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.
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 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.
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.
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 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.
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.