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Anal Cancer: Radiation Therapy

What is radiation therapy?

Radiation therapy is one way to treat anal cancer. It uses strong rays of energy to destroy and control the growth of cancer cells. This is a local treatment. That means it affects the cancer cells only in the area that's treated.

To get this treatment, you'll see a radiation oncologist. This doctor specializes in the use of radiation to kill cancer cells. He or she decides what kind of radiation you need, how often you need it, and what dose should be used.

How is radiation therapy used for anal cancer?

It's common to use radiation therapy at the same time as chemotherapy to treat anal cancer. This is called chemoradiation.

Radiation may be given after surgery to kill any cancer cells that may be left in your body.

It might be used to treat anal cancer that has come back in nearby lymph nodes after treatment.

If the cancer isn't responding to treatment and is causing problems, radiation can be used to ease symptoms the tumor is causing, like blockages or pain.

Radiation is most often given 5 days a week for 5 to 6 weeks.

What to expect during external radiation therapy

Before you start treatment, your healthcare provider will do imaging scans. This is to measure the tumor so the beams of radiation can be exactly focused there. You may be on your back or, more commonly, your belly during treatment. Your healthcare provider may put small marks on your skin to mark the treatment area. These marks might be made with permanent ink or tiny tattoos. They're used to aim the radiation at the same place every time, and not healthy parts of your body. A mold or cast might also be made to hold you still and in the exact same position for each treatment.

On the day of treatment, you'll be asked to have a full bladder before treatment is given. You’re carefully put into the right position. You may see lights from the machine lined up with the marks on your skin. These help the therapist know the radiation is going to the right place. The machine moves but doesn't touch you during the treatment. You can't see or feel the radiation. It’s a lot like getting an X-ray, but it takes longer.

The therapist will leave the room while the machine sends radiation to the tumor. During this time, he or she can see you, hear you, and talk to you. When the machine sends radiation to your tumor, you’ll need to be very still. But you don’t have to hold your breath. Treatment lasts only a few minutes, and the whole process will likely take less than an hour.

What are common side effects of radiation therapy for anal cancer?

Radiation affects both normal cells and cancer cells. This means it can cause side effects. Some start during treatment, but others start later and can last the rest of your life. Most side effects can be treated. And there may be things you can do to help prevent some.

Most side effects start a few weeks into treatment and go away over time after treatment ends. Here are some common short-term side effects of radiation for anal cancer:

  • Skin irritation, redness, blistering, itching, or burning in the treated area around the anus

  • Anal irritation and pain

  • Diarrhea, sometimes with some rectal bleeding

  • Discomfort when having a bowel movement

  • Nausea and vomiting 

  • An urgent need to urinate

  • Bladder pain

  • Extreme tiredness (fatigue)

  • Inability to have children (infertility)

  • Impotence (erectile dysfunction)

  • Low blood cell counts

Here are some possible long-term side effects of radiation for anal cancer:

  • Scar tissue can form and cause problems with bowel movements.

  • Fertility in both men and women can be affected.

  • The pelvic bones can be damaged, increasing the risk of fractures or breaks.

  • Blood vessels in the rectum can be damaged, which can cause rectal pain and bleeding. This is called chronic radiation proctitis.

Talk to your healthcare team about side effects you could have and what you should watch for.

Working with your healthcare provider

It's important to know how the radiation will work and what side effects you might have. Ask what can be done to help prevent or ease them. Also know which side effects are short-term and which could affect the rest of your life.

Talk with your healthcare team about what signs to look for and when to call them. For instance, radiation for anal cancer can cause diarrhea, bleeding, and other bowel problems. Know what number to call with questions. Is there a different number for evenings and weekends?

It may be helpful to keep a diary of your side effects. Write down physical, thinking, and emotional changes. A written list will make it easier for you to remember your questions when you go to your appointments. It will also make it easier for you to work with your healthcare team to make a plan to manage your side effects.

Online Medical Reviewer: Kimberly Stump-Sutliff RN MSN AOCNS
Online Medical Reviewer: Raymond Kent Turley BSN MSN RN
Online Medical Reviewer: Todd Gersten MD
Date Last Reviewed: 2/1/2021
© 2021 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare provider's instructions.
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