Radiation Therapy

Radiation therapy, or radiation oncology, involves using targeted, penetrating rays of energy (radiation) to destroy cancer cells. In the treatment of colorectal cancer, radiation therapy can be used before surgery to shrink a tumor or after surgery to kill any remaining cancer cells.

Radiation Therapy Team

Our team of radiation oncologists who specialize in in the use of radiation therapy to treat cancer, oncology nurse specialists, dosimetrists, physicists and therapists at the the Swedish Cancer Institute and its Center for Advanced Targeted Radiation Therapy work together to provide the very best care and is influential in the development and delivery of the latest radiation technologies available.


Radiation Therapy for Colorectal Cancer

As with any cancer treatment, a detailed treatment plan must be developed for radiation therapy. The treatment plan helps determine the exact area where the treatment needs to be focused. This area is called the "treatment field."

Technologies used at the Swedish Cancer Institute (SCI) to develop a treatment plan and then ultimately treat colorectal cancer with radiation therapy include:

PET/CT Scanner


Radiation oncologists at Swedish were among the first in the Northwest to use a 16-slice PET/CT scanner for radiation-treatment planning. The scanner combines Computerized Tomography (CT) and Positive Emission Tomography (PET), two standard medical imaging tools. The PET/CT scanner allows the tumor to be defined more precisely by better identifying the junction between cancer and inflamed normal tissue. This, in turn, allows the radiation oncologist to more effectively plan the dose of radiation to the cancer while sparing more of the healthy tissue.

External Beam Radiation Therapy

Produced by a machine called a linear accelerator, short and targeted bursts of x-rays are fired at the cancer. During radiation treatment, the tumor can move because of breathing and normal movement in the intestines. Previously, to compensate for the movement and make sure the entire tumor was treated, radiation oncologists had to expand the treatment area. This meant healthy tissue near the tumor was also affected during treatment. The Center for Advanced Targeted Radiation Therapy uses these advanced, targeted external radiation therapies to more accurately pinpoint the cancer while sparing as much normal tissue as possible:

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

External Beam Radiation Therapy can be delivered more precisely by using a special computed tomography (CT) scan and a targeting computer. This capability is known as three-dimensional conformal radiation therapy, or 3D-CRT. The use of 3D-CRT appears to reduce the chance of injury to nearby body structures. Since 3D-CRT can better target the area of cancer, radiation oncologists are evaluating whether higher doses of radiation can be given safely and with greater cancer cures.

Image-Guided Radiation Therapy (IGRT)

Swedish was the first in the Northwest and among the first in the world to offer this innovative procedure. Radiation beams come out of the linear accelerator in a square-shaped manner. To spare as much of the surrounding normal tissue as possible, the radiation oncologist designs special blocks to shape the radiation beam. With IGRT, the linear accelerator is joined to a CT scanner. This allows for near real-time imaging of the tumor prior to treatment, improving the precision of the radiation delivery while reducing the exposure of radiation to normal tissue.

Intensity-Modulated Radiation Therapy (IMRT)

For years, Swedish physicians have been at the forefront of researching IMRT applications. With IMRT, the radiation beams are broken up into numerous pencil-sized beams. These smaller beams, or beamlets, can be conformed to the shape of the tumor in three dimensions. As a result, high doses of radiation can be directed at the cancer while reducing damage to nearby tissue.

Volumetric Modulated Arc Therapy (VMAT)


SCI was one of the first cancer centers in the United States to introduce this novel radiation therapy delivery technique. During VMAT treatment, the radiation machine rotates around the patient in a series of arcs delivering focused beams of radiation to the cancer. The shape and intensity of the radiation beams changes as the machine rotates. These features mean that, in effect, the beam of radiation can come from an infinite number of angles, thereby reducing the dose of radiation to normal tissue while increasing the dose to the cancer. The arc-based delivery also allows the radiation oncologist to treat tumors that are adjacent to critical structures in the body, such as a tumor that may be wrapped around an organ.

More Information

Treatment Options by Stage


Chemotherapy / Targeted Therapy

About Colorectal Cancer