Radiotherapy for stomach cancer

Radiotherapy uses high energy waves, similar to x-rays, to kill cancer cells.

You usually have external beam radiotherapy for stomach cancer. External beam radiotherapy directs radiotherapy beams at the cancer from a machine outside of the body.

When do you have it?

Radiotherapy isn't a common treatment for stomach cancer.

If you do have radiotherapy, you usually have it with chemotherapy (chemoradiotherapy). You might have chemoradiotherapy after surgery to remove your stomach cancer. You will usually have treatment every day for a few weeks.

Or you might have radiotherapy to control symptoms of stomach cancer that has spread (advanced cancer). You might have a single treatment, or a few treatments over a few days. Radiotherapy might:

  • stop or reduce bleeding from your stomach
  • shrink the tumour if it’s causing a blockage
  • control your pain

Where do you have it?

You have external radiotherapy in the hospital radiotherapy department, usually as an outpatient. Some hospitals have rooms nearby that you can stay in if you have a long way to travel. You go to the radiotherapy department from your ward if you’re already in hospital.

Planning radiotherapy

The radiotherapy team plan your external radiotherapy before you start treatment. This means working out the dose of radiotherapy you need and exactly where you need it.

Your planning appointment takes from 15 minutes to 2 hours.

You usually have a planning CT scan in the radiotherapy department.

The scan shows the cancer and the area around it. You might have other types of scans or x-rays to help your treatment team plan your radiotherapy. The plan they create is just for you.

Photo of a CT scanner

Your radiographers tell you what is going to happen. They help you into position on the scan couch. You might have a type of firm cushion called a vacbag to help you keep still.

The CT scanner couch is the same type of bed that you lie on for your treatment sessions. You need to lie very still. Tell your radiographers if you aren't comfortable.

Injection of dye

You might need an injection of contrast into a vein in your hand. This is a dye that helps body tissues show up more clearly on the scan.

Before you have the contrast, your radiographer asks you about any medical conditions or allergies. Some people are allergic to the contrast.

Having the scan

Once you are in position your radiographers put some markers on your skin. They move the couch up and through the scanner. They then leave the room and the scan starts.

The scan takes about 5 minutes. You won't feel anything. Your radiographers can see and hear you from the CT control area where they operate the scanner. 

Ink and tattoo marks

The radiographers make pin point sized tattoo marks on your skin. They use these marks to line you up into the same position every day. The tattoos make sure they treat exactly the same area for all of your treatments. They may also draw marks around the tattoos with a permanent ink pen, so that they are clear to see when the lights are low.

Photograph of radiotherapy tattoo marks

The radiotherapy staff tell you how to look after the markings. The pen marks might start to rub off in time, but the tattoos won’t. Tell your radiographer if that happens. Don't try to redraw them yourself. 

After your planning session

You might have to wait a few days or up to 3 weeks before you start treatment.

During this time the physicists and your radiotherapy doctor (clinical oncologist) decide the final details of your radiotherapy plan. They make sure that the area of the cancer will receive a high dose and nearby areas receive a low dose. This reduces the side effects you might get during and after treatment. 

Having radiotherapy

Radiotherapy machines are very big and could make you feel nervous when you see them for the first time. The machine might be fixed in one position. Or it might rotate around your body to give treatment from different directions. The machine doesn't touch you at any point.

Before your first treatment, your radiographers Open a glossary item will explain what you will see and hear. In some departments, the treatment rooms have docks for you to plug in music players. So you can listen to your own music while you have treatment.

Photo of a linear accelerator

Before your treatment

Your radiographers help you get into position on the treatment couch. They line up the radiotherapy machine, using the marks on your skin.

Then they leave you alone in the room for a few minutes for the treatment. This is so they aren't exposed to radiation. 

During the treatment

You need to lie very still. Your radiographers might take images (x-rays or scans) before your treatment to make sure that you're in the right position. The machine makes whirring and beeping sounds. You won’t feel anything when you have the treatment.

