Planning radiotherapy for prostate cancer

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 such as an MRI to help your treatment team plan your radiotherapy. The plan they create is just for you.

Before you have your planning scan, your nurse or radiographer ask you to sign a consent form.

Your planning CT scan

Before the scan, you might need to empty your bowels and fill your bladder. Having an empty bowel and a comfortably full bladder can help to reduce the movement of the prostate. And it can lower the dose of radiation to nearby healthy tissues. To do this your radiographers might ask you to use an enema Open a glossary item and tell you to drink a certain amount of water. 

Your radiographers will tell you whether you need to do this. 

The scan 

You lie on the scanner couch. You usually have to remove your trousers before you get on the couch. Your radiographers need to see the treatment area. So they usually ask you to lower your underwear. But they keep you covered up. 

Photo of a CT scanner

The radiographers put some markers that show up on the scan on your skin. 

Once you are in position the radiographers move the couch up and through the scanner. You need to lie very still. Your radiographers leave the room and the scan starts. It takes about 5 minutes. You won't feel anything. The radiographers watch from the room next door. 

Metal markers

Your doctor might put small metal markers into your prostate gland. These are called fiducial markers.

To place the markers, your doctor inserts a needle into the prostate. They do this while you have an ultrasound scan Open a glossary item during an outpatient appointment. Once the tip of the needle is in the right place your doctor releases the metal marker. The markers are about 2 to 3 millimetres. You might have some antibiotics before or following this procedure. This is to lower the chance of an infection.

Fiducial markers are one way of making sure that your treatment is accurate. The metal shows the position of your prostate. Your radiographers take images (x-rays or scans) before each of your treatments. They match the position of your fiducials. This should mean your prostate is in the same position for treatment as it was during your planning 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

It can take around 2 to 3 weeks before you start treatment. During this time the physicists and your radiotherapy doctor create your radiotherapy plan. They make sure that the area of the cancer will receive a high dose and surrounding areas receive a low dose.

  • Prostate cancer: diagnosis and management
    National Institute for Health and Care Excellence (NICE), 2019. Last updated December 2021

  • Cancer: Principles and Practice of Oncology (12th edition)
    VT DeVita, TS Lawrence, SA Rosenberg
    Wolters Kluwer, 2023

  • Prostate cancer: ESMO clinical practice guidelines for diagnosis, treatment and follow up
    C Parker and others
    Annals of Oncology, 2020. Vol 31, Issue 9. Pages 1119-1134

Last reviewed: 
25 Jun 2025
Next review due: 
25 Jun 2028

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