherapy is radiation therapy that’s delivered by implanting a small radioactive source—such as a seed, pellet, wire, needle, or capsule—inside your body. A doctor places the source next to or inside the tumor using a tube-like applicator. Depending on your specific situation, you might need a high-dose radiation source that’s inserted for a short time (and then removed) on several occasions. Or you might need a low-dose radiation source that’s inserted once and left for weeks, for months, or permanently.
  • Systemic radiation therapy
    • Radioactive medicines can be taken by mouth or injected in a vein. These medicines travel throughout the body, collect where there’s cancer, and give off radiation to kill cancer cells. One example is radioactive iodine therapy, used to treat thyroid cancer.


External-beam radiation therapy (EBRT)

External-beam radiation therapy refers to treatments in which the radiation is generated from a source outside your body, usually a machine called a linear accelerator, or linac. The radiation beams are then pointed precisely at your tumor. This is the most common type of radiation therapy that people receive to treat cancer.

External-beam radiation therapy includes the following, all of which SCCA offers:

Three-dimensional conformal radiation therapy (3D-CRT)

In 3D-CRT, the radiation treatment plan is specifically tailored to the patient’s anatomy. At the beginning of the planning process, the radiation therapists perform a computed tomography (CT) scan of the part of the body being treated. These images are loaded into a specialized computer and used to create the radiation treatment plan. The plan is designed to deliver a beam of radiation that conforms closely to the size, shape, and contours of the tumor. This type of treatment is typically given five days a week (Monday through Friday) for two to eight weeks.

Intensity-modulated radiation therapy (IMRT)

IMRT is one kind of 3D-CRT. The basic idea is the same: The treatment plan is designed so that the beam of radiation conforms closely to the patient’s tumor. With IMRT, the beam can be split into smaller beams of different strengths. This helps the radiation oncology team deliver a higher dose of radiation to the tumor and lower doses to nearby healthy tissue.

Stereotactic radiosurgery

Stereotactic radiosurgery delivers a high dose of radiation to a precise area from many angles, typically in one treatment session. Despite the name, it’s not like conventional surgery—it doesn’t involve any cutting. Gamma Knife is one form of radiosurgery. It’s usually used to treat brain tumors or other tumors inside the head. The patient wears a head frame during treatment to keep their head still and help aim the radiation at the right spot.

Stereotactic body radiation therapy (SBRT)

Like stereotactic radiosurgery, SBRT aims many beams of high-dose radiation from different angles, but this form is used to treat tumors outside the head, such as in the liver, lungs, adrenal glands, and spine. To target the radiation beams precisely, a specially designed body frame, which reduces movement, is used for each treatment.

Intraoperative radiation therapy (IORT)

When tumors can’t be removed completely from the pelvic or abdominal regions because they are attached to important organs or nerves, or if residual cells are left over after a tumor is resected, IORT might be an option. In IORT, surgeons move normal structures out of the way during surgery to expose the tumor for high-dose radiation treatment. University of Washington Medical Center (UWMC) is the only hospital in the Pacific Northwest to offer IORT.

UW Medicine surgeons and SCCA radiation oncologists have years of experience with intraoperative radiation therapy (IORT). University of Washington Medical Center (UWMC) is the only hospital in the WAMI region (Washington, Alaska, Montana and Idaho) to offer this treatment.

How IORT is done

During surgery, a special radiation machine called the Mobetron is docked into position over a patient but never touches the patient. The machine is aligned to the patient with a special cone that focuses the treatment beam on the target so there is little effect from stray radiation on surrounding tissues and organs. Using a fraction of the total radiation given over a traditional multi-week course of external-beam treatment, IORT delivers precise bursts of radiation to the tumor.

Patients remain in the sterile surgical environment throughout the IORT procedure. The procedure adds about 60 minutes to the total length of surgery, but the treatment itself takes only a few minutes.

Tumors treated with IORT

At UWMC, SCCA radiation oncologists use IORT to treat:

  • Locally advanced rectal cancers that are attached to normal structures, such as nerves, blood vessels, or the pelvic side wall, that cannot be removed
  • Abdominal and pelvic sarcomas that are attached to the back wall of the abdomen
  • Locally advanced gynecologic tumors, such as uterine or cervical cancers
  • Some pancreatic cancers
  • Recurrent tumors
  • Select early stage breast cancers

IORT is a powerful tool that helps increase control rates for tumors that are difficult to remove completely with surgery. Used selectively and appropriately, along with neutron therapy, brachytherapy, and proton therapy, IORT is one of the many radiotherapeutic technologies available to cancer patients treated at UWMC and SCCA.

Total body irradiation (TBI)

TBI is radiation therapy delivered to the whole body to prepare for a bone marrow transplant. This may be part of conditioning, described in more detail in the section about the transplant process.

Electron therapy

This is a type of radiation that does not penetrate as deeply into the body as X-rays or photons do, so it is best used to treat tumors on or near the surface of the body, like skin cancers.

Proton therapy

Proton therapy is a form of radiation treatment that targets protons at cancer cells. It delivers higher, more effective doses of radiation than traditional X-ray radiation therapy with great precision, significantly limiting radiation exposure to surrounding healthy tissue. Doctors can pinpoint the treatment so most of the radiation is deposited exactly at the tumor site, regardless of whether the tumor is near the surface of the skin or deep inside the body.

