Chemoradiotherapy for anal cancer

Chemoradiotherapy means having chemotherapy and radiotherapy treatment together. It is the most common treatment for anal cancer that hasn't spread to other parts of the body.

Chemotherapy uses anti cancer (cytotoxic) drugs to destroy cancer cells. And radiotherapy kills the cancer cells using high energy waves similar to x-rays.

This page is about having chemoradiotherapy for anal cancer that hasn't spread elsewhere in your body. Chemotherapy without radiotherapy is the main treatment for anal cancer that has spread (advanced anal cancer).

When you have chemoradiotherapy for anal cancer

You usually have chemoradiotherapy for anal cancer that is number stage:

  • 1 to 3 and in the anal canal
  • 2 to 3 and in the anal margin

Chemoradiotherapy after surgery

Some people might have low dose chemoradiotherapy after surgery for stage 1 cancer of the anal margin. This is usually when there is a risk that some cancer cells might have been left behind.

Types of chemotherapy

You usually have a combination of chemotherapy drugs with radiotherapy. The most common combinations are:

  • mitomycin C and fluorouracil (5FU)
  • mitomycin C and capecitabine

Your doctor will talk with you about which combination they recommend and why.

How you have chemotherapy

You have mitomycin and fluorouracil into your bloodstream. You take capecitabine as a tablet.

Into your bloodstream

You have treatment through a thin short tube (a cannula) that goes into a vein in your arm each time you have treatment.

Or you might have treatment through a long line: a central line, a PICC line or a portacath. These are long plastic tubes that give the drug into a large vein in your chest. The tube stays in place throughout the course of treatment. This means your doctor or nurse won't have to put in a cannula every time you have treatment.

Taking your tablets

You must take tablets according to the instructions your doctor or pharmacist gives you.

Speak to your pharmacist if you have problems swallowing the tablets.

Whether you have a full or an empty stomach can affect how much of a drug gets into your bloodstream.

You should take the right dose, no more or less.

Talk to your healthcare team before you stop taking a cancer drug or if you miss a dose.

Treatment cycles

You take some cancer medicines in treatment cycles. This means you take the drug for a set period, followed by a break. For example, you might take a drug every day for a week and then not take it for 2 weeks. This 3 week period in total is one cycle of treatment.

Take your cancer drugs exactly as your doctor, specialist nurse or pharmacist has told you to. The break from treatment is important too. For many cancer drugs, it allows your body to recover.

Before you start chemotherapy

You need to have blood tests to make sure it’s safe to start treatment. You usually have these a few days before or on the day you start treatment. You have blood tests before each round or cycle of treatment.

Your blood cells need to recover from your last treatment before you have more chemotherapy. Sometimes your blood counts are not high enough to have chemotherapy. If this happens, your doctor usually delays your next treatment. They will tell you when to repeat the blood test. 

DPD deficiency

Between 2 and 8 out of 100 people (2 to 8%) have low levels of an enzyme called dihydropyrimidine dehydrogenase (DPD) in their bodies. A lack of DPD can mean you’re more likely to have severe side effects from capecitabine or fluorouracil. It might take you a bit longer to recover from the chemotherapy. These side effects can rarely be life threatening.

Before starting treatment with capecitabine or fluorouracil you have a blood test to check levels of DPD. So you may start treatment with a lower amount (dose) of the drug or have a different treatment. Your doctor or nurse will talk to you about this.

Dietary or herbal supplements and chemotherapy

Let your doctors know if you:

  • take any supplements
  • have been prescribed anything by alternative or complementary therapy practitioners

It’s unclear how some nutritional or herbal supplements might interact with chemotherapy. Some could be harmful.

Where you have chemotherapy

You usually have treatment into your bloodstream at the cancer day clinic. You might sit in a chair for a few hours so it’s a good idea to take things in to do. For example, newspapers, books or electronic devices can all help to pass the time. You can usually bring a friend or family member with you.

You have some types of chemotherapy over several days. You might be able to have some drugs through a small portable pump that you take home.

For some types of chemotherapy you have to stay in a hospital ward. This could be overnight or for a couple of days.

Some hospitals may give certain chemotherapy treatments to you at home. Your doctor or nurse can tell you more about this.

Watch the video below about what happens when you have chemotherapy. It is almost 3 minutes long.

Radiotherapy treatment

You have your first radiotherapy treatment on the day you start chemotherapy.

Before you begin radiotherapy treatment, the radiotherapy team work out how much radiation you need. They divide it into a number of smaller treatments. They call each treatment a fraction. At your planning appointment, the radiographers might make pen marks or small tattoos on your skin in the treatment area. You start your treatment up to 3 weeks after the planning appointment.

You have your radiotherapy treatment in the hospital radiotherapy department. You normally have it every weekday for 5 and a half weeks.

Side effects

Which side effects you may get depends on:

  • which chemotherapy drugs you have
  • how much of each drug you have (the dose)
  • how you react to the treatment

Side effects from chemoradiotherapy to the anus can be caused by the chemotherapy, the radiotherapy or both.

The most common side effects are: 

  • feeling tired 
  • having frequent loose poos (diarrhoea)
  • sore skin - this can be in the area you had the radiotherapy or on your hands and feet due to the chemotherapy (hand-foot syndrome)

Other side effects can include:

  • feeling sick
  • an increased risk of infections
  • needing to pee often or pain and stinging when you do pee
  • blood or mucus from your bottom
  • constipation
  • hair loss

Tell your treatment team about any side effects that you have.

Infections can make you very unwell very quickly. Contact your advice line immediately if you have signs of infection. This includes a temperature of 37.5C or above, a temperature below 36C or you feel generally unwell.

  • Anal cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up
    S Rao and others
    Annals of Oncology, 2021. Volume 32, Issue 9, Pages 1087-1100

  • Association of Coloproctology of Great Britain & Ireland (ACPGBI): Guidelines for the Management of Cancer of the Colon, Rectum and Anus (2017) – Anal Cancer
    I Geh and others
    Colorectal Disease, 2017. Volume 19, Issue S1, Pages 82-97

  • Anal Cancer
    BMJ Best Practice
    Accessed May 2025

  • Clinical Oncology: National guidance for volumetric modulated arc therapy (VMAT) or intensity-modulated radiotherapy (IMRT) in anal cancer
    Royal College of Radiologists, May 2024

  • Cancer: Principles and Practice of Oncology (12th edition)
    VT DeVita, TS Lawrence, SA Rosenberg
    Wolters Kluwer, 2022

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. Please contact patientinformation@cancer.org.uk if you would like to see the full list of references we used for this information.

Last reviewed: 
27 May 2025
Next review due: 
27 May 2028

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