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A patient receiving radiation therapy at Moffitt.

When developing a colon cancer treatment plan, a physician may prescribe radiation therapy, which uses high-energy beams to destroy cancerous cells in a non-invasive manner. Often, radiation therapy is combined with chemotherapy for enhanced effectiveness. Known as chemoradiation, this approach may be used before surgery to shrink a tumor and make it easier to remove, or after surgery to help prevent a recurrence.

Although radiation therapy is not generally used as a standalone treatment for colon cancer, it may be considered if surgery is not recommended due to the potential risks or side effects. Radiation therapy can also help alleviate some of the symptoms of colon cancer, such as pain, bleeding and difficulty with bowel movements. Finally, if a colon tumor has spread to other organs or tissues, such as the liver, radiation therapy can be used to target those areas.

Several types of radiation therapy may be used for colon cancer treatment, including:

Image-guided radiation therapy

Image-guided radiation therapy (IGRT) incorporates the use of advanced imaging technologies, such as computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET), allowing the physician to target the tumor with heightened accuracy while minimizing any exposure to the surrounding healthy tissues. The machine used to deliver the radiation therapy (linear accelerator) is equipped with high-tech imaging equipment, allowing the physician to confirm the precise location of the tumor both before and during treatment. This approach can also help the physician compensate for any changes in the positioning of nearby organs, such as the bladder and rectum, that occur during treatment.

External beam radiation therapy

External beam radiation therapy (EBRT) is delivered via a linear accelerator that focuses high-energy X-rays from multiple angles to precisely match the shape of the tumor. Usually, EBRT is given once daily, five days per week, for one to five weeks. Each treatment session takes approximately 20 minutes.

There are several types of EBRT, including:

Three-dimensional conformal radiation therapy

By incorporating the use of sophisticated targeting data, three-dimensional conformal radiation therapy (3D CRT) allows a physician to precisely tailor the radiation beams to the exact location, size and shape of the tumor. As such, 3D CRT allows for the safe delivery of higher doses of radiation, which are more effective for shrinking and destroying tumors.

Intensity-modulated radiation therapy

More targeted than 3D CRT, intensity-modulated radiation therapy (IMRT) allows a physician to adjust the radiation dose within millimeters to spare surrounding healthy tissues. Through IMRT, the physician can divide the radiation treatment into many small, computer-controlled beams of varying strengths. Together, the beams closely conform to the location, size and shape of the tumor.

Volumetric modulated arc radiation therapy

Volumetric modulated arc therapy (VMAT) is an advanced variation of IMRT that delivers a continuous arc of radiation around the patient’s body. Instead of repeatedly starting and stopping to adjust the radiation delivery, the linear accelerator revolves around the patient in one or more 360-degree rotations, automatically changing the beam shape and treatment dose as it moves.


If colon cancer spreads to the liver, a physician may use radioembolization to deliver targeted radiation directly to the cancerous cells while sparing the nearby healthy cells. During this procedure, the physician will insert a catheter into the skin on the patient’s arm, then use the catheter to place tiny beads filled with the radioactive isotope yttrium (Y-90) into the blood vessels that feed the tumor. These microspheres will then travel through the bloodstream to reach the tumor. Over several weeks, the radiation will gradually decrease and eventually disappear.

Benefit from world-class care at Moffitt Cancer Center

The experienced radiation oncologists in Moffitt’s Gastrointestinal Oncology Program develop individualized radiation therapy plans tailored to each patient’s needs. Using the latest technologies to obtain detailed images of the tumor and surrounding tissues and organs, our multispecialty team can determine how to best target the cancer while sparing healthy structures. In delivering radiation therapy, our goal is to maximize the therapeutic effects while minimizing the risk of side effects.

If you have questions about radiation therapy for colon cancer, you can request an appointment with a specialistin our Gastrointestinal Oncology Program by calling 1-888-663-3488 or submitting a new patient registration form online. We do not require referrals.