Neutron therapy

UWMC is one of only three facilities in the United States that offer neutron therapy, an especially powerful kind of radiation therapy effective against salivary gland tumors and some other cancers. It bombards cancer cells with neutrons, depositing about 20 to 100 times as much energy into the target tissue as regular radiation therapy does using electrons or photons. Neutron beams are more likely to damage both strands of a cell’s DNA, whereas regular radiation in general damages only one strand.

Your EBRT visits

Most people with cancer who have radiation therapy have the type called external-beam radiation therapy (EBRT). The information here will describe what to expect during visits for this type of therapy. If you are having a different type, your radiation oncology team will explain the steps involved in your care.

Initial visit

During your first visit to the radiation oncology department, you will meet with the members of your radiation therapy team. Your radiation oncologist will review your history, perform a physical exam, and discuss the recommended course of treatment with you, including expected outcomes and possible side effects.


Simulation is usually the second visit to the radiation oncology department. This is when measurements are taken to find the best way to perform your radiation treatments. Depending on the type of treatment, this may involve taking a computed tomography (CT) scan of the part of the body being treated, or it may involve creating special cushions to help keep your body in the same position every time you have the treatment. Our radiation therapists may draw marks on your skin or even place small, pinpoint tattoos to help make sure you are lined up exactly the same way every day for your treatment. For radiation involving the head, the team creates a positioning mask to help hold your head in the right place.

Treatment planning

Treatment planning happens behind the scenes. Your radiation oncologist, dosimetrists, and a medical physicist use the measurements and images from your simulation to create your radiation plan. Their goal is to maximize the effects of the radiation on the part of your body being treated and minimize the effects on other parts of your body. Treatment planning often requires the use of specialized computers with sophisticated radiation treatment planning software. This part of the process may take several days.

Verification simulation

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 essentially a final check or “dry run” to confirm your positioning on the treatment machine and other details of your radiation plan before you begin treatment.


EBRT is usually given in a series of outpatient visits that last 20 to 30 minutes each, five days a week (Monday through Friday). Treatment courses typically last somewhere between two and eight weeks, depending on the tumor type, location, and size. Your doctor will see you for a check-up at least once a week while you are going through radiation treatments.


After you have completed all of your radiation treatments, you will visit your radiation oncologist to create a follow-up plan.

Your EBRT visits

Most people with cancer who have radiation therapy have the type called external-beam radiation therapy (EBRT). The information here will describe what to expect during visits for this type of therapy. If you are having a different type, your radiation oncology team will explain the steps involved in your care.


Radiation oncology is a branch of medicine that treats cancer by using high-energy radiation in the form of photons (such as X-rays or gamma rays) or subatomic particles (such as electrons or protons). About 60 percent of people with cancer receive radiation therapy, according to the American Cancer Society.

How does radiation therapy work?

Radiation therapy (also called radiotherapy) works by damaging the DNA inside the cancer cells. When the DNA sustains enough damage, the cells cannot multiply, and they die. The goal of radiation therapy is to destroy as many cancer cells as possible with the least amount of damage to healthy cells.

Why is radiation therapy used?

The exact role of radiation therapy in your care depends on many factors, including the type, size, location, and stage of your cancer. Radiation therapy may be used as any of these:

  • Primary treatment. This means it’s the main treatment you receive to cure, stop, or slow the disease. 
  • Adjuvant therapy. This means you receive it after one or more other treatments, like surgery or chemotherapy, to reduce the risk that your cancer will come back.
  • Palliative therapy. This means it’s used to relieve symptoms, like pain, by shrinking your tumor.


Your radiation oncology team

A team of health care professionals works together to deliver radiation therapy. A team typically includes these people:

  • Radiation oncologist. This is a doctor who specializes in treating cancer with radiation. This doctor will prescribe, plan, and oversee your radiation treatment.
  • Radiation therapist. When you come in for radiation treatment, this person will position you for your treatment and operate the machines that deliver the radiation.
  • Radiation oncology nurse. This is a nurse who will explain your treatment, answer your questions, and help you manage side effects.

Some members of the radiation oncology team work behind the scenes.

  • Medical dosimetrist. This person will complete the calculations needed to carry out your treatment to ensure that you receive the exact dose of radiation prescribed by your radiation oncologist in precisely the right places. 
  • Medical physicist. This person will help plan your treatment and will maintain the equipment used to deliver radiation therapy.


Taking care of yourself during radiation therapy

Your radiation oncology team will work with you before, during, and after radiation therapy to help keep you as healthy and comfortable as possible throughout the process. Along with your radiation oncologist, radiation therapist, and radiation oncology nurse, you’ll have many others to provide support, like a nutritionist and a social worker.

Radiation therapy may cause side effects. These depend on the type of radiation therapy you have and the part of your body that’s treated. Your team will give you details about which side effects to expect, for how long, and how you can manage them. They will be available to help you with whatever comes up during your treatment.

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Where will I be seen?

Patients of Seattle Cancer Care Alliance (SCCA) may receive radiation therapy at these locations:

  • SCCA Radiation Oncology at the SCCA clinic on Lake Union
  • SCCA Radiation Oncology at UWMC-Northwest
  • SCCA Peninsula 
  • SCCA Proton Therapy Center
  • University of Washington Medical Center
  • Gamma Knife Center at Harborview Medical Center

Each of these facilities features state-of-the-art equipment so your team can plan and deliver effective treatment for you. Not all types of radiation therapy are available at every facility. Your oncology team will give you details about the type of service you need and where you will be seen.