Planning radiotherapy for advanced cancer

The radiotherapy team plans your external beam radiotherapy before you start treatment. This means working out how much radiation you need to treat the cancer and exactly where you need it.

Your planning appointment takes from 15 to 30 minutes. You have a planning CT scan in the radiotherapy department. The scan shows the cancer and the area around it.

Photograph showing Radiotherapy treatment machine

You lie on the scanner couch with the treatment area exposed. You might need to raise your arms above your head for a while. The radiographers put some markers on your skin. You need to lie very still.

Once you are in position the radiographers move the couch up and through the scanner. The radiographers leave the room and start the scan. It takes about 5 minutes. You won't feel anything.

Before the planning appointment, you might also have other scans, such as an MRI scan.

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 radiographer 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. 

Last reviewed: 
27 Aug 2019
  • Gastric cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up 
    E Smyth and others, 
    Annals of Oncology, 2016. Volume 27, Pages v38–v49

  • Guidelines for the management of oesophageal and gastric cancer.
    British Society of Gastroenterology (BSG), 2011.

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