Chemoradiotherapy for rectal cancer

Treatment with chemotherapy and radiotherapy together is called chemoradiotherapy. You might have this treatment for cancer of the back passage (rectal cancer). 

Chemotherapy uses anti cancer (cytotoxic) drugs to destroy cancer cells. The drugs circulate throughout the body in the bloodstream.

Radiotherapy uses radiation, usually x-rays, to destroy cancer cells.

Giving these treatments together before surgery can lower the chance of your cancer coming back.

When do you have chemoradiotherapy?

You usually have chemoradiotherapy before surgery. Doctors also call this long course chemoradiotherapy.

You might have chemoradiotherapy before surgery if:

  • your rectal cancer has spread to nearby structures and tissues
  • it might be difficult for your surgeon to remove the rectal cancer with a clear border of tissue (margin)

What chemotherapy will I have?

The most common chemotherapy is fluorouracil (5FU).

You might have fluorouracil in one or more of the following ways:

•    through a drip (an infusion)
•    as an infusion through a pump you wear 24 hours a day
•    as a series of injections into a vein before radiotherapy treatment

A nurse puts a small tube into one of your veins and connects it to the drip or you might need a central line. This is a long plastic tube that gives the drug into a large vein, either in your chest or in your arm. It stays in while you’re having treatment.

Or you might have a drug called capecitabine (Xeloda). Capecitabine is a tablet. 

You must take tablets according to the instructions your doctor or pharmacist gives you. Whether you have a full or empty stomach can affect how much of a drug gets into your bloodstream.

You should take the right dose, not more or less. Never stop taking a cancer drug without talking to your specialist first.

You might have the chemotherapy before the radiotherapy starts. You continue to have it during the radiotherapy treatment.

Blood tests

You have blood tests before and during your treatment. They check your levels of blood cells and other substances in the blood. They also check how well your liver and kidneys are working.

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.

Radiotherapy treatment

You have treatment in the hospital radiotherapy department.

Before you begin 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.

Your treatment starts a few days or up to 3 weeks after the planning session. You have radiotherapy from an external machine as a daily treatment, five days a week for around 5 weeks.

Side effects of chemoradiotherapy

The side effects vary from person to person. You might not have all of the effects mentioned. Side effects depend on the type of chemotherapy you have. They also depend on the radiotherapy treatment area.

The side effects gradually get worse during the treatment. They can continue to get worse after your treatment ends. But most of the effects begin to improve after 1 or 2 weeks.

Some common side effects of chemoradiotherapy for rectal cancer include:

An increased risk of infection

Increased risk of getting an infection is due to a drop in white blood cells. Symptoms include a change in temperature, aching muscles, headaches, feeling cold and shivery and generally unwell. You might have other symptoms depending on where the infection is.

Infections can sometimes be life threatening. You should let your doctor or nurse know urgently if you think you have an infection.

Contact your doctor or nurse immediately if you have signs of infection, including a temperature above 37.5C or below 36C, or generally feel unwell. Infections can make you very unwell very quickly.

Breathlessness and looking pale

You might be breathless and look pale due to a drop in red blood cells. This is called anaemia.

Bruising, bleeding gums or nose bleeds

This is due to a drop in the number of platelets in your blood. These blood cells help the blood to clot when we cut ourselves. You may have nosebleeds or bleeding gums after brushing your teeth. Or you may have lots of tiny red spots or bruises on your arms or legs (known as petechiae).

Tell your doctor or nurse if you notice these symptoms. 

Tiredness and weakness

You might feel very tired and as though you lack energy. It tends to get worse as the treatment goes on and can continue for some weeks after the treatment has finished. 

Various things can help you to reduce tiredness and cope with it, for example exercise. Some research has shown that taking gentle exercise can give you more energy. It is important to balance exercise with resting.

Feeling or being sick

Feeling or being sick is usually well controlled with anti sickness medicines. Avoiding fatty or fried foods, eating small meals and snacks, drinking plenty of water, and relaxation techniques can all help.

It is important to take anti sickness medicines as prescribed even if you don’t feel sick. It is easier to prevent sickness rather than treating it once it has started.

Sore mouth and ulcers

Mouth sores and ulcers can be painful. Keep your mouth and teeth clean; drink plenty of fluids; avoid acidic foods such as oranges, lemons and grapefruits; chew gum to keep the mouth moist and tell your doctor or nurse if you have ulcers.


Tell your doctor or nurse if you have diarrhoea. Drink at least 2.5 litres of fluid a day to help keep you hydrated. Let your doctor or nurse know straight away if the diarrhoea is severe or getting worse.

Ask your nurse about soothing creams to apply around your back passage (anus). The skin in that area can get very sore.

Changes in how your heart works

You may have changes to how your heart works. This can cause changes to your heart rhythm and how well it is able to pump blood around your body. Symptoms that your heart is not working properly might include breathlessness when resting or after an activity; feeling tired and lacking energy most of the time and swollen ankles and legs.

Your doctor might ask you to have tests to check your heart, such as an electrocardiogram (ECG).

Soreness, redness and peeling on palms and soles of feet

The skin on your hands and feet can become sore, red, and peel. You might also have tingling, numbness, pain and dryness. This is called hand-foot syndrome or palmar plantar syndrome.

Tell your doctor or nurse straight away if you have pain, swelling, redness or tingling of your hands or feet. 

Hair thinning  

Your hair may thin or you may lose it completely. It usually begins falling out gradually within 2 to 3 weeks after treatment starts.

Your hair grows back once your treatment has finished. This can take several months and your hair is likely to be softer.

Raised uric acid levels in the blood

High levels of uric acid in your blood can lead to a build up of crystals in body tissues and cause inflamed joints. You’ll have regular blood tests to check your levels. Drinking plenty of fluids helps to flush out the excess uric acid. You might also have medicines to control the uric acid levels.

Less common side effects can include:

  • skin problems including rash, dry skin, increased sensitivity to sunlight, hives, darkening of the skin
  • nail problems including thickening, pain, changes in colour of the nail and nail bed
  • eye problems including rapid eye movement, inflammation, blocked tear ducts, blurred vision, eyelid turning outwards, watery eyes and double vision
  • constipation
  • loss of fertility – talk to your doctor before starting treatment if you think you want to have a baby in the future
  • headaches and dizziness
  • liver changes
  • tummy (abdominal pain) 
  • loss of appetite
  • periods stopping 
  • confusion or unsteadiness
  • low blood pressure
  • a feeling of intense happiness and confidence (euphoria)
  • numbness or tingling in fingers and toes
  • lighter or darker skin in the area being treated with radiotherapy 
  • very rarely you may develop a severe skin reaction that may start as tender red patches which leads to peeling or blistering of the skin. You might also feel feverish and your eyes may be more sensitive to light. This is serious and could be life threatening

Long term side effects

Most side effects gradually go away in the weeks or months after treatment. However, some side effects can continue or might start some months or years later. 

  • Rectal cancer: ESMO Clinical Practical Guidelines for diagnosis, treatment and follow up
    R Glynne-Jones and others
    Annals of Oncology, 2017. Volume 28, Pages 422-440                                                                                                                                                                       

  • Colorectal cancer 
    The National Institute for Health and Care Excellence (NICE), 2020. Updated December 2021

  • Colorectal cancer
    British Medical Journal (BMJ) Best Practice Online (Accessed February 2022)


Last reviewed: 
21 Feb 2022
Next review due: 
21 Feb 2025

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