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Types of Radiation Therapy

Radiation therapy uses high energy x-rays to destroy cancer cells. It is used to treat both colon and rectal cancers. There are many new ways that the radiation oncologist can customize your treatment. The goal is to try and kill as much cancer while sparing as much normal tissue as possible. Radiation therapy may be given either alone, or with surgery or chemotherapy.

The radiation oncologist will determine how many treatments you will receive. Each treatment generally only takes a few minutes.

External Beam

In external beam radiation therapy, radiation is produced by a machine called a linear accelerator. Short bursts of x-rays are fired from the machine at the cancer. The x-rays come out in a square-shaped manner. The radiation oncologist designs special blocks to shape the radiation beam so that it treats the cancer and as little normal tissue as possible.


Endocavitary radiation therapy is used to treat some rectal cancers. A high-intensity dose of radiation is delivered through the anus and into the rectum. This may cause fewer side effects because endocavitary radiation spares the skin and other abdominal tissue. It may also be used in combination with external beam radiation.


This is also called internal radiation therapy. Small pellets with radioactive material are placed near the cancer. Since radiation does not travel far from the pellets, it is less damaging to normal tissue. Brachytherapy is sometimes used in rectal cancer treatment.

Yttrium-90 Microsphere Radioembolism

This form of radiation therapy is given through the hepatic artery near the liver. Radioactive glass beads are inserted through a tube and into the artery. It kills cancer cells by blocking their blood supply. This treatment is used in people who have cancer that has spread to the liver, but not to other distant parts of the body.

Radiation of a Tumor

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Side Effects of Radiation Therapy

Like chemotherapy , the side effects from radiation result from injury to the normal tissues. Common radiation therapy side effects include:

  • Skin irritation where radiation enters the body
  • Nausea
  • Fatigue
  • Rectal irritation
  • Diarrhea
  • Pain during bowel movements
  • Blood in the stool
  • Stool leakage
  • Bladder irritation
  • Pain or burning during urination
  • Blood in the urine
  • Impotence in men, vaginal irritation in women

Talk to your doctor about what treatments may be appropriate for you to manage these side effects, Be certain to contact your doctor as soon as you begin to experience side effects. The earlier side effects are addressed, the more likely they will be controlled with a minimum of discomfort.


Colon cancer treatment option overview. National Cancer Institute website. Available at: Accessed May 15, 2013.

Colorectal cancer. American Cancer Society website. Available at: Updated January 17, 2013. Accessed May 15, 2013.

Colorectal cancer. EBSCO DynaMed website. Available at: Updated May 3, 2013. Accessed May 15, 2013.

Rectal cancer treatment option overview. National Cancer Institute website. Available at: Accessed May 15, 2013.

Last reviewed May 2015 by Mohei Abouzied, MD, FACP

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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