Radiation Therapy for Colorectal Cancer

This content has been reviewed and approved by

Howard Burris, MD
Director, Drug Development
Sarah Cannon Cancer Center
Tennessee Oncology

Radiation therapy uses high-energy x-rays or other types of radiation to kill cancer cells. Radiation therapy is often used before surgery to shrink the tumor. It is also used after surgery to prevent the tumor from coming back, kill cancer cells that have spread to other parts of the body, and relieve pain (palliative treatment).

Radiation can be given internally or externally:

• External beam radiation therapy (EBRT) - This is the most common type of radiation treatment for people with colorectal cancer. A machine called a linear accelerator directs the radiation at the tumor from outside your body. The treatments last just a few minutes and are given 5 days a week for several weeks.
• Endocavity radiation therapy - This radiation is also given by a machine outside the body. A hand-held device is put into your anus. The device delivers high-intensity radiation for a few minutes. This is done three more times every 2 weeks or so. This procedure lets the radiation reach your rectum without going through the skin or other tissues in the abdomen. It might let you avoid major surgery and colostomy, but it is usually only used for small tumors. Sometimes it is given in combination with external beam radiation.
• Internal radiation therapy - Internal radiation therapy is also called brachytherapy. In this type of treatment, small pellets that contain radioactive materials are placed in your body near the tumor. Brachytherapy lets the doctor use a higher dose of radiation, but it can only be used if the doctor can reach the tumor to place the pellets. Brachytherapy is sometimes used for people with rectal cancer, especially if they are too sick or weak to have curative surgery. This type of treatment is a one-time procedure.
• Intraoperative radiation therapy (IORT) - Radiation is sometimes given during surgery if the surgeon is not able to take out all of the cancerous tissue. IORT allows a strong beam of radiation to reach the cancerous tissues directly without hurting healthy tissue.