Anal Cancer Overview

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Treating Anal Cancer TOPICS

Radiation therapy for anal cancer

Radiation therapy is treatment with high energy rays (like x-rays) to kill cancer cells or shrink tumors. The radiation may be given from outside the body (external radiation) or from a radioactive substance placed directly in the tumor (internal or implant radiation). Sometimes doctors give radiation to shrink a tumor so it is easier to remove during surgery.

External radiation

This is the most common way to give radiation for anal cancer. It uses a focused beam of radiation from a machine outside the body. Treatment is often given 5 days a week for about 5 weeks. It is much like getting a normal x-ray. The radiation field may include some of the pelvis in order to treat lymph nodes in the groin, because the cancer will often spread to these lymph nodes.

Sometimes, doctors use some newer techniques that let them give higher doses of radiation to the cancer while reducing the radiation to nearby healthy tissues.

Side effects

There can be side effects from radiation treatment. These side effects vary based on the part of the body treated and the dose of radiation given.

Some common short-term side effects include:

  • Skin changes (like a sunburn)
  • Temporary anal irritation and pain
  • Discomfort during bowel movements
  • Fatigue
  • Nausea
  • Diarrhea
  • In women, radiation may irritate the vagina. This can lead to discomfort and drainage (a discharge).
  • Swelling in the legs (lymphedema) if radiation is given to the lymph nodes in the groin

These side effects often improve after radiation stops.

Long-term side effects can also occur. Radiation to the pelvis can also weaken the bones, increasing the risk of fractures of the pelvis or hip later on. It can also damage blood vessels that nourish the lining of the rectum which can lead to the lining of the rectum becoming inflamed (chronic radiation proctitis). This can cause long-term rectal bleeding and pain.

Radiation can also cause infertility (not being able to have children) in both women and men. In women, it can also lead to vaginal dryness and even cause scar tissue to form in the vagina The scar tissue can make the vagina shorter or more narrow, which can make sex painful. A woman can help prevent this problem by stretching the walls of her vagina several times a week. This can be done by using a plastic or rubber tube to stretch out the vagina (a vaginal dilator).

Internal radiation (brachytherapy)

This kind of radiation treatment involves minor surgery to put radioactive seeds or pellets inside the body, in or near the tumor. The radioactive pellets slowly release their dose over a period of time. Though the pellets stop being radioactive after a while, they stay in place for the rest of your life. Fewer trips to the doctor are needed with this treatment. This approach is used less often than external radiation. When it is used, it is usually given along with external radiation. The possible side effects are often like those seen with external radiation.

To find out more about radiation treatment, please see our document Understanding Radiation Therapy: A Guide for Patients and Families.


Last Medical Review: 01/14/2013
Last Revised: 01/17/2013