Colorectal Cancer Overview

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Treating Colon/Rectum Cancer TOPICS

Radiation treatment for colorectal cancer

Radiation treatment is the use of high-energy rays (such as x-rays) to kill cancer cells or shrink tumors.

When is it used?

Before surgery: If the size or place of a tumor makes it hard to take it out, radiation may be used before surgery to shrink the tumor. Radiation is also used sometimes before surgery for rectal cancers, because it lowers the risk of the cancer coming back later. When it is used for rectal cancers before surgery, radiation is often combined with chemotherapy. This is called chemoradiation. The chemo helps the radiation work better, but adds to the side effects.

After surgery: Radiation can also be used after surgery, to kill any cancer cells that may have been left behind (but couldn’t be seen). This lowers the chance that the cancer will come back later.

For people who can’t have surgery: Radiation can be given to help control rectal cancers in people who are not healthy enough for surgery.

For advanced cancers: Radiation can also be used to ease symptoms of advanced cancer, such as intestinal blockage, bleeding, or pain. It is also be used to treat colon cancer that has spread, most often if the spread is to the bones or brain.

Types of radiation treatment

External-beam radiation therapy: In this treatment, radiation is focused on the cancer from a machine outside the body. This is the type most often used for people with colon or rectal cancer. Treatments are given 5 days a week for many weeks. Each treatment lasts only a few minutes, but the setup time -- getting you into place for treatment -- usually takes longer.

Endocavitary radiation therapy: For some small rectal tumors radiation can be given with a small device that is placed through the anus and into the rectum. Each treatment takes just a few minutes and then the device is removed. This is repeated about 3 more times about 2-weeks apart for the full dose. This treatment allows radiation to reach the rectum without passing through the skin and other nearby tissues.

Brachytherapy (internal radiation therapy): In this method, small pellets or seeds of radioactive material are placed next to or right into the cancer. The radiation travels only a short distance, limiting the effects on nearby healthy tissues. This method is sometimes used in treating people with rectal cancer, particularly sick or older people who would not be able to go through surgery.

Radioembolization: Some patients who have a lot of spread to the liver but little or no spread to other distant parts of the body may get treatment with infusion through the artery that goes to the liver. The doctor injects tiny glass "beads" that are coated with a radioactive atom (yttrium-90). These beads block some of the small blood vessels that feed the tumors and their radioactivity helps kill the cancer cells.

Side effects of radiation therapy

Some of the common side effects of radiation therapy for colon or rectal cancer include:

  • Skin changes in the area where the radiation passes
  • Nausea and vomiting
  • Diarrhea
  • Rectal irritation, which can lead to trouble controlling your bowels
  • Bladder irritation which can make you feel like you have to pass urine often
  • Tiredness.

Sexual problems may also occur.

Side effects often go away or lessen over time after treatment is finished, but problems such as rectal and bladder irritation may remain. If you have these or other side effects, talk to your doctor. There are often ways to reduce or relieve many of these problems.

You can learn more about radiation in Radiation Therapy – What It Is, How It Helps.


Last Medical Review: 08/15/2013
Last Revised: 01/31/2014