Radiation Therapy for Anal Cancer

Radiation therapy uses high-energy x-rays or other types of radiation to kill cancer cells. It can be given internally or externally.

• External beam radiation therapy (EBRT) - EBRT is the most common type of radiation treatment for anal cancer. Radiation from a high-energy x-ray machine (linear accelerator) outside the body is focused on the cancer cells. The radiation may focus on some of the pelvis to treat lymph nodes in the groin because anal cancer often spreads to these lymph nodes. EBRT can harm both the cancer cells and nearby healthy tissue. Most people are treated with EBRT for a few minutes 5 days a week for 5 or 6 weeks as an outpatient.

• Internal radiation therapy (brachytherapy or interstitial radiation therapy) - Small pellets (or “seeds”) that contain radioactive materials are placed in your body in or near the tumor. The radioactive pellets release their radiation slowly over time. Brachytherapy lets the doctor use a higher dose of radiation than EBRT. It is sometimes used for people with anal cancer, especially if they are too sick or weak to have curative surgery. This type of treatment involves a one-time procedure.

Sometimes, internal and external radiation therapies are used together.

If you have been infected with the human immunodeficiency virus (HIV, the virus that causes AIDS), you are more likely to have side effects during and after radiation treatment. The radiation can weaken your immune system, which is already vulnerable because of the HIV. These side effects could make it harder for you to go through and complete treatment. For this reason, your doctor may recommend lower doses of radiation if you have HIV.

This content has been reviewed and approved by Myo Thant, MD.