Your radiographers can see and hear you on a CCTV screen in the next room. They can talk to you over an intercom and might ask you to hold your breath or take shallow breaths at times. You can also talk to them through the intercom or raise your hand if you need to stop or if you're uncomfortable.

You won't be radioactive

This type of radiotherapy won't make you radioactive. It's safe to be around other people, including pregnant women and children.

Side effects of radiotherapy

The side effects of radiotherapy for stomach cancer can include feeling or being sick and loss of appetite. 

These side effects usually start a few days after the radiotherapy begins. They might gradually get worse during your treatment or after treatment ends. You usually start to get better 1 to 2 weeks after you finish treatment.

The side effects are usually less severe if your treatment is for a short period of time. And more severe if treatment is longer, for example over a few weeks.  Chemotherapy combined with radiotherapy can sometimes make some side effects worse.

Feeling or being sick

Radiotherapy to the stomach area can make you feel sick or be sick. This can start a few hours after treatment and last for a few days. Anti sickness injections and tablets can help. Tell your doctor or nurse if you feel sick. You might need to try different anti sickness medicines to find one that works.

Contact your doctor or nurse straight away if you’ve been sick more than once in a day.


  • Avoid eating or preparing food when you feel sick.
  • Avoid foods that are fried, fatty, or have a strong smell.
  • Drink plenty of liquid to stop you from getting dehydrated.
  • Relaxation techniques help control sickness for some people.
  • Ginger can help – try it as crystallised stem ginger, ginger tea or ginger ale.
  • Fizzy drinks help some people when they’re feeling sick.


Radiotherapy to the stomach area might cause diarrhoea. Your poo (stool) may be very watery and have a strong smell. And you might need to poo more often or need to go the toilet more urgently.

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.

Loss of appetite

Radiotherapy to your stomach can damage the cells of the stomach lining for a short time. This makes eating more difficult. Ask to see a dietitian if you have problems with eating and drinking.


  • Drink about 3 litres of water a day while having treatment. Eating soft foods can be easier.
  • Make sure that you eat slowly and avoid eating late in the day.
  • Eat small amounts often, rather than big meals.
  • Try different foods. You can have high calorie drinks to boost your calorie intake if you need them.

You might need to have liquid food into your vein or through a tube into your nose or stomach if you can’t eat enough.

Tiredness and weakness

You might feel tired during your treatment. It tends to get worse as the treatment goes on. You might also feel weak and lack energy. Rest when you need to.

Tiredness can carry on for some weeks after the treatment has ended. But it usually improves gradually.

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

Reddening or darkening of your skin in the treatment area

Your skin might go red or darker in the treatment area. You might also get slight redness or darkening on the other side of your body. This is where the radiotherapy beams leave the body. 

The red or darker areas can feel sore. Your radiographers will give you creams to soothe your skin. The soreness usually goes away within 2 to 4 weeks of ending the treatment. But your skin might always be slightly darker in that area.

Tell the radiotherapy staff if you notice any skin changes.

Radiotherapy to other areas of the body

You might have radiotherapy to treat cancer that has spread elsewhere in the body. So your side effects will depend on the part of the body you have treatment to.

For example, some people have radiotherapy to treat cancer that has spread to their lungs. The aim of radiotherapy is usually to control cancer growth and relieve symptoms. But it might cause breathlessness at first.

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    F Lordick and others, 
    Annals of Oncology, 2022

  • Palliative care for advanced gastric cancer
    K Harada and others
    Expert Review in Anticancer Therapy, 2020. Volume 20. Pages 575-580

  • Radiotherapy Dose Fractionation (Third Edition)
    Royal College of Radiologists, 2019

  • National Oesophago-Gastric Cancer Audit
    The Royal College of Surgeons of England, 2021

  • Health-related quality of life in locally advanced gastric cancer: A systematic review
    RM van Amelsfoort and others
    Cancers, 2021. Volume 13. Page 5934

  • 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 with details of the particular issue you are interested in if you need additional references for this information.

Last reviewed: 
13 Sep 2022
Next review due: 
12 Sep 2025

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